4:58PM

DAYS 1-5 (JANUARY 3-7)
This is an update to the morning post with a few cosmetic changes and minor tweaks to the snowfall and wind forecast. Generally added 1 or 2 inches to the snowfall forecast and 5 MPH to the wind forecast. A major storm will impact the region on Thursday. Significant snow will occur Thursday for much of the region, except starting as rain east of a line from near Plymouth MA to Newport RI including all of Cape Cod before changing to snow during the course of the storm. Based on the current expected track I’m expecting the following…
Snow accumulation: 8-12 inches in a wide swath from eastern CT and western RI to Worcester to Metro West of Boston to southeastern NH but with pockets of 12-16 inches possible favoring interior eastern MA mainly to the southwest of Boston and possibly along the North Shore communities, 4-8 inches of fluffy snow to the west of this area, and 4-8 inches of wetter snow to the east of this area lowering to 2-4 inches Outer Cape Cod and Nantucket as these areas start as rain first.
Visibility: Blizzard conditions are likely especially along the coast from near Boston and its immediate southern suburbs northward to the North Shore of MA and NH Seacoast, extending down through the South Shore and eventually Cape Cod after rain changes to snow – blizzard conditions are defined as very low visibility due to falling and/or blowing snow with winds sustained or frequently gusting to 35 MPH or greater.
Wind: Gusts as high as 45 MPH inland, 55 MPH coast, and 65 MPH or greater Cape Cod (see detailed forecast for more).
Coastal impact: Moderate to significant flooding likely especially at the time of high tide, especially northeast and north facing shores. Also, ice shoves are possible where ice has formed along the shore due to persistent very cold.
Timing of storm: Snow (rain Cape) arrives between 4AM and 7AM from south to north, peaks early to mid afternoon, ends early evening.
After the storm comes a blast of arctic air equal to or more intense than the one just-departed for Friday and Saturday.
Other notes: There could be a few surprises including a track wobble, dry slots, and synoptic bands of heavier snow, so please check the comments below and the Facebook page if you have access to it for updates.
Forecast details…
TONIGHT: Increasing clouds. Snow developing south to north 4AM through dawn except rain much of southeastern MA and southeastern RI. Temperatures remain stead interior but rise to 30-37 coast with warmest Cape Cod. Wind variable under 10 MPH becoming N.
THURSDAY: Overcast. Snow except rain changing to snow far southeastern areas. Snow will be heavy at times in bands. See above for details of snow accumulation and other storm impacts. Highs 25-37, mildest Cape Cod, in the morning, with slowly falling temperatures during the afternoon. Wind N increasing to 15-30 MPH interior and 25-40 MPH coast with higher gusts (see above for peak expected gusts).
THURSDAY NIGHT: Snow ending south to north evening. Clearing overnight. Temperatures fall to 15-22. Wind N to NW 25-35 MPH, higher gusts. Blowing and drifting snow where dry snow fell and a flash freeze where wetter snow fell.
FRIDAY: Mostly sunny. Temperatures fall to 5-12. Wind NW 25-35 MPH, higher gusts. Wind chill falling well below 0 at times. Blowing and drifting snow where dry snow fell.
SATURDAY: Partly cloudy. Isolated snow showers. Lows -5 to +5. Highs 5-15.
SUNDAY: Mostly sunny. Lows -15 to 0. Highs 10-20.

DAYS 6-10 (JANUARY 8-12)
Potential unsettled weather (snow/mix) at the start and end of this period. Fair in between. Temperatures below normal overall but variable.

DAYS 11-15 (JANUARY 13-17)
Potential unsettled weather early in the period (favoring snow but possible mix). Variable temperatures remaining below normal overall.

