Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
492 FXUS61 KGYX 291818 AFDGYX Area Forecast Discussion National Weather Service Gray ME 218 PM EDT Tue Sep 29 2026 .WHAT HAS CHANGED... No significant changes were needed. && .KEY MESSAGES... 1. High pressure brings dry conditions for Wednesday and Thursday along with a warming trend. 2. A cold front will move through the area on Friday, with cooler and more seasonable weather expected this weekend. && .DISCUSSION... KEY MESSAGE 1 DESCRIPTION... The weakening nor`easter is centered just west of Nova Scotia as of early this afternoon but is still close enough to support a few light showers or patchy drizzle across western ME with enough low- level moisture still around. These chances will quickly fade toward evening with the system further exiting to the east through tonight and high pressure beginning to build into New England from the west. There won`t be much in the way of wind tonight, and given the widespread recent rainfall, patchy fog is fair game for most the area and could be locally dense, especially in and around river valleys. Once fog clears up by mid-morning Wednesday, broad high pressure over the eastern CONUS will bring dry conditions and partly sunny weather for both Wednesday and Thursday. With the center of the high well to the south, New England will see prevailing southwest winds bring warmer temperatures into the area. 850mb temps of approximately +9C to +10C supports highs mostly in the lower 70s Wednesday, and +11C to +12C supports mid-upper 70s Thursday. The exception is the southwest winds off the ocean keeping the Midcoast a few degrees cooler. Valley fog is possible Wednesday night, but an upper disturbance may bring too much mid and high clouds. KEY MESSAGE 2 DESCRIPTION... On Friday, a shortwave looks to move through the northeast. Ahead of this low Thursday night, a marginally unstable environment may allow for the development of showers. Despite benign instability, the lack of forcing ahead of the front will likely keep shower activity isolated Thursday night and into Friday morning. By Friday evening, the center of the low moves through southern New Hampshire and could bring steady rain Friday night. Confidence is still very low on rainfall amounts, with some model guidance suggesting more rain than others. In addition, the placement of the rainfall too is another thing the models seem to struggle with too. The 12Z run of the NAM today had the bulk of the rain north of the mountains, while the ECMWF deterministic had a more southerly placement of said rain. Taking a look at the ECMWF ensemble, NH and western ME have a 50-80% chance of exceeding 0.1" of rain and between a 15% and 30% chance of exceeding 0.5" of rain. After the frontal passage Friday night, temperatures look to get much cooler for the weekend, with highs in the 60s. Radiational cooling Saturday night could also lead to some frost in locally colder parts of the interior. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Through 18Z Wednesday...MVFR cigs remain mostly likely across western ME into tonight while southern NH terminals could be VFR or MVFR. For this evening and tonight, fog is possible at all sites but is mostly likely to bring IFR to LIFR at LEB, HIE, and CON. Fog should lift by mid-morning Wednesday with mostly VFR through 18Z, except there is potential for a period of MVFR cigs at PWM and the southern NH terminals. Outlook: Rest of Wednesday-Thursday: Mainly VFR, except valley fog is possible Wednesday night into Thursday morning to bring IFR or lower at HIE and LEB. Friday: MVFR possible due to showers. Saturday: VFR expected. Sunday: MVFR possible due to showers. && .MARINE... Through Thursday...SCA conditions are not expected. Winds and seas continue to subiside through tonight as the weakening nor`easter exits to the east and high pressure builds in from the west. The high pressure becomes centered south of the waters Wednesday into Thursday with winds becoming southwesterly. These begin to increase later in the day Thursday but are currently expected to remain below SCA levels. Marine conditions look to stay below SCA levels Thursday night through the weekend. Wind gusts over the open waters could get near SCA levels occasionally. Seas of 2-4ft expected. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ DISCUSSION...Combs/Palmer