C-19 Chat Post – September 21 2021

DAYS 1-5 (SEPTEMBER 20-24)

High pressure will be the dominant force in our weather through Wednesday, and at least into if not all the way through Thursday too. As the high center, which is just to the north of our area now, slides offshore toward midweek, the transition will be from low dew point weather with cool nights and mild days early week to a more humid southerly air flow by midweek. The biggest weather question remains the timing of the next trough and frontal system from the west. At one point, guidance was aiming at Wednesday / Thursday for this, and as we’ve gotten a little closer the guidance remains spread on timing with the quickest model bringing the most rainfall through the region Thursday, and the slowest guidance indicating most of the rainfall will occur later Friday through Friday night. For this update, I am making no changes in the timing from yesterday’s post, but don’t be surprised if additional tweaks are going to be needed. For now, just “reserve” late Thursday through Friday as the potential unsettled time period. Rewinding back a bit, a reminder that summer ends and fall arrives with the autumnal equinox at 3:20 p.m. EDT Wednesday September 20, and back a bit more, look for the rise of the full Harvest Moon tonight just after 7 p.m., reaching it’s “peak fullness” at 7:55 p.m. as it sits low in the eastern sky on its rise and will light the landscape brightly all night.

TODAY: Sunny. Highs 68-75. Wind variable to E up to 10 MPH.

TONIGHT: Clear except patches of ground fog forming in lowest elevations. Lows 47-54. Wind calm.

TUESDAY: Sunny. Highs 68-75. Wind variable to E up to 10 MPH.

TUESDAY NIGHT: Clear. Patchy ground fog interior lower elevations again. Lows 55-62. Wind SE under 10 MPH.

WEDNESDAY: Mostly sunny to partly cloudy. Highs 72-79. Wind S 5-15 MPH.

WEDNESDAY NIGHT: Partly cloudy. Lows 56-63. Wind S 5-15 MPH.

THURSDAY: Partly sunny. Highs 73-80. Wind S 5-15 MPH.

THURSDAY NIGHT: Mostly cloudy. Chance of showers overnight. Lows 60-67. Wind S 5-15 MPH, higher gusts.

FRIDAY: Mostly cloudy. Showers likely. Highs 68-75. Wind S 10-20 MPH.

DAYS 6-10 (SEPTEMBER 25-29)

The weekend forecast depends highly on the speed of the frontal system moving in late this week and how quickly it departs the region. Leaning toward the potential for early showers September 25 with the departure of that system on the slower side, and late-day showers September 26 with the approach of the next one from the west, with rain-free weather for the bulk of the weekend in between. Still adjustments are likely to be needed. Potentially unsettled weather into September 27 and one more shower threat near the end of the period as we start a cooling trend.

DAYS 11-15 (SEPTEMBER 30 – OCTOBER 4)

More west-to-east flow is expected, with a bit more northwesterly flow possible, which means minor shower threats with passing fronts and an overall cooling trend. With uncertainties in the pattern leading up to this, this is still a low confidence forecast at this time.

C-19 Chat Post – September 20 2021

DAYS 1-5 (SEPTEMBER 19-23)

High pressure builds into our region today then hangs around for 5 days. Currently favoring a slower-changing pattern so high pressure once it moves from just north of to just east of the area should be able to hold fair weather in place for this entire 5-day period. The autumnal equinox occurs at 3:20 p.m. Wednesday.

TODAY: Early clouds southern and eastern areas otherwise mostly sunny. Highs 70-77. Wind NW 5-15 MPH.

TONIGHT: Clear. Areas of ground fog in lower elevations. Lows 48-55. Wind calm.

MONDAY: Sunny. Highs 72-79, coolest coast. Wind variable to E up to 10 MPH.

MONDAY NIGHT: Clear. Areas of ground fog in lower elevations. Lows 48-55. Wind calm.

TUESDAY: Sunny. Highs 73-80, coolest coast. Wind SE up to 10 MPH.

TUESDAY NIGHT: Clear. Patchy ground fog interior lower elevations. Lows 55-62. Wind SE to S under 10 MPH.

WEDNESDAY: Mostly sunny. Highs 75-82. Wind S 5-15 MPH.

WEDNESDAY NIGHT: Partly cloudy. Lows 56-63. Wind S 5-15 MPH.

THURSDAY: Partly sunny. Highs 75-82. Wind S 5-15 MPH.

