Area Forecast Discussion
Issued by NWS Caribou, ME

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928 FXUS61 KCAR 131551 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 1051 AM EST Fri Dec 13 2019 .SYNOPSIS... Low pressure tracks from the Mid-Atlantic States Saturday morning, to the Lower Saint Lawrence River by Sunday morning. The trailing cold front crosses the region Sunday, followed by high pressure building in through Monday. Low pressure tracks into southern New York and New England Monday night, then tracks across the Gulf of Maine on Tuesday. && .NEAR TERM /THROUGH TONIGHT/... Update... High pressure will exit across the Maritimes today, with a developing warm front across the region. Isolated snow showers are possible across mostly northern areas this morning. Expect a slight chance/chance of light snow this afternoon. Have also included patchy freezing drizzle later this afternoon across portions of the west-central highlands. Little or no snow or ice accumulation is expected through this afternoon. Otherwise, expect cloudy/mostly cloudy skies this afternoon. Afternoon high temperatures will range from the upper 20s to around 30 north, to the mid to upper 30s interior Downeast with upper 30s to around 40 along the Downeast coast. Have updated to adjust for current conditions along with afternoon temperatures, clouds and precipitation chances. Previous Discussion... Continued southerly flow tonight will result in increasing low level moisture this evening. This could result in some patchy freezing drizzle developing across the higher terrain late this afternoon into early this evening. Deeper moisture begins to arrive after midnight as an area of low pressure begins to track northward from the mid atlantic region. Across central and downeast areas, precipitation will be mainly in the form of rain overnight. However, across the north, it will be cold enough to support snow. The snow will then begin to mix with and gradually change to rain toward daybreak. The exception will be across northwest areas and the St. John Valley where snow will persist, where an inch or two of snow is possible by daybreak. Lows tonight will occur early this evening, with temperatures gradually rising overnight. Temperatures by daybreak Saturday are expected to range from the lower 30s across the far north and upper 30s to lower 40s across central and downeast areas. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Diffluent flow over the region Saturday as the axis of a deep layered ridge lifts to the NE (how quickly it does so will determine how fast heavier/steady rain moves in) and a developing closed low slides into the eastern Great Lakes. AS a result expect moderate to locally heavy rainfall to overspread the area from S to N Saturday morning (starting off as some snow across the north). The rain should continue into Saturday evening before tapering off from S to N as the dry slot associated with the developing cutoff low moves in. Expect rainfall amounts to total around 0.75"-1" across the north, 1- 1.25" across Bangor and Upper Penobscot Valley and 1.25-2" across Downeast Maine. There is also the potential for 1-2" of snow to fall across the North Woods before changing to all rain there by afternoon. With generally less than an inch of snow expected (outside of higher elevations) elsewhere across the North. The heaviest rain Saturday should be in response to a 60-70 kt 950- 850 hPa low level jet passing just S of coastal SE Maine Saturday morning. Fortunately, should be fairly inverted in the low levels, so outside of higher elevations on Mt Desert Island, should not see much in the way of wind mixing down from this low level jet. So could see some 35 mph gusts near the coast (possibly some lower 40 mph peak gusts) and 20-25 mph gusts possible across the north. The gusty winds and recent heavy rains should allow for some smaller trees to possibly come down across Downeast Maine with the strongest winds on Saturday. Highs Saturday should be around 15-20 degrees above normal and lows Saturday night around 10 degrees above normal. With persistent low level warm advection - would not be surprising to see temperatures slowly rise through the night (for now have rising in the evening then leveling off overnight). The cutoff low tracks into Newfoundland Sunday, then into the Canadian Maritime Waters Sunday night. The result will be some isolated to scattered rain and snow showers (North) and just rain showers elsewhere Sunday with some mainly flurries possible across the North Sunday evening. It will be breezy to windy (but for now sub-advisory level winds) with falling temperatures due to strong low level cold advection. Highs on Sunday should be around 10-15 degrees above normal and occur during the morning and off to the mid 20s to mid 30s (NW to SE across the area) by late Sunday afternoon. Lows Sunday night should be a few degrees above normal. && .LONG TERM /MONDAY THROUGH THURSDAY/... Deep layered ridging builds over the area Monday, with dry conditions and diminishing winds. The ridging exits Monday night allowing snow ahead of a northern stream shortwave trough moving into the eastern Great Lakes to move into mainly SW portions of the forecast area late Monday night. This shortwave helps spawn a coastal low that moves across the Gulf of Maine on Tuesday. This will bring some snow to most of Northern and Eastern Maine, except for a mix of rain and snow right near the immediate coast. This precipitation should taper off from W to E Tuesday night as the low exits to the SE of Nova Scotia. There is still quite a bit of uncertainty as to the exact track and strength of this low, but based on a track to the S of Nova Scotia would expect the highest snow totals across the Penobscot/Bangor Region and interior Downeast Maine. Given the uncertainty, its too early to forecast amounts at this time. A closed upper low then tracks across S Quebec Wednesday then across N Maine/New Brunswick Wednesday night. This should bring some isolated-scattered snow showers to the region, with the highest chance across the North. Weak northern stream ridging is currently progged to cross the area Thursday so it should be dry. Temperatures should be below normal Monday-Thursday. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... NEAR TERM: Generally VFR conditions are expected this morning, with VFR/MVFR conditions this afternoon. Could have isolated snow showers across northern areas this morning. Will then have a slight chance/chance of light snow developing this afternoon. Have also included patchy freezing drizzle later this afternoon across the west-central highlands to include KGNR. Low level wind shear is a concern across northern areas this morning into the afternoon, then developing across the entire region tonight. Expect IFR to develop after midnight in rain at the downeast terminals (KBGR/KBHB) and in snow and rain at the northern terminals. SHORT TERM: Saturday-Saturday night...IFR/LIFR. Snow or a wintry mix transitioning to rain north, with rain Downeast. The rain ends from SW to NE Saturday night. LLWS possible Bangor/Downeast terminals. Sunday...IFR or lower with Isolated-scattered rain/snow showers North and Isolated-Scattered rain showers elsewhere, improving to MVFR-VFR late. SW-W winds G20-30KT possible. Sunday night-Monday evening. VFR. W winds G25-35KT possible. Late Monday night-Tuesday...MVFR or lower possible in snow, with a rain/snow mix possible near the immediate coast. NE-N winds G15-25KT possible. && .MARINE... NEAR TERM: Winds/seas are expected to be below small craft advisory levels this afternoon, though a few gusts to 25 knots are possible. Winds/seas will then increase to small craft advisory levels tonight. A Small Craft Advisory has been issued beginning late tonight. SHORT TERM: SCA conditions on all waters Saturday-Saturday night, with some isolated gusts to 35-40kt possible on the coastal ocean waters mainly Saturday morning with the passage of a low level jet. Gales then probable all waters Sunday-Sunday night with strong low level cold advection. Winds diminish to SCA levels Monday then to sub-small craft levels Tuesday (depending on exact evolution of a coastal low progged to track across the Gulf of Maine Tuesday). SCA level seas could linger on Tuesday on the coastal ocean waters. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory from 5 AM Saturday to 6 AM EST Sunday for ANZ050>052. && $$ Near Term...Norcross/Duda Short Term...Maloit Long Term...Maloit Aviation...Norcross/Duda/Maloit Marine...Norcross/Duda/Maloit is the U.S. government's official web portal to all federal, state and local government web resources and services.