Area Forecast Discussion
Issued by NWS Caribou, ME
Issued by NWS Caribou, ME
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382 FXUS61 KCAR 261104 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 704 AM EDT Wed Jun 26 2024 .SYNOPSIS... A cold front will approach later today, then cross the area Wednesday night and Thursday morning. High pressure then builds in from the west through Friday, then slowly slides offshore Friday night and Saturday. A cold front approaches Saturday night, then crosses the area on Sunday. && .NEAR TERM /THROUGH TONIGHT/... 700 AM Update: Isolated showers have spread across the forecast area this morning. As seen on current radar imagery and CAMs guidance, several rounds of showers will cross the area later today along a few weak boundaries ahead of the next incoming cold front. No major adjustments needed to the previous forecast with this update. Previous Discussion: Current satellite imagery shows the approaching low pressure system, right now centered in the Quebec province, and gradually shifting eastward towards northern New England. A warm front continues to lift northwards, with our forecast area in the warm sector which has kept early morning temperatures in the 60s. As warm air advection continues into the day today, highs will lift into the 80s once more. Isolated rain showers will span across the region early this morning, followed by a brief dry sector. Another round of scattered rain showers will return this afternoon, likely staying in the northern half of the CWA and closer to the center of the low. A few thunderstorms are possible with some CAPE around 500 to 600 J/kg, but otherwise downsloping off the Longfellows combined with the placement in the right exit region of a strengthening upper level jet streak will limit the thunderstorm threat. For tonight, a cold front will gradually shift over the forecast area and begin to stall, while a center of low pressure rides up along this boundary through the forecast area. Recent model trends have slowed the forward progression of this front tonight, such that the low tracks along the coast versus being out over the Gulf of Maine. This could put the area of heaviest precipitation into the Interior Downeast region up into the Central Highlands, instead of being confined to just along the coast. Since this shift in low track settles on a track in agreement with model guidance over the last day and a half, there is higher confidence in this location for moderate to heavy rainfall. Though there are no large hydro concerns for river flooding, these rainfall rates could result in localized ponding on roadways and minor flooding in any areas with poor drainage. It is key to remember to always turn around, don`t drown in any areas of flooding! && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Rain associated with a fast-moving shortwave will quickly exit the area Thursday morning and some clearing is expected to develop. The cold frontal boundary is expected to remain stalled in the area by the time of max afternoon heating. Deep layer shear will be in abundance as a strong jet moves over the area in advance of an amplifying upper trough. The big question will be how much SBCAPE can develop. Over 1000 J/kg should be enough to generate storms with severe potential. That would be enough to overcome a cap that is keeping afternoon convective activity from showing up in most CAMS guidance. The ECMWF remains the biggest proponent of afternoon convection in a corridor between southern Piscataquis/Penobscot counties towards southern Aroostook County...along the stalled front. While other guidance hints at that corridor, models such as GFS/GEMS/NAM promote a scenario with weaker convective activity in the evening towards the North Woods and northern Aroostook. For now, have hit most of the forecast area inland of the Downeast with a slight chance of thunderstorms. The cold upper trough crosses Thursday night with continued shower activity in northern zones. Still might have an isolated thunderstorm as mid level lapse rates steepen with the trough. There is strong cold air advection Thursday night as 850mb temps plummet towards 2 to 4C by early Friday morning. Expect Thursday night lows to drop into the 40s to lower 50s. Would go into the upper 30s for the North Woods if it clears out earlier than currently expected. The cool air mass sets the area up for a pleasant Friday with highs reaching the low 70s only due to a very deep mixed layer. Humidity will be low with dew points in the 40s. The cool air will be fairly short-lived as upper level ridging quickly builds Friday afternoon and night. A shallow radiation inversion will likely still yield comfortable lows in the upper 40s to lower 50s Friday night. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Surface ridging moves rapidly offshore Saturday. A strong upper flow seems likely to advect a lot of high clouds into the area on Saturday ahead of a warm front. In spite of warming aloft, increasing clouds will keep Saturday highs mostly in the lower 70s. The warm front will arrive later Saturday with rain that will continue Saturday night. There are signs of another heavy rain event Saturday night with PWs increasing towards 2 inches, elevated instability above the frontal inversion, a strong low level jet promoting powerful 850mb moisture transport, and a deep warm cloud layer. Fortunately, this will be another progressive event with rain moving out of the area. Models are in decent agreement on a heavy rain event Saturday night. The next concern will be potential for strong thunderstorms Sunday afternoon. Once again, shear will be in ample supply and a stalled frontal boundary is expected to be in place. Saturday night rainfall will leave abundant low level moisture/high dew points. An approaching upper trough will generate cooling aloft. SBCAPE production remains in question...dependent in part on high temps. GFS and ECMWF feature higher temps (upper 80s) than we have forecast using NBM (lower 80s). The remainder of the extended forecast calls for dry conditions and temperatures trending below normal as cool Canadian high pressure builds. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... NEAR TERM: VFR conditions expected across all terminals through the day today. Scattered rain showers moving in from the west could briefly lead to MVFR cigs but should quickly clear as the shower moves through. Rain shower chances continue through the afternoon, though cigs will generally remain around VFR. SW winds today will increase to 10 to 15 kts and gusts 20 to 25 kts. Tonight, winds become light and variable as more numerous rain showers move in and cigs fall to IFR/LIFR in moderate to heavy rainfall. SHORT TERM: Thursday...Chance of morning IFR cigs at BHB and coastal sites with MVFR cigs during the morning inland. VFR in the afternoon outside of isolated thunderstorms, most likely towards FVE and Clayton Lake. Light west winds. Thursday night through Saturday...VFR. Northwest winds on Friday at 5 to 10 will become southerly on Saturday at 10 to 15 kt. Saturday night into early Sunday morning...IFR cigs and tempo IFR vis in rain. Isolated embedded thunderstorms. LLWS likely. South winds 10 to 20 kt. Sunday...Becoming VFR with a chance of afternoon thunderstorms. Southwest winds 10 to 15 kt. && .MARINE... NEAR TERM: Winds and seas should remain below SCA criteria today, though as a system approaches from the west, swell may lead to seas approaching 5 ft on the outermost reaches of the coastal waters. Gusts may briefly reach 25 kts, but will likely remain below 20 kts through today and continue to diminish into the night tonight. SHORT TERM: Fog will be possible Thursday, but should move away from the waters Thursday night. Fog returns Saturday night into Sunday morning. An SCA is possible is spite of strong stability for Saturday night into Sunday. Did reduce guidance winds due to the inversion and expect model sea heights will tend to decrease in future runs as the models catch on to the lower winds. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...AStrauser Short Term...MCW Long Term...MCW Aviation...AStrauser/MCW Marine...AStrauser/MCW