Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 220236 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 1036 PM EDT Wed Mar 21 2018 .SYNOPSIS... High pressure over Hudson Bay will dominate area weather this evening. Low pressure will track south of the Gulf of Maine towards eastern Nova Scotia tonight and Thursday. The low will exit across the Maritimes Friday. && .NEAR TERM /THROUGH THURSDAY/...
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1035 PM Update... Hrly temps/dewpoints were adjusted upward using the latest LAV guidance which is in line w/the latest conditions. Clouds continue to push northward helping to put a lid on a significant drop in temps. Low dewpoints will allow for temps to drop some overnight, but it looks as though they will be warmer than previously thought. Plus, winds will be increasing as they are already picking up across the Downeast helping to keeps temps up. Therefore, overnight mins were pushed up. The 00Z has come in and is much further east. Attm, stayed close to the previous forecast bringing some snow to the coast by around midnight or just after midnight. Previous Discussion... The snow forecast for later tonight and Thursday is challenging to say the least. There`s two separate pieces. The first involves the wraparound occlusion propagating northward towards the coast later tonight while weakening as it meets dry air. This first part is expected to provide several inches of snow along the coast. This band will decay as it continues northward into the dry air such that areas north of Hancock, Washington and southern Penobscot counties will receive very little or no snow. The second piece involves a shortwave rotating around the closed upper low from the Atlantic towards the Down East coast during Thursday morning. The big questions will be how far westward this shortwave rotates towards the Maine coast, the exact track of the upper low and the location of the trowal on the backside of the upper low. The concern is that trowal feature intensifies and lingers over coastal Hancock and Washington counties through the day Thursday...resulting in persistent banding that dumps snow far in excess of our current forecast with snowfall rates well over an inch an hour. Conversely, a lot of guidance maintains the banding offshore with a more easterly upper low track and minimal snow in the forecast area. Our current forecast goes for around 6-7 inches in the coastal counties...roughly following the GEFS, ECMWF and SREF...and just under warning criteria. Amounts taper to the north...with around 3-4 inches at Bangor and less than an inch north of Caribou. Winds are the other concern for tonight into Thursday. There`s a very strong NEerly LLJ with a strength of around 60kts along the coast tomorrow morning. The jet core is closer to H900-H850, but wind gusts to 45 mph could accompany heavy snow on the coast and create blizzard-like conditions. The combination of heavy wet snow and these winds can be expected to cause power outages along the coast. The overall strength of the LLJ decreases inland with distance from the low, but gusts to 35 mph will be possible all the way northward towards Fort Kent. Blowing snow remains in the forecast where accumulations are forecast.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... Surface/upper level low pressure will exit across the Maritimes Thursday night through Friday. Lingering snow will taper to snow showers before ending across much of the region early Thursday night. However, snow showers could persist across mostly the north and mountains overnight. Mostly cloudy skies along with a slight chance of snow showers are expected across the north and mountains Friday, with partly/mostly cloudy skies Downeast. A disturbance rotating around the exiting upper low will approach northern areas later Friday night then begin to cross the region Saturday. Skies will remain mostly cloudy across the forecast area Friday night through Saturday. Could have a slight chance of snow showers across northern areas Friday night. Will then have a chance of snow showers across the entire forecast area Saturday with the disturbance starting to cross the region. Temperatures will be at near normal, to slightly below normal, levels Friday/Saturday. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... The disturbance will cross the region Saturday night through early Sunday with mostly cloudy skies along with a chance of snow showers. High pressure will then begin to build south across the region later Sunday with decreasing clouds. High pressure will remain across the region Monday into Tuesday with mostly sunny skies Monday, then mostly/partly sunny skies Tuesday. Low pressure could then approach from the west Wednesday with increasing clouds along with a chance of snow/rain showers. Temperatures will be at below normal levels Sunday. Near normal, to slightly above normal, level temperatures are expected Monday through Wednesday. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... NEAR TERM: Expect VFR conditions to deteriorate to IFR tempo LIFR in snow for BHB and BGR late tonight into Thursday morning. There is a chance conditions could be VLIFR in heavy snow towards Machias and Eastport during Thursday morning. Otherwise, most sites will be VFR until Thursday morning when MVFR cigs form. SHORT TERM: MVFR/IFR conditions are expected across the entire region early Thursday night, with MVFR conditions persisting across mostly the north and mountains overnight. Occasional MVFR conditions will remain possible across mostly the north and mountains Friday into Friday night. Occasional MVFR conditions are then possible across the entire region Saturday into early Sunday. VFR conditions are then expected later Sunday into Monday. && .MARINE... NEAR TERM: A strong gale develops tonight and continues Thursday with wind gusts as high as 50 kts at times and seas as high as 14 ft. Visibility will be restricted in snow...which could be heavy. SHORT TERM: Gale force wind gusts are possible early Thursday night. Small craft advisory conditions are then expected later Thursday night through Friday. Conditions should be below small craft advisory levels Friday night into early Saturday, with small craft advisory conditions developing again later Saturday. Visibilities could be reduced in snow early Thursday night, then again in any snow showers Saturday. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Winter Weather Advisory from 2 AM to 4 PM EDT Thursday for MEZ016-017-029-030-032. MARINE...Gale Warning until 6 PM EDT Thursday for ANZ050>052. && $$ Near Term...Hewitt is the U.S. government's official web portal to all federal, state and local government web resources and services.