Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 211337 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 937 AM EDT THU JUL 21 2016 .SYNOPSIS... High pressure will build south of the area today. A cold front will approach Thursday night and cross the region Friday. Another secondary cold front with an upper level low will approach the region from the northwest on Saturday and cross the region Saturday night. && .NEAR TERM /THROUGH TONIGHT/... 940 AM update... Backed up timing of showers/tstms by 2 hrs back across the far wnw areas using the latest run of the Hi Res WRF. This mesoscale guidance shows activity apchg the Maine-Quebec border after 21z. The HRRR is a bit faster and brings a cluster into those areas around 21z. Kept the midnight crew`s pops at 20-30%. Temps/dewpoints were adjusted using latest obs. Dewpoints are projected to fall back some this afternoon w/the wsw wind of 10-15 mph. The rest of the forecast looks in line attm. Previous discussion... High pressure will gradually shift south of the area today, allowing a return southwest flow to set up across New England. Scattered showers will develop over northern Maine late this afternoon in response to warm air advection and spread south through the evening as a pre-frontal trough crosses out of Canada. Instability looks meager as much of the guidance is topping SB CAPE out at 350 J/kg or so, and the SREF indicates only a 40% chance of CAPEs over 500. So have only included isolated thunderstorms for this afternoon. It`ll be a warm day with highs in the lower to mid 80s across much of the region. Showers will continue overnight as the aforementioned pre-frontal trough pushes south. Isolated thunderstorms will continue as well as there will be plenty of elevated instability. Lows will be on the uncomfortable side as temperatures will remain in the lower to mid 60s. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... SPC still has much of New Eng in a slight risk of svr tstms for spcly Fri aftn into erly eve, so we introduced enhanced tstm element wording for winds...hail and hvy rnfl for Fri aftn/erly eve as the first sig s/wv tracks W to E across the FA. Max tstms cvrg will be in the sct to bkn range, so for now we max PoPs in the high likely category for msly Nrn/Cntrl ptns of the FA. Max potential SBCAPEs will be in the 1500-2000 J/kg with mdt 0-6km bulk shear vectors of arnd 30 kt. Another s/wv with an associated secondary cold front from Cntrl Can will bring another round of shwrs/tstms to most of the region on Sat, spcly the aftn into eve hrs again were we max PoPs in the low likely cat. Lower fzg lvls and lesser shear vectors by Sat aftn suggest the potential of larger hail and slower movg tstms capable of producing hvy rn, but will hold off on enhanced tstms element wording given that its still out in day 3, but will keep mention in the HWO. Temps will be a abv normal, with hi temps both days dependent on some available sunshine in the morn to midday hrs. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Any remaining organized shwr/tstm activity from the eve hrs should diminish and move E of the FA durg the ovrngt hrs Sat ngt as the upper trof/closed low alf slowly moves E into NB prov. Sun will be ptly to msly cldy, with isold shwrs possible across Cntrl and Ern ptns pf the FA Sun aftn, as whats left of relatively cold air alf only slowly moves E out of the FA as the upper low moves across the Gulf of St Lawrence. Clrg skies are then xpctd Sun ngt, contg into Mon morn before cldnss increases Mon aftn with the apch of the next s/wv alf from the great lks in a contd progressive wrly zonal ptn alf. Sct Shwrs and possible aftn/eve tstms will then move W to E into the FA from QB prov late in the day thru Mon ngt and perhaps into Tue. Kept max PoPs in the chc cat for now. Tue ngt and Wed should be drier. Temps will cont aoa normal. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... NEAR TERM: VFR conditions will prevail today and tonight. Mid clouds will increase this afternoon and evening as a warm front lifts across the region. Scattered showers with isolated thunderstorms are expected to move into northern Maine late this afternoon and gradually push southward overnight. Localized IFR conditions will be possible in any thunderstorms, especially at the northern terminals. SHORT TO LONG TERM: Msly VFR for the TAF sites Fri thru Mon, xcpt ocnl MVFR clgs/vsbys in mdt rn shwrs and lcly IFR vsbys with hvy rnfl associated with tstms. .MARINE... NEAR TERM: No headlines will be needed through the near term. High pressure will build south of the waters today, allowing winds to turn to the south and increase to 15-20 kt. But any mixing will be very limited due to the cold Gulf of Maine waters, so gusts will remain below 25 kt. Seas will build from 2-3 ft this morning to 3-4 ft late this evening. SHORT TO LONG TERM: An SCA for seas is possible for spcly the outer MZs later Fri into Sat morn as a steady and fairly long SSW wind fetch of 15 to 20 kt occurs Fri aftn into Fri ovrngt generating 5 to 7 sec pd wvs of 4 to 6 ft. Stronger winds alf are not xpctd to reach below 20M abv the sfc due to a strong marine invsn. Wv hts should then slowly begin to diminish later Sat and cont thru the remainder of the weekend. Only went with about 75 percent of WW3 wv ht guidance for fcst wv hts for these ptns of the fcst. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Hastings/Hewitt Short Term...VJN Long Term...VJN Aviation...Hastings/Hewitt/VJN Marine...Hastings/Hewitt/VJN is the U.S. government's official web portal to all federal, state and local government web resources and services.