Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
238 FXUS61 KGYX 210631 AFDGYX Area Forecast Discussion National Weather Service Gray ME 231 AM EDT Fri Aug 21 2026 .WHAT HAS CHANGED... Trended the forecast drier for Saturday. && .KEY MESSAGES... 1. Mainly dry weather expected through Friday night. 2. Rain chances mainly the 2nd half of the weekend. Chance of rain Saturday but chances are lessening. 3. Drier conditions to start next week, but clouds/showers remain possible in the interior. && .DISCUSSION... KEY MESSAGE 1 DESCRIPTION... High pressure builds in behind the a cold front for today, keeping things mostly dry after early morning valley fog lifts. A spotty light shower or two can`t be ruled out along the immediate coast or southern NH today and tonight due to closer proximity to a weak low/surface trough developing south of Long Island but the vast majority of the time should be dry. The most sunshine will be seen in the interior. Dewpoint values should be lower than what we felt on Thursday making for a more comfortable day with highs around 80 most locations. Valley fog is once again expected tonight. KEY MESSAGE 2 DESCRIPTION... An initially stalled front well south of New England will start its climb north towards the region as a warm front on Saturday, bringing increasing humidity. One complexity to this setup is two separate waves of moisture; one originating from the Southeast U.S. on low-level southerly flow, while from the west will be a 500 mb trough amplifying, and likely resulting in a surface low developing. Guidance is beginning to hone in on the outcome of the first wave clipping our coastal regions on Saturday, with the upper- level low bringing more widespread rain chances, but potentially focused in the interior, on Sunday. It will be a favorable environment for efficient rainfall with PWATs above 1.5", dew points in the upper 60s, and some measurable IVT transport. However, scattered coverage to the precipitation with moderate storm motions should preclude a significant threat for excessive rainfall, and it is likely some locations see limited rainfall given the hit-or-miss nature. Clouds and precipitation should allow highs to trend a bit lower than the last few days for the weekend (widespread 70s); however with increased humidity and mild nighttime lows, it will not feel notably "cooler" outside. KEY MESSAGE 3 DESCRIPTION... The upper-level low to our west takes over as the main driver of local weather to start next week, with current indications that it may fully close off and stall over Quebec. This brings cyclonic westerly flow to New England to start the week. A dry punch in the mid-levels combined with downsloping westerly flow should bring pleasant conditions to the coastal plain with sunshine and seasonable temperatures in the mid-upper 70s, while dew points fall to the 40s/50s. With the upper-level low still lingering to our north however, there will likely be some upslope-driven clouds and vertically-shallow precipitation in the White Mountains and surrounding higher-terrain. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Through 12Z Saturday...Mostly VFR. Valley fog is again likely to produce IFR or LIFR at LEB and HIE early this morning, which is likely to clear by 13Z this morning. It`s possible that MHT and CON see a period of ground fog early this morning as well. Mainly VFR tonight although valley fog is once again expected. Outlook: Saturday and Saturday night: MVFR to IFR cigs develop during the afternoon on the coastal plain and portions of southern NH. Fog could also develop into the evening and overnight hours, resulting in lowered vis. Sunday-Sunday night: MVFR to IFR conditions with SHRA expected. Rain may taper off Sunday night giving way to areas of fog that would likely bring about IFR conditions. Monday: Conditions return to VFR, but there may still be some MVFR and/or IFR conditions along the US/CAN border. && .MARINE... Through Friday night...Conditions are expected to remain below SCA levels. Weak low pressure may track into the Gulf of Maine Saturday, with fog developing overnight into Sunday. Broad southerly flow continues into Sunday as large low pressure exits the Great Lakes and begins to move north into Quebec. Winds are expected to remain below SCA criteria, but wind wave slowly increases into the beginning of next week 3 to 4 ft. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ DISCUSSION...Barker/Ekster