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.

6:39AM

DAYS 1-5 (DECEMBER 20-24)
The final day of astronomical autumn today will present a return to the feel of winter as the wind picks up and temperature goes down behind a cold front. High pressure will move in tonight and Thursday with dry and cold weather, appropriate for the winter solstice, which occurs at 11:28AM Thursday. This is the point at which the sun is directly above the Tropic of Capricorn or 23.5 degrees south latitude. Technicalities aside, it’s the beginning of winter, but also marks the beginning of increasing daylight as we step on the proverbial bottom rung of the ladder on the climb back to spring and summer. But let’s not get ahead of ourselves. There is a long period of time ahead in which winter weather can and will occur, including some of that in this 5-day period. This will take place as a warm front approaches Friday and probably does not pass through the entire region until later Saturday, if at all. There is an increasing chance this boundary never makes it into at least northern MA northward. This will result in some snow/ice/rain across the region. We’d see plain rain take over where the air makes it above freezing, more likely near the coastline and especially southern areas if the warm front makes it through. Still some details to work out here. Regardless of how far north that boundary gets, a cold front from the west will push it all out of here by early Sunday, putting a new cold air mass into the region on Christmas Eve. Forecast details…
TODAY: Sun and passing clouds. Highs 38-44 this morning then falling through the 30s. Wind W 10-20 MPH, higher gusts.
TONIGHT: Clear. Lows 15-23. Wind NW 5-15 MPH, higher gusts.
THURSDAY: Sunny. Highs 28-35. Wind N 5-15 MPH.
THURSDAY NIGHT: Increasing clouds. Lows 18-25. Wind light N.
FRIDAY: Cloudy. Snow developing, changing to ice/rain depending on location with ice more likely away from the coast. Highs 30-38. Wind light NE.
SATURDAY: Mainly cloudy. Periods of rain coast and south, freezing rain interior. Areas of fog. Large temperature contrast from near 30 many interior areas to the 40s to near 50 South Coast.
SUNDAY – CHRISTMAS EVE: Partly sunny day. Cloudy with a risk of mix/snow by late night. Lows from the upper 20s to lower 30s. Highs from the middle 30s to near 40.

DAYS 6-10 (DECEMBER 25-29)
Watching for possible mix/snow Christmas Day then mainly dry with below normal temperatures for the balance of this period.

DAYS 11-15 (DECEMBER 30-JANUARY 3)
1 or 2 minor to moderate events are possible, snow/mix favored over rain.

7:41AM

DAYS 1-5 (DECEMBER 19-23)
Watch for patchy icy areas early today!!
The milder air is in but won’t be here long as a cold front approaches today and passes tonight, returning windy and cold weather to the region for Wednesday, then tranquil but cold weather for Thursday, the first day of astronomical winter (solstice 11:38AM). Warm front approaches Friday and brings a risk of precipitation to the region before a push of warm air arrives at night into early Saturday, being cut off by a cold front by the end of the day Saturday.
TODAY: Partly sunny. Chance of a late-day rain shower. Highs 42-48. Wind SW 5-15 MPH.
TONIGHT: Clearing. Lows 30-36. Wind W 10-20 MPH, higher gusts.
WEDNESDAY: Partly cloudy. Isolated snow showers possible. Highs 37-44 early then falling through the 30s. Wind WNW 15-25 MPH, higher gusts.
THURSDAY: Mostly sunny. Lows from the middle 10s to lower 20s. Highs from the upper 20s to middle 30s.
FRIDAY: Mostly cloudy. Chance of snow/mix, ending as mix/rain late. Lows from the middle to upper 20s. Highs from the middle 30s to lower 40s daytime but warming at night.
SATURDAY: Mostly cloudy. Rain showers likely morning. Slight risk of a snow shower at night. Temperature rise to the 50s morning then fall afternoon and night.

DAYS 6-10 (DECEMBER 24-28)
Colder weather during this period. Watching a wave of low pressure for possible snow/ice/rain Sunday night (Christmas Eve) and Monday (Christmas Day). Few snow showers possible later in the period.

DAYS 11-15 (DECEMBER 29-JANUARY 2)
Expect fast-moving systems, temperatures averaging near to below normal with a couple snow/mix/rain threats.

