Area Forecast Discussion
Issued by NWS Portland, ME

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550 FXUS61 KGYX 041656 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1256 PM EDT Sat May 4 2024 .SYNOPSIS... High pressure near the coast will provide dry conditions through today, with increasing onshore flow and humidity. Thickening clouds, cooler temperatures, and rain showers are expected by Sunday as a frontal system approaches New England. Clearing is likely not coming until Monday behind a cold front. Warmer and sunnier conditions are expected into Tuesday, then more unsettled weather returns around the middle of next week. && .NEAR TERM /UNTIL 7 PM THIS EVENING/...
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100 PM Update... A weak vorticity maximum is crossing over northern areas and this is allowing for a few widely scattered showers to develop, as seen on latest radar imagery and area webcams. This vort max will continue to sink southeastward through the afternoon and therefore added some low end slight- chance PoPs to account for this. Otherwise, no significant changes were made to the forecast. Previously... 1030 AM Update... Minor changes to reflect latest observational trends. Northeast radar mosaic continues to show weak returns moving southeastward over southern NH but thus far there haven`t been any MPING or ASOS reports of this activity reaching the ground. This is likely due in part to low mid-level RH, as seen on the 12Z KGYX RAOB report. Previously... 648 AM Update...Quick tune up of sky coverage this morning, along with temperature trends through the dawn hours. Little change otherwise. Previously... An upper level ridge moves toward the East Coast while surface high pressure centered near Labrador this morning builds south into the Gulf of Maine today... resulting in another fair weather day, albeit with increasing onshore flow and associated clouds. Signs of increasing low- and mid- level moisture associated with this trend are evident even this morning as patchy ground fog has developed in most places... and a mid- level stratus deck has built over portions of the foothills, where humid NE mid- level flow is dammed against the mountains. The trend for today will be to mix out low clouds and fog initially... but build back some stratocu by the afternoon, mainly over the interior of Maine beneath mixed cirrus decks. The ridge overhead will keep us dry, however it will be cooler than yesterday especially at the coast where temperatures may not or may just barely make it out of the 40s. The warmest and sunniest spots will likely be in the Connecticut and Lower Merrimack River Valleys, with highs in the mid-60s.
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&& .SHORT TERM /7 PM THIS EVENING THROUGH SUNDAY NIGHT/... High pressure extending offshore of the Maritimes combined with an approaching cold front from the Great Lakes continues to support southeast flow off the Gulf of Maine... with low clouds filling into an overcast sky for most places tonight, except for the upper Connecticut River Valley which benefits from the Whites blocking humid onshore flow. Some fog and drizzle are likely to develop too, mainly in southern New Hampshire into southwest Maine where low- level humidity will be at its highest. One of the bigger questions for Sunday will be how efficiently we`ll be able to mix out low stratus, if at all, before a pre- frontal trough brings a moisture axis and associated rainfall across the region. Model trends have been fairly steady with this wave delivering about 0.2-0.4" for most places... locally higher, lower elsewhere... Sunday afternoon and overnight. While ceilings are forecast to lift a bit during the day, hires guidance coming into view suggests a fair amount of overcast to persist. Thus between clouds and onshore flow, temperatures will be limited to the low- or mid-50s... or 40s, nearby to the coast and if ceilings remain low. A building southeasterly breeze will make conditions feel a bit more raw as well. Rain will exit east Sunday night with drier air pushing in aloft, however at the surface conditions will remain humid with fog and low ceilings likely. Winds will gradually pull more southerly and southwesterly, which will at least cut some of the maritime influence down by Monday. && .LONG TERM /MONDAY THROUGH SATURDAY/... Overview: Unsettled weather expected until a cold front passes Monday morning. High pressure and warm temperatures arrive the latter part of Monday, continuing into Tuesday. Additional unsettled weather is expected mid to late week as broad low pressure moves into the eastern Great Lakes. Details:Perhaps some remaining drizzle along the coast early Monday morning, but drying across the CWA should be underway by mid morning. NW breeze will also kick up to enhance drying through the afternoon. Should this stay on track, temperatures will be in for a rebound later in the day with highs in the 70s possible for southern NH and into southern Maine`s interior. Tuesday follows up as warm and dry, before another period of unsettled weather for mid to late week. Current NBM PoPs are likely overdone due to the wide spread of guidance solutions, and have tried to emphasize this uncertainty by keeping just a chance of rain to close out the week. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Short Term...Spotty/low confidence IFR/LIFR in FG possible this morning... clearing to VFR today with increasing light SE or E flow. Brief MVFR decks possible for interior ME (AUG) this afternoon. Widespread restrictions expected to develop tonight... with MVFR/IFR VSBY, CIGs except at KHIE which likely remains VFR. Some improvement possible on Sun, however increasing RA chances bring restrictions again during afternoon/evening. Low CIGs, possibly low VSBY persist at least along the coast into early Mon. Long Term...Ceilings should improve to VFR at all terminals into Monday afternoon through Tuesday. Unsettled weather likely brings more restrictions from mid-week, onward. && .MARINE... Short Term...NE flow 10-20 kts today turns SE by early Sunday with increasing potential for fog, then rain later in the day and overnight into early Monday. A few gusts near 25 kts are possible, with waves 3-5 ft, though conditions will remain predominantly below SCA thresholds. Long Term...The cold front will pass over the waters Monday morning, bringing better vis conditions through Tuesday. Conditions should remain below SCA criteria with the frontal passage through at least Wednesday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Tubbs