Area Forecast Discussion
Issued by NWS Caribou, ME

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754 FXUS61 KCAR 281623 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 1223 PM EDT Sun May 28 2017 .SYNOPSIS... A cold front will move into the area Sunday and stall. The front will return northward Monday as a warm front. An occluded front will cross the region later Monday night. && .NEAR TERM /THROUGH TONIGHT/...
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Update 12:20 PM: Have adjusted temperature, wind, and dew point. No other changes. Daycrew will need to keep an eye on the convective potential across the far w and n later this afternoon and evening. There is some CAPE as stated below, but the latest run of the RAP continues to point to the shear being weak(<20 kts). Attm, stayedthe course and kept the thunder out of the forecast for this update. Previous Discussion... The main challenge will be placement of shower activity and convective potential. Some patchy fog expected this morning will burn off quickly by 7 AM. Temps did drop into the mid and upper 30s in some of the low lying areas this morning. Temps are forecast to warm into the 60s and lower 70s this afternoon before clouds move in from the wnw. A stated above, a cold front is expected to drop across the northern and western areas this afternoon. There is some mid level forcing would be enough to trigger some shower activity. The short range guidance advertises things to destabilize some especially the NAM and RAP. Both indicate CAPE potential of 300-400 joules w/lapse rates steepening some(6.0-6.5 c/km). Some lacking factors are shear is weak and temps might not quite hit the convective temp. The area that could realize this would be the western areas of Aroostook and Somerset County but this would be isolated. Moisture also looks to be limited at first, but the column is expected to moisten by late afternoon. Attm, decided to not to add any thunder to the forecast as confidence is low. Will re-visit this w/the morning update. The front is forecast to stall across northern Maine tonight w/showers around. Kept 30-40% going across the northern and westerns sections. Given the light sse wind and temp/dewpoint spread being less than 3, decided to add patchy fog for the overnight period. Overnight temps are expected to be in the mid and upper 40s.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... A few showers will be possible Monday morning as the warm front exits northern zones northward into Canada. Otherwise, the day looks fairly dry until later when an occluded front approaches from the west. The predominant feature on Monday will be a southerly to southeasterly flow of moist marine air northward such that cloudy conditions will prevail with highs only reaching the upper 50s to near 60F. The occluded front has weakening dynamics with no surface-based or elevated instability. Rainfall amounts will reach a quarter inch at most and that`s most likely on the western fringes of the forecast area since the front will decay as it crosses the area. The occluded front slowly exits eastward on Tuesday morning...leaving the southerly flow intact and resulting in another cool and cloudy day. Highs will be just slightly warmer into the lower 60s. Another shortwave will rotate around a broad closed upper low in Ontario. This shortwave and associated surface trough will reach the area later Tuesday into Tuesday night. With a bit more cooling aloft, this trough may have some instability aloft and a few thunderstorms, but current indications are so modest, that it`s best to hold off including any mention of thunder in the forecast for now. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... A large closed upper low over northern Ontario will be a persistent feature with shortwaves rotating around the low into Maine every day in the longer range. This means seasonally cool temperatures and afternoon/evening showers. Temperatures will finally warm back towards 70F on Wednesday as winds become more southwesterly...producing some sunny breaks. This will likely generate surface-based instability as yet another surface trough and upper level shortwave rotates around the Ontario upper low and arrives Wednesday afternoon. As a result, have included a chance of thunderstorms for the afternoon and evening. This front will bring in slightly cooler and drier air for Thursday, but scattered shower activity will remain a risk with the possibility of another shortwave rotating around the Ontario low. A more vigorous shortwave will arrive later Friday or Friday night for a potentially heavier round of showers. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... NEAR TERM: Generally VFR w/a brief period of MVFR this morning due to radiation fog. The fog will burn off by 730 AM. Conditions are expected to drop down to MVFR and possibly IFR for KBGR and KBHB after midnight w/some fog and low cigs. SHORT TERM: Monday will start with IFR cigs towards BGR and BHB and MVFR cigs further north. All sites will become VFR Monday afternoon, but return to IFR by later Monday night into Tuesday morning. Conditions will slowly rise to MVFR Tuesday afternoon, but again return to IFR Tuesday night into Wednesday morning. VFR is expected by Wednesday afternoon...outside of thunderstorms and the VFR will continue into Thursday. && .MARINE... NEAR TERM: No headlines anticipated through this term. Winds and seas are forecast to be around 10 kts w/seas 2 to 3 ft mainly for outer zones. SHORT TERM: Some patchy fog is possible Monday morning. The fog will return later Monday night, but will really set in Tuesday night into Thursday morning. Two to three foot swell is expected during the period. Adjusted model winds down due to stable conditions over the cold waters. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Mignone

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