Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
199 FXUS61 KGYX 200555 AFDGYX Area Forecast Discussion National Weather Service Gray ME 155 AM EDT Wed Aug 20 2025 .SYNOPSIS... A wave of low pressure tracks across southern New England today bringing chances for light rain, mainly across southernmost NH and far SW Maine. High pressure builds in Thursday and remains over the area through Saturday for fair weather and warming temperatures. High pressure shifts offshore Sunday with a slow moving frontal system crossing the region Sunday night through Monday bringing widespread chances for showers. && .NEAR TERM /THROUGH TODAY/... Surface high pressure will hold firm over much of central and and northern New England today while a short wave trough moves by just to the south. The result will be a lot of mid and high clouds over the forecast area today. However, dry air will win out for most of the forecast area today with light rain showers generally relegated to southernmost NH and York County ME. The result will be high temperatures only in the 60s across southern zones with lower 70s north and northeast. && .SHORT TERM /TONIGHT THROUGH 6 PM THURSDAY/... The trend will be for clearing skies from north to south tonight as the low pressure wave moves away well to our southeast. Valley fog will likely result, especially in the CT and Pemi River Valleys. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... The main thing to watch in the extended continues to be for increased wave action and potentially dangerous rip currents from Tropical Cyclone Erin, which is progged to cross roughly 500 miles east of our coastline on Friday. Otherwise, warm temperatures into the 80s and dry conditions look to prevail on Friday and Saturday before cooling back down late this weekend into early next week. There is a rather strong ensemble signal for some beneficial rainfall late Sunday night into Monday night. Previously... High pressure shifts offshore Sunday as a trough deepens to the west of New England. This trough will be slow to translate east with one frontal system poised to cross the area late Sunday into Monday. Models do diverge on the timing, with some models keeping Sunday mostly dry until late in the day. Have stuck with the NBM which brings PoPs 30 to 40 percent across NH and NW Maine with PoPs around 20 percent along the coastal plain Sunday afternoon. PoPs will increase Sunday night and Monday when a slow moving front will cross the area bringing the potential for a widespread soaking rainfall. There is a large spread in ensembles with respect to QPF with ensemble means around 0.25 to 0.5 inches. Troughing will linger over the Northeast through the middle of next week keeping slight chances for showers in the forecast into Tuesday. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... Short Term...A disturbance moves just to our south today with the highest potential for showers across the southern NH terminals. IFR to MVFR ceilings and fog are also possible for valley areas tonight in fog night, but highest chances are across NH. Long Term...Mainly VFR Thursday through Saturday with the exception being nighttime valley fog at KLEB and KHIE. && .MARINE... Short Term...Winds and seas will likely remain below SCA levels through tonight, but seas will start building as long- period swells from distant Hurricane Erin begin arriving over the waters by Thursday night. Long Term...Hurricane Erin is forecast to track well southeast of the Gulf of Maine Thursday night through Saturday. Long period swell from this system will bring wave heights greater than 5 feet Thursday night building to 10 feet Friday night before slowly subsiding through the weekend. The gradient between this system and high pressure to the north will bring winds close to 25 kts Thursday night into Friday morning. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Ekster SHORT TERM...Ekster LONG TERM...Schroeter/Tubbs