Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 220807 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 407 AM EDT Sat Jul 22 2017 .SYNOPSIS...
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Dry, hot weather today with lower humidity. High pressure from Canada builds over northern New England Sunday, then moves off to the east. Several waves of low pressure will pass to the south of southern New England Saturday night and Sunday. It will be cooler in eastern sections Sunday but still warm in the Connecticut Valley. A couple waves of low pressure will bring some showers at times along with cooler than normal temperatures Sunday night through Tuesday. Temperatures will moderate a bit by mid to late next week, but still remain below normal with another chance for some showers Thursday and/or Thursday night.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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405 AM update... Dew point front progressing southward across CT/northern RI per surface observations (61 at BDL but still 69 at IJD) and on Doppler radar. 925 mb jet now exiting southeast MA. Showers out ahead of these features extended from Long Island eastward across Block Island. The HRRR forecasts these to move rapidly east-southeast and exit the waters south of Nantucket by 12Z. Today will be dry but still hot. 925 mb temps of +22C should yield highs in the upper 80s to lower 90s. This could be the 5th day of the heat wave at BDL. We are watching a solid area of mid level cloudiness covering western and central New York state. Mid and high cloudiness is forecast to increase over southern New England this morning and afternoon, but as is often the case in the summertime, it is likely to erode after sunrise. Satellite imagery already showing some signs of the leading edge eroding. With enough filtered sunshine, we should still hit the upper 80s/loweA couple waves of low pressure will bring some showers at times along with cooler than normal temperatures Sunday night through Tuesday. Temperatures will moderate a bit by mid to late next week, but still remain below normal with another chance for some showers Thursday and/or Thursday night.r 90s away from the coast. Winds will be diminishing along the eastern MA and RI coasts early this morning and thus expect onshore sea breezes to take hold late this morning and early this afternoon. Although the atmosphere is dry, K and TQ indices rise to 28 and 17, respectively late in the afternoon in northeast MA. Although most shower activity should remain to our northwest, have introduced a slight chance of a shower in the Merrimack Valley of northeast MA.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
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Tonight... Southern New England will be in between sprawling high pressure over southeast Canada and northernmost New England...and low pressure somewhere along the Mid-Atlantic coast from NJ to DelMarva. The low to our south will likely be the remnants of a mesoscale convective system affecting that area late this afternoon and tonight. For us, winds will turn to a northeasterly direction. Skies will be cloudy and there is a chance of showers, mainly over northern CT, RI, and southeast MA, closer to the low pressure. Lows in the 60s. Sunday... A bit of a tricky forecast. Low pressure will continue passing southeast of the region. It may cause scattered showers mainly along the south coast in the morning. But then we should see a period of increasing sunshine during the late morning through mid afternoon. Light easterly wind flow will keep eastern MA temperatures cool...in the mid 70s near the coast, but the partial sunshine could allow the CT River Valley to soar well into the 80s. ECMWF would suggest 88 degrees but model consensus is much lower. Have bumped temperatures above the consensus, to the mid 80s in that region. Late Sunday afternoon, chances of showers increase again, mainly in northern CT and western MA, ahead of advancing low pressure.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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Highlights... * Sun night/Mon: Below normal temps with some showers likely at times * Tue: A few leftover showers possible w/below normal temps * Temps moderate mid to late next week but still below average * Another round of showers possible Thu/Thu night but not a washout Details... Sunday night and Monday... A complex forecast as another MCS will likely pass well to our southwest Sun night towards the axis of greatest instability. While we should not be directly impacted by that complex, impressive shortwave trough will approach from the Great Lakes. This should increase the forcing for ascent resulting in showers at times Sunday night/Mon, but specific timing uncertain at this point. Severe weather threat looks quite low across our region given lack of surface instability, but some isolated thunderstorms can not be ruled out with a bit of elevated instability. High temps on Monday should be rather cool for July standards. Northeast surface winds and an abundance of clouds should keep highs mainly in the 70s. In fact, it is possible a few locations struggle to break 70. Tuesday... Models indicate that the best synoptic forcing will have exited the region, but low clouds and moist northeast flow may persist. May end up with just a few leftover spot showers, but an abundance of clouds with another day of below normal temps. Highs again mainly in the 70s and it is possible that a few locations struggle to break 70. Wednesday through Friday... A long way off so this is certainly subject to change. Based on latest model data though, initial upper trough lifts out by Wednesday as a ridge of high pressure builds across the region. This should allow for dry weather on Wed. However, another impressive shortwave trough may bring a period of showers/isolated thunderstorms Thu/Thu night with perhaps dry weather returning by Friday. Temps should moderate some from earlier in the week, but this next trough will likely keep readings below normal through the end of the work week.
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&& .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
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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 Sunday/...High confidence. Today...VFR. Increasing mid and high level cloudiness. Onshore sea breezes at the coast. Slight chance of a shower near Nantucket around sunrise. Tonight...VFR. Mainly mid-high clouds. Could see lowering toward low-end VFR overnight. Local IFR ceilings in areas of fog possible on the south coast, mainly Cape Cod and the Islands. Chance of showers late, mainly in CT/RI/SE MA. Wind becoming NE and gusting to near 20 kt over the eastern MA coast well after midnight. Sunday...VFR except IFR/MVFR southeast MA and southern RI in the morning. Scattered showers southeast MA and RI in the morning and in western MA and northern CT late in the afternoon. KBOS Terminal...VFR. Sea-breezes forecast around 15z today. KBDL Terminal...VFR. Outlook /Sunday Night through Wednesday/... Moderate confidence. Sunday night through Tuesday...Moderate confidence. VFR conditions early Sunday evening should deteriorate to MVFR-IFR later Sun night into Mon morning from west to east in some showers, low clouds and fog patches. MVFR-IFR conditions will likely persist the rest of Monday and possibly into part of Tuesday. Wednesday...Moderate confidence. Mainly VFR conditions expected.
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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 Sunday/...High confidence. Today...Light northwest winds allowing for daytime sea breezes. Winds becoming south over the eastern MA waters this afternoon/evening. Seas 1-3 ft. Tonight...Winds shifting to the northeast as high pressure builds to our north and low pressure passes to our south. Winds gust to 20 kt, especially from Cape Ann to Mass Bay and Provincetown. Chance of showers late. Local visibilities reduced to 1-3 miles in fog late. Seas 1-3 ft. Sunday...Northeast winds continue at 15-20 kt with seas building to 3-4 ft. Chance of showers, especially south coast in the morning. Outlook /Sunday Night through Wednesday/... Moderate confidence. Sunday night through Tuesday...Moderate to high confidence. A couple waves of low pressure tracking near or south of our waters will generate an persistent east to northeast winds. The result should be marginal small craft conditions at times across our eastern waters, where wind gusts of 20 to 25 knots and 3 to 6 foot seas are expected. Some showers and fog patches will also reduce vsbys for mariners at times. Wednesday...Moderate to high confidence. Ridge of high pressure temporarily builds across the waters which should keep winds/seas below small craft thresholds.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Field/Frank NEAR TERM...Field SHORT TERM...Field LONG TERM...Frank AVIATION...Field/Frank MARINE...Field/Frank

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