7:54AM

DAYS 1-5 (JANUARY 3-7)
A “Scandinavian Heatwave” hits today as the temperatures reach the middle to upper 20s. This will end Boston’s record-tying streak of days below 20 that belongs to this year, and 100 years ago. As we are enjoying are balmy respite, a storm will be brewing down the coast. The track of this storm has presented a forecasting headache for many, but after riding a veritable roller coaster of information and speculation, it comes down to an update in which I’m not going to make a whole lot of changes to the forecast issued on the last blog. Significant snow will occur Thursday for much of the region, though it is not likely to be of epic proportion anywhere, just a solid snowfall, except starting as rain east of a line from near Plymouth MA to Newport RI including all of Cape Cod before changing to snow during the course of the storm. Based on the current expected track I’m expecting the following…
Snow accumulation: 8-12 inches in a wide swath from eastern CT and western RI to Worcester to Metro West of Boston to southeastern NH but with pockets of 12-16 inches possible favoring interior eastern MA mainly to the southwest of Boston and possibly along the North Shore communities, 4-8 inches of fluffy snow to the west of this area, and 4-8 inches of wetter snow to the east of this area lowering to 2-4 inches Outer Cape Cod and Nantucket as these areas start as rain first.
Visibility: Blizzard conditions are likely especially along the coast from near Boston and its immediate southern suburbs northward to the North Shore of MA and NH Seacoast, extending down through the South Shore and eventually Cape Cod after rain changes to snow – blizzard conditions are defined as very low visibility due to falling and/or blowing snow with winds sustained or frequently gusting to 35 MPH or greater.
Wind: Gusts as high as 45 MPH inland, 55 MPH coast, and 65 MPH or greater Cape Cod (see detailed forecast for more).
Coastal impact: Moderate to significant flooding likely especially at the time of high tide, especially northeast and north facing shores. Also, ice shoves are possible where ice has formed along the shore due to persistent very cold.
Timing of storm: Snow (rain Cape) arrives between 4AM and 7AM from south to north, peaks early to mid afternoon, ends early evening.
After the storm comes a blast of arctic air equal to or more intense than the one just-departed for Friday and Saturday.
Other notes: There could be a few surprises including a track wobble, dry slots, and synoptic bands of heavier snow, so please check the comments below and the Facebook page if you have access to it for updates.
Forecast details…
TODAY: Mostly sunny. Highs 22-29. Wind S under 10 MPH becoming variable.
TONIGHT: Increasing clouds. Snow developing south to north 4AM through dawn except rain much of southeastern MA and southeastern RI. Temperatures remain stead interior but rise to 30-37 coast with warmest Cape Cod. Wind variable under 10 MPH becoming N.
THURSDAY: Overcast. Snow except rain changing to snow far southeastern areas. Snow will be heavy at times in bands. See above for details of snow accumulation and other storm impacts. Highs 25-37, mildest Cape Cod, in the morning, with slowly falling temperatures during the afternoon. Wind N increasing to 15-30 MPH interior and 25-40 MPH coast with higher gusts (see above for peak expected gusts).
THURSDAY NIGHT: Snow ending south to north evening. Clearing overnight. Temperatures fall to 15-22. Wind N to NW 25-35 MPH, higher gusts. Blowing and drifting snow where dry snow fell and a flash freeze where wetter snow fell.
FRIDAY: Mostly sunny. Temperatures fall to 5-12. Wind NW 25-35 MPH, higher gusts. Wind chill falling well below 0 at times. Blowing and drifting snow where dry snow fell.
SATURDAY: Partly cloudy. Isolated snow showers. Lows -5 to +5. Highs 5-15.
SUNDAY: Mostly sunny. Lows -15 to 0. Highs 10-20.

DAYS 6-10 (JANUARY 8-12)
Potential unsettled weather (snow/mix) at the start and end of this period. Fair in between. Temperatures below normal overall but variable.

DAYS 11-15 (JANUARY 13-17)
Potential unsettled weather early in the period (favoring snow but possible mix). Variable temperatures remaining below normal overall.

7:37AM

DAYS 1-5 (JANUARY 2-6)
Arctic cold hangs on today and moderates at midweek, but during this time a very large ocean storm will pass southeast of New England. It’s large enough that even though it may not pass across the “prime region” for a big hit, it will still likely bring significant snowfall. Warm enough air may be blown from over the ocean onto Cape Cod for a change to rain there. Following the storm will be another shot of pure arctic air, perhaps the coldest of the series.
TODAY: Mostly sunny. Highs 12-19. Wind W 5-15 MPH.
TONIGHT: Mostly clear. Lows -3 to +8, coldest interior valleys. Wind light W.
WEDNESDAY: Mostly sunny. Highs 22-29. Wind W 5-15 MPH.
WEDNESDAY NIGHT: Increasing clouds. Lows 12-19. Wind light N.
THURSDAY: Cloudy with snow likely except changing to rain outer Cape Cod and Nantucket. Minor to moderate coastal flooding and ice shoves possible near high tide times, especially north-facing shorelines. Snow accumulation of 5 to 9 inches Boston through South Shore southwestward to most of RI, 3-5 inches in a 25-mile strip either side of this, with a fluffy 1-3 inches to the far west and north and a wetter 1-3 inches Cape Cod before a period of rain. Highs ranging from near 20 far north and west of Boston to near 40 Cape Cod. Wind NE to N 15-35 MPH with gusts 25-55 MPH, strongest along the coast.
FRIDAY: Mostly sunny. Windy. Lows 0-10. Highs 10-20.
SATURDAY: Partly cloudy. Chance of snow showers. Lows -10 to 0. Highs 0-10.

DAYS 6-10 (JANUARY 7-11)
Dry, extreme cold January 7. Chance of snow January 8. Clearing/windy/cold January 9. Fair and cold January 10-11 but not as frigid as recent outbreaks.

DAYS 11-15 (JANUARY 12-16)
Another storm threat during the early to middle portion of this period. Temperatures generally below normal.

7:34AM

Happy New Year to all!

DAYS 1-5 (JANUARY 1-5)
Arctic cold that arrived as 2017 wound down remains in place as 2018 begins. It will ease up slightly by midweek and at this time a large and powerful ocean storm will develop to the south of New England. Current indications are that it will track too far east for a direct hit, but may bring a moderate snowfall and a lot of wind to Cape Cod, and a glancing blow to the remainder of southeastern New England. Will continue to watch. A reinforcement of Arctic air arrives at the end of the week. Forecast details…
TODAY: Mostly sunny. Highs 7-14. Wind NW 5-15 MPH, higher gusts. Wind chill below 0 at times.
TONIGHT: Partly cloudy. Lows -6 to -1 interior valleys, 0-6 elsewhere. Wind NW 5-15 MPH, higher gusts. Wind chill around -10 at times.
TUESDAY: Partly cloudy. Highs 12-19. Wind W 5-15 MPH.
TUESDAY NIGHT: Mostly clear. Lows -3 to +8, coldest interior valleys. Wind light W.
WEDNESDAY: Mostly sunny. Highs 22-29. Wind W 5-15 MPH.
THURSDAY: Mostly cloudy. Snow likely east, slight chance of snow west, ending late. Lows in the 10s. Highs in the 20s.
FRIDAY: Mostly sunny. Windy. Lows in the 0s. Highs in the 10s.

