Area Forecast Discussion
Issued by NWS Caribou, ME

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908 FXUS61 KCAR 230046 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 746 PM EST Wed Feb 22 2017 .SYNOPSIS...
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High pressure will cross the region overnight. Low pressure will track through Quebec on Thursday and track to our north Thursday night. High pressure will return on Friday.
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&& .NEAR TERM /THROUGH THURSDAY/...
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Update... High pressure will cross the region overnight while low pressure tracking northeast across the Great Lakes draws a warm front across Quebec province. Cloud cover will increase across northern portions of the forecast area tonight. Could also have the slight chance of a light wintry mix late across northwest areas with little or no ice accumulation. Otherwise, generally expect partly cloudy skies across the remainder of the forecast area tonight. Overnight low temperatures will range from the upper 20s to lower 30s across the forecast area. Have slowed the onset of precipitation across northern areas with this update. Have also updated to adjust for current conditions along with overnight temperatures and clouds. Previous Discussion... Low pressure north of the Great Lakes will move to the north of the state Thursday. Light precipitation is possible across the northern most part of the state as the low passes by. Expect Warmer air aloft so after a brief period of snow expect a mixture of sleet and freezing rain. QPF amounts are mostly under a tenth of an inch before changing to rain so accumulation of ice is expected to be minimal. Have used the precipitation from thickness tool run on a blend of the NAM and GFS for precipitation type Thursday. All precipitation should change to rain later Thursday morning as surface temperature warms.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... A sfc low associated with an upper-level shortwave is forecast to pass north of the CWA at the start of the period, dragging a weak cold front across the state Thu night. The front then stalls over the Gulf of Maine during the day Fri. Some rain may be ongoing at the start of the period, especially up north, but this will quickly diminish and move off to the east with the front. Highs will be a few degrees lower on Fri, but still well above normal for late Feb. A more powerful low pressure system backed by a deep upper-level trough will lift NE`ward across the Great lakes and into western Quebec Fri night and Sat. As this happens, the stalled front will lift back north as a weak warm front late Fri night. As it does so, some is likely to develop from Downeast to the central highlands Fri eve and night. Warm moist air overrunning sfc sub-freezing air will likely lead to some sleet and freezing rain, mainly north of a Bangor-Eastport line, before the warm air moving north turns everything to rain after sunrise Sat AM. As warm, moist air streams northward over the statewide snowpack on Sat and dewpts get above 30F, will need to watch out for potential of fog, which could be locally very dense. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... At 00z Sat, the cold front associated with the potent low will just be reaching the eastern border of NY, and will then quickly advance across the state by 12z Sat. Moderate to heavy rain is possible ahead of and with the front. Given the rather deep snowpack remaining across the state, much of this rain will likely get absorbed, though it`s too early to say for sure what the hydrologic impacts may be. Most of the precip will be clear of the state by Sun PM, but a few showers could linger into the evening, until the base of the upper trough crosses the state. A weak front crossing the state Mon afternoon & evening could trigger some snow showers, perhaps even a snow squall, before pushing out of the area. Meanwhile, a more potent low may pass well to the south, keeping clear of the CWA. The ECMWF, GFS, and CMC are all in relatively good agreement on the next significant system impacting the CWA Wed into Thu, so will just have to wait and see how the details unfold. Did go for some low-end likely POPs with this system, due to good agreement between the models. && .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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NEAR TERM: Expect VFR conditions across northern areas into the early morning hours, with MVFR conditions developing overnight. A light wintry mix is possible across northern areas late tonight through early Thursday morning before a transition to rain. Conditions will lower to IFR/LIFR levels across northern areas Thursday. VFR conditions are expected Bangor and Downeast tonight into Thursday morning, with MVFR conditions developing during the afternoon. SHORT TERM: IFR to MFVR conditions are expected Thu night, improving to all MVFR and VFR during the day Fri. Conditions will deteriorate again Fri eve and night, with widespread IFR CIGs likely. IFR vsbys also psbl in snow for KCAR thru KFVE, with ocnl freezing rain possible from KBGR northward Fri night. Sleet and FZRA will change to rain from south to north Sat AM, with areas of dense fog likely to cause patchy IFR to LIFR into Sat night. The fog will break up Sat night, though IFR CIGs may remain thru Sun PM in lingering snow showers. Improvement to MVFR or VFR may occur Sun night, but another round of snow showers and psbl squalls may cause areas of IFR conditions Mon morning and afternoon.
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&& .MARINE...
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NEAR TERM: Conditions are expected to be below small craft advisory levels tonight through early Thursday. Small craft advisory conditions could then begin to develop later Thursday afternoon. For sustained winds Thursday have used the NAM. For waves: Currently a medium period southwesterly swell is being observed at buoy sites. This wave system was generated last night from a fetch confined to the Gulf of Maine. Wind speeds have been well below 10 knots today so wind wave is small. South to southwesterly wind wave will build later Thursday to 3 to 4 feet/6 seconds as wind speeds increase late in the day. Will use the Near Shore Wave Model to populate wave grids. SHORT TERM: Borderline winds and gusts Thu night into Fri AM may require an SCA, though seas will likely be on the low side. SW`ly winds Thu night will shift E-SE`ly by Fri eve as low pressure approaches from the west. Winds will turn more SE-S`ly and increase by Sat as a warm front pushes from the Gulf onto the mainland.
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&& .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Norcross/Mignone Short Term...Kredensor Long Term...Kredensor Aviation...Norcross/Kredensor Marine...Norcross/Mignone/Kredensor

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