Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 270506 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 106 AM EDT Tue Oct 27 2020 .SYNOPSIS... Low pressure will cross the region overnight. High pressure will cross the area Tuesday and Tuesday night, then slide offshore through Wednesday. A couple of cold fronts will cross the region Wednesday night and Thursday followed by low pressure tracking to the south Thursday night. High pressure then builds in Friday. High pressure sticks around through Saturday. && .NEAR TERM /THROUGH TODAY/... 1 AM Update: Stratiform precip will be waning over the next couple hours, and have opted to transition to showers. Mixed precip line is still lingering in the far north. This roughly correlates with the wet bulb zero line. As this line drifts south late tonight, a brief change to sleet is possible before snow showers return for very early Tues morn. Updated temps as many places, namely the north and central areas, didn`t receive quite as strong warm push as expected. Blend of NAM/HRRRE was used for these. Prev Disc: Warm air is expected to push into the area which has caused the region to warm slightly. This will allow for rain to the Downeast and mixed precip to the N as the cold front swings around. Precip is expected to continue throughout tonight across the entire region, keeping cloud cover overcast. Low temperatures tonight will range from the upper 20s to lower 30s north, to around 40 to the lower 40s Downeast. The GFS has the precip moving E much faster than the EC and Canadian as the high pressure begins to push in. Precip should end early Tuesday morning, but clouds should remain. High temperatures Tuesday will range from the mid to upper 30s north, to the mid to upper 40s Downeast. && .SHORT TERM /TONIGHT THROUGH THURSDAY/... High pressure will move across the forecast area Tuesday night, leading to mostly clear skies and relatively calm winds. Low temperatures over land between the 10th and 25th percentile of guidance were preferred given the favorable radiational cooling setup, which yielded lows ranging from the lower teens to mid 20s. Cloud cover will build in progressively from the northwest Wednesday as a shortwave trough moves across southern Quebec and clips northern Maine by Wednesday evening. There are still significant discrepancies with the 250mb jet streak and 500mb shortwave positioning, so PoPs were reduced from blends to eliminate likely wording in favor of chance. A cold front will then move towards the area on Thursday. Flurries or drizzle are possible with and ahead of the boundary, but confidence and timing was not sufficient at this time for inclusion in the official forecast. High temperatures will be sensitive to the timing of the front, particularly across northern Maine. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... A very interesting meteorological setup is expected for the end of this week as an upper level low over the Southern Plains ejects eastward at the same time Hurricane Zeta is making landfall along the Gulf Coast. Both of these features will move northeast and interact with an already strong jet stream and area of low level convergence south of surface high pressure over eastern Ontario and southern Quebec. Well-defined temperature and theta-e gradients over southern New England will lead to plenty of baroclinic processes and coastal cyclogenesis by Friday. There is considerable uncertainty with timing of the upper level low with respect to Zeta and the precise positioning and strength of the southern periphery of the surface high, which will determine where the low develops and the zone of heaviest precipitation sets up. Trends have generally been for a slight north shift, with more 0z European ensemble members and the 12z operational European showing potential for significant snow accumulation across Downeast Maine. Meanwhile, most ensemble members and other 12z guidance such as the GFS and Canadian still bring only a brief period of light snow possibly mixed with rain into Downeast Maine before suppressing precipitation to the south. Blended PoPs were preferred along with weather type derived from the wet bulb temperature, which yielded slight chance to chance PoPs across the southern half of the forecast area, mainly in the form of snow or a rain and snow mix. These may be too low given the trends, but a little more consistency is preferred before increasing probabilities. The system will move off to the east Friday night into Saturday with surface and upper level ridging building over the area. Dry and cool conditions are expected, followed by a warming trend as the high moves off to the east by Sunday. An upper level trough will then move into the area Sunday night into Monday, bringing the next chance of precipitation, which should be mostly in the form of rain. A cold front will move through the area by Monday evening, though as expected there are timing differences between guidance. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... NEAR TERM: Generally expect IFR/LIFR conditions across the region tonight. A mix of mostly snow, sleet and rain across northern areas tonight with a slight chance of freezing rain. Precipitation in the form of rain Downeast. All precipitation diminishes later tonight. Southwesterly low level wind shear a concern across the entire region this evening into the early morning hours. MVFR/IFR conditions early Tuesday, then improving to VFR through the morning. SHORT TERM: Tuesday night to Wednesday: VFR. Wednesday night: MVFR to IFR with low clouds and rain/snow showers for Aroostook County terminals. VFR elsewhere. Thursday: VFR with modestly breezy WNW winds. Thursday night to Friday: VFR north with potential for MVFR or IFR from mainly KGNR/KMLT south. Breezy NNE winds. Friday night to Saturday: VFR with breezy WNW winds. && .MARINE... NEAR TERM: Seas and winds below SCA. Waves will remain 2 to 3 ft with SE winds shifting NW late tonight. Rain will overspread the waters tonight. Tuesday could have a possibility of a SCA due to winds SHORT TERM: Conditions below small craft advisory thresholds are expected Tuesday night through Thursday. Coastal low pressure will develop Thursday night through Friday, increasing the chance for rain, snow, and at least small craft advisory conditions. Potential exists for higher winds and waves compared to the current forecast at the end of this week. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Cornwell/VJN Short Term...MStrauser Long Term...MStrauser Aviation...Cornwell/VJN/MStrauser Marine...Cornwell/VJN/MStrauser

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