Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 200518 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 1218 AM EST Tue Feb 20 2018 .SYNOPSIS... Warm high pressure at the surface and aloft will remain to our south. A cold frontal boundary from Quebec will cross northern portions of the region very late tonight then stall over Downeast areas by late Tuesday afternoon. This front will move back across the region as a warm front beginning overnight Tuesday crossing far northern Maine by Wednesday afternoon. && .NEAR TERM /THROUGH TODAY/... 12:18 am update: One batch of precipitation has shifted east of the CWA early this morning, although there are still some pockets of very light rain or drizzle Downeast. Made some tweaks to the PoPs and temperatures overnight based on the latest observations, radar trends, and near term model trends. Previous discussion: Tonight will be mild as high pressure remains to our southeast and moisture wrapping over the ridge pushes into the area. Some light rain may push across central and downeast areas this evening and some light sleet, snow and freezing rain could push into the north late tonight. Overnight into Tuesday a frontal boundary will become increasingly well defined across our region. Cold high pressure over Quebec will push cooler air in across far northern areas while the high out in the Atlantic continues to push warm air north across the southern part of our region. Moisture continuing to push east along this front will bring spotty light rain to Downeast and central areas while some freezing rain and sleet will be likely over the far north as the subfreezing air seeps into the low levels from Canada. A winter weather advisory will be issued for northern Aroostook county for the freezing rain late tonight into Tuesday night. && .SHORT TERM /TONIGHT THROUGH THURSDAY/... On Tuesday night, the cold front will sag southward towards the coast with a shallow wedge of cold air due to a large 1040mb high anchored in Quebec. The cold air damming won`t have a lot of time to get established. Strong warm air advection associated with an anomalously powerful 596 decameter H500 high off the Carolina coast will push the front back northward later in the night. Throughout the entire night, warming at H850 to H700 occurs and creates a progressively steeper frontal inversion. In terms of precipitation, the frontal boundary will cause rain for most of the area. The only areas that will dip below freezing will be in Aroostook County and it won`t be much below freezing. Furthermore, wet bulbs will also be near freezing. Thus, it`s a marginal set-up for freezing rain, with worse case accretions around a tenth of an inch. A Winter Weather Advisory will be issued for northern Aroostook where confidence is highest in the cold surface temps. Zone 5, southeastern Aroostook, will need another look as the event gets closer. Fog will be an issue Tuesday night for most of the area. On Wednesday, a LLJ and strong southwest winds are expected to make quick work of the frontal inversion for Bangor and the coastal zones...propelling highs into 60s. High temperature records stand a good chance of being broken at Bangor, not only for the date, but the entire month. Further north, the clouds and inversion will hang on until the cold front draws closer, but highs around 50F at Caribou will be near record territory. Furthermore, dew points will reach the 50s and promote rapid snowmelt for the entire area. The cold front crosses later Wednesday afternoon into early evening with isolated to scattered showers. On Wednesday night, cold air will filter into the area with a fairly rapid freeze in northern zones that could produce some slick roadways. Further south, temperatures will remain above freezing until later in the night. On Thursday, high pressure builds with temperatures still above normal, but substantially cooler than Wednesday. Went on the higher side of guidance due to the expected sunshine and increased insolation of late Feb. Rivers will require watch into Thursday night at least. See the hydro section for detail. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... On Thursday night, a 1040mb high pressure crests over the area. Lows were adjusted downward due to good potential for strong radiational cooling. On Friday, clouds increase with a weak overrunning event that will produce light snow Friday night. This will be a fast-moving system in the southern stream with a relatively flat upper level shortwave. Sub-advisory snowfall is expected with precipitation ending as rain in southern zones. Temperatures will be warmer behind this system on Saturday with highs in the upper 30s to lower 40s. Somewhat cooler air arrives Saturday night into Sunday and sets the stage for snow Sunday night into Monday. This system remains a wild card with a wide variety of configurations shown in guidance and questions as to whether northern and southern streams phase. Nonetheless, it looks like a viable threat to produce advisory or warning snow. With respect to the coast, higher astronomical tides will be returning and strong east or southeast winds could cause some trouble. && .AVIATION /05Z TUESDAY THROUGH SATURDAY/... NEAR TERM: Ceilings will drop to IFR tonight in lowering clouds, and remain IFR through Tuesday in low clouds, some spotty rain and fog Downeast, and light mixed precipitation over the far north. SHORT TERM: The prognosis is for VLIFR on Tuesday night with freezing rain for HUL north to FVE. The VLIFR lifts to IFR and MVFR by Wednesday afternoon. VFR returns Wednesday evening and continues until later Friday when IFR in snow arrives. Snow ends by Saturday way to MVFR cigs from HUL northward and VFR further south. && .MARINE... NEAR TERM: A SCA will be up for south southwesterly winds tonight. Winds should diminish below SCA late tonight as the strongest gradient shifts south with the frontal boundary forming across our area. SHORT TERM: Fog is expected Tuesday night into Wednesday. An SCA for the outer waters seems likely later Wednesday into Thursday. Another SCA for the outer waters is possible Friday night. An SCA or Gale Warning may be needed later Sunday into Sunday night. && .HYDROLOGY... In the Bangor area, a prolonged period of above freezing temperatures capped by the potentially highest temp ever recorded in Feb on Wednesday heightens hydro concerns. Fog on Tuesday night and dew points exceeding 50F on Wednesday will accelerate snowmelt. While precipitation amounts will be light, snowmelt could cause rivers to rise just enough for ice break up...and the potential for subsequent jamming. The areas for concern are the Piscataquis Basin, lower Penobscot Basin, Kenduskeag in well as other small streams in Hancock, Washington, southern Penobscot and southern Piscatquis counties. The relatively short duration of the record the 50s and 60s...and lack of significant rainfall does alleviate hydro concerns somewhat at this time and no Flood Watch will be issued right now. Nonetheless, the situation will require close watch. GEFS, NAEFS, and SREF hydrographs do not show the potential for significant river rises to flood stage, but they do show enough of a rise...2-3.5 promote ice break-up worries. && .CLIMATE... Record high temperatures are possible Wednesday, 2/21. The record highs are as follows, with forecast highs in parenthesis: Bangor: 60F, 1937 (63F) Millinocket: 62F, 1994 (57F) Houlton: 50F, 1953 (53F) Caribou: 50F, 1994 (50F) The all-time record for the month of February in Bangor is 60F. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Winter Weather Advisory from 9 AM this morning to 4 AM EST Wednesday for MEZ001-002. Winter Weather Advisory until 1 PM EST this afternoon for MEZ003-004-010. MARINE...Small Craft Advisory until 5 AM EST early this morning for ANZ050>052. && $$ Near Term...CB/VJN Short Term...MCW Long Term...MCW Aviation...CB/VJN/MCW Marine...CB/VJN/MCW Hydrology...MCW Climate...MCW/CB is the U.S. government's official web portal to all federal, state and local government web resources and services.