Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 110744 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 244 AM EST Mon Dec 11 2017 .SYNOPSIS...
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Weak low pressure will move east this afternoon. High pressure will build across the region tonight. Strong low pressure will lift across the region later Tuesday through early Wednesday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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The model guidance is in good agreement through the near term period of the forecast. A short wave through will be moving into NW Maine at the start of the period and will move east of the area by early afternoon. Higher pressure will ridge into the area ahead of the next frontal system that will move into NW Maine early Tuesday morning and will remain across the area through the end of the period. Loaded a blend of the GFS/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.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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An upper trough digging into the Great Lakes is expected to close off across the eastern Great Lakes Tue afternoon and a deep upper low is forecast to track across Maine Wed with 500H heights dropping to around 500 Dam. A surface low is forecast to deepen and track from the eastern Great Lakes Tue morning and into northern NY State and western New England by 00z Wed. The surface low is expected to track along the western Maine/Quebec border Tue night with the low near or a little north of Quebec City by 00z Thursday. Snow will overspread most of the central Highlands and Downeast Region just after the morning commute Tue, and is expected to spread into the Saint John Valley early to mid afternoon. Initially there will be an excellent surface to overrun with very cold air in the low levels, but given the track of the low there is a major surge of warm air into the region with 925H temps progged to surge to +7C Tue evening in the Bangor Region, and perhaps above 0C all the way north to the eastern Saint John Valley by late Tue night. Expect the snow Downeast will transition to rain by late afternoon or early evening in the Greater Bangor Region with the transition working north Tue night, perhaps reaching all the way north to the eastern Saint John Valley around the time the precipitation winds down late Tue night. The snow ratios will initially be high, i.e. 20:1, but will lower rapidly late in the day Tue and Tues night to more like 10:1 in the north where most of the precipitation falls as snow. The total QPF is on the order of 6 to 8 tenths of an inch. The best chance of reaching low end warning level snowfall is across the far northwest in zones 1, 3 and 4. After collaboration with WFO Gray have elected to keep these areas in a watch as it is still somewhat borderline as to whether or not most of the area reaches low end warning level snowfall. Will maintain the watches in the next tier of zones to the south and east, but given the latest trends suspect that the day shift may want to place the southern tier of zones in an advisory. Again, after collaboration with WFO Gray will hold onto the watch, but will end it much earlier by 00z Wednesday when temps should be well into the 30s Downeast and the precipitation should have changed to rain. There is certainly the potential that snow accumulations will only be in the 2 to 4 inch range in the Bangor area, but with the possibility of some higher snowfall rates from around 18-22Z will keep the watch with the morning package. Did lower the amounts a bit where the transition to rain is expected, but it is possible that later shifts may need to lower amounts even more.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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A cold pattern expected. Clouds and scattered showers across the north and mountains Wed night into Thu as deep low pressure lifts well north of the area toward Labrador. Partly cloudy Downeast during this time. Friday into Saturday are looking mainly dry and cold, however, an area of low pressure offshore could clip the far southeast zones late Fri night or early Sat with a period of snow, but most of the models and ensembles keep this system far enough east for minimal impacts. A weak clipper coming in from the Great lakes may bring a little snow to the area Sunday, but at this time does not look like a big event.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/...
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NEAR TERM: MVFR conditions across northern Maine with scattered snowshowers. VFR conditions for Southeastern Maine today. High pressure builds into the area this afternoon bring clearing conditions. Conditions at all sites will improve to VFR. Increasing clouds and decreasing ceilings late evening with MVFR condition returning to FVE after midnight. MVFR conditions will spread south by morning to CAR, PQI and HUL. Then spread to BGR and BHB by noon. IFR conditions will move into northern Maine by the end of the period. SHORT TERM: Conditions will lower to IFR and LIFR from south to north across the area Tue as snow overspreads the area. The snow will transition to rain at KBGR and KBHB by late in the day Tue. Conditions should improve to predominately VFR Wed morning at the Downeast terminals with IFR improving to mostly MVFR from KHUL north to KFVE. VFR should continue into Thu Downeast, with mainly MVFR at the northern terminals. Mainly VFR expected Fri.
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&& .MARINE...
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NEAR TERM: A Small Craft Advisory for seas will be in effect through much of the near term portions of the forecast. SHORT TERM: At least small craft advisory conditions likely to persist Tue into Thu morning, with a short period of gales possible late Tue afternoon into early Tuesday evening, with a longer period of gales possible Wed afternoon into Wed night.
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&& .CAR WATCHES/WARNINGS/ADVISORIES...
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ME...Winter Storm Watch from Tuesday morning through Wednesday morning for MEZ002-005-006-010-011-031-032. Winter Storm Watch from Tuesday morning through Wednesday morning for MEZ001-003-004. Winter Storm Watch from Tuesday morning through Tuesday evening for MEZ015>017. MARINE...Small Craft Advisory for hazardous seas until midnight EST tonight for ANZ050-051.
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&& $$ Near Term...Norton Short Term...CB Long Term...CB Aviation...Norton/CB Marine...Norton/CB

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