Area Forecast Discussion
Issued by NWS Caribou, ME

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928 FXUS61 KCAR 181118 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 618 AM EST Mon Dec 18 2017 .SYNOPSIS... A weak area of low pressure will approach from the west today and then move east tonight. Another low pressure system will pass to the north of the region Tuesday through Tuesday night followed by the approach of Canadian high pressure for Wednesday and Thursday. && .NEAR TERM /THROUGH TONIGHT/... 610 AM update... High clouds continue to stream across northern and down east Maine early this morning. Temperatures had fallen to 10 to 15 below zero earlier this morning in the colder valley locations of far northern Maine, but temperatures have leveled off in response to the increasing cloud cover. MRMS radar reflectivity data shows the nearest returns were down across southern New Hampshire at this hour. With very dry low level air in place, it will take a while for any snow to make it into the forecast area, but still expecting some snow to spread across portions of central and down east Maine by afternoon. Only minor tweaks to ongoing forecast otherwise no significant changes at this time. previous discussion Cold high pressure at the surface will continue to move east through early today. As it does so, overunning snow is expected to develop across central and down east areas by early afternoon, in advance of a weak short wave approaching from the great lakes region. There will be a sharp cut off to the northern edge of the snow shield, with the steadiest snow confined to a line south of a Greenville- Millinocket-Danforth. Very little in the way of snow is expected to the north of this line, with far Northern Aroostook county not expected to see any in the way of any measurable snow, under mainly cloudy skies. Elsewhere, as far as snow totals go, looks like generally about one inch of snow can be expected from the central highlands through the upper Penobscot Valley. Across down east areas, including the greater Bangor region, we are generally expecting two to three inches, thus will not be issuing any advisories. That being said, commuters should expect the potential for some snow covered roads by the afternoon drive time across down east areas, including the greater Bangor region. Afternoon high temperatures will be a few degrees warmer than the last few days. Highs across northern areas will range from the low to mid teens and upper teens to mid 20s across central and down east areas. Snow is expected the continue into early this evening across down east areas before tapering off to snow showers by midnight, as the short wave moves east into the Canadian Maritimes. Otherwise, it will remain mainly cloudy overnight. Couldn`t rule out the possibility of patchy freezing drizzle very late tonight with abundant low level moisture expected and some drying aloft, although not confident enough to mention quite yet. Tonight will be much milder than previous nights with abundant cloud cover expected and light southerly flow. Therefore, expecting lows to range from the low to mid teens north and upper teens to mid 20s along the coast. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... Immediately on the heels of Mon/Mon ngt`s s/wv, will be a more nrn s/wv and associated sfc low movg e from NE Ont and Cntrl QB provs for Tue aftn into Tue ngt, with the main impact from this system with ovrrng snfl xpctd across the N as the sfc low tracks ewrd just N of the St John vly. Snfl amts by erly Wed morn will range from 2 to 3 inches across the far N with progressively lesser amts swrd to the coast. In fact, milder marine air brought into the Rgn from a S wind with this system could result in a mix of lgt sn/rn ovr Downeast and perhaps even Cntrl ptns of the FA Tue aftn and erly eve. After the passage of this s/wv, other s/wvs crossing the FA from Cntrl Can and QB will bring intermittent sn shwrs msly to Nrn/Wrn ptns of the FA very late Tue ngt thru Wed alg with a return to brisk NW winds and much colder conditions as a new batch of arctic air moves into the Rgn. Sct sn squalls/St Lawrence streamer sn bands cannot be ruled out Wed across the N to as late as Wed eve across the far N. Any remaining sn shwrs across the N should end late Wed ngt as the subsidence invsn alf lowers below 850mb, but brisk NW winds will continue. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Thu will cont fair and brisk and cold with winds diminishing Thu ngt as the sfc ridge axis crests the Rgn by erly Fri morn. Some potential radiational cooling is xpctd Thu ngt with ovrngt lows sig below zero with the only lmtg factor some hi cldnss. Cldnss then thickens and lowers durg the day Fri as a sig regime chgng s/wv alf and associated sfc low from the midwest and great lks begins to apch our Rgn. Sn from this system will break out across the Rgn by late day Fri, but at this point, all model guidance has now shifted the track of the sfc low well NW of our FA. Subsequently, the potential of chgovr to rn has now encompassed all of the Rgn beginning ovr Downeast areas by late Fri ngt aft an inch or two of snfl and reaching the the St John vly tentatively by midday Fri aft 2 to 4 inches of snfl. We indicate a sn, sleet, and rn transition for this fcst update, but could easily see a sleet/fzra transition potentially requiring a wntr wx adv for our Rgn, but a little erly to advertise fzra in our fcst grids attm. Following a pd of all rn Sat aftn, a cold front followed by a sharp dry slot alf will end ovrrng precip for the Rgn by Sat eve, perhaps followed by isold-sct sn shwrs Sat ngt with a returns to fair wx and seasonably cold temps on Sun. && .AVIATION /11Z MONDAY THROUGH FRIDAY/... NEAR TERM: There will be a wide variation in aviation weather conditions from north to south across the forecast area. Across the far north, KFVE/KCAR/KPQI/ expect generally VFR today. Further south, especially KBGR/KBHB/, VFR conditions this morning will give way to IFR in developing snow from mid morning and continuing into tonight. Expect the potential for MVFR ceilings to develop across the far north late tonight. SHORT TO LONG TERM: VFR all TAF sites until late Tue morn then clgs/vsbys lowering to IFR/LIFR Tue aftn in sn across Nrn TAF sites and MVFR for lgtr sn and mixed precip Downeast sites. Nrn TAF sites remain MVFR clgs in bkn-ovc SC and ocnl sn shwrs Tue ngt into Wed while Downeast sites improve to low VFR. All sites should be VFR Wed ngt, xcpt KFVE which may hold MVFR into Wed eve, with all sites contg VFR Thu thru Fri. && .MARINE... NEAR TERM: Winds/seas will remain below headline levels through tonight. Visibility will be reduced to 1 to 3 NM at times today through tonight in snow this afternoon and in snow and rain this evening. SHORT TO LONG TERM: Initially no hdlns Tue morn, then winds with seas potentially ramping up to gale force msly in gusts by Tue ngt and cont so at least thru Wed morn, which tm pds we advertise a gale watch for all of our waters. Winds and seas then remain at or below SCA range Wed aftn thru Thu. Used a blend of WW3 and NWPS guidance for fcst wv hts. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Gale Watch from Tuesday evening through Wednesday morning for ANZ050>052. && $$ Near Term...Duda Short Term...VJN Long Term...VJN Aviation...Duda/VJN Marine...Duda/VJN

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