7:36AM

DAYS 1-5 (DECEMBER 18-22)
No big changes from yesterday’s outlook. Warm front approaches today with spotty precipitation. Cold front brings a rain shower risk late Tuesday. Wind and cold return for Wednesday, then a calmer cold Thursday as high pressure moves in. Next warm front approaches Friday but takes its time arriving.
TODAY: Mostly cloudy. Periods of light snow with traces to possible coatings mainly southern NH and northern MA, patchy light freezing drizzle then a slight chance of light rain southern MA/CT/RI. Highs 28-35. Wind SE up to 10 MPH, shifting to SW late.
TONIGHT: Mostly cloudy. Temperatures rising slowly through the 30s. Wind SW up to 10 MPH.
TUESDAY: Partly sunny. Chance of a late-day rain shower. Highs 42-48. Wind SW 5-15 MPH.
WEDNESDAY: Partly cloudy. Isolated snow showers possible. Lows in the lower 30s. Highs in the lower 40s but falling later in the day.
THURSDAY: Mostly sunny. Lows from the middle 10s to lower 20s. Highs from the upper 20s to middle 30s.
FRIDAY: Mostly cloudy. Lows from the middle to upper 20s. Highs from the middle 30s to lower 40s daytime but warming at night.

DAYS 6-10 (DECEMBER 23-27)
Briefly warmer followed by rain showers December 23, then colder air likely returns by that night. Dry and chilly December 24. Watching wave of low pressure with rain/mix/snow threat December 25-26 based on current timing, but may need to be adjusted.

DAYS 11-15 (DECEMBER 28-JANUARY 1)
Expect fast-moving systems, temperatures averaging near to below normal with a couple snow/mix/rain threats.

8:24AM

DAYS 1-5 (DECEMBER 17-21)
The final four official days of autumn and the day of the winter solstice is covered in this 5-day segment and will present weather fairly typical of this time of year for the type of pattern we’re in, starting with cold high pressure in control today and nice weather, a warm front approaching the region tonight and Monday with some spotty light frozen and freezing precipitation, i.e. snow and possibly freezing drizzle, a passing of the warm front with a milder push of air Monday night and Tuesday, before a cold front arrives with a rain shower risk later Tuesday and returns a December chill, along with wind and the risk of a snow shower for the final day of astronomical autumn on Wednesday. Solstice day will be much like today, dry and cold with high pressure in control. Forecast details…
TODAY: Mostly sunny. Highs 28-35. Wind NW up to 10 MPH.
TONIGHT: Increasing clouds. Lows 22-28. Wind variable under 10 MPH.
MONDAY: Mostly cloudy. Periods of light snow, with trace amounts to coatings possible, and a slight risk of freezing drizzle with very minor icing on untreated surfaces. Highs 28-35. Wind SE up to 10 MPH, shifting to SW late.
MONDAY NIGHT: Mostly cloudy. Temperatures rising slowly through the 30s. Wind SW up to 10 MPH.
TUESDAY: Partly sunny. Chance of a late-day rain shower. Highs 42-48. Wind SW 5-15 MPH.
WEDNESDAY: Partly cloudy. Isolated snow showers possible. Lows in the lower 30s. Highs in the lower 40s but falling later in the day.
THURSDAY: Mostly sunny. Lows from the middle 10s to lower 20s. Highs from the upper 20s to middle 30s.

DAYS 6-10 (DECEMBER 22-26)
As high pressure ridging tries to build over the US Southeast and very cold air tries to send progressive troughs across the Northeast, the battle zone will set up and periods of unsettled weather will result. There is low confidence in trying to do anything more than generalize this far out in this pattern. Current leaning is for a light snow/mix/rain episode December 22 and a few rain showers December 23, then another precipitation risk during the December 24-26 period. That does not mean all 3 days will be unsettled. It means we need to watch the period right around Christmas for possible impact from another low pressure system.

DAYS 11-15 (DECEMBER 27-31)
Look for the same general pattern to continue but with a tendency for colder weather to win out.