DAYS 6-10 (SEPTEMBER 24-28)

A trough from the west should arrive September 24 with shower chances. High pressure attempts to build in behind this for the September 25-26 weekend but with the trough still nearby and weakening we may end up in a mild to warm southerly air flow rather than a drier westerly one. This leaves the end of the period less certain as guidance now shows dry weather where it showed unsettled weather yesterday, so will re-evaluate this going forward..

DAYS 11-15 (SEPTEMBER 29 – OCTOBER 3)

The overall weather pattern should feature a general west-to-east flow but with the uncertainty at the end of the period before this, the timing of any systems beyond that is also uncertain. Still eyeing a quick cool-down somewhere during this time.

C-19 Chat Post – September 19 2021

DAYS 1-5 (SEPTEMBER 18-22)

A saturated air mass has provided a foggy overnight and early morning for a fair portion of the WHW forecast area as the wind field has been very weak from the northeast with maritime modified polar air in place. Other than a few wind gusts around 20 MPH over Cape Cod, the region has weak wind between TS Odette well offshore and a weak approaching cold front from the northwest. The proximity of Odette will not allow the circulation to drag too much drier air into the region today, as well as being on the “humid” side of the approaching cold front. This combines to make for stubborn cloud cover and areas of fog. The fog will gradually dissipate where it is as we slowly warm the air mass enough to elevate the temperatures away from the dew points, but the clouds may be very slow to break, with the greatest chance for at least partial sun being away from the shoreline and especially southern NH through central MA to northeastern CT. If you see much if any sun in southeastern MA, for example, it will be a bonus. All in all though, not a terrible day if you can handle a little humidity without heat, and a lack of sunshine. It’s not a wash-out or a heavy rain event like we’ve seen a fair amount of times during the last 2 1/2 months of summer. The aforementioned cold front will be the introduction to drier air from Canada, and as the boundary crosses the region from northwest to southeast later this evening it can produce a few showers and even a brief thunderstorm in a few locations. Some areas will be missed by the showers, but nobody will be missed by the drier air moving in during the early morning hours of Sunday. This is the beginning of a stretch of very nice weather which is going to last for the remainder of astronomical summer, ending the season on a note much different than it will be remembered for. High pressure will still be centered to the northwest of New England Sunday, with dry air coming in on a modest northerly air flow under lots of sun. Pretty much 100% of the possible sun is expected both Monday and Tuesday as the center of the high slides across northern New England then into the waters east of New England, with enough dry air to keep ocean clouds from forming and moving ashore despite a regionwide northeast to southeast air flow Monday / Tuesday. By Wednesday, this high will have sunk a little further to the south, putting our region into a more southerly air flow. The forecast dilemma for that day when it was in the medium range was the timing of the next trough / frontal system from the west. Typical model differences have been present, with 2 out of 3 major global models holding the next front off until after Wednesday, keeping that day dry, warmer, and a little more humid. The other model, which has faster timing, has indicated shower activity and higher humidity for Wednesday, but the last 2 runs of this model have actually slowed the trough and front down a little, not quite to the timing of the other guidance, but slower nonetheless. Based on this, I’m leaning toward the rain-free scenario with warmer temperatures and a slight up-tick in humidity for the final hours of astronomical summer. The autumnal equinox occurs at 3:20 p.m. Wednesday.

TODAY: Cloudy with areas of fog and patchy light drizzle through mid morning. Mostly cloudy to partly sunny (best shot of sun inland areas) midday-afternoon. Highs 68-75, coolest coast. Wind NE to N up to 10 MPH.

TONIGHT: Variably cloudy. A passing shower possible mid to late evening from northwest to southeast. Slight chance of a thunderstorm. Lows 56-63. Wind N to NW up to 10 MPH but a few gusts around 15 MPH are possible.

SUNDAY: Mostly sunny. Highs 70-77. Wind NW 5-15 MPH.

SUNDAY NIGHT: Clear. Areas of ground fog in lower elevations. Lows 53-60. Wind calm.

MONDAY: Sunny. Highs 72-79, coolest coast. Wind variable to E up to 10 MPH.

MONDAY NIGHT: Clear. Areas of ground fog in lower elevations. Lows 53-60. Wind calm.

TUESDAY: Sunny. Highs 73-80, coolest coast. Wind SE up to 10 MPH.

TUESDAY NIGHT: Clear. Patchy ground fog interior lower elevations. Lows 56-63. Wind SE to S under 10 MPH.

