Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 072029 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 429 PM EDT Sun Aug 7 2022 .SYNOPSIS...
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Heat and humidity will continue to be the main weather story well into next week. Heat Advisories continue through Monday. A cold front will bring a better chance of thunderstorms on Tuesday. The front will stall just south of the area Wednesday with low pressure passing along it, which might bring welcome rain Wednesday into Thursday. While the heat will break on Wednesday, the humidity won`t ease up in a meaningful way until Friday.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Forecast is on track this afternoon, with cumulus bubbling across southern New England but only sparse showers so far which continue to pulse up and quickly collapse. As we go through the afternoon the coverage of showers and storms may increase, mainly along and north of the MA pike. Mesoanalysis shows 2000-2500 J/kg of CAPE but with no shear and lackluster mid level lapse rates which should keep any thunderstorms of the garden-variety. With sunset and loss of diurnal heating storms will rapidly diminish in coverage leaving mostly clear skies, save for the south coast where low level moisture will once again bring the threat of low stratus to the Cape and islands. Low temps will be quite warm owing to the very moist airmass, in the mid 70s. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Monday we rinse and repeat, as has been the story for days now. The hot and humid airmass remains overhead with little change to speak of. SW winds continue and advect in marginally warmer air in the low levels (850 mb temps increase from 18C to 19-20C) so temperatures will be a few degrees warmer, especially in the Connecticut Valley. Highs in the low to mid 90s and dewpoints in the mid 70s mean another day of heat indices at or above 100F. Instability will once again be high (CAPE >1500 J/kg) with poor shear (though a bit higher than Sunday). Not expecting a severe threat with any storms that pop up on Monday afternoon and evening. Any convection that does fire will die down after sunset leaving a dry forecast for the overnight hours. Increasing winds late in the day and overnight will take the edge off, especially along the south coast and offshore. && .LONG TERM /TUESDAY THROUGH SUNDAY/...
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Highlights... * Hot and humid Tuesday with a slow moving cold front bringing the likelihood of afternoon and evening thunderstorms. * Low pressure moving along the front just south of New England may bring a period of welcome rain Wednesday into Thursday. * Heat will break on Wednesday, but humidity won`t return to comfortable levels until Friday. Tuesday and Tuesday night... Models are now more in line with the cold front sagging southward across our region Tuesday and Tuesday night. Ahead of the front, high temperatures are forecast to again rise to between 90 and 95 degrees, with heat indices reaching 96-102, highest in northern CT and in RI and interior southeast MA. The front will provide the focus for more numerous showers and thunderstorms than today or Monday. CAPE will be moderately high, but there is little in the way of shear to support organized severe storms. With that much heat and humidity, there undoubtedly will be a isolated severe storm that pops up, however. Also, there could be localized street flooding with any slow-moving storms. Wednesday and Thursday... The front slips just south of New England then stalls, with weak low pressure traveling along it. We will have much cooler northeast wind flow, with highs only from 76-83, bringing an end to the heat wave. Ensembles signal a decent chance of a much-needed rather wipdespread soaking rainfall from Wednesday into Thursday, with the highest probabilities Wednesday night. There could be an isolated rumble of thunder, mainly along the south coast. Rainfall totals could approach 1 to 1.5 inches in some areas. Tough to forecast this when we`ve been so dry...will fine tune as time goes on. Friday through Sunday... Significant model differences Friday through Sunday. Ensembles still show clearing skies Friday and mainly dry weather through the weekend. But operational ECMWF shows strong upper low cutting off to our west, becoming negatively tilted, and spawning another coastal low that brings additional rain chances here Friday and Saturday. GFS also has upper low developing over SNE with coastal low and rain chances in easternmost SNE Saturday. In any case, cooler weather prevails through the weekend. Stay tuned for more revisions in upcoming forecasts for this period.
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&& .AVIATION /20Z SUNDAY THROUGH FRIDAY/...
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Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 18z TAF Update; This afternoon...High confidence. VFR. Iso to widely sct SHRA/TSRA through 02Z, mainly along/north of I-90. SW winds around 10 kt, gusts 18 to 22 kt. Tonight...Moderate Confidence. Mainly VFR. Areas of IFR in stratus expected towards the south coast late. Light SW winds. Monday...Moderate Confidence. Mainly VFR. IFR stratus more likely to persist towards the south coast around daybreak. Brief periods of MVFR in any afternoon showers or thunderstorms. SW winds 5-10 kt with gusts up to 20 kt. Monday night...High confidence. VFR. SW winds 5-15 kts gusting to 25 kts for southeast MA. KBOS...Moderate confidence in TAF due to uncertainty as to whether any TSRA makes it to the terminal this afternoon. Greatest risk, though still low, is no sooner than 20z. KBDL...Moderate confidence in TAF due to uncertainty as to whether any TSRA makes it to the terminal this afternoon. Greatest risk, though still low, is no sooner than 19z. Outlook /Tuesday through Friday/... Tuesday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA, chance TSRA. Tuesday Night: Mainly MVFR, with areas IFR possible. Chance SHRA, chance TSRA. Wednesday: Mainly MVFR, with areas IFR possible. Chance SHRA, isolated TSRA. Wednesday Night: Mainly MVFR, with local IFR possible. SHRA likely. Thursday: Mainly MVFR, with areas VFR possible. Chance SHRA, isolated TSRA. Thursday Night: Mainly VFR, with areas MVFR possible. Slight chance SHRA, isolated TSRA. Friday: Mainly VFR, with areas MVFR possible. Slight chance SHRA.
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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. Through Monday night...High Confidence. This afternoon and tonight, SW winds 15-20 kt with gusts up to 25 kt. Seas increase to 5-6 ft on the southern waters tonight. Winds and seas diminish some into Monday, with rough seas lingering across the outer coastal waters the longest. Winds and seas increase once again Monday evening and overnight. Outlook /Tuesday through Friday/... Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Chance of rain showers, chance of thunderstorms. Tuesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, chance of thunderstorms. Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, isolated thunderstorms. Wednesday Night: Winds less than 25 kt. Rain showers likely, slight chance of thunderstorms. Thursday through Thursday Night: Winds less than 25 kt. Chance of rain showers, isolated thunderstorms. Friday: Winds less than 25 kt. Slight chance of rain showers, isolated thunderstorms.
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&& .CLIMATE...
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Record Maximum Temperatures August 7th: BOS 98F [1924] ORH 94F [1924] ...corrected from previous AFD PVD 95F [2001] BDL 100F [1918] August 8th: BOS 96F [1983] ORH 94F [1916] PVD 95F [1909] BDL 98F [2001]
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...Heat Advisory until 8 PM EDT Monday for CTZ002>004. MA...Heat Advisory until 8 PM EDT Monday for MAZ002>023-026. RI...Heat Advisory until 8 PM EDT Monday for RIZ001>007. MARINE...Small Craft Advisory until 8 AM EDT Tuesday for ANZ231>235-237. Small Craft Advisory until 1 AM EDT Monday for ANZ236-250. Small Craft Advisory until 8 PM EDT Tuesday for ANZ254>256. && $$ SYNOPSIS...BW/GAF NEAR TERM...BW SHORT TERM...BW LONG TERM...GAF AVIATION...BW/GAF MARINE...BW/GAF CLIMATE...Staff

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