11:24AM

DAYS 1-5 (DECEMBER 16-20)
No big changes in the overall outlook today. Pretty clear-cut for this 5-day period with a trough moving through today with a gusty breeze and a slight risk of a passing snow flurry, then high pressure moving in tonight into Sunday, followed quickly by light warm frontal precipitation (snow to mix) scattered to general across the region Sunday night into Monday. A brief warm-up follows this as we get into the warm sector for late Monday into Tuesday then a cold front comes along with perhaps a rain shower before cold air returns Wednesday.
TODAY: Mostly sunny to partly cloudy. Slight risk of a passing snow shower. Highs 28-35. Wind W 10-20 MPH, higher gusts.
TONIGHT: Clearing. Lows 15-22. Wind NW 10-20 MPH, diminishing late.
SUNDAY: Increasing clouds. Chance of light snow at night. Highs 30-37. Wind light variable.
MONDAY: Mostly cloudy. Chance of light snow/mix mainly morning to midday. Temperatures steady in the 30s.
TUESDAY: Variably cloudy. Chance of late day rain showers. Lows in the 30s. Highs in the 40s.
WEDNESDAY: Partly cloudy. Windy. Lows in the 10s. Highs from the middle 20s to lower 30s.

DAYS 6-10 (DECEMBER 21-25)
Fair and cold for the Winter Solstice on December 21, then being between a warmer ridge of high pressure in the US Southeast and very cold air in Canada sets up episodes of unsettled weather, precipitation type indeterminate at this time, during the December 22-25 period.

DAYS 11-15 (DECEMBER 26-30)
The region will likely be near the border between warmer weather in the southeastern US and very cold weather in Canada with a tendency for the cold to win out during this period. A few mix/snow events are possible with fast-moving weather systems.

7:32AM

DAYS 1-5 (DECEMBER 15-19)
Two pieces of energy try to phase up as low pressure develops off the Mid Atlantic Coast later today and passes southeast of New England tonight. This phasing takes place too late for a big storm but soon enough for a brief shot of snow this evening. The next system approaches late Sunday into Monday but looks fairly weak with a bit of light snow/mix Sunday night into Monday. A brief warm up follows this Tuesday but a cold front will already be charging toward the region. Forecast details…
TODAY: Increasing clouds. Highs 24-31. Wind light variable.
TONIGHT: Cloudy. A period of snow accumulating 1/2 to 2 1/2 inches along and southeast of a line from northeastern CT to Boston MA, and less than 1/2 inch elsewhere. Lows 17-24. Wind light variable.
SATURDAY: Clearing. Highs 28-35. Wind NW 10-20 MPH with higher gusts.
SATURDAY NIGHT: Clear. Lows 16-23. Wind NW 10-20 MPH, diminishing late.
SUNDAY: Increasing clouds. Chance of light snow at night. Highs 30-37. Wind light variable.
MONDAY: Mostly cloudy. Chance of light snow/mix mainly early. Temperatures steady in the 30s.
TUESDAY: Variably cloudy. Chance of late day rain showers. Lows in the 30s. Highs in the 40s.

DAYS 6-10 (DECEMBER 20-24)
A few snow showers possible December 20 otherwise fair and cold December 20-21. Unsettled weather possible in the December 22-24 period but the track of low pressure is highly uncertain this far in advance.

DAYS 11-15 (DECEMBER 25-29)
The region will likely be near the border between warmer weather in the southeastern US and very cold weather in Canada with a tendency for the cold to win out here. A few mix/snow events are possible with fast-moving weather systems.

7:35AM

DAYS 1-5 (DECEMBER 14-18)
The “South Coast Special” snow event will wind down soon and the dry/cold will return to the region for the balance of the day. Another system makes a quiet run at the region late Friday but stays in 2 pieces instead of merging. This limits the impact to just a little light snow or flurries Friday night. A similar disjointed system passes through Monday after fair weather weekend.
Detailed forecast…
TODAY: Mainly cloudy with lingering snow South Coast through Cape Cod early then clearing. Highs 26-33. Wind W 5-15 MPH with higher gusts.
TONIGHT: Clear. Lows 12-19. Wind NW 5-15 MPH.
FRIDAY: Increasing clouds. A period of snow possible at night. Highs 26-33. Wind light N to NE.
SATURDAY: Partly cloudy. Lows from the upper 10s to middle 20s. Highs in the 30s.
SUNDAY: Mostly sunny then increasing clouds late. Lows in the 20s. Highs from the upper 30s to lower 40s.
MONDAY: Mostly cloudy with a little light snow/mix possible. Lows from the lower to middle 30s. Highs from the upper 30s to lower 40s.