WEDNESDAY: Mostly sunny. Highs 75-82. Wind S 5-15 MPH.

DAYS 6-10 (SEPTEMBER 23-27)

A trough and cold front arriving from the west is expected to bring lots of clouds and periods of showers to the region September 23. Current timing favors cooler/drier air arriving September 24 but a chance of a shower as an upper level disturbance crosses the region from west to east. High pressure brings fair weather to the region for the September 25-26 weekend. Next trough from the west brings an unsettled weather threat for the end of the period.

DAYS 11-15 (SEPTEMBER 28 – OCTOBER 2)

The overall weather pattern should feature a general west-to-east flow. Shower chances are present early in the period and again at the end of the period. We may see a brief but significant shot of cool air in the September 29 to October 1 window.

C-19 Chat Post – September 18 2021

DAYS 1-5 (SEPTEMBER 17-21)

The cold front that crawled across our region late Wednesday and Thursday is washing out near the South Coast today, never really having delivered much dry air, and now we have an established onshore air flow for today and tonight as low pressure organizes off the US Mid Atlantic Coast and heads north then northeastward. A combination of moisture from this low and the old frontal boundary keeps the chance of showers near the South Coast, especially Cape Cod and the Islands, for a while today, but the bulk of the moisture from this low will be passing southeast of New England through early Saturday. The low itself is acquiring tropical characteristics and will likely become a tropical depression and eventually a tropical storm as it makes its trek over the water off the coast. This has some indirect impact on our weekend, sending higher swells and rough surf back to the coast, increasing rip current risk for late-season beach visits. Use caution if planning to be in the water, especially Sunday. As for our weekend weather, drier air will start to move in as that low moves away during Saturday, but a weakening cold front will also be moving across the region from the northeast Saturday evening. It looks like most of the shower activity with this front will stay to the north of our area. High pressure then builds in during Sunday through early next week, the center of it probably staying just north to east of the region, with fair weather being the result.

TODAY: Mostly cloudy. Scattered showers Cape Cod and Islands region mainly this morning. Patchy drizzle possible eastern coastal locations. Highs 67-74. Wind E 5-15 MPH.

TONIGHT: Mostly cloudy. Foggy areas. Lows 60-67. Wind NE under 10 MPH.

SATURDAY: Mostly cloudy start with areas of fog, then increasing sun especially away from the coast. Highs 68-75. Wind N 5-15 MPH.

SATURDAY NIGHT: Variably cloudy. A passing shower possible mid to late evening. Lows 55-62. Wind NW up to 10 MPH.

SUNDAY: Mostly sunny. Highs 70-77. Wind NW 5-15 MPH.

SUNDAY NIGHT: Clear. Areas of ground fog in lower elevations. Lows 53-60. Wind calm.

MONDAY: Sunny. Highs 72-79, coolest coast. Wind variable to E 10 MPH.

MONDAY NIGHT: Clear. Areas of ground fog in lower elevations. Lows 53-60. Wind calm.

TUESDAY: Sunny. Highs 73-80, coolest coast. Wind SE up to 10 MPH.

DAYS 6-10 (SEPTEMBER 22-26)

High pressure shifts offshore by the beginning of this period with a warm start to the period. The next weather questions to answer will be the timing of a trough / cold front from the west, which I think comes through sometime September 23 with an opportunity for showers, before drier and cooler air comes in behind that for September 24 before it warms up September 25. Will watch for the approach of the next weather system with wet weather chances for the very end of the period, though it may be slow enough to allow our region to get through the September 25-26 weekend rain-free.

DAYS 11-15 (SEPTEMBER 27 – OCTOBER 1)

Wet weather may start this period before a shot of dry and cooler air, a quick warm-up, more unsettled weather, then another shot of cool air to end September and start October. While timing is lower confidence the confidence is higher for an overall west-to-east pattern being the cause of the changeable weather.

