Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
264 FXUS61 KGYX 011811 CCA AFDGYX Area Forecast Discussion...Corrected. National Weather Service Gray ME 211 PM EDT Mon Sep 1 2025 .SYNOPSIS... Mostly fair weather continues through mid week as high pressure remains in control. A disturbance moving through Quebec will bring chances for showers and isolated storms Wednesday afternoon, mainly north of the foothills. A trough swinging into the Great Lakes will send a cold front towards New England Friday that will bring better chances for showers. Troughing remains over the Northeast into the upcoming weekend bringing continued chances for showers. && .NEAR TERM /THROUGH TONIGHT/... Forecast will be similar to previous nights except with more in the way of high cloudiness across the local area sweeping north overnight. This will help to keep temps slightly warmer than the last couple of nights...but overall I still expect it to radiate and still expected valley fog. I trimmed areal coverage of fog to just in and north of the mtns based on persistence. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... High clouds move on Tue with another pleasant day in store and sea breezes in the afternoon. Did make sure to mix down dewpoints temps from forecast mixing height...as recent dry weather has tended to keep RH values a little lower than guidance. Tue night in addition to valley fog there may be enough moisture advection to get some coastal fog to develop just inland from the water as flow encounters some friction. I added this based on the latest HRRR guidance...but otherwise no change from NBM. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... The 500mb pattern from Wednesday into the first part of the upcoming weekend will be longwave troughing across the eastern half of the CONUS with an upper low setting up near the Great Lakes/James Bay region. A few shortwaves within the longwave pattern will bring some opportunities for rainfall with higher chances arriving Friday and Saturday as a couple of shortwaves cross through as well as a cold front. The first shortwave arrives Wednesday, bringing scattered showers and isolated storms, mainly from the foothills northward. Lowering freezing levels and cooling aloft could support small hail in thunderstorms as well as low-level inverted V profiles supporting a gusty wind potential. To the south, moisture is less favorable, and soundings do show a lingering subsidence inversion. Outside of any precipitation, temperatures will be in the mid 70s to lower 80s. Once this wave passes, clearing skies and light winds should allow valley fog to form in some areas with lows generally in the mid 40s to low 50s. Shortwave ridging brings dry and mostly sunny conditions for Thursday, and then this will shift east through late week as the upper low moves eastward across Quebec and sends a couple of shortwaves and a cold front through New England. This will increase shower chances from Thursday night through Saturday night with thunderstorms also possible during the day on Friday. GFS/ECMWF ensembles are favoring western and northern NH and into the foothills and mountains of western ME for the higher probablilites of over half an inch of rainfall during this time. Highs looks pretty steady state with highs continuing to be mostly in the 70s, but overnight lows will be on an upward trend as southerly flow increases. Marine fog and stratus will also be possible by late week. Global models are in pretty good agreement in the last of these fronts crossing by the early part of Sunday. Should this come to fruition, Sunday looks to feature a chance of upslope showers with more clouds in the mountains and partly sunny skies elsewhere. Building high pressure looks to bring further drying into early next week. && .AVIATION /17Z MONDAY THROUGH FRIDAY/... Short Term...VFR conditions prevail thru Tue night. Tonight valley fog is likely again at LEB and HIE...and I used persistence for timing. By Tue night sustained moisture advection may allow some coastal fog to develop alongside valley fog. At this time confidence is fairly low on whether this will impact TAF sites. Long Term...Scattered showers may bring brief restrictions to HIE, AUG, and LEB on Wednesday, and this may be followed by patchy fog and/or low stratus Wednesday night into early Thursday. Mainly VFR during the day Thursday, but an approaching cold front will bring increasing precipitation chances Friday into Saturday. Outside of showers, low ceilings and fog will also be possible ahead of the front with the increase in southerly flow and moisture. && .MARINE... Short Term...Winds and seas will remain below SCA thresholds. Seabreezes are likely to develop again Tue afternoon. Long Term...High pressure will be in control Wednesday and Thursday but will shift to the east of the waters Friday into Saturday as a cold front approaches from the west. There may be a period of SCA conditions as southerly flow increases ahead of the front as well as increasing potential for marine fog and stratus. The front looks to cross the waters Saturday night and into early Sunday with conditions likely remaining under SCA conditions as high pressure builds in across the Northeast into early next week. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Legro SHORT TERM...Legro LONG TERM...Combs