Area Forecast Discussion
Issued by NWS Portland, ME

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030 FXUS61 KGYX 301930 AFDGYX Area Forecast Discussion National Weather Service Gray ME 330 PM EDT Fri Sep 30 2016 .SYNOPSIS...
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An upper level low pressure will slowly meander across the Northeast through the weekend. Showers will move into New Hampshire and eventually western Maine this evening and overnight as the low drifts closer. The low moves overhead on Sunday and cross the region on Monday brining more scattered showers. High pressure will build in for the middle of next week.
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&& .NEAR TERM /TONIGHT/...
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Strong high pressure remains branched across Srn Canada this afternoon. This is holding dry air in place across much of the forecast area...allowing clouds to repeatedly break up as they move N. This has also been holding precip back thru the day. Showers and areas of RA will steadily move N into Srn NH this evening...reaching parts of Wrn ME near midnight. Given the dry antecedent air...I do not expect precip to be all that heavy. Precip will be most likely for Srn NH...and highest amounts should stay under a half inch.
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&& .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
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Early Sat the remaining band of showers will continue crossing the Nrn parts of the forecast area as forcing lifts N. Sly flow aloft will continue the WAA...and as a result I do not want to eliminate the chance for showers as warm air rides over the low level colder air. With the cool...dry high to the N and precip falling into the column...we should see a fair cold air damming signature on Sat. I undercut the high temp guidance...especially across the favored middle part of the forecast area. A secondary s/wv trof moves N later Sat...and could increase coverage of showers a bit. I have PoP likely along the coast...but keep it chance or lower across the interior. Upper lows are notoriously tricky for model guidance...and typically see more dry wx than not...so I do not want to overdo it with likely or higher PoP. So I will play it as two time periods of increased chances...early Sat and late Sat.
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&& .LONG TERM /SUNDAY THROUGH THURSDAY/...
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High Impact Weather: Low Overview: An upper level closed low will slowly move out of the midwest and cross New England early next week as it weakens brining some rain to start the week. High pressure will build in through the middle of the week. Sunday: Sunday the last of the weak ridging will decay as the upper low moves eastward out of the great lakes. Skies will be cloudy as upper level moisture moves in. Along the coast...the flow continues to have a slight onshore component. The moisture doesn`t look quite deep enough to support widespread drizzle, but expect higher pops and some low clouds hugging the immediate coastline. Monday: Monday the upper level low will cross the region. This will bring scattered showers, initially starting in the southwest and gradually spreading out across the region. While most areas will see some rain through the day the amounts won`t be much. Cold temperatures aloft will help to enhance the shower activity, and a few bits of graupel mixing in are possible. Tuesday- Wednesday: High pressure will move into the region for Wednesday and Tuesday. Once again northeast flow will set up parallel to the coast which should keep most of the region sunny.... All but the midcoast peninsulas and islands where the slight onshore component will lead to some low clouds over the Gulf of Maine. Temperatures will remain seasonable with highs in the 60s and lows in the 40s. Thursday and beyond: The end of week is a very low confidence forecast at this point. At 500mb we have the ridge which built in at the start of the week starting to progress eastward while in the western CONUS a trough strengthens. Model solutions differ quite a bit in how quickly they allow that upper level progression. In all longer term scenarios persistence and blocking tend to win out over any fast progression.. so I would tend to favor the slower ECMWF solution over the GFS. Nevertheless both ensembles have a wide variety of solutions. This upper level pattern will be watched closely over the next several days as how it sets up will determine what happens to Hurricane Matthew after it turns northward next week and begins to interact with the mid latitudes. This entire scenario is still 6+ days away and really beyond the time in which any confidence can be assigned to specific predictions.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
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Short Term...A BKN MVFR deck remains more or less stationary across Srn NH. As moisture continues N this evening this deck should gradually fill in and lift N. I expect widespread MVFR tonight S of the mtns. SHRA and some areas of -RA will move S to N across the Srn half of the forecast area tonight. MHT...PSM...CON...LEB and PWM are most likely to see precip before dawn. Some local IFR conditions are possible near the coast tonight. SHRA become a little more scattered Sat...but MVFR conditions should linger for most terminals into the day. Long Term... Low ceilings and IFR conditions possible for RKD PWM and PSM Sunday in onshore flow. Monday showers will bring periods of MVFR to the entire region. VFR returns for Tuesday.
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&& .MARINE...
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Short Term...Seas remain above 5 ft S of Port Clyde. SCA will remain in effect thru tonight as NE flow continues this swell. Seas may diminish slightly late tonight...only to build again tomorrow as low pressure moves closer. Will keep the SCA going for winds and seas...as gusts will be near 25 kts. It is possible Sat afternoon that winds and seas increase enough to bring all zones into a SCA. Long Term...Northeast flow will continue through Sunday but remain below sca. Winds and seas will be calm through mid week as high pressure builds in.
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&& .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ150- 152. Small Craft Advisory until 6 AM EDT Saturday for ANZ154. && $$ NEAR TERM...Legro SHORT TERM...Legro LONG TERM...Curtis AVIATION...Curtis/Legro MARINE...Curtis/Legro

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