Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 081926 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 326 PM EDT Sat Aug 8 2020 .SYNOPSIS... High pressure will remain across the area this weekend. An upper level disturbance will cross the region Monday. A cold front will begin to cross the region later Tuesday, then slowly move toward the Gulf of Maine by Thursday. && .NEAR TERM /THROUGH SUNDAY/... Latest radar ref imagery conts to show isold shwrs/tstms transiting the the nrn St John vly and this activity should cont til erly eve as a weak upper trof moves E from Ern QB mainly N of the FA toward the Gaspe Peninsula and sfc htg wanes with a setting sun. Other shwrs ovr wrn Downeast areas should dissipate even sooner as a s/wv moves ESE across the Gulf of ME. Otherwise, Skies will be fair tngt under a weak ridge of sfc hi pres with ovrngt lows some 3 to 7 deg F warmer than last ngt. With slowly increasing dwpts after sunset, we cannot rule out patchy vly fog well aft mdngt lasting into erly morn hrs. Latest 12z dtmnstc models cont to be in good agreement with the s/wv movg ESE from NE Ont weakening as it moves into and crosses just SW of the FA later Sun aftn into Sun ngt, so we cont with isold shwrs/tstms PoPs later aftn and erly eve across Wrn and inland Srn areas with a small area of sct shwrs/tstms ovr SW Piscataquis and Penobscot counties. Went with low cnvctv rnfl amts based on PoP distribution for the Sun 18-24z tm frame. Hi temps Sun aftn will likely be warmest across the NE which will likely have the most sunshine. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... In general, the trend will be for increasing heat and humidity through the period. Surface high pressure dominates through the period, but a weak upper trough slowly crossing the area Sunday night into Monday brings a slight chance of showers or thunderstorms. Instability looks unimpressive and timing is a bit off with the upper trough crossing Sunday night rather than during peak daytime heating on Monday. Current SBCAPE projections look best towards southern Penobscot for Monday afternoon. Coastal fog and low clouds will creep inland each day and have maintained lower temps towards the coast with the onshore flow persisting during the period. On Tuesday, an upper trough will approach from Quebec and upper level lapse rates look unusually robust. Accompanied by dew points hitting the upper 60s and highs in the upper 80s, SBCAPE could hit some values not often seen in northern Maine. Lacking is shear...and would prefer a bit more moisture. A pre-frontal trough is the only plausible trigger and that would be for the northern and western zones only. The surface cold front is expected to stay well west through Tuesday. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... The cold front will slowly creep southward across the forecast area Tuesday night into Wednesday night. Tuesday night looks very warm and humid with lows in the upper 60s. Coastal fog and stratus will cover much of the Downeast region. The best instability on Wednesday will shift to the southern half of the forecast area...although SBCAPE doesn`t look quite as strong as Tuesday and shear remains uninspiring. Will maintain mention of thunderstorms Wednesday afternoon. Expect the front to slowly sag into the Gulf of Maine Wednesday night. Another round of coastal fog and stratus will likely occur. While there`s not much cold air advection behind the initial cold front, a stronger upper trough will eventually catch up to the stalled front Wednesday night into Thursday. It will reinvigorate the front, but am expecting the front to be offshore by that point. Otherwise, cooler and drier air will gradually advect into the area Thursday into Saturday. Temperatures will finally trend closer to normal readings by Saturday. Can`t rule out a shower with the upper trough passage Friday, but there may not be much moisture available and will not introduce PoPs at this time. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... NEAR TERM: VFR all TAF sites xcpt very brief MVFR clgs/vsbys in any shwr/tstm late this aftn mainly at KFVE across the far N and possible MVFR/IFR vsbys very late ngt/erly morn in patchy vly fog. Lgt winds. SHORT TERM: Sunday night...Primarily VFR for all sites with the exception of BHB receiving IFR coastal fog and low clouds Sunday night. Monday...Afternoon thunderstorms possible for BGR. Monday night...Coastal fog and low clouds possible at BGR and BHB. Tuesday...Chance of afternoon thunderstorms north of GNR and HUL. Tuesday night...Coastal fog and low clouds possible at BGR and BHB. Wednesday...Chance of afternoon thunderstorms south of HUL and GNR. Wednesday night...Coastal fog and low clouds possible at BGR and BHB. Thursday...VFR. && .MARINE... NEAR TERM: No hdlns anticipated. Went with about 85 to 90 percent of blended wv guidance for fcst wv hts resulting in overall sig wv hts of arnd a foot for inner bay/harbor waters and around 2 ft for our outer MZ waters. Spectral wv groups will include about equal contributions from a shorter 7 sec Nwrd propagating group and an open Atlc background 11 sec NW propagating swell group. SHORT TERM: Fog is the primary threat with each night Sunday night into Wednesday night. The fog threat is greater Monday night into Wednesday night. Expect the fog to retreat from the coastline each morning. Winds were adjusted down for the high stability. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Beach Hazards Statement until 6 PM EDT this evening for MEZ029- 030. MARINE...None. && $$ Near Term...VJN Short Term...MCW Long Term...MCW Aviation...VJN/MCW Marine...VJN/MCW is the U.S. government's official web portal to all federal, state and local government web resources and services.