DAYS 6-10 (DECEMBER 19-23)
Near the borderline of a warmer air mass to the south and very cold air in Canada starting out with fair weather but turning unsettled later in the period.

DAYS 11-15 (DECEMBER 24-28)
Again near the borderline of mild to the south and much colder to the north. Uncertain on precipitation events at this time.

1:53AM

DAYS 1-5 (DECEMBER 13-17)
And now that we are beyond that December 10 marker and the pattern has had a chance to readjust, the cold has arrived. This cold pattern will be good for this 5 day period with the coldest days being the first 3, today through Friday, and slow moderation over the weekend. Behind our departed low pressure area of yesterday comes a fast-moving clipper system which now appears it will be far enough north to bring a light snowfall to southern areas in the early hours of Thursday. A second system will make a run at the region Friday night with a shot at snow, again favoring southern areas, departing Saturday at which time high pressure will build in for the balance of the weekend. We still have to keep an eye on the late Friday system as it still has the potential to grab extra moisture and throw it at us here. Detailed forecast…
TODAY: Partly cloudy. Isolated snow showers possible. Highs 24-31. Wind W 15-25 MPH gusting 30-45 MPH at times. Wind chill below 20 at times.
TONIGHT: Increasing clouds. A period of snow especially near and south of I-90 overnight with a coating to 1 inch possible in these areas and just a little very light snow with no accumulation to the north. Lows 17-23. Wind W 10-20 MPH gusting 25-35 MPH, diminishing overnight.
THURSDAY: Mainly cloudy with lingering snow possible Cape Cod early then clearing. Highs 26-33. Wind W 5-15 MPH with higher gusts.
THURSDAY NIGHT: Clear. Lows 12-19. Wind NW 5-15 MPH.
FRIDAY: Increasing clouds. A period of snow possible at night. Highs 26-33. Wind light N to NE.
SATURDAY: Partly cloudy. Slight chance of snow showers. Lows from the upper 10s to middle 20s. Highs in the 30s.
SUNDAY: Mostly sunny then increasing clouds late. Lows in the 20s. Highs from the upper 30s to lower 40s.

DAYS 6-10 (DECEMBER 18-22)
Briefly milder to start the period then a weak system comes through with a minor precipitation event and colder air then returns. There may be a clipper system around December 21 or 22 with a snow threat but not confident of this at this time.

DAYS 11-15 (DECEMBER 23-27)
The cold is likely to win out along with a couple snow/mix chances but far too early to really time or detail anything.

7:31AM

DAYS 1-5 (DECEMBER 12-16)
Low pressure will move across south central New England today, with a track far enough north to allow mild enough air in for a mainly rain event in much of the forecast area with snow that accumulates confined to north central MA and southwestern NH with a hint of accumulation slightly south and east of there. This will be the mildest day for a while as a very cold airmass awaits behind this system to move in for the middle of the week. This may be accompanied by some snow showers as temperatures fall and winds pick up on Wednesday. A wave of low pressure will rapidly move southeast then east, passing south of New England on Thursday. A little snow from this may skirt the South Coast but the bulk of the precipitation shield with the low will stay south of the region. Another disturbance will dive southeastward and ignite another storm on the boundary well to the south of New England by Friday and this new low may make a run far enough north to bring a snow shield into at least a portion of southern New England Friday night, moving out by Saturday. Confidence on this part of the forecast is low. Forecast details…
TODAY: Cloudy. Snow with up to an inch and locally 2 inches higher elevations north central MA and southwestern NH mixing with and changing to freezing rain then rain, snow with up to 1/2 inch before changing to rain with pockets of freezing rain briefly in the I-495 belt north of I-90, brief snow/mix to rain I-95 belt, rain elsewhere. Band of heaviest precipitation will be rain all areas first half of afternoon and may include thunder. Highs 35-42 north central MA and southern NH, 43-50 elsewhere with mildest in southeastern MA and RI. Wind SE 5-15 MPH, shifting to S late.
TONIGHT: Mostly cloudy with scattered rain showers evening. Variably cloudy with scattered snow showers overnight. Watch for patchy icy areas overnight. Lows 22-28. Wind SW 10-20 MPH evening, W 10-20 MPH with higher gusts overnight. Wind chill falling below 20 overnight.
WEDNESDAY: Partly sunny. Isolated snow showers. Temperatures steady 22-28. Wind W 10-20 MPH, higher gusts. Wind chill below 20.
WEDNESDAY NIGHT: Mostly clear. Lows 12-18. Wind W 5-15 MPH, higher gusts. Wind chill near to below 10 at times.
THURSDAY: Filtered sun and a period of heavier clouds and a slight chance of snow near the South Coast. Highs 22-28. Wind W 5-15 MPH.
FRIDAY: Increasing clouds. Chance of snow late-day or night. Lows from the middle 0s to lower 10s. Highs in the 20s.
SATURDAY: Clearing. Lows in the 20s. Highs in the 30s.

