Area Forecast Discussion
Issued by NWS Caribou, ME
Issued by NWS Caribou, ME
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566 FXUS61 KCAR 262224 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 624 PM EDT Thu Sep 26 2024 .SYNOPSIS... Low pressure will cross the area tonight, then exit across the Maritimes Friday. High pressure will build down from the north this weekend and remain over the area through early next week. && .NEAR TERM /THROUGH FRIDAY/... 6:24 PM Update...Radar trends show steady rain exiting the area from west to east quicker than forecast. The back edge of the steady rain is approaching the Katahdin region at this time. Decided to adjust PoPs downward over the next several hours from west to east. Also moved up the timing of the transition from rain to showers to late evening. Kept PoPs in the North later tonight as the upper- level low moves closer and reinvigorates shower development there. Previous Discussion... Surface low pressure will begin to cross the forecast area later tonight with an occluded front. Aloft, the supporting upper low reaches northern Maine overnight. Rain will persist across the forecast area early tonight. The better moisture will then begin to exit across the Maritimes later tonight, allowing the steadier rain to taper to showers. The most extensive showers overnight will occur across northern areas in the vicinity of the upper low. The surface/upper systems exit across the Maritimes Friday. However, a disturbance moving around the exiting upper low will cross the forecast area. The upper disturbance will help support the risk of showers across the forecast area Friday, most extensive across northern and eastern areas. Otherwise, moisture wrapping around the exiting system will keep mostly cloudy skies across much of the forecast area Friday, with partly sunny/mostly cloudy skies across southwest areas. Low temperatures tonight will range from around 50 to the lower 50s north, to the lower 50s Downeast. High temperatures Friday will range from around 60 to the lower 60s north, to the mid to upper 60s Downeast. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... Low pressure will continue to exit to the southeast Friday night through Saturday, with high pressure building over the forecast area in its place. With this change in air mass will come a return of drier air in the upper levels, limiting shower chances. That said, an inverted trough behind the departing low may still lead to isolated rain showers Saturday afternoon, which coincide with peak diurnal heating. Any showers which do develop will likely remain confined to the north. Patchy fog may form early each morning as low level moisture lingers, and is particularly likely in any areas which see rainfall the day before, increasing the low level moisture prior to nocturnal surface decoupling. As high pressure builds in and skies begin to clear late Saturday night, surface decoupling may allow for temperatures to fall into the mid 40s across the north and upper 40s Downeast. Fog development should help limit temperatures from falling much further, but if fog fails to form, lows could make a run for the upper 30s early Sunday morning. Temperatures may lift back into the upper 60s to around 70 during the day on Sunday as skies continue to clear. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... A ridge of high pressure will remain over the forecast area through early next week. This subsidence pattern could lead to mostly clear skies and subsequent surface decoupling which may allow for temperatures to plummet overnight. The most likely coldest night through the extended forecast period is Monday night, with cold air advection through the day on Monday followed by mostly clear skies and light winds Monday night. If river valley fog does not develop under these conditions, then there could be the chance for frost development, particularly across more sheltered valleys in the north which tend to run colder. For later Wednesday into the day on Thursday, another front could approach from the west, bringing another chance for rain showers into the forecast area. Recent model trends suggest the high pressure from earlier in the week may be strong enough to hold off the front, such that the front weakens as it pushes into the area, and rain may not be widespread across the area. At the same time, the remnants from Helene will be pushed off the coast by this front. The blocking high pressure should be enough to keep this rainfall south of the area, but if the high trends weaker, some of this moisture could enhance rainfall into the Downeast region. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... NEAR TERM: MVFR/IFR, occasional LIFR, tonight. Rain early this evening, then tapering to showers. Patchy fog tonight. Across northern areas Friday, MVFR/IFR early then VFR/MVFR during the afternoon. Scattered to numerous showers. Patchy fog early. Across Downeast areas Friday, VFR/MVFR early then VFR during the afternoon. Isolated to scattered showers. Patchy fog early. South/southeast winds around 10 knots, becoming south/southwest tonight. Variable winds 5 to 10 knots, becoming north/northwest Friday. SHORT TERM: Fri night: Conditions improving to VFR across all terminals. Brief IFR possible late in patchy fog. N wind around 5 kts. Sat: Mostly VFR. Brief -SHRA possible across northern terminals. N wind. Winds light and variable. Sat night...VFR conditions across all terminals, though brief IFR vis possible in patchy fog at any terminals which see rain on Sat. Winds light and variable. Sun - Tues: VFR across all terminals. Winds NW around 5 kts, shifting SE by Tues 5 to 10 kts. && .MARINE... NEAR TERM: Winds/seas below small craft advisory levels tonight through Friday. Rain early tonight, tapering to showers late. Patchy fog tonight into Friday morning. SHORT TERM: Winds and seas will likely remain below SCA criteria through the end of the week and into the weekend. Fog could limit visibility Friday night through Sunday. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Clark/Norcross Short Term...AStrauser Long Term...AStrauser Aviation...Clark/Norcross/AStrauser Marine...Clark/Norcross/AStrauser