Area Forecast Discussion
Issued by NWS Portland, ME

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915 FXUS61 KGYX 252256 AFDGYX Area Forecast Discussion National Weather Service Gray ME 656 PM EDT Tue Apr 25 2017 .SYNOPSIS... Cloudy, cool, and wet conditions are expected through Wednesday as low pressure slowly moves north along the coast. Expect an inch or two of rain east of the mountains through Wednesday. By Thursday there will be some improvement west of the mountains with warmer temperatures arriving, while east of the mountains it will stay cloudy and cool. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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655 PM...Updated forecast to adjust pops bit early this evening /not raining yet in ern zones/, and to adjust temps somewhat based on current obs, and tweak mins a bit, as it looks like most places will bottom out in the 40-45 range, which mean in places its already raining temps won`t change by more than a couple degrees tonight. Otherwise rain and drizzle expected through the night. Previously...The next area of rain is on its way north into southern New Hampshire and southern Maine this afternoon. This round will be a bit heavier than the last. Expect more rain arriving through the night as a slow moving cut off low tracks north along the East Coast. Easterly flow to the north of the low will transport cool, moist air in off the Gulf of Maine while also promoting cold air damming. At the interface between the damming and the onshore easterly flow a coastal front will form and could enhance rainfall rates along the immediate coastline.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Axis of heaviest rain shifts east along the coast during the day on Wednesday. Continued damming will keep temperatures cool, but increasing moisture from rain and moist advection off the Atlantic will allow temperatures to warm into the low to mid 50s. Meanwhile to the west of the mountains downsloping conditions will promote some clearing and warming during the afternoon, with northern New Hampshire warming into the mid 60s. While the synoptic scale forcing for rain moves east Wednesday night, a lingering low level onshore flow will promote clouds, fog, and drizzle through the night. With all the excess moisture near ground level and at least some nocturnal cooling, there is the possibility for dense fog to form. && .LONG TERM /THURSDAY THROUGH TUESDAY/...
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The models are in decent agreement on the longwave pattern through early next week. We begin the period with a shortwave impulse exiting into the maritimes. It`ll be followed by brief ridging ahead of a broad deep upper trough over the western two- thirds of the CONUS. A northern stream impulse crosses eastern Canada and New England on Saturday with ridging to briefly follow for Sunday. By Monday...a strong shortwave is lifting north into the Great Lakes with associated surface system moving into the Northeast CONUS for the start of the new work week. While the mean jet position will limit cold air intrusion into the region... we`ll still average near or only slightly above normal for the period given the abundance of clouds and unsettled conditions.
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&& .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Short Term...Conditions will gradually become more permanently IFR or worse this evening as steady rain moves in from south to north. Conditions northwest of the White Mountains may remain MVFR or even VFR depending on the intensity of the rain. Steady rain moves east on Wednesday while low clouds and possible fog and drizzle continue through Wednesday night. Long Term... Thu...Areas of MVFR with lcl IFR in -shra and fog. Fri - Sat...Areas of MVFR in -shra. && .MARINE... Short Term...Easterly flow tonight shifts to southeast tomorrow as low pressure approaches. Winds diminish below advisory levels but wave heights will likely stay above 5 FT for several days. Long Term... Fri...Small Craft conditions are possible outside the bays. Sat...Small Craft conditions are possible. && .FIRE WEATHER... Expect wet conditions areawide through Wednesday. Could see some warming and drying west of the mountains on Thursday while it remains cloudy, cool, and damp east of the mountains. && .HYDROLOGY... With continued snow melt river levels remain high. Add another 1 to 2 inches of rain on top of that and at least a few rivers could rise close to flood stage. At this time no river is forecast to reach flood stage, but it would not be out of the question for some minor flooding to occur depending on how much rain falls in key areas. && .TIDES/COASTAL FLOODING... High tide tonight at Portland is 11.0 FT. With a moderate easterly flow over the waters expect a surge of 0.5 to 1 FT with building wave heights. Have issued a Coastal Flood Advisory to highlight the potential for splash over and beach erosion tonight near the time of high tide south of Portland. High tide Wednesday night is 11.5 FT. Although winds will become more southeasterly at this point, there will likely be a residual surge left in the Gulf of Maine which could cause another 0.5 to 1 FT surge leading to the potential for minor flooding and splash over again. The next two nighttime tides are 11.7 FT but expect the surge to be slowly draining by then and coastal flooding is not anticipated. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT Wednesday for MEZ023-024. NH...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT Wednesday for NHZ014. MARINE...Small Craft Advisory until 6 PM EDT Wednesday for ANZ150>154.
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&& $$ SYNOPSIS... NEAR TERM...Cempa/Kimble SHORT TERM...Kimble LONG TERM...Schwibs AVIATION... MARINE... FIRE WEATHER... HYDROLOGY... TIDES/COASTAL FLOODING...

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