DAYS 6-10 (DECEMBER 17-21)
Colder than normal pattern with a risk of a couple passing systems in a general west northwest flow. Will fine-tune.

DAYS 11-15 (DECEMBER 22-26)
Brief moderation may occur but overall the same general pattern is expected.

7:35AM

DAYS 1-5 (DECEMBER 11-15)
A disturbance exits the region this morning. A clipper system crosses the region Tuesday, too far north for all of the region to see snow but not far enough for all of the area to escape it, redeveloping over Maine then exiting via Canada. As it intensifies it will drag down the coldest air of the season for the middle of this week ahead of the next clipper system that brings a chance of snow Friday. Details…
TODAY: Mostly cloudy with passing snow showers possible early, then mostly sunny. Highs 33-40. Wind W 10-20 MPH.
TONIGHT: Clouding over. Precipitation arriving pre-dawn as snow or mix northwest of a Boston-Providence line, mix or rain to the southeast. Lows 28-35. Wind light SE.
TUESDAY: Cloudy morning with snow central MA into southern NH, rain southeastern MA and RI, snow to rain in between. Snow accumulation 1-3 inches outside of I-495 and north of I-90 but 3-6 inches higher elevations north central MA and southwestern NH, and less than an inch to the southeast. Mostly cloudy afternoon with a few rain showers possible. Highs 38-45. Wind variable 5-15 MPH, higher gusts.
WEDNESDAY: Partly cloudy. Windy. Temperatures fall to the 20s early then remain there.
THURSDAY: Sunshine then late clouds. Lows from the upper 0s to middle 10s. Highs in the 20s.
FRIDAY: Cloudy. Chance of snow. Lows in the 10s. Highs from the middle 20s to lower 30s.

DAYS 6-10 (DECEMBER 16-20)
The pattern will feature near to below normal temperatures in a general northwesterly flow with a series of clipper systems passing through. Current timing brings them through about December 17 and 20.

DAYS 11-15 (DECEMBER 21-25)
The pattern is expected to continue generally the same. There is a slight chance of brief temperature moderation at some point during this period but not enough evidence for me to be confident of it.

11:50AM

STORM SUMMARY
Just a quick look back on our first widespread snowfall of the 2017-2018 season. This was the first of what I believe will be several snow events from now until mid January during a pattern that is overall colder than normal, and a pattern in which we may get greater than half of our snow for the season. Right or wrong about the long range, this first system delivered nicely for most of the region, except for the expected areas discussed in yesterday’s forecast. My error was similar to many I have made in having difficulty forecasting the intensity of banding and therefore my top number of 6 should have been 7 or 8. But overall the storm did not throw any real surprises at us, and occurring on a weekend eliminated the issue of a “work day” commuting nightmare, at least for the vast majority of people. Here at the WHW headquarters, my final total was 6.6 inches.