DAYS 6-10 (JANUARY 6-10)
Risk of snow showers early in the weekend then fair and extremely cold. A risk of snow/mix with moderating temperatures January 8 followed by colder and drier again later in the period.

DAYS 11-15 (JANUARY 11-15)
Another storm threat during the middle of this period. Temperatures generally below normal.

8:43AM

DAYS 1-5 (DECEMBER 31-JANUARY 4)
Arctic cold is reinforced for this final day of 2017 and the first couple days of 2018 as a healthy northerly air flow is in full control. Moderation arrives about January 3, allowing temperatures to be below normal, instead of much below normal. This will all be with dry weather other than the risk of a passing snow shower sometime New Year’s Day with a disturbance crossing the region. Although this threat is several days away, we’ve been watching for the evolution of an ocean storm around next Thursday. At this point I’m expecting 2 main areas of energy, the one offshore with the main storm, and another one coming across the Great Lakes, to not phase up in time to create a big winter storm here, but rather being missed or grazed by an ocean storm. So based on this idea, will carry a chance of snow on the day 5 forecast for Cape Cod but leave the remainder of the region dry for now.
TODAY: Sunny. Highs 8-13 except 13-18 Cape Cod. Wind N to NW 15-25 MPH, higher gusts. Wind chill will below 0 at times.
NEW YEAR’S EVE: Clear. Temperatures fall to 0-10. Wind N to NW 10-20 MPH, higher gusts. Wind chill often -5 to -15.
OVERNIGHT: Clear. Lows -8 to +3. Wind NW 5-15 MPH, higher gusts. Wind chill often -10 to -20.
MONDAY – NEW YEAR’S DAY: Mostly sunny. Highs 9-17. Wind NW 10-20 MPH, higher gusts. Wind chill often below 0.
TUESDAY: Mostly sunny. Lows -5 to +5. Highs 10-20.
WEDNESDAY: Mostly sunny. Lows 0-10. Highs 15-25.
THURSDAY: Cloudy with a chance of snow favoring Cape Cod. Partly cloudy elsewhere. Lows -3 to +7. Highs 12-22.

DAYS 6-10 (JANUARY 5-9)
Snow or snow shower threats January 6 and 8 otherwise a very cold and mainly dry pattern during this 5-day period. Records may fall.

DAYS 11-15 (JANUARY 10-14)
Temperatures remain below normal but with at least a period of moderation possible. Winter storm threat may appear later in the 11-15 day period.

9:39AM

DAYS 1-5 (DECEMBER 30-JANUARY 3)
Very short summary, no changes being made. Weak wave of low pressure passes south of the region and tries to throw some snow back into the region as it starts to strengthen through this evening before moving away. It does serve to reinforce the arctic air for the final day of 2017 and first day of 2018. High pressure will dominate Tuesday and Wednesday with more dry and cold weather.
TODAY: Mostly cloudy. A period of snow possible mainly from the Boston area to Worcester area southward. Expected snow accumulations from a coating to 1 inch Boston area to Worcester area to the Plymouth MA and Providence RI areas (coatings favored), 1-3 inches closer to the South Coast and 3-6 inches on the islands and outer Cape Cod. Highs 15-22. Wind N to NE 5-15 MPH.
TONIGHT: Clearing. Lows -5 to 0 interior, 0-5 coast. Wind N to NW 10-20 MPH with higher gusts. Wind chill near to below -10 at times.
SUNDAY – NEW YEAR’S EVE: Sunny day. Clear evening. Daytime highs 8-13 except 13-18 Cape Cod. Evening temperatures fall toward 0 interior and 10 or a little below Boston and coast. Wind N to NW 15-25 MPH, higher gusts. Wind chill will below 0 at times.
MONDAY – NEW YEAR’S DAY: Increasing clouds. Lows -8 to +3. Highs 10-20.
TUESDAY: Clearing. Lows -5 to +5. Highs 10-20.
WEDNESDAY: Sunny. Lows 0-10. Highs 15-25.

DAYS 6-10 (JANUARY 4-8)
3 potential snow threats, January 4, 6, and 8. Favoring the middle one at this point for the largest impact (don’t read this as a major storm forecast at this point). Temperatures below to much below normal.

DAYS 11-15 (JANUARY 9-13)
Temperatures continue below normal. Next storm threat comes late in the period.

1:53AM

DAYS 1-5 (DECEMBER 29-JANUARY 2)
The deep freeze goes on and will only slightly loosen its grip for a day Saturday as a wave of low pressure passes just south of the region with a threat of some snow (not a big storm) especially for southern areas. Behind this will come a reinforcement of arctic cold for the changing of the year. A wave of low pressure should bring some clouds later Monday and early Tuesday but at this time it looks like any snow will stay to the south. Details…
TODAY: Partly cloudy. Early morning snow showers possible outer Cape Cod. Highs 10-15 except 15-20 Cape Cod. Wind light NW.
TONIGHT: Partly cloudy. Lows 5-10 interior, 10-15 coast. Wind light N.
SATURDAY: Mostly cloudy. A period of snow possible mainly from the Boston area to Worcester area southward. Expected snow accumulations from a coating to 1 inch Boston area to Worcester area to the Plymouth MA and Providence RI areas, 1-3 inches closer to the South Coast and 3-6 inches on the islands and outer Cape Cod. Highs 15-22. Wind N to NE 5-15 MPH.
SATURDAY NIGHT: Clearing. Lows -5 to 0 interior, 0-5 coast. Wind N to NW 10-20 MPH with higher gusts. Wind chill near to below -10 at times.
SUNDAY – NEW YEAR’S EVE: Sunny day. Clear evening. Daytime highs 8-13 except 13-18 Cape Cod. Evening temperatures fall toward 0 interior and 10 or a little below Boston and coast. Wind N to NW 15-25 MPH, higher gusts. Wind chill will below 0 at times.
MONDAY – NEW YEAR’S DAY: Increasing clouds. Lows -8 to +3. Highs 10-20.
TUESDAY: Clearing. Lows 0-10. Highs 10-20.

