Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 220802 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 402 AM EDT WED JUN 22 2016 .SYNOPSIS...
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Seasonable temperatures are expected for tomorrow with a few showers possible. Low pressure passes just south of New England Thursday, bringing showers and cooler temperatures. High pressure builds over the region Friday through Monday bringing a spell of dry weather. An approaching cold front may bring showers by Tuesday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1045 PM Update... While the cold front ever so slowly shifts S this evening, scattered showers developed from the far northern fringe of convection that moved off the N NJ coast. These showers have tracked across the southern waters, including the south shore of the lower and mid Cape, Nantucket and Martha`s Vineyard over the last few hours. Lightning has remained well S of the Islands, though have noted a couple of C/G strokes well E of Nantucket since 02Z. Also noting light patchy fog across the outer Cape and Nantucket, as well as some haze that was reported early this evening by the Nantucket and Vineyard ferry boats. Expect continued low temp/dewpt spreads across the Cape and Islands, so should see low clouds and fog develop overnight. May see some fog also develop around or after 08Z along S coastal areas, but should be brief there. Elsewhere, will see mainly clear skies with diminishing winds as a weak ridge crosses. Have adjusted temps along the S coast a bit with the low temp/dewpt spreads, otherwise appears they are in good shape. Have updated the near term forecast to bring conditions current. Previous discussion... The front will be slow to move offshore with a slow decrease in dewpoints over Cape Cod and especially the islands. As the boundary layer cools, this will set up favorable conditions for areas of fog to develop over the south coastal waters and the adjacent islands. Otherwise, expect a pleasant night with comfortably dry air and diminishing winds which will allow low temps to drop into the 50s most locations. The low dewpoints should preclude fog development outside of the islands. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... WEDNESDAY... Very potent shortwave will move through the region. This wave combined with cold pool aloft will yield to diurnal showers. Highest coverage will be across route 2, which is closer to the better dynamics, with more scattered showers north of the Mass Pike. Some instability will develop which could trigger a few isolated thunderstorms, but the better chance will be north of the region where the temps aloft are cooler. Shortwave will already be moving out of the region by 18z so any precip will be confined to the morning to early afternoon hours. Appears a pleasant afternoon is on tap for the region with clearing skies and temps warming into the mid to upper 70s. A few spots reaching into the 80s. Dewpoints will remain in the mid 40s to low 50s, very comfortable! WEDNESDAY NIGHT... Weak ridging will build into the region as heights aloft rise. Anticipate a mostly dry night with high level clouds overspreading ahead of the next weather system. Temperatures will remain in the low to mid 50s. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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Big Picture... Longwave scale shows a persistant trough in Eastern North America and ridge over the West. Shortwave scale shows high pressure building over New England Friday and slipping east over the weekend. A shortwave originating over the Pacific Northwest approaches through the Great Lakes Monday and Tuesday. The upper trough suggests temps Friday a little below seasonable. But with a building ridge aloft and a developing Southwest flow at the surface over the weekend temps should trend to warmer than normal. Model forecast mass fields are similar through the weekend, then diverge a little early next week. This encourages confidence in the forecast through the weekend, then somewhat lower confidence Monday and Tuesday. Details... Thursday night through Monday...Moderate to High confidence. Offshore low pressure moves off to the east and high pressure builds in at the surface. This should bring drier air to the region and a clearing trend. Light flow on Friday suggests afternoon sea breezes on all coasts. As the high shifts east Saturday the pattern becomes less favorable, but the flow remains light and so sea breezes are still possible. By Sunday the high is well offshore and flow over New England is more southwest. Temps aloft at 10-13C Friday climb to 13-16C Saturday and 16-18C Sunday and Monday. Max surface temps should climb through the 80s during this period with low 90s possible in the warmer places especially on Sunday and Monday. Monday night-Tuesday...Low to Moderate confidence. Upper shortwave approaches, driving a surface cold front toward New England. Models show some difference in timing of these features with the GFS faster than the ECMWF. The GFS brings measureable pcpn into Western and Central sections late Monday night while the ECMWF loses pcpn Monday night and then redevelops it over New York Tuesday. We will feature slight chance pops west of Worcester late Monday night and chance pops Tuesday.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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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 Thursday/... Overnight...High Confidence. VFR through the period. IFR CIGS/VSBYS in low stratus/fog likely developing over the outer Cape and KACK. Wednesday...Moderate Confidence. Scattered showers during the first half of the day with a low risk for thunder. Mainly VFR conditions through the period. Wednesday night...High Confidence. VFR. KBOS TAF...High confidence. VFR. Low risk for -TSRA early Wed afternoon. KBDL TAF...High confidence. VFR. Outlook /Thursday night through Sunday/... Moderate to High confidence. Thursday night... Any low cigs/vsbys from Thursday will improve to VFR during the night. Areas of IFR in fog after midnight especially in the CT Valley and the normal fog spots. Friday through Sunday... VFR. Sea Breezes likely, especially Friday.
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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 Thursday/...High confidence. Weak cold front will push through the waters tonight switching the winds to a more westerly directions. Seas and winds will relax this evening and into tonight so have dropped SCA. Showers and isold thunder possible across the eastern waters Wednesday afternoon. Otherwise building southerly swell on Wednesday will result in seas reaching 5-6 feet. Issued a SCA for seas where confidence was highest that this would occur. Seas will begin to relax by Wednesday night. Outlook /Thursday night through Sunday/... Moderate confidence. Winds remain below 25 knots and seas below 5 feet through the period. The southern waters may experience a 4 foot swell Friday. Local sea breezes expected Friday, possible Saturday.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory for hazardous seas until 11 AM EDT Thursday for ANZ254>256. Small Craft Advisory for hazardous seas from 2 PM this afternoon to 5 AM EDT Thursday for ANZ235-237.
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&& $$ SYNOPSIS...WTB/Dunten NEAR TERM...KJC/EVT SHORT TERM...Dunten LONG TERM...WTB AVIATION...WTB/Dunten/EVT MARINE...WTB/Dunten/EVT

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