Area Forecast Discussion
Issued by NWS Portland, ME

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785 FXUS61 KGYX 250800 AFDGYX Area Forecast Discussion National Weather Service Gray ME 400 AM EDT Wed Apr 25 2018 .SYNOPSIS... Low pressure moves north into the area today allowing rain to overspread the area from the southwest in the morning and work northeast by afternoon. A good soaking rain is expected for most of the region. This system will slowly exit the region Thursday. A cold front Saturday evening will allow cooler air to push back into New England. A warming trend is expected early next week however. && .NEAR TERM /TODAY/... First batch of rain already trying to move into the area from the southwest. Expect top-down moistening of the air mass as this moves in, with likely some evaporational cooling into the 40s as rain begins. Rain becomes steadier and more widespread as the day goes on and low pressure approaches from the southwest. High temperatures today will not be that far from current temperatures, except perhaps northeastern areas which could warm up a bit this morning before rain arrives. Went below most guidance on highs today, more in line with higher resolution guidance due to the onshore flow from the cold Gulf of Maine as well as evaporationally-cooled low level inversion expected. && .SHORT TERM /TONIGHT AND THURSDAY/... Axis of steadier rain shifts east across the area tonight, moving into eastern Maine on Thursday. With increasing moisture levels and limited cooling we could see fog developing as well. When it`s all said and done, most areas on the coastal plain and into the eastern foothills will see about an inch of rainfall. Worth noting that there is a fairly broad range in model forecast rainfall amounts, with the NAM generally being dry (maybe a half inch?) and the Canadian and GFS being the wettest (1.5 inches?). Current forecast is a bit of a blend, with some emphasis on terrain-enhanced areas as well as higher amounts along the immediate coastline. As steady precipitation moves east on Thursday, expect more showers to develop under the cold core upper low moving in from the west during the day Thursday. So although the steady rain ends, more showery weather continues. With better mixing expected on Thursday, temperatures make another run at 60, with southern areas most likely to top this threshold while northern areas stay cloudier and may not reach it. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... The extended forecast looks progressive with a large cutoff low centered near Nunavut offering continued chances for precipitation this weekend and into next week. Several spokes of energy cycle through the Northeastern CONUS the next several days. Friday evening surface low pressure will develop over the east coast and move northeast. Models are not in agreement with the location of the dominant surface low, but a warm front should arrive sometime Friday evening with a cold front following for Saturday evening. This will produce widespread rain showers across the region. Friday and Saturday will be relatively warm with upper 50s to mid 60s in southerly flow ahead of the system. Increasing clouds and precipitation will cool things off with 850mb temperatures dropping about 10 degrees by Sunday morning. Highs at the surface will struggle into the mid 40s over the mountains and foothills, with mid 50s elsewhere. This is not overly cool for this time of year, but after warmer weather recently, it will feel more than a couple degrees below normal. A warming trend looks on tap for next week with modified high pressure pushing up from the south and skirting fast moving flow to our north. This looks like a good stretch of precipitation free weather...except for the mountains which may see just enough short wave energy to produce partly cloudy skies and showers. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... Short Term...Expect deteriorating conditions from southwest to northeast today, with conditions becoming IFR by evening in rain. Could stay MVFR on the other side of the mountains up in Whitefield. There is the potential for fog to develop this evening into tonight which would cause further reduction in visibility, possibly as low as 1/4 mile. Conditions improve fairly rapidly Thursday morning from west to east, with scattered showers moving in from the west especially during the afternoon. Long Term...Prevailing VFR is expected Thursday night through Friday morning, but conditions may deteriorate to MVFR or IFR at times late Friday into Saturday in rain showers. Lingering -SHRA/-SHSN are possible for KHIE and KLEB Saturday night into Sunday with other sites VFR. Gusty NW winds are forecast for Sunday afternoon and evening. && .MARINE... Short Term...Increasing onshore southeast flow expected today and tonight, likely topping out at about 30 KT. Prolonged southeast fetch will also increase the wave heights to over 5 FT, and as high as 10 FT in the central Gulf of Maine waters near Matinicus. Winds shift to the west and decrease on Thursday, though it will take a little while for seas to subside. Long Term...Waves may increase in southerly flow Saturday. Winds and seas also approach SCA conditions in west flow behind a cold front Saturday night into Sunday. && .HYDROLOGY... There is still a good amount of snow left especially in the higher terrain. Warm temperatures yesterday brought rises to many of the headwater gages. Expect continued snow melt to combine with about an inch of rainfall to bring further rises to all rivers, but especially the headwaters that drain eastward out of the mountains toward the Atlantic. These are the areas most likely to see minor flooding, and some locations are currently forecast by the RFC to reach minor flooding. Because of this, we have issued a Flood Watch covering the most likely impacted areas, including the upper Saco River as well as tributaries of the Androscoggin River. Flooding cannot be ruled out on the upper Pemigewasset River as well as along the Kennebec. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Flood Watch from this evening through Thursday afternoon for MEZ007>009-012>014-021. NH...Flood Watch from this evening through Thursday afternoon for NHZ001>006. MARINE...Small Craft Advisory from 5 PM this afternoon to 8 PM EDT Thursday for ANZ150-152-154. && $$ NEAR TERM...Kimble SHORT TERM...Kimble LONG TERM...Hanes

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