DAYS 6-10 (JANUARY 3-7)
Will watch 2 storm threats, leaning toward a graze or miss for the first (about January 4) and a graze or hit for the second (about January 6), but this is very preliminary and will be watched and fine-tuned. More confidently, temperatures will continue below to much below normal.

DAYS 11-15 (JANUARY 8-12)
More cold weather. Snow/mix threats early and again late in the period with dry weather between.

2:52AM

DAYS 1-5 (DECEMBER 28-JANUARY 1)
No changes. Arctic cold continues. Ocean-effect snow showers may occur on outer Cape Cod tonight due to a more northerly wind flow. A snow threat still exists Saturday from a clipper system passing by the region, and will serve to reinforce the cold air in time for New Year’s Eve celebrations and the first day of 2018. Details…
TODAY: Mostly sunny. Highs 9-14 except 14-19 Cape Cod. Wind NW 5-15 MPH, higher gusts. Wind chill near to below 0 at times.
TONIGHT: Mostly clear except partly cloudy with snow showers and possible minor accumulations outer Cape Cod. Lows -10 to -5 interior valleys, -5 to 0 most other interior areas, 0-5 coast except 5-10 Cape Cod. Wind NW to N 5-15 MPH, except near calm in valleys.
FRIDAY: Partly cloudy. Highs 10-15 except 15-20 Cape Cod. Wind light NW.
FRIDAY NIGHT: Partly cloudy. Lows 5-10 interior, 10-15 coast. Wind light N.
SATURDAY: Mostly cloudy. A period of snow possible. Highs 15-22. Wind N to NE 5-15 MPH.
SUNDAY – NEW YEAR’S EVE: Sunny. Lows -5 to +5. Highs 8-18.
MONDAY – NEW YEAR’S DAY: Sunny. Lows -8 to +3. Highs 10-20.

DAYS 6-10 (JANUARY 2-6)
Temperatures average much below normal. One storm likely passes south of the region early in the period and another threatens later in the period with a chance of snow.

DAYS 11-15 (JANUARY 7-11)
Temperatures below normal. One or two snow threats possible during the period.

2:27AM

DAYS 1-5 (DECEMBER 27-31)
Arctic air will dominate through this period. High pressure will control most of the time with dry weather. The exception will be Saturday when low pressure passing south of the region may be close enough to bring a period of snow to the region. Will keep an eye on this. Forecast details…
TODAY: Mostly sunny. Highs 13-18 except 18-23 immediate shore and Cape Cod. Wind WNW 5-15 MPH, higher gusts at times. Wind chill near to below 10 at times.
TONIGHT: Clear. Lows -2 to +3 interior valleys, 3-8 most locations, 8-13 immediate shore and Cape Cod. Wind WNW up to 10 MPH.
THURSDAY: Sunny. Highs 8-13 except 13-18 Cape Cod. Wind NW 5-15 MPH.
FRIDAY: Partly cloudy. Lows -5 to 0 and 0-5 coast except 5-10 Cape Cod. Highs in the 10s.
SATURDAY: Cloudy. Chance of snow. Lows in the 0s. Highs in the 10s.
SUNDAY: Mostly sunny. Lows -5 to +5. Highs from the middle 0s to lower 10s.

DAYS 6-10 (JANUARY 1-5)
As a new year gets underway the cold pattern will continue. Will watch a potential storm threat around January 1-2 and possibly by the very end of the period.

DAYS 11-15 (JANUARY 6-10)
A winter storm threat is possible early in this period followed by more dry and cold weather.

9:43AM

DAYS 1-5 (DECEMBER 26-30)
The predicted colder pattern is here and will remain here for some time to come. The next winter storm threat is for Saturday, and is too far away to pinpoint any details for, but will be monitored through the week. In the mean time, it will be about the cold and dry weather, with the tiny exception of the slightest risk of a snow shower later today as a few bubbles of moisture from the Great Lakes come along in the westerly air flow delivering the arctic air, which will be in good supply all the way through this forecast period, taking until Friday for its center to migrate from the Upper Plains to the Northeast. Forecast details…
TODAY: Mostly sunny to partly cloudy. Slight risk of a passing light snow shower. Highs 22-27 except 28-33 immediate shore and Cape Cod. Wind W 5-15 MPH gusting 20-25 MPH.
TONIGHT: Mostly clear. Lows 2-7 except 8-13 immediate shore and Cape Cod. Wind W 5-15 MPH, higher gusts at times. Wind chill near 0.
WEDNESDAY: Mostly sunny. Highs 13-18 except 18-23 immediate shore and Cape Cod. Wind WNW 5-15 MPH, higher gusts at times. Wind chill near to below 10 at times.
WEDNESDAY NIGHT: Clear. Lows -2 to +3 interior valleys, 3-8 most locations, 8-13 immediate shore and Cape Cod. Wind WNW up to 10 MPH.
THURSDAY: Sunny. Highs 8-13 except 13-18 Cape Cod. Wind NW 5-15 MPH.
FRIDAY: Partly cloudy. Lows -5 to 0 and 0-5 coast except 5-10 Cape Cod. Highs in the 10s.
SATURDAY: Cloudy. Chance of snow. Lows in the 0s. Highs in the 10s.

