Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 290154 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 954 PM EDT SUN AUG 28 2016 .SYNOPSIS... A cold front enters southern New England tonight and then exits Monday afternoon, which may be accompanied by a spot shower or thunderstorm. Weak high pressure brings dry weather Tuesday. Warm and humid weather returns Wednesday ahead of another cold front, which will bring the chance for showers and thunderstorms Wednesday afternoon into Thursday morning. Large Canadian high pressure will bring dry, fall-like weather late this week into the weekend, with mild days and cool nights. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Changed timing of rainfall chances this evening. Starting to lose confidence in any thunderstorms across southern New England overnight. Latest mesoanalysis showed very little instability to work with. Radar trends have also indicated any convection weakening/dissipating as it approaches western New England. Believe this to be the result of stronger convection over central and western PA dominating the southerly inflow. Despite that, still left a mention of isolated thunderstorms after midnight, generally along and north of Route 2, for now. Will continue to evaluate, and make changes as needed. Besides that change, brought the next several hours back in line with observed trends. Previous Discussion... Gorgeous late summer weather this evening with warm temps...comfortable humidity and light winds with high pressure anchored from the Maritimes thru the northeast. Short wave trough and attending cold front approach the region later tonight. As of 715 PM, the HRRR had the best handle on thunderstorms across central NY state. The mid level trough deamplifies with time and west-southwest winds ahead of the front limit convergence. Thus overall weak synoptic lift. However sufficient moisture and marginal instability will allow for a slight chance for a shower or isolated thunderstorm mainly north of the Route 2 corridor in northern MA into northeast MA later tonight. However most of the region remains dry overnight. No changes to current forecast of precipitation probabilities. It will be a mild night given the prefrontal environment/warm sector. Increasing humid as dew pts climb into the low and mid 60s especially across CT/RI and southeast MA. This may result in some patchy fog toward morning. Made minor downward adjustments to temperature on Cape Cod and the Islands, since Nantucket was reporting only 67 degrees. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Monday ... Low risk of an isolated shower/T-storm in the morning with greatest risk over eastern MA. Most places remain dry as cloud cover limits instability and west-southwest winds yield weak convergence. Mid level dry air and associated subsidence rush in from the northwest to southeast yielding dry and partly sunny conditions by afternoon...mid afternoon south coast and islands. Warm with highs in the mid to upper 80s...perhaps briefly touching 90 in a few spots. However west-northwest winds 10-20 mph behind the front will yield lower humidity during the afternoon. Hence a very nice afternoon shaping up. Monday night ... Post frontal airmass overspreads the region resulting in dry weather...less humid and cooler conditions along with light winds and mostly clear skies. Leaned toward the cooler MOS given decoupling of the blyr is likely. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Highlights... * Cold front brings the chance for showers/thunderstorms Wednesday afternoon into Thursday morning. * Dry, fall-like conditions move in for Friday and Saturday with mild days and cool nights Tuesday...Weak high pressure ridge builds across southern New England, then off the coast. Skies will be sunny with highs in the lower 80s away from the coast. Humidities will be on the low side with dewpoints in the mid and upper 50s. With a light pressure gradient across the region, sea breezes will bring slightly cooler temperatures along the shoreline. Wednesday and Wednesday night... Another cold front begins to approach N and W Mass Wed. afternoon. now appears that there will be a little more ridging over southern New England...induced by a weak tropical system off the mid-Atlantic coast...that remains well to our south. This may delay the frontal passage until Wed night...then off the coast Thursday morning. Will see warm and more humid conditions ahead of this front as SW winds pick up. Noting the PWATs do increase by Wednesday evening to around 1.6 inches, so could see some brief heavy downpours with any showers or thunderstorms across central and southern