Area Forecast Discussion
Issued by NWS Portland, ME

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758 FXUS61 KGYX 220228 AFDGYX Area Forecast Discussion National Weather Service Gray ME 928 PM EST Tue Nov 21 2017 .SYNOPSIS... Low pressure will track southeast of the region on Wednesday, bringing a period of mostly rain to the area. Some snow will be found in the mountains. This low will pull a cold front across the area Wednesday night. Thanksgiving will mainly sunny but chilly, with a warming trend Friday into Saturday. Another cold front crosses the area on sunday and could bring some rain or snow showers, with another blast of cold air expected early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 930 PM Update...Have updated temperatures and sky cover and little bit, but otherwise the forecast is on track. We expect to remain dry overnight, with the rain from the next system getting into southernmost NH around sunrise. 6 PM Update...Little change to the going forecast. Have lowered min temps in the north a little bit based on the trend of faster cooling this evening. Otherwise, partly cloudy skies will be the rule with winds becoming lighter. Any precipitation should hold off until sunrise in the far south. Previously... Southwesterly flow continues tonight as an upper trough and associated cold front move east toward the region. Expect increasing clouds overnight and temperatures generally only falling into the 30s. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Two waves are headed in our general direction within the southwest flow between the Atlantic ridge and the Canadian trough. The first is a southern stream wave riding around the periphery of the Atlantic ridge. Moisture has built up over the southeastern United States pulling from the Caribbean and Gulf of Mexico. This moisture will spread northward along the East Coast tonight and arrive in northern New England just in time for the cold front to arrive Wednesday morning. With more moisture available, it is becoming increasingly likely that some precipitation will fall along the northern New England coastline ahead of the front. The second wave is the deeper one, featuring a large scale trough over Ontario and the upper Great Lakes. This will move east northeast and arrive in New England on Wednesday, dragging a cold front along with it. This second wave is expected to capture and merge with the first southern stream wave with the two linking up near Nova Scotia, too far east for us to see a heavy precipitation event here. However, there will be enough moisture streaming northward ahead of the southern wave that we should see rain and mountain snow break out particularly as the cold front drops out of the mountains midday Wednesday. Ahead of the front there will be enough warm/moist air to keep things as rain, but behind it especially in the mountains this could fall as snow. Not looking at a lot in terms of total precipitation, with generally 0.1 to 0.5 inches of rain expected. It may also be a fairly short duration rainfall as the eastward progression of the cold front will pull in cold, dry air out of Canada and work to shut off precipitation. With the cold front moving through during the day Wednesday, it should be a colder night Wednesday night. Low level wind flow remains light to moderate deep into the night, but we should still see temperatures fall into the 20s to perhaps a few teens as the core of the cold air arrives. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Fairly persistent 500MB blocking downstream of New England, with ridge taking residence over Greenland, and pushing N to the pole, along with ridging over the wrn CONUS, will effectively push the coldest air over the hemisphere toward Siberia. It will also continue to help promote a faster flow, that will trend toward broad cyclonic, but still feature some fast-moving waves and frequent temp changes into early next week. Overall, Thanksgiving day looks mainly sunny with light winds but chilly with highs only in the 30s, probably closer to 30 in the colder mountain spots, and maybe reaching 40 in the more urbanized areas of srn NH. Thursday night will see a 500 mb wave pass to our north, and bring some clouds in overnight and maybe a few SHSN in the mountains. Should see skies clear somewhat Fri morning, with temps a few degrees warmer than Thursday, mainly in the mid 30s to mid 40s. 500 BM ridging builds in on Saturday in response to trough digging SE toward the Great Lakes. This should allow a decent SW flow and help push highs up into the mid 40s to low 50s, which is above normal. The next chc of precip will be Sat night into Sunday as 500 mb trough continues to deepen as it moves into New England. 12Z Euro phases the the system far enough east that it would have limited effect on CWA, other than maybe a round of SHRA/SHSN with passage of the cold front. Once again, it will turn sharply colder behind the front with highs on Monday limited to the 30s once again. The trend for next week beyond Monday looks to be warmer and mainly dry conditions. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Short Term...VFR today with southwest wind gusts dropping off early this evening. Clouds increase through the night, with MVFR conditions possibly by Wednesday morning. Rain is most likely along the coast during the day Wednesday, with MVFR to IFR conditions expected. A cold front moves in from the northwest during the day, with some snow showers north of the mountains and MVFR conditions there. The cold front is a dry front so it should clear things out as it moves through leading to VFR conditions by Wednesday evening. Long Term...Mainly VFR Thu through Sunday. Possible SHRASN possible Sunday which may briefly cause flight restrictions. && .MARINE... Short Term...South to southwest winds continue to gust to 25 to 30 KT this evening, but should diminish a bit overnight. A cold front moves through Wednesday with north winds gusting to 25 to 30 KT again. Thus there may only be a brief few hour period where Small Craft Advisory conditions are not observed. Long Term...May need SCA Sat into Sunday. Initially on Sat due to SW flow ahead of a cold front, and then on Sunday into Sun night in NW flow behind the cold front. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 5 AM EST Wednesday for ANZ150>152- 154. && $$ NEAR TERM...Ekster SHORT TERM...Kimble LONG TERM...Cempa

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