Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
099 FXUS61 KGYX 082305 AFDGYX Area Forecast Discussion National Weather Service Gray ME 705 PM EDT Fri Aug 8 2025 .SYNOPSIS... Showers and thunderstorms in and around the mountains this afternoon will fizzle this evening. High pressure builds back in over the weekend for fair weather and increasing temperatures. Temperatures and humidity continue to rise through the first half of next week as a ridge of high pressure builds over the Northeast. The ridge starts to break down mid week that will allow for some chances of showers and thunderstorms. && .NEAR TERM /UNTIL 5 AM SATURDAY MORNING/... 7 PM Update...Isolated showers and thunderstorms in the far interior will continue to weaken and dissipate with the loss of daytime heating. Otherwise we expect some patchy valley fog overnight. Previously... Impacts and Key Messages: * No significant weather impacts expected A shortwave trough moves through the area today and we have already seen some isolated showers and storms this afternoon as a result, mainly in and around the terrain as that has been the main lifting mechanism. With no real steering flow these are slow movers. The KALB 12Z RAOB observed PWAT values around 1.25" and KCAR observed around 0.80, so with us somewhere in the middle and modeled PWATs around an inch, some brief downpours are occuring with these. With how dry we have been, there should be no issues even if a location happens to pick up a quick 1" or 1.5". This activity is getting its energy from diurnal heating so it should fizzle heading into the evening hours and be done not long after sunset. Mostly clear skies and light winds should lead to a period of radiational cooling tonight, so went ahead and blended in some MAV guidance to adjust low temperatures down a couple degrees from the NBM. Expect low to mid-50s through the mountains, foothills, and valleys, with mid- to upper 50s along the coastal plain. This will lead to patchy, locally dense, valley fog. && .SHORT TERM /5 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Impacts and Key Messages: * No significant weather impacts expected The shortwave lifts off to the northeast and the resulting height rises should keep any chances of showers/storms very low. CAMs are still pegging the International Border as an area where something could develop off the terrain, but as we have seen the past couple days anything would be isolated as surface high pressure and dry air remain in place. PWATS are again modeled around 1-1.25", so any more robust showers/storms would contain downpours. High temperatures look to end up similar to today with the exception of a stronger seabreeze keeping the coastal areas cooler. Temperatures climb into the low to mid 80s across the mountains and foot hills, with more in the way of mid-70s to around 80 in the coastal plain. It looks like some clouds and maybe even some showers may ride the ridge into the area from ongoing convection in the Great Lakes Region, mainly in the north. Even so there should once again be a good window for radiational cooling before any of that arrives if it does. Therefore, I used some MAV guidance to knock low temperatures down a couple degrees. Dewpoints will be trending up so it still might end up warmer than tonight with mid to upper 50s across the board. Northern Somerset and Northern Franklin counties may be the "warm" spot, closer to 60, if clouds do encroach early. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Key Messages: * Hot temperatures arrive late this weekend through the middle of next week. This could be the longest stretch of upper 80s/lower 90s of the year so far, but there will be some complicating factors * Daily showers and storms will be possible through early next week, mainly across the interior and mountains Details: Under high pressure through midweek next week, heat will be the main point of conversation. Supportive 850mb temps increase to around 18 to 20 C Monday through Wednesday, with resulting surface temps in the upper 80s to low 90s across the interior and foothills. Temperatures jump Sunday, and then further to start next week. ECMWF Extreme Forecast Index stands out on Monday and Tuesday, with some SoT contours of 1 to 2 across most of the forecast area. This is a good signal for temperatures well above normal, but exact values will continue to refine over the coming days. While NBM probs of greater than 90 degrees are fairly consistent Mon-Wed, there are some items that bring uncertainty to the forecast: 1) High pressure centered to the south and east will aid in low level onshore flow. The advecting marine air, while weak in this environment, could be enough to keep coastal communities a few degrees cooler than inland. How far inland this influence make it should be better represented in high res guidance as next week approaches. This could be defeated by a more prominent offshore flow, if it develops. 2) Building instability and moist mid- levels will create a similar environment to the past week...with daytime showers and thunderstorms. Rain cooled air and additional cloud could hamper insolation, albeit locally. So far this is a missing item from guidance of next week, but the pattern supports these isolated to scattered showers. Storms that develop during the daytime next week will be lacking wind shear through much of the column. Should low and mid-level lapse rates stay in the 6 to 7 C/km range, would need to watch for gusty winds from failing updrafts in taller storms. This pattern looks to finally change into late next week as a cold front pushes into the region Wednesday night. There remains many different iterations of this feature to be fully confident in its timing and placement, but most global solutions bring the front over the CWA during this overnight period. && .AVIATION /23Z FRIDAY THROUGH WEDNESDAY/... Short Term...Some showers and storms are present in the mountains, but this activity will fizzle this evening. Patchy valley fog is likely again tonight with restrictions possible at LEB and HIE. Fog will clear in the morning and then VFR will prevail through Saturday. Showers and storms are possible in the mountains again Saturday afternoon. Increasing low level moisture may lead to valley and coastal fog Saturday night/early Sunday morning. Wind gusts near 15kts are possible at coastal terminals Saturday afternoon. Long Term...VFR is expected through Tuesday as high pressure brings mostly dry conditions. Any restrictions are expected to revolve around coastal fog, mainly along ME Midcoast terminals in the evening and overnights. Of low coverage will be the occurrence of SHRA or TS across interior ME/NH during the afternoon and early evening. && .MARINE... Short Term...Wind gusts and seas remain below SCA criteria through Saturday night as high pressure remains over the waters. Winds will be generally southerly at 10-15kts. Increasing low level moisture may aid in the development of areas of fog Saturday night. Long Term...Under continued high pressure through next Wednesday, conditions are expected to remain under SCA criteria. There will be light onshore flow through the period, but only enough to build wave heights to 2 to 3 ft through Tuesday. A cold front approaches the waters Thursday morning. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...Baron/Ekster SHORT TERM...Baron LONG TERM...Cornwell AVIATION... MARINE...