Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 151336 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 936 AM EDT Sun Oct 15 2017 .SYNOPSIS...
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Skies gradually become partly sunny in most locations by mid afternoon, resulting in an unseasonably warm afternoon. A sharp cold front sweeps across the region tonight and will be accompanied by scattered showers into Monday morning. Behind the front it turns sharply cooler and brisk Monday afternoon with temperatures dropping down close to freezing into Tuesday morning. Gradual warm-up Wednesday followed by highs in the 70s Thursday into next weekend along with dry weather.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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935 am update... Still an abundance of low clouds across the region at late morning, but satellite imagery was showing a few breaks developing. Still a tricky forecast on how quickly these low clouds persist, but expect partly sunny skies to emerge across most of the region by mid afternoon. Low clouds may linger longer though near the south coast, given the moist onshore flow. Once partial sunshine develops, southwest low level jet of 35 to 40 knots and 850T around +16C should yield mid to late afternoon high temps in the middle to upper 70s in many locations. Readings will be a bit cooler on the south coast with a marine influence and clouds persisting a bit longer. Warming surface temps and low level jet should yield southwest wind gusts of 25 to 35 mph developing by mid to late afternoon but a few gusts up to 40 mph can not be ruled out. These winds may take a bit edge of the humidity, since dewpoints will be in the lower to middle 60s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... Tonight... Strengthening low pressure system over the Great Lakes crosses southern Quebec and northern New England. Associated cold front will push SE across the region through the overnight hours. Area of showers associated with the front tends to weaken as the front moves across as best lift and moisture shifts NE. Could still see some scattered showers mainly across central and western areas through midnight or so, becoming spotty as the front shifts across. Some question whether some wind gusts may push across portions of the interior, especially over the higher terrain, as the front passes as a secondary low level jet approaches. Noting some potential gusts up to 35 kt or so across the higher terrain of the Berkshires and possibly as far W as the Worcester hills around or after midnight. Good cold air advection as H925 temps drop quickly around or after 06Z. Readings in the lower- mid 60s this evening across the higher inland terrain may fall back to the upper 40s by 09Z-10Z. Will need to monitor potential for even higher gusts as the cold air wraps in behind the front. Expect lows by Mon morning ranging from the mid-upper 40s across the higher terrain to the lower 60s along the coastal plain. && .LONG TERM /MONDAY THROUGH SATURDAY/... * Highlights... - Chilly Monday and Tuesday - Gradual warming begins Wed then 70s Thu into next weekend - Extended dry stretch of weather Mon afternoon into next weekend * Synoptic Overview... Ensembles from both the GFS and EC in good agreement that a series of northern stream short waves will temporarily erode the subtropical ridge over currently over the southeast states. The core of the coldest air arrives Mon night into Tue associated with trailing/secondary short wave energy. Then a gradual warming trend starts mid week as heights begin to rise behind departing northern stream short wave. By Thu the subtropical ridge reemerges over the southeast states and peaks at 591 dam into the weekend. This pattern will support a prolong period of dry weather across southern New England along with temps warming into the 70s Thu into next weekend! * Daily Details... Monday and Tuesday... Could be some leftover showers over southeast MA Monday morning associated with departing cold front, otherwise deep layer dry air invades the area from the northwest. Model time sections reveal post frontal strato-cu likely to develop so a mix of sun and clouds for the afternoon. Noticeable cool down behind the front with 925 mb temps falling to about +7C 18z Mon, supporting afternoon temps in the upper 50s, few degs cooler than normal. Although it will feel cool with NW winds up to 25 mph at times. Strong short wave trough moves across the area late in the