Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 131357 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 957 AM EDT Thu May 13 2021 .SYNOPSIS... A cold front will cross the region today. High pressure will move south of the region Friday through Monday. && .NEAR TERM /THROUGH TONIGHT/...
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952 AM Update: Tmg of shwrs was advcd a little quicker thru our FA durg the aftn and erly eve hrs based on consensus model tmg of best dynamics ahead of the cold front and upper lvl s/wv. Otherwise, fcst hrly cld cvr, temps, and dwpts were adjusted thru the day based on latest sat imagery and sfc obs trends with fcst aftn hi temps adjusted upwards a deg or two F. Prev Disc: A cold front behind the exiting low will move across the region today starting in the St John Valley and moving south. The day will begin with mostly sunny skies, allowing for surface heating and creating convective clouds across the north. As the front moves through, the convective clouds are expected to produce scattered showers. As the day continues into the afternoon, surface and elevated CAPE values increase into hundreds J/kg across the region, 300+ J/kg from Southern Aroostook northward, busting through the decreasing CIN. In addition, very steep lapse rates, wind sheer, and strong upper level divergence create the prefect environment for thunderstorms. Upper air sounding also shows a low freezing level with Hail CAPE in the hundreds J/kg for the same area, thus small hail is forecasted for the afternoon. Cant rule out the possibility of max hail size up to 0.75 for the above mentioned northern areas. The inverted V sounding and current high-res models point to the possibility of gusty NW winds for the region. Areas with thunderstorm threat could see much higher wind gusts up to 40 mph. High temperatures will be around average across the north, reaching into the lower 60s before the cold front moves through. Temperatures will rise a little more Downeast, reaching into the mid-60s. By tonight, the cold front should move out to the Gulf of Maine, bring cooler and drier air into the region. Expect clearing skies and below normal temperatures.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... A very dry post-frontal air mass will set up across northern and eastern Maine on Friday with highs ranging from the low 60s across the north to low 70s Downeast. Temperatures overnight Friday night will cool into the 30s to low 40s with generally favorable radiational cooling conditions, although cloud cover will begin to build in across western parts of the forecast area after midnight. Frost is likely across northern Maine. By Saturday a 500 mb shortwave trough moving across Quebec will help transport a more moisture-rich air mass across the area from the southwest, leading to the return of diurnal convection Saturday afternoon. The degree of moisture return remains uncertain, but enough instability should develop regardless for a chance of thunder. It will be nearly the warmest day so far this year with highs around 70 across a majority of the area. By Saturday night a weakening cold front associated with the departing shortwave trough will clip northern Maine, causing showers to linger into the evening. Cloud cover and greater low level moisture will keep lows from falling below the 40s. While not mentioned in the forecast currently, areas that receive rain during the day Saturday will be subject to patchy fog development overnight. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Seasonable temperatures and chances for diurnal convection will continue Sunday into next week as a 500mb ridge builds across eastern Canada and Maine. Sunday looks particularly active with showers and thunderstorms as a weak upper level low undercuts the building ridge and enhances mid-level lapse rates. Activity on Monday will be more scattered without any significant forcing mechanisms in the area. A 500 mb shortwave trough and surface cold front will approach the area Monday night into Tuesday. There are significant discrepancies among guidance regarding timing and trajectory of this feature. However, regardless of the outcome the feature will help maintain chances for showers and possibly thunderstorms until it passes. Overnight lows during the period from Sunday to Wednesday are expected to remain in the 40s with limited potential for frost. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... NEAR TERM: Generally expect VFR conditions Thursday, though local MVFR conditions are possible during the afternoon with any showers. An isolated thunderstorm with small hail is also possible across northern/central portions of the forecast area Thursday afternoon. NW winds will increase to 10-15 kts with gusts up to 20 kts for all terminals. Gusts could be much higher in thunderstorms near 40 kts. Returning to VFR by tonight with decreasing winds and drier conditions. SHORT TERM: Friday to Friday night...VFR with NW wind gusts to 20 kts during the afternoon. Saturday...VFR except tempo MVFR/IFR in thunderstorms. Light SSW winds outside of showers and thunderstorms. Saturday night...VFR. Lower visibility possible in patchy fog. Sunday...VFR except tempo MVFR/IFR in thunderstorms. Light winds outside of showers and thunderstorms. Sunday night...VFR. Monday...VFR except tempo MVFR/IFR in thunderstorms. South winds gusting to around 15 kts. && .MARINE... NEAR TERM: Winds and seas will remain below SCA for today and tonight. Wind gusts will increase this afternoon to around 20 kts as a cold front crosses the waters. Waves between 1-3 ft. SHORT TERM: Winds and seas will remain below SCA criteria throughout the period. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...VJN Short Term...MStrauser Long Term...MStrauser Aviation...VJN/MStrauser Marine...VJN/MStrauser

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