Area Forecast Discussion
Issued by NWS Caribou, ME

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424 FXUS61 KCAR 250307 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 1007 PM EST Fri Feb 24 2017 .SYNOPSIS... A weak back door cold front will move southward into Downeast portions of the region overnight and then become stationary early Saturday morning. This front will lift back to the north across all of the region later Saturday morning and afternoon as low pressure tracks northwest of the region Saturday evening. This same low will bring cold front across the area late Saturday night. Canadian high pressure will then build across the region on Sunday. && .NEAR TERM /THROUGH SATURDAY/... 1005 pm update... Temps are dropping acrs nrn Aroostook in wake of bndry that mvd thru this evng. Snow is falling acrs the St. John Vly with sleet occurring further south attm. Temps are still abv frzg south of about a Caribou to Billy-Jack Depot line with a vry slow drop. 00z raob out of CAR indicated from the surface up to 825mb with latest HRRR about a degree too cold with sfc/925 and 850mb temps. RAP was even colder than HRRR and hv adjusted things accordingly as models continue to be too cold for the ovrngt hrs. Thus hv boosted temps up by a degree or so with low temps being reached arnd 06z bfr stabilizing and then rising twd daybreak. This has impacted ptypes tonight with just patchy light frzg rain expected mainly for nrn Aroostook, hwvr colder vly locations in nrn Somerset and nrn Piscataquis may see a light glazing and hv kept frzg rain advisory going for current areas. Next question bcms dense fog for the ovrngt. Dwpt depressions are around zero with locally dense fog from about Bangor over twd the NB border. Coastal zones rmn out of fog with srly flow allowing some mixing to prevent fog dvlpmnt with areas just to the north in dead calm winds. Thus, wl issue dense fog advisory thru 12z. No other chgs needed at this time. Prev discussion blo... Rain is finally ovrsprdng the region late this aftn, but temps both at the sfc and alf up to 850mb are much milder attm then thought 6 to 12 hrs ago. Also, all models have backed off some with regard to how much llvl cold air will move Swrd into the FA behind a weak back door cold front xpctd to settle to Downeast ptns of the region by very erly Sat morn. This resulted in making a difficult decision to canx the fzra adv for zones 10...5 and 6, the N Cntrl ptns of the region, orgnly slated for late tngt into Sat morn. We still believe enough llvl cold air will likely be present later tngt for lgt fzra for NW and far NE ME, but not with 100 percent confidence, so this ptn of the fzra adv remains in effect from 11 pm tngt til 10 am Sat. Any ice accumulation will be msly a tenth of an inch or less ovr the fzra adv area. With most of the first batch of organized ovrrng precip exited N of the FA by daybreak Sat, msly Chc fzra pops in the adv area will be left across the adv area Sat morn with sct shwrs and patchy dz mentioned Swrd to the coast. Fog, which we assigned with sct shwrs and patchy dz, will become more prominent S to N across the region late tngt into Sat as both temps and dwpts rise abv fzg spcly as the front lifts back to the N across the region later Sat morn into the aftn. Fcst hi temps will not be achieved until erly eve given the late day surge of llvl warm air behind the cold front. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... Saturday evening will bring a mild southeasterly breeze ahead of an approaching cold front. Some scattered showers or patchy drizzle are possible during the evening ahead of the front. The cold front will then move across the area around midnight Saturday night bringing a period of rain. Some of the showers may be heavy and there`s a potential for an isolated rumble of thunder. Elevated cape values are up to 300 J/KG as the front pushes through. Showers will move east and away early Sunday morning as colder air pushes in. Some snow showers are likely in the higher elevations to the west early Sunday morning. Colder air will follow on Sunday as low pressure over eastern Canada moves away and high pressure builds onto the east coast. Sunday night will be cold and dry as high pressure moves off the east coast. Clouds will increase late at night ahead of a weak shortwave approaching from southern Quebec. Some snow showers will then be likely across the north late Sunday night into Monday morning as the shortwave and weak secondary cold front slides across the north. Temperatures Monday afternoon will then modify into the mid 30s north and mid 40s Downeast with partial sunshine. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Monday night into early Tuesday should be mainly dry as high pressure ridges over the region. A weak low with one center racing across southern New England and another center over the great lakes will approach Tuesday afternoon possibly bringing some rain or wet snow Downeast. The main low will approach on Wednesday. Boundary layer temperatures will likely be cold enough for some snow over the north. However, a mix changing to rain will be likely Downeast on Wednesday. The low pushes through and quickly moves away Wednesday night followed by dry weather in high pressure Thursday into Thursday night. Another weak low will move in on Friday bringing a chance for some light snow across the area with the best chances Downeast as the low tracks south of the Gulf of Maine. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... NEAR TERM: Northern terminals expected to bounce back and forth between VFR and MVFR for the first several hours this evening before eventually settling at MVFR after 03z. BGR and BHB will likely be IFR/LIFR through the day Saturday in -DZ, FG and low clouds. Ptypes will be in question north of PQI with -FZRA expected after 03z, possibly mixing with PL early. Expect IFR conditions during the day Sat. Northern zones will likely see LLWS at FL020 toward end of TAF valid time from 19040kt. SHORT TERM: IFR conditions in low clouds, rain and fog are likely Saturday night. Conditions should improve to VFR Downeast early Sunday morning then improve to VFR across the north mid morning Sunday. VFR conditions across the north Sunday night will lower to MVFR over the north late Sunday night and remain VFR Downeast. VFR conditions Downeast and MVFR conditions across the north are likely on Monday. && .MARINE... NEAR TERM: No headlines will be needed tngt and Sat...with winds and seas increasing Sat aftn to near SCA thresholds by erly eve. Marine fog will likely present spcly late tngt into Sat morn. SHORT TERM: An SCA will likely be needed Saturday night into Sunday for gusts up to 30 kt in S winds ahead an approaching cold front. The SCA will likely have to continue for gusty westerly winds following the front on Sunday. && .HYDROLOGY... No changes to the Flood Watch were made with this forecast cycle. Snow melt from the deep snowpack continues tonight through Saturday night with rainfall amounts of just over a half inch by Sunday morning. Water levels are starting to rise modestly on the river gauges on the Piscataquis and its branches, but the best response should be later Saturday night into Sunday. NERFC and ensemble river forecasts continue to rises into Sunday morning, but nothing that generates strong concerns at this point. The focus will remain on the southern half of the forecast area where temperatures will stay above freezing into Sunday and where more melting has already occurred with this thaw. Localized ice movement followed by jams is the scenario to watch...mostly for southern Piscataquis and Penobscot basins. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Freezing Rain Advisory until 10 AM EST Saturday for MEZ001>004. Flood Watch from 7 AM EST Saturday through Sunday evening for MEZ010-011-015>017-031-032. MARINE...None. && $$ Near Term...Farrar/VJN Short Term...Bloomer Long Term...Bloomer Aviation...Farrar/VJN/Bloomer Marine...Farrar/VJN/Bloomer Hydrology...

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