Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 180811 AFDGYX Area Forecast Discussion National Weather Service Gray ME 411 AM EDT Mon Mar 18 2024 .SYNOPSIS...
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Cyclonic flow this week promotes breezy west-northwest flow, temperatures trending cooler toward seasonal averages, and light snow and rain showers driven by instability. Showers will be mostly confined to the mountains, however, a quick-hitting clipper will likely bring more widespread showers all the way to the coast Wednesday into Thursday. Cool high pressure returns late in the week, with a low potential for another system this weekend.
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&& .NEAR TERM /TODAY/...
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Low pressure over the Gulf of Saint Lawrence and high pressure over the nation`s Heartland keeps cyclonic, westerly gradient flow over New England today. This pattern is conducive to good mixing with steady cold advection through the low- and mid- levels. With a cooler airmass in place today versus yesterday we can expect cooler highs mostly in the 30s north and 40s to near 50 south. Somewhat gusty winds can be expected too, with gusts in the 20-30 mph range today... becoming a bit more muted as clouds build this afternoon. Looking at moisture profiles, strong mixing today ought to tap the humid mid-levels and produce a fair amount of stratocu across the region, resulting in an overcast or broken overcast afternoon for many. Unblocked flow ensures clouds track past the mountains and to the coast in this case. Similarly, embedded snow showers driven by an upper level wave will be mostly in the mountains, however a few showers are likely to track out of the mountains and toward the coast during the afternoon. Snow squall parameters indicate some of these snow showers may become intense, again mostly in the higher terrain of the north and west... however the steep lapse rates driving instability will also have cloud bases elevated enough to where the surface may not see much more than flurries or sprinkles in weaker showers.
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&& .SHORT TERM /TONIGHT THROUGH TUESDAY/...
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Another shortwave and accompanying cold front drop down from Canada overnight, maintaining snow shower activity over the mountains. A loss of mixing leading to increasingly blocked flow will however limit the degree to which these showers track into the lower terrain. Still, some flurries and occasionally gusty winds can be expected overnight with the front. While not particularly well- mixed, except with the front itself, enough gradient flow will remain overnight to keep temperatures from completely falling out, with lows in the 20s to around freezing.. warmest along the coast, coolest in interior valleys that manage to decouple. Tomorrow will be similar to today meteorological, although the airmass in place will be a bit cooler and less humid with flow aloft a bit more zonal. Thus, while strong mixing will produce another breezy day with unblocked flow across the mountains, it should have more sunshine with afternoon highs similar if not a touch cooler than today... in the 30s and 40s. Would expect scattered snow shower activity to persist across the mountains, but with lesser intensity and coverage.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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Overview... A trough deepens across the Northeast this weekend, bringing a bout of cooler temperatures and at least a couple chances for snow. A clipper system moves through the Great Lakes on Wednesday and strengthens near the coastline on Thursday as it moves off into the Canadian Maritimes. High pressure builds in for late in the week, and then a coastal storm likely develops south of the region next weekend. Details... The clipper system approaching on Wednesday presents the best chance for accumulating snowfall across much of the forecast area this week, with the greatest chances across northern and western locations. Wednesday itself looks mild ahead of the system, with highs warming into the 40s in most spots. Temps then quickly drop as precip approaches and temps fall to near the wet bulb temps. Showers likely start to arrive into northwestern areas late in the day on Wednesday, while waiting until the overnight hours to expand farther southward and eastward. Precip may start out as rain showers, but would change to snow showers soon after as the temps cool. The system will likely develop a second low pressure center in the Gulf of Maine by late Wednesday night and Thursday. This will bring a more steady shield of snow, but exactly where this tracks and how quickly it strengthens remain big questions. There would also likely be an area between the two lows that sees very little in the way of precip, so this will need to be sorted out as well. These systems in recent memory have a tendency to be a little bit slower to develop and result in an over-forecast of precip. While it`s still too early to say that will be the case with this one, both POP and QPF have been restrained in this forecast to account for the uncertainty. The low then moves into New Brunswick on Thursday with high pressure building in behind it. Gusty winds are likely on Thursday behind the system, and these may linger into early Friday as well. By late Friday and into next weekend, high pressure will set up across New England as a strong low pressure center develops near the Carolina coast. Right now the bulk of this system looks to remain south of New England, but there is a chance some moisture could press further north, but will struggle with the high in place. There is still a low chance this low could track further north along the coast, but the high would have to trend weaker and further north to make this scenario happen. Another weak shortwave may try to move eastward in the presence of the high next weekend as well, but this would likely be a minor feature.
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&& .AVIATION /07Z MONDAY THROUGH FRIDAY/...
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Short Term...VFR, except developing MVFR at KHIE, prevails across the region for today with broken to overcast decks during the afternoon. Brief VSBY restrictions will be possible in SHSN anywhere however the best odds for this to happen remains at KHIE and other mountainous terminals... at around 40 percent. Winds gust to around 20-25 kts out of the west, strongest this morning. Steady W flow continues into tonight, turning NW with a crossing cold front with VFR/mtn MVFR continuing. VFR on Tuesday with WNW winds gusting 15-25 mph. Long Term...VFR conditions are expected most of Wednesday, and then a period of IFR is likely with periods of snow showers Wednesday and Thursday at most terminals. Gusty westerly winds of up to 35kt are possible Thursday afternoon. VFR conditions and easing winds are likely for Friday, with another chance for some rain or snow showers over the weekend.
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&& .MARINE...
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Short Term...Westerly flow persists across the waters today through tomorrow, with sustained winds mostly hovering between 12 and 18 kts. Gusts upwards of 25 kts are possible at times, with greatest confidence and coverage existing off the Midcoast today... and likely everywhere as winds turn slightly NWerly with a cold front crossing later this evening and overnight. Seas meanwhile are expected to be hovering around 3-5 ft... lower yet along the southern coast, and up to around 6 ft near Matinicus. Long Term...Low pressure approaches the waters on Wednesday, with the low then strengthening in the Gulf of Maine late Wednesday night and Thursday. Westerly gales are possible behind this low Thursday afternoon and night as the low moves into the Canadian Maritimes. High pressure then builds across the waters late in the week behind the low. Low pressure develops south of the waters off the Carolina coast next weekend.
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&& .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None. NH...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ150- 152.
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&& $$ NEAR TERM...Casey SHORT TERM...Casey LONG TERM...Clair

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