DAYS 6-10 (DECEMBER 31-JANUARY 4)
Potential snow early December 31. Will watch another storm threat but may never materialize or may form and pass to the south around January 1-2. A lot of uncertainty on the evolution of things there. Dry and cold finish to the period.

DAYS 11-15 (JANUARY 5-9)
A winter storm threat is possible early in this period followed by more dry and cold weather.

10:05AM

Merry Christmas!!!

DAYS 1-5 (DECEMBER 25-29)
There is lots going on in the weather department but I’ll make this as short as possible. First the storm system we’ve been watching is moving through now and it appears it is behaving about as outlined in yesterday’s blog post. Low pressure is about to explode in the waters just east of here but move rapidly northeastward, pulling the snow (rain to the southeast) away with it, but not before a final burst of snow occurs from northern RI through eastern MA and south central and southeastern NH. It looks like the southern extent of this burst should be near the Cape Cod Canal with the rain/snow line from near northern Narragansett Bay to about Plymouth MA where areas near there that have not seen snow may get coated at the end. This will also be true for the tip of Cape Ann MA which also had a longer rain period. Where the heaviest burst of snow occurs, an additional 1/2 to 1 1/2 inch will occur along with a risk of a clap of thunder, bringing the accumulations mostly into the expected ranges across the region. So what this means is white Christmas for most of the region except the far southeast (Cape Cod). Once the storm pulls away it will be about the wind this afternoon. There are no big changes to the outlook going forward. A cold day is expected Tuesday with a passing snow shower as a reinforcing cold front arrives later in the day, and then the very cold air arrives for the middle of the week and into Friday as well. By late Friday we may be watching to see if a snow threat materializes for the region. It is too early to know the track and intensity of that system as far as how it will impact this area but will be watching.
TODAY – CHRISTMAS DAY: Snow (rain southeast) ends by late morning. Partial clearing this afternoon. Temperatures ranging widely from as low as the lower 20s central MA to the middle 40s southeastern MA will remain steady or slightly rise in the coldest areas and fall more rapidly in the warmest areas during the day. Wind becoming NW and increasing to 15-30 MPH interior and 25-40 MPH coast especially Cape Cod with higher gusts.
TONIGHT: Clear. Lows 10-18. Wind NW 10-20 MPH, higher gusts. Wind chill near 0 at times.
TUESDAY: Partly cloudy. Isolated afternoon snow showers. Highs 20-28. Wind W 10-20 MPH, higher gusts.
TUESDAY NIGHT: Clearing. Lows 5-12. Wind NW 10-20 MPH, higher gust. Wind chill below 0 at times.
WEDNESDAY: Mostly sunny. Highs 17-24. Wind NW 10-20 MPH. Wind chill below 10 at times.
THURSDAY: Sunny. Lows from near 0 to near 10. Highs in the 10s.
FRIDAY: Increasing cloudiness. Lows from near -5 to +5. Highs from the middle 10s to lower 20s.

DAYS 6-10 (DECEMBER 30-JANUARY 3)
Watching 2 storm systems for possible impact favoring snow during this period. Temperatures below normal.

DAYS 11-15 (JANUARY 4-8)
Below normal temperatures. Another storm may threaten later in the period.

8:16AM

DAYS 1-5 (DECEMBER 24-28)
** WATCH FOR ICY AREAS UNTIL THE TEMPERATURE GOES BACK ABOVE FREEZING THIS MORNING **
No changes to yesterday’s discussion. Short range models will be fine-tuning the details of rain/snow line to guide us along but the overall thought process remains the same. Still expect the rain/snow line to spend most of its time near to southeast of I-95 for the Christmas morning event and a burst of heavy precipitation with possible thunder at the end. It should all by out of here by midday so afternoon travel plans will be less impacted. Current expected accumulation: 3-6 inches across north central CT, all of central to interior northeastern MA and southern NH, or basically the I-84 belt and central and northern portions of the I-495 belt with pockets of 6-8 inches favoring higher elevations, 1-3 inches along the I-95 belt including Boston and its immediate suburbs west and southwest, down through northern RI and parts of interior southeastern MA which would be closer to the 2, and then a coating from the South Shore to about the Cape Cod Canal at the end of the event. The remainder of the day would be windy and colder with a few light snow showers around. Tuesday and Wednesday we will find ourselves immersed in a cold northwesterly fair flow delivering arctic air and presenting the chance of a few passing snow showers in otherwise mainly dry conditions. An even colder reinforcement of air arrives Thursday. To the detailed forecast…
TODAY: Partly sunny. Highs 35-43. Wind NW 5-15 MPH.
TONIGHT – CHRISTMAS EVE: Clouding over. Precipitation arriving late as rain Boston south, mix/snow elsewhere. Lows 26-34. Wind light E shifting to N.
MONDAY – CHRISTMAS DAY: Overcast through mid morning with snow except rain changing to snow southeast. A brief burst of heavy snow possible with a slight risk of thunder. See discussion above for expected snow accumulations. Breaking clouds and passing snow flurries midday and afternoon. Early-day highs 28-40, warmest southeastern MA, then falling temperatures. Wind N to NW increasing to 15-25 MPH with higher gusts possible.
TUESDAY: Partly cloudy and windy. Slight chance of snow showers. Lows in the 10s. Highs from the middle 20s to lower 30s.
WEDNESDAY: Partly cloudy and windy. Slight chance of snow showers. Lows from the middle 0s to lower 10s. Highs in the 20s.
THURSDAY: Mostly sunny. Lows in the 0s. Highs from the middle 10s to middle 20s, coldest interior and north, least cold Cape Cod.

