Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 110253 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 953 PM EST Sun Dec 10 2017 .SYNOPSIS... Weak low pressure will approach from the west tonight and then move east Monday. High pressure will build across the region Monday night. Strong low pressure will lift across the region later Tuesday through early Wednesday. && .NEAR TERM /THROUGH MONDAY/...
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935 PM Update: Larger scale models indicate a sfc wv of low pres crossing from NW to SE ME across a stalled arctic front that just recently entered Nrn ME this eve, very late tngt into Mon, with latest HRRR sim radar ref showing an intially band of sn shwrs with this sfc wv affecting Nrn ptns of the FA in addition to lgt mixed precip/sn alg the Downeast coast very late tngt and erly/mid mon morn. Therefore, we added chc PoPs to Nrn ptns of the FA for the late ngt into the Mon morn tm frame alg with associated lgt 6hrly QPFs/snfls. Otherwise, fcst hrly temps/dwpts were updated thru the late ngt hrs based on trends from latest sfc obs, with not enough deviation from the prior fcst update to make any chgs to fcst ovrngt lows attm. Orgnl Disc: The low pressure system that brought the first measurable snowfall to much of the region last night has moved well east of the Canadian Maritimes. A westerly flow of drier air has moved into the area in the wake of the low. Our attention now turns to an arctic frontal boundary just to the northwest of the state. Behind the boundary, temperatures this afternoon were only in the single digits above zero to lower teens across much of Quebec province. This boundary will begin to cross northern portions of the region tonight. An upper disturbance will also cross northern areas through early this evening with a chance of snow showers, and even a brief snow squall mainly across far northern areas and the St. John Valley. We should then see a brief break in any snow shower activity through the first half of the night. However, a weak area of low pressure across southern Quebec is expected to track east along the boundary and across far northern Maine toward daybreak on Monday. This will result in another chance for snow showers after midnight, mainly across northern and western areas. In addition, another weak area of low pressure is expected to develop along the down east coast as short wave energy rotates east around the upper trof. This low is expected to move quickly east into the Canadian Maritimes early Monday. Near term models are keeping the bulk of the moisture with this feature just offshore and to our east. However, it looks like the immediate down east coast could see a brief period of light snow with this system after midnight into early Monday morning. Precipitation amounts look to be light, less than a tenth of an inch, so any snow accumulation looks to be an inch or less. Brought the western edge of likely pops(60%) just into the immediate down east coast late tonight into early Monday morning. Otherwise, any morning snow showers across the north and light snow along the down east coast will give way to at least partly sunny conditions, with perhaps a few lingering afternoon flurries by afternoon. Lows tonight will range from the single digits above zero across the St. John Valley to the upper teens to around 20 down east. Highs on Monday will range from the mid teens to around 20 north and upper 20s to lower 30s Downeast.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... High pressure will exit to the east Monday night while intensifying low pressure tracks across the eastern Great Lakes. Cloud cover will increase across the region Monday night. The low will track toward southern Maine Tuesday. Snow will expand northeast across the region Tuesday. Onshore winds will draw warmer air toward the Downeast coast during the afternoon, which could allow the snow to mix with rain or transition to rain during the afternoon into the evening. The low will lift northeast across Maine Tuesday night, though the exact track is still uncertain. Snow will persist across northern areas Tuesday night. However, dependent on the track, warmer air being drawn north could allow the snow to transition to a wintry mix particularly across eastern areas. Snow, or a wintry mix, early Tuesday night Downeast will taper to snow showers overnight. Have issued a Winter Storm Watch for most of the forecast area, with the exception of the Downeast coast, Tuesday morning into Wednesday morning. The heaviest snow totals are expected across northern Aroostook county, where amounts in excess of 8 inches are possible. Lesser snow accumulations are expected southward across the remainder of the forecast area, dependent on the eventual track of the low. The least snow is expected along the Downeast coast where the snow should transition to rain or mix with rain. The surface low lifts toward the Gulf of Saint Lawrence Wednesday while the upper low crosses the region. Deformation zone snow or snow showers will persist across the north and mountains Wednesday with the upper low and wrap around moisture from the surface low. Mostly cloudy skies along with a chance of snow showers are expected Downeast Wednesday. Temperatures will be at below normal levels Tuesday, with slightly below normal level temperatures Wednesday. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Could still have a chance of snow showers across the north and mountains Wednesday night, with decreasing clouds Downeast. High pressure will build across the region Thursday. Low pressure should intensify east of the region Friday. Dependent on the track of the low, the western edge of the precipitation shield could bring a chance of snow to the region. High pressure is expected Saturday. Low pressure should approach from the west Sunday with a chance of snow. Temperatures will be at below normal levels Thursday through Sunday. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... NEAR TERM: VFR conditions to start the evening but we could see brief MVFR/IFR conditions developing this evening in any sct snow showers activity associated with an approaching frontal boundary. Mainly VFR on Monday but again could see briefly lower conditions in scatterd snow showers, mainly north. SHORT TERM: VFR conditions are expected Monday night. Conditions will lower to IFR/LIFR levels across the region Tuesday morning through the afternoon. IFR/LIFR conditions are then expected Tuesday night into Wednesday morning. Occasional MVFR conditions will then persist Wednesday afternoon. Occasional MVFR conditions will persist across the north and mountains Wednesday night into Thursday. Occasional MVFR conditions are possible Downeast early Wednesday night, with VFR conditions overnight into Thursday. Conditions Friday will be dependent on the eventual track of low pressure and whether snow is wrapped back across the forecast area. && .MARINE... NEAR TERM: A small craft advisory is in effect through early Monday morning. Small craft advisory may be needed into Monday. SHORT TERM: Small craft advisory conditions are expected Monday night into Wednesday. Visibilities will be reduced in rain and snow Tuesday morning into Wednesday morning. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Winter Storm Watch from Tuesday morning through Wednesday morning for MEZ001>006-010-011-015>017-031-032. MARINE...Small Craft Advisory until 7 AM EST Monday for ANZ050>052. && $$ Near Term...VJN Short Term...Norcross Long Term...Norcross Aviation...VJN/Norcross Marine...VJN/Norcross

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