Area Forecast Discussion
Issued by NWS Caribou, ME

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065 FXUS61 KCAR 210146 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 946 PM EDT Thu Apr 20 2017 .SYNOPSIS... Weak high pressure builds over the area tonight. Low pressure will slowly drift towards the area from Ontario into Quebec Friday and Friday night. Another low will form south of the state on Saturday and move eastward into the open Atlantic. && .NEAR TERM /THROUGH FRIDAY/...
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935 PM Update: Minor adjustments were made to fcst hrly temps and dwpts into the ovrngt based on trends from latest sfc obs with fcst ovrngt lows lowered about 2 deg F across Nrn lctns due to weak radiational cooling with thin cld cvr there allowing mid eve temps to fall close to prev fcst lows. Orgnl Disc: A weak surface trough that moved over the area this morning continues to decay and lose its identity over the region. Meanwhile, high pressure has been building southwestward from Labrador with a moist easterly flow. The net result has been significant low level moisture trapped under a subsidence inversion. This situation will continue tonight into Friday morning for the forecast area. With nightfall, fog will reform along with light rain and drizzle...mostly south of a line from Houlton towards Greenville. Lows won`t drop much due to the clouds. In terms of the next frontal system arriving Friday, timing has been delayed a bit with the highest pops in the afternoon. In fact, the eastern border may stay dry all day. As a result, have raised highs to the east with some upper 40s towards Washington County. Have used shower terminology for areas that will be under chance pops during Friday to reflect the more intermittent nature of precip. Further west, precip will reach the western mountains in Piscataquis County during the morning and locations over 1000 feet elevation will have snow. Accumulations will be under an inch and shouldn`t cause any travel issues with temperatures at or above freezing.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... The model guidance is in good agreement through the near term period. A Low over southern Quebec, with an occluded front extending through Maine are the main weather features through early portions of the period. Saturday morning the low will move east into western Maine, and slowly cross the area Saturday into Sunday morning. Sunday morning the low will move east into New Brunswick. Higher pressure will build into the area through the end of the period. Loaded a blend of the GFS/GEM/NAM/ECMWF to smooth out the minor differences in the models. Loaded NAWAVE4 for seas in the coastal waters. Loaded windgust by factor tool. For QPF used GFS. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... The extended models are in good agreement. A cold frontal system approaching northern Maine at the start of the period will move through Monday morning higher pressure will build into the area and will dominate the weather through Tuesday evening. A low along the coast of SC Monday, will deepen as it moves north along the coast. By early Wednesday morning the warm front ahead of the deepening low along the coast of DELMARVA will move into the Downeast coast. Another frontal system moving east across the central Great Lakes early Wednesday will interact with the coast system. The GFS and ECMWF differ a bit on position but generally agree that there will be interaction between the two fronts. The GFS hold the coastal system along the Downeast coast, and moves the other front east/west across southern Quebec. The EC moves the coastal system in to northern Maine, holding the frontal system over Canada to central Quebec. Thursday morning these differences continue. The GFS moves the coastal system east of Maine into eastern New Brunswick, the low of the second front moves to western Quebec with the cold front extending south through VT. The EC move the low front the Canadian system to northern Maine, the front east of Maine, with wrap around precipitation across western Maine. Higher pressure will build into the area Friday evening and will remain through the end of the period. Loaded a blend to smooth out the differences in the models, however the solution leans more towards the GFS solution. Used NAWAVE4 for seas in the coastal waters. Used windgust by factor tool. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... NEAR TERM: IFR cigs will persist south of a line from HUL to MLT to GNR until mid-morning Friday. Drizzle and fog will drop vis to LIFR at times tonight. Snow and tempo LIFR vis will be an issue at GNR Friday morning. North of HUL, MVFR cigs will drop to IFR later tonight and persist into mid-morning Friday. SHORT TERM: IFR conditions in rain, or a mix of rain and snow Friday night through early Sunday morning. Higher pressure will build into Maine Sunday morning bring clearing conditions. MVFR early Sunday morning becoming VFR by mid morning Sunday. A cold front will move through northern and central Maine Sunday night bringing conditions back to MVFR for FVE, CAR, PQI and HUL. The front will clear the area Monday morning VFR conditons will return through the end of the period. && .MARINE... NEAR TERM: Winds and seas creep up again on Friday as a low moves towards the waters, but with the cold water temperatures and stable conditions, will cap wind gusts to 25 kts and seas at 5 ft at this time. If confidence in SCA issuance increases tonight, then we`ll issue the advisory for Friday into Friday night. SHORT TERM: Winds and seas will be just below SCA criteria early in the period, then subsiding. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...VJN Short Term...Norton Long Term...Norton Aviation...VJN/Norton Marine...VJN/Norton

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