Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 171946 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 346 PM EDT Sun Mar 17 2024 .SYNOPSIS...
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Clear and cool tonight with steady west winds. Mainly sunny and warm tomorrow with gusty west winds and elevated fire weather concerns. Temperatures trending near to cooler than seasonable for much of the upcoming week. Isolated showers possible each day, especially Wednesday along with gusty winds. Dry by Friday then uncertainty increases for when wet weather may return for the weekend.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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Tonight: Winds turn WNW this evening as the low pressure over Quebec continues to pull away to the east. Not expecting winds to go completely calm overnight with 15-20 knot winds at 925mb and some CAA promoting mixing. However, the 20-30 mph gusts from this afternoon should diminish overnight. Even with clear skies, steady winds should keep overnight lows from bottoming out, only dropping into the low to mid 30s.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
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Key Points * Elevated Fire Weather Concerns Tomorrow * Gusty WNW Winds 20-30 mph Tomorrow: Upper level trough and associated cold pool aloft begins to move into the region. With a strong WNW pressure gradient and good boundary layer mixing up to 700mb, winds will become gusty again up to 20-30 mph. High temps tomorrow should top out in the low to mid 50s before colder air works in with the cold pool aloft. Dewpoints tomorrow will be dropping into the teens which will bring minRH values down below 30%. In collaboration with our fire weather partners, we have opted to issue a SPS due to elevated fire weather concerns for tomorrow afternoon in CT and RI. There is a low chance for isolated pop up rain/snow showers across western MA where the cold pool may be able to work in before the loss of daytime heating. Otherwise mainly dry tomorrow with diurnal cumulus in the afternoon again. Tomorrow night: The core of the 500mb cold pool works in overhead with temperatures of -35 aloft. Strong CAA along with clear skies and diminishing winds will allow for overnight temps to drop below freezing with mid to upper 20s across the high terrain in northern MA. Any showers that do form tomorrow afternoon will quickly come to an end with the loss of daytime heating.
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/...
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Key Points... * Temperatures seasonable this week with highs in the 40s. * Spotty showers possible Tue and more widespread on Wednesday, possibly lingering into Thursday for some; not a washout. * Dry on Friday before another system may arrive next weekend but confidence is low. The forecast remains largely unchanged from what we`ve been looking at for the past few days, with the exception of continued uncertainty as to how/when the pattern may break down for unsettled weather next weekend. In the mean time we`ll be under the influence of broad cyclonic flow aloft with a series of shortwaves rotating through the base of the trough before brief ridging arrives for Friday. This means generally cool and cloudy weather for much of the week. The first of these disturbances moves overhead on Tuesday bringing increased cloudiness at least, given an anomalously cold airmass overhead. This, with diurnal heating will lead to low level lapse rates of 6-8C. This may be enough to overcome limited moisture in order to produce some spotty rain or even graupel showers; best shot is in the orographically favored high terrain of western MA. As the previous forecaster mentioned, though, temperatures will be cooler thanks to cold advection aloft and the well mixed boundary layer will lead to drying of the airmass on breezy west winds. Thus, dewpoints have been lowered into the teens and low 20s. Wednesday is the best shot of any particular location seeing a rain or snow shower as another shortwave and stronger surface low passes to our north, but meager moisture and dynamics will keep this from being a widespread precipitation event. One thing to note will be the ramping up of the winds in the afternoon as the pressure gradient tightens with the passage of the low, gusting 20-30 mph in the afternoon. This is the start of the gusty winds, as Thursday will be the windiest day. BUFKIT soundings indicate a very well mixed boundary layer up to at least 850 mb where a 35-45kt LLJ resides, mixing down gusts as high as 35 to 45 mph Thursday morning. Winds will then decrease, but remain breezy all day. Friday will be the quietest day of the week with a dry forecast and little wind thanks to a transient high pressure. As for the weekend, we continue to track a potential storm system around Saturday or Sunday, but the GFS and ECMWF guidance remain in different camps as to the strength and track of the low. For now have stuck to ensemble guidance indicating increasing POPs starting Saturday.
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&& .AVIATION /20Z SUNDAY THROUGH FRIDAY/...
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Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight...High Confidence. VFR. W winds diminishing to 5-10 knots higher near the coasts. Monday...High Confidence. VFR. W winds increasing to between 10 and 15 knots. Should see those gusts picking up to 20-25 kts by roughly 14-18Z Monday Night: VFR. West winds diminish to 10-15 knots . KBOS TAF...High confidence in TAF. VFR, gusty WNW winds at 20-25 knots. KBDL TAF...High confidence in TAF. VFR, gusty WNW winds at 15-20 knots. Outlook /Tuesday through Friday/... Tuesday through Tuesday Night: VFR. Breezy. Wednesday: VFR. Windy with local gusts up to 30 kt. Slight chance RA. Wednesday Night: VFR. Windy with gusts up to 30 kt. Slight chance RA. Thursday: VFR. Windy with gusts up to 35 kt. Thursday Night: VFR. Windy with areas of gusts up to 30 kt. Friday: VFR. Breezy.
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&& .MARINE...
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Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight... Decreasing westerly winds across the southern waters of 10 knots or less, while the northern waters could see continued gusts of 15-25 knots. Seas slowly diminish to 3-4 feet, with lingering 5 footers in the far outer waters. Tomorrow... Winds become gusty out of the west again at 15-25 knots. This results in increasing sea back to 4-5 feet esspically for the southern waters. Tomorrow night. Winds remain out the west, but continue to gust 10-20 knots. Seas diminish to 3-4 feet. Outlook /Tuesday through Friday/... Tuesday through Tuesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain. Wednesday Night: Low risk for gale force winds with gusts up to 35 kt. Local rough seas. Slight chance of rain. Thursday: Moderate risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Thursday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
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&& .FIRE WEATHER...
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Monday and Tuesday... There are some fire weather concerns for Monday and Tuesday. We expect afternoon westerly wind gusts of 20 to 25 mph with minimum relative humidity values between 20 to 30 percent Monday and 25 to 35 percent Tuesday. Would not be surprised if RH values ended up on the lower side of those numbers given very dry air aloft. In coordination with our fire weather partners, we opted to issue a SPS for CT and RI due to elevated fire weather concerns Monday and possibly again on Tuesday.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 5 PM EDT this afternoon for ANZ230- 231-236-251. Small Craft Advisory until 8 PM EDT this evening for ANZ232>235-237. Small Craft Advisory until 8 PM EDT Monday for ANZ250. Small Craft Advisory until 2 AM EDT Tuesday for ANZ254>256.
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&& $$ SYNOPSIS...BW/KP NEAR TERM...KP SHORT TERM...KP LONG TERM...BW AVIATION...BW/KP MARINE...BW/KP FIRE WEATHER...KP

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