DAYS 1-5 (DECEMBER 10-14)
We get a break today with the clouds having departed and sunshine dominant for the several short hours it is up at this time of the year. Tonight and early Monday, a disturbance will cross the region and may produce a few snow showers, and then along comes a fairly potent clipper system for Tuesday, the track of which will be extremely critical in determining where and how long an initial period of snow is. At the moment, anyone along and northwest of a Boston-to-Providence line can expect to see this start as snow as best I can tell. A rain/snow line will likely advance rapidly northwestward but just as that happens the precipitation may cut off, especially if the storm center is moving just north of the region (across northern New England) before it redevelops in the Gulf of Maine. So during the next day I will be trying to pinpoint this, as even a quick inch or two of snow can cause travel issues, and this is certainly possible somewhere early Tuesday. Regardless of how the details of that clipper system play out, what is much more certain is the arctic air mass that will arrive for the middle of the week. Along with wind, especially Wednesday, it’s going to have a bite to it. We’ll already be watching the approach of the next clipper system by late Thursday with clouds advancing into the region. On to the forecast details…
THIS AFTERNOON: Mostly sunny. Highs 35-42. Wind W 5-15 MPH.
TONIGHT: Variably cloudy. Scattered snow showers mainly after 10PM. Lows 24-31. Wind SW 5-15 MPH.
MONDAY: Mostly cloudy with passing snow showers possible early, then mostly sunny. Highs 33-40. Wind W 10-20 MPH.
MONDAY NIGHT: Clouding over. Precipitation arriving pre-dawn as snow or mix northwest of a Boston-Providence line, mix or rain to the southeast. Lows 28-35. Wind light SE.
TUESDAY: Cloudy morning with snow and a minor accumulation likely from eastern CT through central MA and southern NH except the coast, snow/mix/rain with minor snow accumulation possible NH coast down the I-495 and I-95 belts, and rain likely to the southeast. Variably cloudy afternoon with a few rain showers possible. Highs 38-45. Wind variable 5-15 MPH, higher gusts.
WEDNESDAY: Partly cloudy. Windy. Temperatures fall to the 20s early then remain there.
THURSDAY: Sunshine then late clouds. Lows from the upper 0s to middle 10s. Highs in the 20s.

DAYS 6-10 (DECEMBER 15-19)
The pattern will feature near to below normal temperatures in a general northwesterly flow with a series of clipper systems passing through. Current timing brings them through December 15 and December 17/18. The first one has a shot at producing widespread snow. Too early for details on the follow-up.

DAYS 11-15 (DECEMBER 20-24)
The pattern is expected to continue generally the same. There is a slight chance of brief temperature moderation at some point during this period but not enough evidence for me to be confident of it.