C-19 Chat Post – September 17 2021

DAYS 1-5 (SEPTEMBER 16-20)

A slow moving cold front is now across RI and southeastern MA and crawling to the southeast, and will come to a stop and lose its identity over the next 24 hours. Before that happens, some energy moving across our region, combined with the contrasts created by the frontal boundary, continue to produce a fairly decent area of showers and embedded thunderstorms in the vicinity of the boundary, and lighter scattered showers to the northwest. This activity will gradually diminish during the day. Clouds will hang around though for the remainder of today, tonight, and through Friday. We will also be watching low pressure to the south of New England which will be moving north to northeast, staying offshore, but close enough to possibly toss some bands of shower activity into the region at times Friday and Friday night. The low should pull far enough to the northeast so that drier air is drawn in during Saturday with improving weather, but cannot rule out a few pop up showers from leftover instability. High pressure builds in with fair, warming weather Sunday and Monday.

TODAY: Cloudy with scattered to numerous showers including embedded thunderstorms favoring RI and southeastern MA during this morning. Mostly cloudy with a chance of a few showers this afternoon. Highs 68-75. Wind NE 5-15 MPH.

TONIGHT: Mostly cloudy. Areas of fog. Chance of showers. Lows 60-67. Wind NE 5-15 MPH.

FRIDAY: Cloudy. Chance of showers. Highs 68-75. Wind NE 5-15 MPH.

FRIDAY NIGHT: Cloudy. Chance of showers evening. Areas of fog. Lows 58-65. Wind NE 5-15 MPH.

SATURDAY: Mostly cloudy to partly sunny. Isolated midday and afternoon showers possible. Highs 66-73. Wind NE to N 5-15 MPH.

SATURDAY NIGHT: Partly cloudy. Lows 55-62. Wind NW under 10 MPH.

SUNDAY: Mostly sunny. Highs 70-77. Wind NW 5-15 MPH.

SUNDAY NIGHT: Clear. Areas of ground fog in lower elevations. Lows 53-60. Wind calm.

MONDAY: Sunny. Highs 73-80. Wind variable up to 10 MPH.

DAYS 6-10 (SEPTEMBER 21-25)

High pressure is expected to bring dry weather and above normal temperatures to the region September 21-22. Current indications are that a trough and cold front will pass through from west to east sometime September 23 with a shower threat, followed by another area of high pressure building in with more fair weather for the end of the period.

DAYS 11-15 (SEPTEMBER 26-30)

General west-to-east flow. Expected timing of disturbances with passing shower threats September 26 and 29. A brief shot of cooler air follows the first one and a sharper shot of chilly air may follow the second one to end the month.

C-19 Chat Post – September 16 2021

DAYS 1-5 (SEPTEMBER 15-19)

A warm front is pushing through the region early this morning and will open the door for a late-season summer blast of warmth and humidity today with a gusty wind to go along with it. A cold front will be approaching later in the day but won’t get here until the late night hours tonight into the early morning hours of Thursday. A line or two of thunderstorms spawned by the front will be quite strong to our northwest and west later in the day, but will be on a weakening trend as it enters the northwestern part of the WHW forecast area by this evening. We’ll have to keep an eye on it still for a few surviving stronger cells and some gusty winds, but I think the more powerful severe potential will have been lost in a lot of the activity by the time it gets here. The remnants of this line and the spawning of newer showers as the front crosses the region overnight will bring the shower chance to most areas. The front will hang up near the South Coast and wash out, its remnants pushing back to the north during Thursday as the focus for some scattered shower activity in the region with lots of clouds lingering. Low pressure to the south may develop into a tropical depression or even minimal tropical storm as it makes a run at our region on Friday, but the trends continue to be for the bulk of this system to pass southeast of our area. It still brings the threat of some rainfall for a portion of Friday, but it doesn’t look like a widespread heavy rainfall event. I still like the trend for the weekend. Improvement is expected Saturday as the low pulls away, and a great late summer day is expected Sunday as high pressure builds in.

TODAY: Mostly cloudy start, then partly sunny. Highs 80-87. Humid – dew point upper 60s to near 70. Wind S increasing to 10-20 MPH, higher gusts.

TONIGHT: Variably cloudy. Showers likely and a chance of thunderstorms. Areas of fog overnight. Lows 63-70. Humid – dew point above 60. Wind SW 5-15 MPH with higher gusts becoming variable.

THURSDAY: Mostly cloudy. Scattered showers and thunderstorms especially RI and southeastern MA during early and mid morning. Isolated showers possible thereafter. Highs 69-74. Wind N to NE 5-15 MPH.

THURSDAY NIGHT: Variably cloudy evening. Mostly cloudy with areas of fog overnight. Lows 58-65. Wind NE to E up to 10 MPH.

FRIDAY: Cloudy. Chance of rain. Highs 67-74. Wind E 5-15 MPH.

