Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 220011 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 711 PM EST Wed Feb 21 2018 .SYNOPSIS... A cold front will push offshore tonight. High pressure will build in from the west on Thursday and crest over the area Thursday night. Low pressure will approach on Friday. && .NEAR TERM /THROUGH THURSDAY/...
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630 PM Update: Temps briefly surged upwards of 5 to 10 deg F with the passage of a prefrontal trof, allowing more Wrly component winds to mix down what was left of near record warm air alf of our Rgn. Since then, temps have fallen with the actual cold front passage with winds veering more to the NNW and increasing to to 10 to 20mph with gusts up to 30 mph immediately behind the cold front. This update included incorporating these late day hrly hi temps and merging them to falling temps this evening into the ovrngt. No chgs to fcst ovrngt lows attm. Another chg was to include more realistic higher trrn winds tngt which were under fcst in our last update and to add a little more in the way of trrn feature cldnss. Orgnl Disc: This evening will begin mild as a cold front pushes off the coast. Any lingering fog along the coast should dissipate as winds behind the front become northwesterly. The air will then become cooler and drier overnight as high pressure builds in bringing clearing from north to south. Tuesday will feature plenty of sunshine as the high continues to build over. Temperatures will be near seasonal norms ranging from the mid 20s north to the mid 30s Downeast.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... On Thursday night, the 1040mb high pressure crests over the area. Lows were maintained well below available guidance due to good potential for strong radiational cooling and resulting steep inversion. On Friday, an ill-defined flatwave in the southern stream will rapidly approach from the southwest. Clouds increase later in the day with a weak overrunning event that will produce snow Friday night. With weak isentropic lift, sub-advisory snowfall of no more than 1-2 inches is expected with precipitation ending as sleet or rain in southern zones. Am carrying some freezing rain, but confidence is low as the warm layer looks very shallow and close to H850. After rising...or remaining steady Friday night...temperatures will be warmer behind this system early Saturday with highs in the upper 30s to lower 40s. Unstable lower levels could produce a few snow showers as colder air advects into the area on Saturday, but will not include any pops for now. This will also mix some gusty NW winds to the surface. Gusts could reach 25 to 30 mph. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... High pressure building Saturday night presents another good opportunity for radiational cooling...especially in northern zones. A combination of increasing high clouds and potential onshore flow makes radiational cooling less certain in the southern half of the forecast area. Clouds will increase quickly on Sunday ahead of yet another shortwave moving in the southern stream out of the lower Mississippi Valley. This system will have better upper level support and will take the form of a warm occlusion as it approaches. A triple point secondary low will develop along the coast and cut off warm air advection. As a result, this system should be all snow except along the coast. Most areas should receive around 4 to 5 inches as it stands now..which is consistent with yesterday`s assessment. The exception would be the coastal zones where P-type issues will cause a significant decrease in accumulations. There`s still uncertainty on how far north the rain/snow will advance northward on Sunday night. Went with non-diurnal temp curve for Monday night. High pressure gradually builds Monday into Wednesday with seasonal temperatures. A blocking pattern in the Atlantic looks like it keep the high parked to our west early in the week...promoting a persistent NW flow and some gusty winds on Tuesday. Can`t rule out some snow showers on Monday with cold air advection. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... NEAR TERM: VFR conditions are expected tonight as a cold front pushes offshore and clearing builds down from the north. VFR conditions are expected in high pressure on Thursday. SHORT TERM: VFR conditions are expected Thursday night until early Friday evening. A period of IFR to VLIFR vis in snow is expected to develop Friday evening, but will end not too long after midnight...giving way to MVFR cigs. VFR returns to all sites Saturday morning and persists into later Sunday morning. Snow will bring IFR to VLIFR vis Sunday afternoon into Sunday night. MVFR cigs are expected Monday morning north of HUl with VFR further south. && .MARINE... NEAR TERM: A SCA will be up overnight for gusty northwest winds following the cold frontal passage this evening. Winds should then diminish on Thursday as high pressure builds over. SHORT TERM: A weak SCA for the outer waters is possible Friday night, but low confidence. A brief gale is still expected later Sunday afternoon into the evening. && .CAR WATCHES/WARNINGS/ADVISORIES...
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ME...None. MARINE...Small Craft Advisory until 7 AM EST Thursday for ANZ050>052.
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&& $$ Near Term...VJN Short Term...MCW Long Term...MCW Aviation...VJN/MCW Marine...VJN/MCW

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