DAYS 6-10 (DECEMBER 29-JANUARY 2)
Watching 1 or possibly 2 low pressure areas that may impact the region with wintry precipitation and favoring December 30 to early 31 at this time, but there is a fair chance a lot of this may pass south of the region. Temperatures below normal.

DAYS 11-15 (JANUARY 3-7)
Similar pattern, below normal temperatures, additional threat or 2 of a winter precipitation event.

11:15AM

DAYS 1-5 (DECEMBER 23-27)
I know everyone is eager about the Christmas storm threat, but first we have something much more important in progress and that is an icing event for much of the region, save for a few immediate coastal areas and especially Cape Cod where temperatures remain above freezing. As of late morning, temperatures ranged from the upper 20s to very low 30s over the vast majority of the region to the middle and upper 30s along the immediate shoreline to the south of Boston and the lower to middle 40s over Cape Cod. A classic cold air damming situation is ongoing in which the cold air is trapped at the lower levels, most stubbornly over inland valleys. It’s easier to scour out this air, or prevent it from settling in, on Cape Cod, surrounded by water and where even a northwest wind, which keeps ocean influence away, is still able to bring modified ocean air in there. Very gradually the milder air will eat away at the cold, but it is going to take all day for a good part of the region to go above freezing, and some valleys may never even make it that far. The biggest push of “warm air”, in a relative sense, will take place this evening as we rid ourselves of the influence of the series of low pressure waves along the stuck frontal boundary and push a main cold front through from the west. The wind will attempt to turn southwest for a very brief time ahead of this but some of it may still ride up over dense cold air trapped at the surface (valleys most vulnerable, not to sound like a tape loop). During the day, episodes of rain/drizzle will be ongoing, with icing in all areas below freezing, with this area gradually shrinking as the temperature creeps up. A last round of moderate to heavy rain showers and even possible thunder may accompany the main cold front. And then… all of that exits and sets up what will be a rather pleasant Christmas Eve Day on Sunday by late December standards. It should climb above freezing pretty much everywhere, though not by more than about ten degrees maximum. This will be the best opportunity to get rid of the ice and snow/ice layer where it exists, but use caution as a temperature above freezing does not automatically eliminate slippery ground where ice exists. Now, to the next event. Models will be fine-tuning the details and yes, there will be a rain/snow line involved since we’re not going to be in air that is cold enough to guarantee a region-wide snow event from start to finish. The low track will be critical. Some short range guidance has it tracking over southeastern MA, which I think may be a bit too far northwest. My reasoning for this is a colder land mass than the model will “know of” and also that I believe it is over-forecasting the strengthen of the westernmost of 2 low pressure areas. This may look like a small model error if the thought process is correct, but could make the difference by 10 to 20 miles in a rain/snow line, which is significant when it comes to local impact. Also, there are solid signs of a rapid intensification of low pressure as it passes the region. It will be moving rather quickly, so it will not be a long-duration event, but it may end with a hard hit of snow for an hour or 2, even in areas that start out as rain. Can’t rule out hearing thunder in a situation such as this. But what about that rain/snow line? I think when precipitation arrives from southwest to northeast between 10PM and 2AM it will be in the form of rain along and southeast of a line from about Boston through central RI to southeastern CT, mix just northwest of this line, and snow beyond that. This line may waver around for several hours, but the progressive nature of the system and its rapid intensification will likely pull the rain/snow line eastward so Boston and Providence are snowing by or shortly after sunrise, it remains snow everywhere northwest of there, and turns to snow from west to east in the areas that it has been raining prior to the entire area exiting the region southwest to northeast by late morning. With this, I’d expect snow accumulations of 4-6 inches across north central CT, all of central to interior northeastern MA and southern NH, or basically the I-86 belt and central and northern portions of the I-495 belt, 2-4 inches along the I-95 belt including Boston and its immediate suburbs west and southwest, down through northern RI and parts of interior southeastern MA which would be closer to the 2, and then a coating to 2 inches from the South Shore through Cape Cod at the end of the event with the least amount across Cape Cod. The remainder of the day would be windy and colder with a few light snow showers around. Tuesday and Wednesday we will find ourselves immersed in a cold northwesterly fair flow delivering arctic air and presenting the chance of a few passing snow showers in otherwise mainly dry conditions. To the detailed forecast…
TODAY: Overcast. Freezing rain except rain immediate South Shore, South Coast, and Cape Cod, steadiest through midday with dangerous travel conditions, but most significant ice accretion in central MA and southwestern to south central NH where tree damage is possible. Temperatures very slowly rising to 27-34 interior, 34-40 coast, 40-46 Cape Cod. Coldest air remaining in deepest valleys. Wind light NW.
TONIGHT: Overcast evening with one more period of rain which may still freeze in deepest valleys. Slight chance of thunder during the passage of the last batch of rain. Breaking clouds overnight. Temperatures rise slightly to 32-37 interior, 38-43 coast. Wind variable to SW 5-15 MPH, shifting to NW overnight.
SUNDAY: Partly sunny. Highs 35-43. Wind NW 5-15 MPH.
SUNDAY NIGHT – CHRISTMAS EVE: Clouding over. Precipitation arriving late as rain Boston south, mix/snow elsewhere. Lows 26-34. Wind light E shifting to N.
MONDAY – CHRISTMAS DAY: Overcast through mid morning with snow except rain changing to snow southeast. A brief burst of heavy snow possible with a slight risk of thunder. See discussion above for expected snow accumulations. Breaking clouds and passing snow flurries midday and afternoon. Early-day highs 28-35 then falling temperatures. Wind N to NW increasing to 15-25 MPH with higher gusts possible.
TUESDAY: Partly cloudy and windy. Slight chance of snow showers. Lows in the 10s. Highs from the middle 20s to lower 30s.
WEDNESDAY: Partly cloudy and windy. Slight chance of snow showers. Lows from the middle 0s to lower 10s. Highs in the 20s.

