Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 270636 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 236 AM EDT SAT AUG 27 2016 .SYNOPSIS...
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High pressure builds over Northern New England, bringing dry weather for much of this weekend. There is the chance of showers and thunderstorms Sunday into Monday ahead of a sweeping cold front. A brief period of high pressure follows for Tuesday prior to another cold front for Wednesday with another chance of wet weather. Low confidence forecast from Thursday onward as competing airmasses present the double-sided possibility of either wet weather or remaining completely dry.
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&& .NEAR TERM /THROUGH TODAY/...
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Cold front had finally moved past Nantucket around 2 AM, and will continue to slowly move offshore the rest of today. Meanwhile, high pressure will move east across southeast Canada. Dew points around 60 degrees will be more common today, which is about a 10 degree drop from Friday. Max temperatures will be a little, too. The lower temperatures will be more noticable toward the coasts, where seabreezes will develop later this morning.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/...
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The center of the high pressure shifts east tonight into Sunday. Expecting mainly clear skies and light winds to prevail through this portion of the forecast. Once the high pressure reaches the Maritimes late Sunday, there is a small possibility for a mid level shortwave to bring isolated showers to northwest MA late in the day. Temperatures expected to be slightly above normal, despite seabreezes along both coasts Sunday.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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*/ Highlights... - Shower and Thunderstorm chances Sunday Night into Monday - Keeping it dry for Tuesday - Another cold front and chances of wet weather for Wednesday - Low confidence forecast from Thursday onward - Keeping Invest-99L out of the picture and out to sea */ Discussion... Interpreting the N Hemispheric pattern. Atmospheric teleconnections continuing a -WPO/-EPO trend through the beginning of September with a waffling PNA. Of certainty, we`re seeing a buckling in the height pattern across the N Pacific in concert with a -WPO/-EPO yielding a high latitude block and stronger than normal Pacific jet within the deepening troughs. Given the PNA trend, there is no clear signal as to outcomes downstream. Nevertheless, during -EPO/-WPO trends it is noted that anomalous cyclonic circulations can occur over E portions of N America, drawing cooler air S. So while the late-August early- September cyclone in vicinity of the NE CONUS per deterministic guidance may seem erroneous, it can not entirely be rule out. Will for the sake of simplicity keep with an ensemble-weighted forecast. Inclined to believe per ensemble members and deterministic forecasts that at this point whatever becomes of Invest-99L (AL99) will sweep out N/E ahead of preferred troughing prior to and during the Labor Day Holiday Weekend. So will lean with the following forecast: Sunday Night into Monday a deamplifying disturbance which will introduce lower heights and cyclonic flow, a slight kink to the near-zonal flow. Surface cold frontal feature, there is the chance of showers and thunderstorms. Prefer to keep it dry for Tuesday. Another cold front for Wednesday and the chance of showers and thunderstorms. Thursday and Friday remain up in the air. If a deep cyclone does develop and remains in the vicinity of the NE CONUS, then the combination of cooler air aloft and daytime heating/destabilizing boundary layer below, along with continued impulses through the cyclonic flow, could yield a setup for diurnally-forced storms. But it is possible that drier air and high pressure win out. Toss up at this point and subsequently a low confidence forecast. For Labor Day Weekend, going by ensemble means, it does appear the trough-ridge- trough pattern across the CONUS shifts subtly E thereby putting the NE CONUS at least the influence of high pressure. As to airmass depends on the preferred wind flow aloft (i.e., NW vs. SW). No threats or impacts just yet to speak of throughout the long-term forecast, as well as no end in sight with regards to current drought conditions.
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&& .AVIATION /06Z 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/... Today...High Confidence. VFR. Light north winds, with seabreezes developing along both coasts. Tonight...High Confidence. VFR. Light and variable wind. Patchy fog after midnight in the usually prone locations, mainly in the CT River Valley, with IFR/LIFR cigs/vsbys through sunrise. Sunday... VFR with winds turning S and increasing. Increasing mid and high clouds across the region, with the possibility of a few SHRA N/W late in the day. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Sunday Night through Wednesday/...Moderate Confidence. Monday... Chance of SHRA/TSRA. S/SW winds, breezy with gusts up to 20 kts, backing out of the W/NW towards Monday evening. Tuesday... Will prevail VFR with W/NW winds initially veering out of the S/SW. Anticipating increasing mid to high cloud late in the period. Wednesday... Chance of SHRA/TSRA. S/SW winds, breezy with gusts up to 20 kts, backing out of the W/NW during the evening into overnight period.
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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. Winds and seas expected to remain relatively light through Sunday. Seabreezes near shore expected both today and Sunday. Seas increase across the outer coastal waters Sunday in response to arriving southeast swell from distant Tropical Storm Gaston. Outlook /Sunday Night through Wednesday/... Monday... Chance of showers and thunderstorms, mainly over the near-shore waters. S/SW winds, breezy with gusts up to 20 kts continuing, backing out of the W/NW towards Monday evening with a cold frontal passage. Persistent wind stress plus swell associated with Gaston, will introduce 5 foot seas on the outer waters. Tuesday... W/NW winds initially, fairly benign, veering out of the S/SW through the day. Will keep it dry. Continued swell from Gaston, will keep with 5 foot seas on the outer waters. Wednesday... Another cold front and another chance of showers and thunderstorms. S/SW winds ahead of the front with gusts up to 20 kts, backing out of the W/NW into the evening and overnight period.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/Sipprell NEAR TERM...Belk SHORT TERM...Belk LONG TERM...Sipprell AVIATION...Belk/Sipprell MARINE...Belk/Sipprell

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