areas toward evening and overnight. Have gone with 40 to 50 percent probabilities. Highs Wed in the mid 80s. Lows Wed night in the 60s. Thursday...The ECMWF model slows the front down the most and since this has been consistent, have continued the chance of showers in southeastern sections through the morning and early afternoon. Will still see mild temperatures as the cooler air does not work into the region until later in the day. Dewpoints drop to the upper 40s and lower 50s Thursday night. Expecting lows Thursday night in the 50s except 60-65 Cape and Islands. Friday through Sunday...Large sprawling high pressure will move from the Great Lakes Fri to New England Sat...then off the coast Sunday. It will bring cool temps especially Friday and Saturday mornings, with lows reaching the upper 40s in northwest MA and lower 50s elsewhere. Highs both Fri and Sat should hold in the 70s. As the high moves off the coast, will see a slight warmup on Sunday with highs reaching the lower 80s. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/...High Confidence. VFR, but isolated shower or thunderstorm with highest probs across northwest MA, then shifting into northeastern MA toward sunrise. High forecast confidence. Monday...VFR with low risk of a spot shower or T-storm eastern MA in the morning then shifting to south coast midday, then offshore by mid afternoon. West-southwest winds in the morning becoming NW 10-20 kt by midday. High confidence. Mon night...light NNW winds becoming variable late. VFR and dry weather too. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Tuesday through Friday/... Tuesday...High confidence. VFR. Light W-SW winds inland. Sea breezes along both coasts likely. Patchy fog late Tue night with local MVFR-IFR VSBYS. Wednesday...Moderate confidence. Mainly VFR. May see local MVFR conditions in scattered SHRA/TSRA across N central and W Mass during the afternoon. Wednesday night-Thursday...Moderate confidence. Mainly VFR. Local MVFR-IFR CIGS/VSBYS in scattered SHRA/TSRA as cold front crosses the region Wed night/early Thu. Scattered showers may linger until around midday Thursday before improving. Friday...High confidence. VFR. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/...High confidence. 715 pm update ... Tonight... Fairly light winds with ridge of high pres over the waters. However southeast swells from Hurricane Gaston beginning to enter the waters southeast of Nantucket as of 3 pm. Dry weather and good vsby with just a small chance of an isolated shower/T-storm well after midnight. Monday ... light west-southwest winds in the morning become west-northwest during the afternoon with gusts up to 20 kt near shore possible. Isolated shower/T-storm possible until early afternoon then offshore. Southeast swells of 3-6 ft across the ocean waters. Monday night ... NNW wind with high pres building in from the west. Dry weather and good vsby. Southeast swells of 3-6 ft from Gaston persist. Outlook /Tuesday through Friday/... Tuesday...High confidence. Light N-NE winds shift to SE during the day. May see briefly reduced visibilities late Tue night in patchy fog on the nearshore waters. S-SE swells from Hurricane Gaston continue on the outer waters. Small craft advisories may need to be continued for some 5 ft seas...will evaluate in subsequent forecasts. Wednesday...Moderate to high confidence. SW winds increase, with gusts up to 20 kt mainly across the eastern waters where seas will increase to around 5 ft. Local visibility restrictions in scattered showers/thunderstorms may approach the eastern waters Wednesday afternoon. Wednesday night-Thursday...Moderate confidence. A cold front crosses the waters with scattered showers/thunderstorms Wednesday night into early Thursday morning. A few showers may linger through midday across the southern waters. Winds shift from SW to W-NW by Thursday morning, then N-NE on the eastern waters Thursday afternoon. Seas will be diminishing to 3 to 4 ft. Friday...High confidence. North or north-northwest winds at 15 to 20 kt with seas between 3 and 5 ft. A marginal small craft advisory is not out of the question, especially for the outer waters. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 2 AM Monday to 8 AM EDT Tuesday for ANZ250. Small Craft Advisory from 6 AM Monday to 8 AM EDT Tuesday for ANZ254. Small Craft Advisory from noon Monday to 8 AM EDT Tuesday for ANZ255-256. && $$ SYNOPSIS...Nocera/GAF NEAR TERM...Belk/Nocera/GAF SHORT TERM...Nocera LONG TERM...GAF AVIATION...Belk/Nocera/GAF MARINE...Nocera/GAF is the U.S. government's official web portal to all federal, state and local government web resources and services.