9:12AM

DAYS 1-5 (DECEMBER 9-13)
Here comes the first widespread snow event to include most of the region, and it will be the result of a wave of low pressure moving along a cold front offshore. This wave of low pressure is wave #2 of 2 that we’d been eyeing, with #1 having gone by overnight with a few raindrops reaching Nantucket during the night. But that rain is important. It tells us that it is warm enough for rain somewhere, and without a ton of cold air draining in it also tells us that it will remain warm enough for rain somewhere, so this does not become a measurable snow event for all. But we’ll get back to that in a moment. Just to go back briefly and touch upon why this and many forecasts leading to an event are not so clear cut. We’ve been eyeing a batch of energy diving out of Canada and into the upper Midwest and Great Lakes. The timing of this was key to whether or not one of these offshore waves would evolve more and come close enough to deliver precipitation to everyone. One theory for the difficulty in timing this a few days ago outside of normal model uncertainty is the fact that there is less data coming out of Alaska available for models, i.e., fewer upper air soundings. How much of a roll this may have played is not really known, but it will be interesting to see if similar situations occur going forward. Also, as a little fun fact, it seems that December 9 and 17 have become favorable dates for snow over the years. Looking back in history, and I won’t list a bunch of dates here at this point, there have been quite a few events of one type of another on these 2 dates. Today will be no exception. Once upon a time I thought today’s event would occur but would be placed far enough northwest for a lot of the region to have rain. This turned out to be a medium range forecasting error. So today we will once again attempt to foretell the future with minimal errors! Basically the forecast from my perspective is not really changed since yesterday so there is not much to say other than recapping we’ll have precipitation expanding across the region today, first with just spotty areas of very light snow except rain Cape Cod during this morning, becoming more steady from south to north later in the morning through midday and peaking during the afternoon and evening before ending west to east tonight. The rain/snow line will start out around Cape Cod and progress west northwest to at least to a Plymouth / New Bedford line. It will also bend up to include parts of Cape Ann where a northerly wind comes off a warmer ocean surface. It will likely expand to include most of the South Shore and possibly mix right up to near Boston. As everything winds down this rain/snow line will head back to the east. For road impact, look for moderate impact due to snow especially this afternoon into tonight where it is all snow, and less impact with mainly wet roads from the South Shore through Cape Cod. Overnight and early Sunday look for some icy areas on untreated surfaces. Looking ahead, a disturbance may produce a few snow showers Sunday and a lingering trough will keep some cloudiness around and maybe even a few additional flurries on Monday. The early call on the next system is a clipper that tracks over southern New England and redevelops to the east but too far north to give a significant snow event to the WHW forecast area. Still more details to iron out on this. Time for forecast details…
TODAY: Overcast. Spotty light snow except rain Cape Cod this morning. Steadier precipitation advancing northward late morning and midday mainly as snow except rain Cape Cod and a change from snow to rain into the South Shore towns of MA as well as Cape Ann MA. Highs 30-40, coldest in north central MA and southwestern NH and mildest South Shore to Cape Cod MA. Wind light N.
TONIGHT: Overcast evening with snow except rain South Shore to Cape Cod, then breaking clouds with snow tapering off west to east and rain changing to snow before ending South Shore to Cape Cod. Lows 25-32. Wind N to NW 5-15 MPH. Snow accumulation for this event: Under 1 inch Cape Cod, 1-3 inches Cape Ann and MA South Shore, 3-6 inches elsewhere.
SUNDAY: Variably cloudy. Scattered snow showers. Highs 32-39. Wind NW 10-20 MPH with higher gusts.
SUNDAY NIGHT: Partly cloudy. Lows 22-29. Wind NW 10-20 MPH with higher gusts, diminishing overnight.
MONDAY: Variably cloudy. Slight chance of snow showers. Highs 33-40. Wind W up to 10 MPH.
TUESDAY: Cloudy. AM snow to mix/rain. PM rain showers. Evening snow showers. Lows in the 20s. Highs from the upper 30s to lower 40s.
WEDNESDAY: Partly cloudy and windy. Lows in the 10s. Highs in the 20s.

DAYS 6-10 (DECEMBER 14-18)
Fair and very cold December 14. Next clipper brings a risk of snow or snow showers December 15. Fair but not as cold over the weekend of December 16-17 and then another clipper may follow that with a rain/snow risk. Timing obviously uncertain this far in advance.

DAYS 11-15 (DECEMBER 19-23)
Overall temperatures below normal with a couple opportunities for precipitation, favoring snow or snow showers, from passing clippers.

7:27AM

DAYS 1-5 (DECEMBER 8-12)
A wave of low pressure will move up along a front offshore and will come close enough for the region’s first widespread snowfall of the season on Saturday and Saturday night. An upper level disturbance will bring additional snow showers during Sunday. The next storm threat is Tuesday but the track of this one remains uncertain. Detailed forecast…
TODAY: Sun and high clouds. Highs 38-45. Wind light SW.
TONIGHT: Clouding over. Lows 28-35. Wind light variable.
SATURDAY: Cloudy. Snow/rain developing in the afternoon, turning to snow most areas but remaining as mix/rain Cape Ann, immediate South Shore through Cape Cod. Highs 33-40. Wind light N.
SATURDAY NIGHT: Cloudy. Snow likely except mix/rain immediate coast especially outer Cape Ann and Cape Cod. Snow accumulations under 1 inch outer Cape Ann and Cape Cod, 1-3 inches South Shore and Logan Airport, 3-6 inches elsewhere. Lows 25-33. Wind N to NW 5-15 MPH.
SUNDAY: Partly sunny. Scattered snow showers. Highs 33-40. Wind NW 10-20 MPH with higher gusts.
MONDAY: Variably cloudy. Lows in the 20s. Highs in the 30s.
TUESDAY: Overcast. Chance of snow/mix/rain. Lows from the upper 20s to lower 30s. Highs from the middle to upper 30s.

DAYS 6-10 (DECEMBER 13-17)
Much colder early in the period, temperatures still below normal but not quite as cold later in the period. Best opportunity for additional snow is around December 15 probably from a clipper type system.

DAYS 11-15 (DECEMBER 18-22)
Still looking for the dominant trough, colder than normal temperatures, and a couple clipper systems.