FRIDAY NIGHT: Cloudy. Chance of rain evening. Areas of fog. Lows 58-65. Wind E to NE 5-15 MPH.

SATURDAY: Mostly cloudy to partly sunny. Highs 66-73. Wind NE to N 5-15 MPH.

SATURDAY NIGHT: Partly cloudy. Lows 55-62. Wind NW under 10 MPH.

SUNDAY: Mostly sunny. Highs 70-77. Wind NW 5-15 MPH.

DAYS 6-10 (SEPTEMBER 20-24)

High pressure is expected to bring dry weather and above normal temperatures to the region September 20-22. A trough approaching from the west brings an increased chance of shower activity later in the period.

DAYS 11-15 (SEPTEMBER 25-29)

A transition to a stronger westerly flow will start to take place, but we will have to keep an eye on potential tropical activity off or near the East Coast. Temperature departure from normal expected to be above but may turn sharply cooler at the very end of the period.

C-19 Chat Post – September 15 2021

DAYS 1-5 (SEPTEMBER 14-18)

A weak area of high pressure to the north today is enough to provide some nice weather. The warm front approaching from the southwest doesn’t have a solid area of cloudiness with it, instead being the focus of clusters of showers and thunderstorms in a fairly narrow zone southwest of New England. This frontal boundary will move across our region overnight / early Wednesday with the chance of a few showers and a thunderstorm along it, but not a solid area of rainfall. It will introduce a gusty southwesterly wind and high humidity for Wednesday, a day that will have the feel of summer with a sun/cloud mix. A cold front approaching from the northwest parented by low pressure moving eastward to our north will be timed late enough that I still think we escape a severe weather threat. We likely see general showers and thunderstorms moving in Wednesday night, in weakening form, that had been much stronger to the west during the day. The frontal boundary will then slog its way across the WHW forecast area early Thursday with additional showers possible, and while the boundary itself never gets that far beyond us, we may see enough dry air work in for some partial improvement Thursday afternoon. It’s at that time our attention will turn to low pressure to the south. While this system may become a tropical depression or even minimal tropical storm, it doesn’t concern me just for being a potential tropical entity, as it doesn’t look like it would turn into a formidable system with wind and torrential rainfall. However, it will contain tropical moisture, and its track should be close enough to at least bring some rainfall into the region during Friday. There are still some differences of output across models as to how much rain gets in here and with the track of the system itself, and also its speed of movement. I remain optimistic at this time that it does move far enough to the north, and far enough to the east, that drier air is drawn into our region as early as Saturday for improving weather in time for the weekend, but a slower and/or further west system would change this outlook, so it’s low confidence at the time.

TODAY: Mostly sunny to partly cloudy. Highs 70-77. Wind variable to E up to 10 MPH.

TONIGHT: Partly to mostly cloudy. Chance of a shower or thunderstorm overnight. Lows 60-67. Wind SE up to 10 MPH shifting to SW.

WEDNESDAY: Partly sunny. Highs 78-85. Humid – dew point upper 60s. Wind SW 10-20 MPH, higher gusts.

WEDNESDAY NIGHT: Variably cloudy. Chance of showers/thunderstorms. Lows 63-70. Wind SW 5-15 MPH becoming variable.

THURSDAY: Mostly cloudy. Chance of showers especially in the morning. Highs 70-77. Wind variable 5-15 MPH becoming NE.

THURSDAY NIGHT: Partly to mostly cloudy. Lows 58-65. Wind NE to E up to 10 MPH.

FRIDAY: Cloudy. Chance of rain. Highs 67-74. Wind E 5-15 MPH.

FRIDAY NIGHT: Cloudy. Chance of rain evening. Areas of fog. Lows 58-65. Wind E to NE 5-15 MPH.

SATURDAY: Mostly cloudy to partly sunny. Highs 66-73. Wind NE to N 5-15 MPH.

DAYS 6-10 (SEPTEMBER 19-23)

High pressure builds in with a dry stretch of weather early to mid period, along with a warming trend. A trough and frontal system from the west brings the chance of unsettled weather back by later in the period.

DAYS 11-15 (SEPTEMBER 24-28)

General west-to-east flow resumes with up and down temperatures and limited shower chances but still need to watch the western tropical Atlantic for potentially putting a system somewhere near or off the East Coast.

C-19 Chat Post – September 14 2021