Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 170223 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1023 PM EDT Sun Jul 16 2017 .SYNOPSIS... Typical summer pattern for the workweek ahead with warm and humid conditions along with a low risk of scattered afternoon thunderstorms each day. However by no means a washout with many hours of dry weather. A cold front approaches Thursday, which looks to slowly push across during Friday. Behind this front, not as hot or humid late in the week into early next weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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Satellite images show patches of cirrus clouds over the CT River Valley moving east. Also signs of fog/stratus east and southeast of Nantucket. High pressure over the region shift offshore. Expect rain-free weather overnight...hard to call it dry since dew points will be in the low to mid 60s. Fog and low clouds will work into Nantucket and possibly parts of Cape Cod. With dew points in the low to mid 60s, expect min temps in the 60s.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Monday... closed mid level low along the Ontario/Quebec border moves slowly eastward. This yields cyclonic mid level flow across southern New England. However the closed low is deamplifying with time along with the western Atlantic ridge building northwest into southern New England. So despite the cyclonic flow over the area mid level heights are rising. This will provide a weak cap across the region with the best chance of breaking the mid level cap across northwest MA into VT/NY state where temps aloft will be cooler along with stronger jet dynamics. Therefore greatest risk for scattered afternoon T-storms will be over northwest MA, with an isolated strong storm possible. Otherwise the remainder of the region should remain dry with typical summer-like conditions, highs in the 80s and dew pts in the 60s. Monday night... Warm and muggy night with dew pts well into the 60s to near 70. Moist mid level cyclonic flow continues so can`t rule out the risk for a few showers or isolated T-storm. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Highlights... * Threat for scattered showers and thunderstorms at times through Wednesday * Better chance for showers/thunderstorms Thursday into Friday morning along a slow-moving front Overview... 16/12Z model suite remains fairly consistent through much of this portion of the forecast, with good run-to-run consistency, too. Bigger differences develop toward next weekend. Will continue to favor a consensus approach as the basis for the forecast. Nearly zonal flow mid week should transition to another mid level trough late this week. Its the timing of this trough which is the greatest difference in the guidance suite, with most of the medium range guidance agreeing on the overall amplitude. Details... Tuesday... A weak cold front will slowly push east towards New England. High dewpoints should remain in place, which will help to trigger scattered showers and thunderstorms during the late morning and afternoon. Could see some locally heavy rainfall in any shower or thunderstorm activity. Wednesday and Thursday... High humidity continues through this portion of the forecast. Typical summer-like weather, featuring at least a low risk for scattered showers and isolated thunderstorms. Only have a weak surface trough Wednesday to supply additional lift and focus, with a slow-moving cold front Thursday. Thus, expecting the greater rainfall chances to be on Thursday. Thursday night through Sunday... Model solutions diverge during this period, leading to lower confidence. As mentioned for a few days now, the timing of a slow-moving cold front is the issue. Drier and somewhat less humid conditions forecast for Saturday and Sunday at this point. && .AVIATION /02Z MONDAY THROUGH FRIDAY/...
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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 Monday Night/... Tonight... VFR to start but areas of IFR-MVFR in patchy fog. Otherwise dry weather prevails. Will have to watch the south coast overnight, where its is possible more LIFR status develops. Nantucket most at risk. Monday...moderate confidence. Any early morning MVFR-IFR in patchy fog will burn off by 14z- 15z and give way to VFR and dry weather. The only exception is across northwest MA where afternoon T-storms are possible in MVFR conditions, an isolated strong T-storm possible. Monday night...low confidence. MVFR-IFR in areas of fog especially along the coast. Isolated shower possible. KBOS Terminal...South winds tonight becomes SE in a sea breeze Monday late morning. Dry weather prevails. High confidence in TAF. KBDL Terminal...High confidence in TAF. VFR, except a period of MVFR later tonight in patchy fog. Fog possible again Mon night. Outlook /Tuesday through Friday/... Tuesday...Moderate confidence. Any lower CIGS/VSBYS should improve to VFR by mid morning Tuesday. May see local MVFR conditions in scattered late morning and afternoon SHRA/TSRA. Tuesday night through Friday...Moderate confidence. Mainly VFR. Patchy fog possible at the typically prone locations each night, resulting in brief MVFR-IFR conditions. Should see SCT-BKN low- end VFR CIGS with a chance risk for scattered SHRA/isolated TSRA during the afternoon and evening hours, especially Thursday.
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&& .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. Light S-SE winds continue thru Mon night along with tranquil seas. Low risk of patchy fog late tonight/early Mon but highest risk is Mon night with fog possibly widespread and vsbys less than a mile. Also best chance of showers/T-storms Mon night northern MA waters. Outlook /Tuesday through Friday/...Moderate confidence. Winds and seas remain below Small Craft Advisory levels through this portion of the forecast. Scattered showers or thunderstorms may develop at any time Tuesday through Thursday, with reduced visibilities in locally heavy downpours, but more likely nearshore during the afternoon and evening hours. Patchy fog during the late night/early morning hours each day with local reduced visibilities && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/Belk/Nocera NEAR TERM...WTB/Belk/Nocera SHORT TERM...Nocera LONG TERM...Belk AVIATION...Belk/Nocera MARINE...WTB/Belk/Nocera

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