Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 200109 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 909 PM EDT Wed Oct 19 2016 .SYNOPSIS... Cold front settles south of the region tonight. High pressure builds across northern New England and brings us dry weather. Warm moist air moves back to the north and brings a chance of showers Thursday afternoon and night. A more widespread heavier rainfall is likely Friday into Friday night as low pressure tracks across the region. Cooler and mainly dry weather will follow Sunday into early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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910 PM update... Cold front has moved south of the coast with high pres building across northern New Eng. Skies are clear across SNE but some mid/high clouds will be moving in from the west late tonight. Forecast on track. Previous discussion... High pressure builds over New England with center over northern New England. Cool dry airmass with dew points in the 40s north of the Mass Pike and 50s to the south. The high will eventually bring low level winds around from NW to E, although nighttime speeds may be too light to notice the change during the night. The light winds will allow for some radiational cooling in the interior with min temps in the 40s north and 50s south. The low Temp/Dewpt differences may also allow areas of fog.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Thursday... High pressure moves off through the Maritimes Thursday morning. Upper flow turns from the southwest, bringing increasing mid and high clouds during the morning. Ohio Valley low pressure draws a 40-knot low level S-SW jet up through the Appalachians, but aimed at PA and NY. The eastern edge of this jet will slide into New England during the afternoon/evening, and as it rides up over the stalled front to our south it will bring increasing chance of showers, mostly to CT and Western MA. The best lift will remain along the jet axis to our west. And the upper jet will remain over the Great Lakes, so upper dynamics will also linger well to our west. The low level east winds will keep daytime temps cooler. Water temperatures in the lower 60s supports air temps Thursday in the low to mid 60s. Thursday night... Upper level shortwave will continue to dig over the Great Lakes, further slowing the eastward progress of this weather system. Models agree on the low level jet continuing to shift east with time during the night, which should increase the probability of precip in our area with highest values in the west. A cool night but with clouds keeping temps a little milder than tonight. Forecast will mostly show mins in the 50s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Highlights... * Widespread rainfall expected Friday * Warmer than normal temperatures expected Friday * Cooler, still a bit unsettled weather this weekend into next week On a broad scale, the models are in good agreement for the most part. There are some discrepancies, particularly Friday, that extend from potential tropical development in the Bahamas and surface low developing in the mid-Atlantic and how and where they develop, strengthen, and interact. The UKMET is one of the strongest and farthest south solutions, while the Canadian is one of the strongest and farthest north. The GFS and the ECMWF fall in the middle of these solutions both strength and location wise. These solutions indicate some interaction between the extra-tropical and tropical systems but keep it as mostly an introduction of some additional tropical moisture into the extratropical low. Both models show a brief period of heavier rain over some portion of the region, but differ on where exactly this area of heavier rain develops. This will be something to watch in the coming days. Bulk of the guidance indicates about an inch of widespread rainfall, with a relatively small area possibly getting up to two to three inches. Welcome rain once again, but not drought busting. Beyond the end of the work week, models are in decent agreement with the general pattern and we will see a return to more normal autumn weather. Friday and Saturday...Low pressure will intensify as it passes by southern New England to the east, possibly interacting with the above-mentioned tropical low moving up the coast. Saturday the low pressure will move northward into Maine and then Quebec. This will bring widespread rain to the region Friday and additional showers Saturday. Models are showing the higher PWAT values (tropical moisture) mainly over the eastern half of southern New England on Friday with values dropping Saturday. Thus, believe the heavier rain will occur on Friday. There is some indication of some marginal instability, so a few claps of thunder are possible, but rather unlikely. Temperatures will be warmer than normal Friday, then drop back to near normal on Saturday. In addition, Saturday, a strong pressure gradient and decent cold air advection will result in breezy conditions. Wind advisories shouldn`t be necessary based on current forecast (30-40 mph gusts) but it is something to keep an eye on. Sunday and Monday...The upper level trough slowly moves offshore and low pressure moves into the Maritimes while a few shortwaves move through southern New England. Temperatures will be a bit cooler than normal and gusty winds will likely continue through at least a portion of Sunday. Sunny skies will counter the cooler, breezy conditions somewhat but it will definitely feel like typical October out there. The shortwaves moving through may bring a few showers to the area as well, but nothing as widespread as Friday. Tuesday and Wednesday...High pressure starts building into southern New England bringing cooler, dry weather, particularly on Tuesday. Temperatures will be 5-10 degrees below normal Tuesday, cool enough to possibly induce some ocean effect clouds and showers on the Cape and Islands. Temperatures will return to near normal Wednesday. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday Night/... Tonight...High confidence. Mainly VFR. Low confidence on potential for fog formation after midnight. The best chance will be in the CT Valley. Thursday...High confidence. VFR through mid afternoon with patches of MVFR cigs toward evening in the south and west. Thursday night...Moderate to High confidence. Developing MVFR cigs/vsbys in showers early night. Mixed MVFR/IFR cigs and vsbys in showers and fog overnight. South winds of 40 knots will move in at 2000 feet AGL over Western MA and CT late at night and may contribute to some low level wind shear in those areas. East winds at the surface, South-Southwest winds above 2000 feet. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Friday through Monday/... Friday...Moderate confidence. MVFR/IFR in low clouds, rain, and fog at times. Saturday...Moderate confidence. A mix of conditions in scattered showers. Westerly winds increase, gusting to 25 to 30 kts. Sunday...High confidence. VFR. Gusty NW winds continue but will diminish slowly. Monday...Moderate confidence. Mainly VFR. Low confidence in periods of MVFR in SCT -SHRA. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday Night/...Moderate-High confidence. Tonight...Cold front stalls over the southern waters tonight. Winds will remain less than 20 knots. Still a couple reports on the Southern Outer Waters for 5 foot seas, most of it in a SW swell. But waves and swell are both diminishing so we will allow the SCA on the Southern Outer waters to expire. Northeast winds start to increase again late tonight with gusts to 20 knots. Thursday and Thursday night...East winds during the day will turn Southeast Thursday night as a warm front moves north. Wind speeds will remain below 25 knots. Seas will build, especially Thursday night, with heights reaching 5-6 feet on the outer waters Thursday night. A Small Craft Advisory may be needed for those seas. Outlook /Friday through Monday/... Friday...Moderate confidence. Seas and winds increase as low pressure moves along the eastern New England coast. In addition, a potential tropical or sub-tropical low may move up the coast and work in tandem with the low over southern New England. This potential interaction is what keeps our confidence in the moderate range. Especially with wind direction. Small craft advisories will likely be necessary for most of the waters. Saturday and Sunday...High confidence. Small craft advisory conditions will continue with a tight pressure gradient between the departing low pressure system and building high pressure in the Great Lakes. Westerly winds will shift to the northwest on Sunday. Low probability of a period of gale force winds during this time. Monday...Moderate confidence. Marginal small craft advisory conditions occur, mainly on the outer waters as pressure gradient starts to slacken a bit. && .TIDES/COASTAL FLOODING... Astronomical high tides are subsiding with each tidal cycle. There may still be one or two high tides Thursday and Friday that threaten minor splashover at the more vulnerable spots on the coastline, but the general trend is now moving away from that. && .CLIMATE... Record High Temperatures: Wednesday October 19th Boston 84 in 1945 Worcester 81 in 1963 Providence 81 in 1945 Hartford 82 in 1963 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/RLG NEAR TERM...WTB/KJC SHORT TERM...WTB LONG TERM...RLG AVIATION...WTB/RLG MARINE...WTB/RLG TIDES/COASTAL FLOODING... CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.