DAYS 6-10 (DECEMBER 28-JANUARY 1)
Very cold with fair weather to start the period then 1 or 2 low pressure areas may impact the region with snow/mix (most likely snow). Lots of time to figure out details.

DAYS 11-15 (JANUARY 2-6)
Similar pattern, below normal temperatures, additional threat or 2 of a winter precipitation event.

9:18AM

DAYS 1-5 (DECEMBER 22-26)
There have been no drastic changes in the forecast since the last blog post, so I will try to summarize that with any tweaks built in. Today, it’s basically about snow, steadiest this afternoon in NH and northern MA, though some will occur before that and already has, but little in the way of any steady precipitation to the south with just spotty light snow and even mixed with rain near the South Coast. The advertised warm front will struggle moving through as expected. You have to remember to think of something like a warm front not as a solid object, but a boundary between air masses, which are made of fluid. This warm air will move into areas with less resistance much more easily than others, and one of those areas it has great difficulty doing this is interior valley locations where dense cold air stays near the ground. This will be a classic case of that as it warms aloft and sets up a freezing rain situation. The good news is that some icing may be prevented due to a lull in the precipitation this evening just as it warms aloft to turn snow to rain. A second batch of steadier precipitation is expected to arrive in the pre-dawn hours of Saturday and continue through the morning to the middle of the day. This is when most of the icing will take place as by then it will be too warm aloft for any more snow anywhere. So during this it will become essential to watch the surface temperatures and the amount of rain. There may be some sleet involved closer to the time the first batch of snow moves out this evening and near the beginning of the steadier precipitation from batch number two, but the main issue will be the freezing rain, which will last longest over interior MA and southern NH. However enough cold air may drain southward through eastern MA and into northern RI, areas away from the immediate shore, for a period of freezing rain in many of these locations too. A piece of more positive news lies in the fact there is a good shot at another precipitation lull for a portion of Saturday afternoon, which would limit additional icing and reduce the risk of power outages from downed wires and trees/branches on wires. Of course throughout this watch for hazardous untreated surfaces as always! By Saturday night, it should have warmed up in all but deepest valleys enough for the final batch of precipitation to be in the form of plain rain and not last all that long. By the early hours of Sunday the entire mess is gone and Sunday itself will be a dry day. Temperatures should rise above freezing in most areas to be able to get rid of some of the ice build up, but it may not be enough to melt it all, so keep that in mind going forward as there is more cold and some snow in the forecast. Christmas Eve itself, from day to evening, will be dry. The next precipitation threat will come from a new area of low pressure passing to the southeast of New England late Sunday night and early Monday, but with a trough of low pressure extending from it back to a weaker storm coming out of the Great Lakes, enough cold air will be in place for a period of snow in most of the region with the exception of Cape Cod. We may have to watch a rain/snow line to see if it moves northwestward for a period of time, but I do think at this point that rain will be confined mainly to the Cape and that a couple to several inches of snow will occur elsewhere. I’ll put some numbers to this part of the forecast on the next blog post, leaving the numbers for today’s event (in the detailed forecast section below). Beyond the Christmas snow threat comes a shot of colder air Tuesday. Forecast details…
TODAY: Overcast. Periodic snow southern NH and northern MA becoming steadier midday-afternoon with a coating to 2 inches from near the Mass Pike northward for about 20 miles and 2-4 inches northern MA and southern NH. Spotty light snow to the south except snow or rain South Coast with no snow accumulation. Highs 22-38, coldest north central MA and southwestern NH, mildest southeastern MA and RI. Wind light NE.
TONIGHT: Overcast. Snow / sleet / freezing rain southern NH and northern MA with rain nearer the coast tapering off early with little additional accumulation, spotty light sleet / freezing rain / rain elsewhere. Temperatures nearly steady 22-29 north central MA and interior southern NH, 30-38 elsewhere. Wind light N to NW.
SATURDAY: Overcast. Freezing rain except rain immediate coast through southeastern MA and southern RI, steadiest morning and midday when some significant ice accretion is likely especially north central MA to southwestern and south central NH, then precipitation tapering off for a while in the afternoon. Temperatures rise very slowly to 27-34 interior, 34-40 coast. Coldest air remaining in deepest valleys. Wind light NW.
SATURDAY NIGHT: Overcast evening with one more period of rain which may still freeze in deepest valleys. Breaking clouds overnight. Temperatures rise slightly to 32-37 interior, 38-43 coast. Wind variable to SW 5-15 MPH, shifting to NW overnight.
SUNDAY: Partly sunny. Highs 35-43. Wind NW 5-15 MPH.
SUNDAY NIGHT – CHRISTMAS EVE: Clouding over. Snow likely around or after midnight except mix/rain Cape Cod. Lows 25-33. Wind light N.
MONDAY – CHRISTMAS DAY: Overcast morning with snow likely except mix/rain Cape Cod. Partial clearing afternoon. Temperatures steady 25-33. Wind N to NW 5-15 MPH.
TUESDAY: Partly cloudy and windy. Lows in the 10s. Highs from the middle 20s to lower 30s.