day/evening. However not much moisture with this feature so not expecting much fanfare other than a reinforcing surge of cool air. This CAA (-4C at 850 mb, -1 SD) combined with light low level NNW drainage flow temps will tumble into the 30s regionwide, except low 40s downtown Boston. Given this setup leaned toward the coldest MOS guidance. Will likely eventually need frost/freeze headlines. Tuesday, temps only recover into the mid and upper 50s, a few degs cooler than normal with avg highs for mid Oct 59-64 degs. Although light winds and mostly sunny conditions will help offset the cool temps. Wednesday... Will be our transition day toward milder weather as the high shifts south of New England and low level WAA commences with 925 mb temps jumping from +4C Tue afternoon to +12C Wed afternoon. Blyr will be shallow given 1024 mb surface pressure but full sun and WSW winds will support highs 65-70, about 5 degs warmer than normal. Thu/Fri/Sat... 00z ECENS and GEFS both suggest warming trend continues Thu ahead of an approaching northern stream short wave. Then brief cool down Fri before warming trend returns next weekend as subtropical ridge reemerges over the southeast states into the Mid Atlc region. Not expecting any precip in this pattern. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/...Moderate confidence. Today... LIFR/IFR conditions still quite prevalent across the region late this morning, mainly in lower clouds. Should see gradual improvement into mid afternoon with most locations improving to MVFR to even VFR levels. IFR conditions may linger near the south coast or just offshore through the afternoon. Southwest wind gusts of 25 to 30 knots expected to develop by mid-late afternoon with a few gusts up to 35 knots not out of the question. Tonight... MVFR-IFR CIGS along the S coast. Lesser VSBY impact with continued S-SW winds up to 25-30 kt through 04Z before diminishing as cold front passes. Winds may gust up to around 30 kt or so as they shift to W-NW. Conditions improve to VFR. A few -SHRA possible prior to the wind shift. KBOS TAF...Moderate confidence in TAF. Improvement to MVFR with perhaps VFR by mid afternoon. KBDL TAF...Moderate confidence in TAF. Improvement to MVFR with perhaps VFR by mid afternoon. Outlook /Monday through Thursday/...Moderate confidence. Monday...High confidence. Possible MVFR-IFR in morning showers over southeast MA including Cape Cod and Islands. Then improving to VFR by mid morning. Elsewhere VFR in the morning then marginal MVFR-VFR in afternoon post frontal strato-cu. NNW winds gusting up to 25 kt. Tuesday through Thursday...High confidence. VFR, dry weather and light to modest winds.
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&& .MARINE...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/... Today...Moderate to high confidence. Warm front moves N of the waters this morning, then S-SW winds increase with gusts up to 25-30 kt this afternoon, highest across the near shore and eastern outer waters. Seas will also build. Small Crafts continue for all waters. Areas of dense fog with poor visibility through mid morning or so, then should improve with increasing wind and milder air. Tonight...Moderate confidence. SW wind gusts ahead of the cold front will continue to gust up to 25-30 kt through this evening, then will start to diminish on the near shore waters as the front approaches. Low probability of gale force gusts on the outer waters prior to frontal passage after 06Z. Outlook /Monday through Thursday/...Moderate confidence. Monday... Cold front sweeps across the waters during the morning hours and may be accompanied by scattered showers and patchy fog. Behind the front (by mid morning) NNW winds 15-20 kt with gusts possibly up to 25 kt. Tuesday thru Thursday... High pressure shifts south of New England with winds becoming WSW. Dry weather and good vsby expected.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 1 PM this afternoon to 8 AM EDT Monday for ANZ231>235-237. Small Craft Advisory from 1 PM this afternoon to 5 AM EDT Monday for ANZ230-236. Small Craft Advisory until 9 AM EDT Monday for ANZ250. Small Craft Advisory from 1 PM this afternoon to 6 AM EDT Monday for ANZ251. Small Craft Advisory until 6 AM EDT Monday for ANZ254>256.
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&& $$ SYNOPSIS...Frank/Nocera/EVT NEAR TERM...Frank SHORT TERM...EVT LONG TERM...Nocera AVIATION...Frank/Nocera/EVT MARINE...Nocera/EVT

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