Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 240646 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 146 AM EST Fri Nov 24 2017 .SYNOPSIS... Quiet weather through Friday with dry and cool conditions. Milder air returns Saturday ahead of a cold front. That cold front swings through Southern New England late Saturday and early Saturday night. Blustery and cooler weather follows Sunday. Conditions trend toward dry and milder again Tuesday and Wednesday, and then cool again Thursday behind another cold front. && .NEAR TERM /THROUGH TODAY/... Mid and high level clouds continue to dissipate as they move east across southern New England this morning. The thicker mid level clouds towards the Berkshires will be more stubborn to erode as there is some connection to the Great Lakes to keep the humidity higher, along with the upslope over the Berkshires themselves. Adjusted the forecast through daybreak to reflect observed trends. For today, high pressure to our south will dominate our weather. Dry conditions with relatively light west winds shifting southwest as the day progresses. Abundant sunshine with only a few higher clouds from time to time. This sunshine will permit higher temperatures than Thursday, and close to normal values for late November. && .SHORT TERM /TONIGHT THROUGH 6 PM SATURDAY/... Southwest winds should increase slightly tonight, setting the stage for a warmup Saturday. As noted by prior shift, dewpoints also increase with the southwest flow, but not expecting fog to be an issue. Low stratus is likely across the Cape and islands late tonight. Dry conditions continue. Saturday should be above normal temperature-wise as modest southwest winds continue ahead of a cold front. Latest model suite continues to show pretty good lift and humidity within the 850-700 mb layer, but more drier air beneath it to be overcome. Envisioning a scenario where clouds increase through the day, with dry weather into mid-late afternoon. Since this is a cold frontal passage, and BUFR soundings continue to show the column saturating from the top down, will continue the idea of a slight chance for showers, becoming a greater risk towards the east coast very late in the day Saturday due to proximity to more humid low levels. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Big Picture... Longwave scale shows a broad trough along the USA East Coast and West Atlantic, a second trough over the Eastern Pacific, and a ridge over the the Plains. The Eastern trough lingers much of the week while the overall flow trends zonal. Model consensus shows northern stream shortwaves crossing New England Saturday night/Sunday and again Wednesday. The models also show a southern stream low crossing the Southeast USA Thursday trailing the Wednesday northern shortwave. The mass and thermal fields are similar through Mon night/Tuesday, but then diverge by showing different timing of the northern and southern stream features. The feature that becomes the northern and southern shortwaves next week is currently over the Aleutians and diving south over the Pacific Ocean...and it reaches the USA West Coast by Monday. Expect changeable solutions regarding this feature until that time. Contour heights and thermal fields are a little above normal Saturday, trend colder than normal Sunday-Monday, then trend above normal midweek next. Details... Sunday-Monday... Upper trough digs over New England Sunday. Cold pool will be in place with 500-mb temps at -28C working to destabilize the airmass. Moisture lingers below 800 mb during this time. Expect quite a few clouds to pop during the day, but moisture is too limited for showers. Mixed layer temps will support max sfc temps in the upper 30s and 40s. The trough moves off on Monday and high pressure builds surface and aloft. Expect a fair day with max sfc temps in the 40s. Tuesday through Thursday... Another cold front crosses us midweek, driven by the northern stream shortwave. As noted above, there are timing uncertainties among the models, so we used a blend. This favors a Wednesday passage at this time, but the uncertainties noted above may change that exact timing. This will need to be monitored. The blend of model data supports slight chance pops Wednesday with the cold fropa and mainly dry Thursday. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/...High confidence. VFR. W/NW winds diminish overnight, turning S/SW into today. BKN-OVC MVFR CIGs possible for SE New England into tonight into early Saturday morning. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Saturday Night through Tuesday/... Saturday Night: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA. Sunday: VFR. Windy with local gusts to 30 kt. Sunday Night through Tuesday: VFR. Breezy. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/... Small Craft Advisories adjusted to account for trends in observed seas. Expecting all advisories for the outer coastal waters to be down by daybreak this morning. Will adjust timing as needed. High pressure in control with good boating weather for a time today. Increasing southwest winds tonight into Saturday will likely build seas once more across portions of the outer coastal waters. Additional Small Craft Advisories may be needed for marginal rough seas. Outlook /Saturday Night through Tuesday/... Saturday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Sunday Night: Winds less than 25 kt. Local rough seas. Monday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Monday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory for hazardous seas until 7 AM EST this morning for ANZ254. Small Craft Advisory for hazardous seas until 3 AM EST early this morning for ANZ255. && $$ SYNOPSIS...WTB/Belk NEAR TERM...Belk SHORT TERM...Belk LONG TERM...WTB AVIATION...WTB/Belk MARINE...WTB/Belk

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