DAYS 6-10 (DECEMBER 27-31)
The final 5 days of 2017 will be colder than normal and there is the threat of a storm around December 29-30 that will be watched.

DAYS 11-15 (JANUARY 1-5)
The first 5 days of 2018 will likely be similar to the end of 2017 with another storm threat potentially looming.

1:49AM

DAYS 1-5 (DECEMBER 21-25)
From Solstice to Christmas, this will be an action-packed 5-day period, so let’s get to the details. First, we had a cold and tranquil day as autumn bows out and winter takes its place as of 11:28AM today, but this cold high pressure area over the region is one ingredient and an upcoming complex precipitation event that will be generated by a warm front trying to cross the region later Friday into Saturday. As we often see here in New England, dense cold air will be trapped at the surface and even though it warms aloft, the cold air will hang tough near the ground, especially over interior sections. Before it warms aloft for the rain/ice situation, much of the region will have cold enough air above to start as snow, with the exception of coastal areas south of Boston through the South Coast, which may start as snow, mix, or rain and will have negligible accumulation of snow. A minor accumulation of snow is likely generally from a Boston to northeastern CT line northward, with some moderate amounts possible from near the MA/NH border northward. But snow is the lesser worry in comparison to the icing which may be significant in interior areas especially near and west of I-495 and mostly north of I-90. It may take until sometime around midday or afternoon Saturday to scour out the last of the cold air in much of the region, and it may never leave the deeper valleys. So the degree of icing will depend on how much rain falls once it is warm enough aloft to end the snow. It looks like 2 main surges of precipitation will occur, the Friday midday and afternoon portion which should be the snow (mix south) to ice (rain south) transition, and then another surge sometime Saturday. A developing low pressure wave may bring one final push of heavier rain to the region sometime Saturday night when temperatures should be their relative mildest. Surface temperatures will have to be closely monitored to determine where icing will occur and persist. By the time we get to Sunday, which is Christmas Eve, we’ll be in a slice of drier air but with some cold filtering in. This sets the stage for the next precipitation threat as a new low pressure area develops south of New England and likely passes just southeast of the region. This will be a position that allows snow to occur for at least interior areas, and rain or snow near the coast, for the overnight hours of late Christmas Eve and into Christmas Morning. Leaning toward a colder scenario with more snow than anything else. The details of this threat are yet to be fully determined but whatever happens should be winding down by the end of Christmas Day, based on current timing. So, lots to follow and here are the forecast details…
TODAY: Bright sun into afternoon, filtered by high clouds late. Highs 28-35. Wind NW 5-15 MPH.
TONIGHT: Clouds increase and thicken. Lows 16-24. Wind N under 10 MPH.
FRIDAY: Overcast. Precipitation arrives west to east late morning and midday as snow except snow/mix/rain South Shore to South Coast, continuing through afternoon with accumulation of 1-3 inches northwest of a Boston to northeastern CT line, 3-5 inches north central MA and southwestern NH, and under 1 inch to the southeast of the Boston to northeastern CT line. Highs 28-32 except 33-38 coast. Wind light N to NE.
FRIDAY NIGHT: Overcast. Areas of fog. Any snow changes to rain but freezing rain is likely many interior areas and especially I-495 belt northwestward, and possibly some icing extending to near the coast from Boston north, then precipitation may taper off for a while. Temperatures steady 28-32 interior, 33-38 coast but may rise slowly overnight especially coastal areas and southeastern MA/RI, but may briefly fall in coastal NH and northeastern MA to Boston. Wind light N to NE.
SATURDAY: Overcast. Areas of fog. Periods of rain which may still be freezing in central MA, interior eastern MA, and interior southern NH, especially valleys. One more period of mainly rain possible evening. Temperatures rise very slowly interior valleys to 32-39, 40-50 elsewhere. Wind light N interior areas, light E to SE elsewhere, shifting to W and increasing to 10-20 MPH overnight.
SUNDAY – CHRISTMAS EVE: Partly cloudy daytime. Clouding up at night with a chance of snow overnight. Temperatures 30s interior and 40s coast early, slowly falling later.
MONDAY – CHRISTMAS DAY: Mainly cloudy morning with a chance of snow, possibly mix/rain southern coastal areas. Partial clearing afternoon. Temperatures generally steady upper 20s to middle 30s.

DAYS 6-10 (DECEMBER 26-30)
Mainly dry and cold weather follows the active period and then another storm threat may occur before the end of the 6-10 day period.

DAYS 11-15 (DECEMBER 31-JANUARY 4)
Cold pattern continues and another storm threat presents itself in the very early days of 2018.