Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 231117 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 717 AM EDT Tue Oct 23 2018 .SYNOPSIS... High pressure will build east this morning. Low pressure will approach from the west on Tuesday and intensify as it tracks along the coast Tuesday night into Wednesday. && .NEAR TERM /THROUGH TONIGHT/... 710 AM Update...Hrly temps needed adjustment to match up w/the latest obs. Tweaked pops to match up w/the radar. Previous Discussion... Quiet today and then the action comes into the region tonight. Cold temps this morning w/many sites across northern and western Maine seeing upper teens. Satl imagery showed clouds advancing ene w/the apch of a sfc trof across the central and downeast region. Regional radar showed some light returns showing up along this trof. Most of these returns were aloft due to the dry llvls. Some light snow or sleet possible this morning due to the low dewpoints. As the the column moistens and temps warm, precip will transition to light rain. Tried to show this setup through late morning across the aforementioned areas. Clouds will continue to overspread the entire CWA this afternoon. Temps will rise into the upper 30s and lower 40s across the north and west while central and downeast areas for forecast to hit mid/upper 40s. Low pres moving across NYS is expected to re-organize off the southern New England coast and lift along the Maine coast tonight. The NAM and Canadian GEM are colder w/the blyr temps and keep the bulk of the QPF further s and e in the form of snow as far south as Bangor and Calais. The GFS and ECMWF align a bit closer w/bringing a burst of decent QPF up into northern areas overnight as the upper low moves along the coast. The GFS and ECMWF appear to match up better w/the sfc and upper low while the NAM and GEM look to be a bit dis-jointed w/the position. Therefore, decided to lean w/a blend of the GFS and ECMWF for the position of the low moving along the coast and blyr temps. A nose of milder air is shown by this blend to to push north to Mars Hill and possibly to Fort Fairfield through 06Z (2AM). This would allow for rain/snow mix as far n as the Caribou-Presque Isle region w/rain further south. North of Caribou, precip looks like it will be all snow. As temps fall back overnight, precip will go over to snow from Caribou down to the Greenville and Millinocket region. It looks like there could be a burst of moderate to heavy snowfall as the upper level front sets up across the central and northeastern portions of the area overnight. This feature will aid in strong forcing in the mid levels. The GFS soundings supported this setup and decent snow growth. Would not be surprised to see a period of snowfall rates up to an inch/hr across portions of the Maine Central Highlands and northern Maine. Another thing to consider will be the potential for high snow ratios in the snow bursts as the model guidance appears to be having a hard time showing the high ratio potential. Attm, decided to play it as a 24 hr event w/snowfall totals averaging 4-9 inches w/higher amounts across the higher terrain which could see more than 10 inches. A shift further south as shown the NAM and GEM could lead to lower amounts. Therefore, taking this into account, decided to go w/a Winter Weather Advisory for northern Maine and the Maine Central Highlands late tonight through Wednesday. This was collaborated w/GYX. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... A complex winter storm scenario unfolds Wednesday. Cyclogenesis occurs in the Gulf of Maine Tuesday night and by Wednesday morning, a vertically stacked low will be over the forecast area. The important issue is exactly where. The 00Z suite of guidance generally shifted the entire system further south. Thus areas towards the Allagash and Saint John Valley now receive less snowfall than previously expected. The prime snowmaker will be a deformation band that will propagate north and west Wednesday morning with potentially heavy snow at times. Most of the snow will be north of a line from Greenville towards Millinocket and Houlton and the heaviest accumulations will be elevation dependent. Thus the highest totals will be in the Katahdin region and into the upslope high terrain west of Rt 11 in northern Penobscot into Aroostook counties. Boundary layer issues remain a concern along the eastern border of Aroostook County and may need to knock down totals a bit there. Snow ratios will be decent in the band...towards 10 to 1 with good omega in the dendritic growth zone...but will lower the ratios once the band weakens in the afternoon. Leaned towards NAM and raw temp guidance for Wednesday. The trowal will continue to affect large portions of the forecast area Wednesday evening and have extended the Winter Weather Advisory to 2am Thursday morning when the H700 low and trowal should be safely east of the area. Winds become the next concern in a northwest flow for Thursday. Gust over 30 mph are expected...and may hit 40 mph at usually windy locations such as Greenville and Frenchville. Some snow shower activity may persist towards northern Aroostook County on Thursday in the cold air advection. Cu and sc fields will occur across most of the area Thursday with highs in the 30s north and low 40s for Bangor and the coast. Wind chills will be in the go with fresh snow cover in the northern zones. Winds continue Thursday night with lows in the 20s. && .LONG TERM /FRIDAY THROUGH MONDAY/... High pressure builds Friday with lighter winds, but highs will still only be in the low to mid 30s north and upper 30s to lower 40s in the southern half of the forecast area. Friday night will be the coldest night of the season to date with strong radiational cooling and snow cover dropping lows to the low teens north and teens nearly as far south as Orono and Old Town. Saturday will start with high pressure in control, but low pressure will advance up the eastern seaboard later Saturday into Sunday. A strong, cold easterly flow will be induced between the low and departing high pressure over Labrador. The cold air mass will eventually be displaced, but the question is how quickly and whether snow will fall before the warm air arrives. Using a blend of the warmer ECMWF and colder GFS, went for a period of snow late Saturday into Saturday night before the warmer air and rain arrives for Sunday. The broad area of low pressure will keep rain in the forecast into Monday with temperatures moderating into the 40s to low 50s for Sunday and Monday. && .AVIATION /11Z TUESDAY THROUGH SATURDAY/... NEAR TERM: VFR into early evening and then conditions will drop to MVFR to IFR w/snow across northern sites mainly north of KHUL. KBHB will generally see rain possibly mixed w/some snow for KBGR. SHORT TERM: LIFR to VLIFR in snow is expected from GNR to HUL northward for much of Wednesday into Wednesday evening. Periods of IFR to LIFR in snow may also occur at BGR and BHB Wednesday morning. After the snow ends, winds become an issue Wednesday night into Thursday. Gusts to 35-40 kts are possible. VFR conditions are forecast Thursday into Saturday. && .MARINE... NEAR TERM: No headlines expected into tonight. E winds will pick up overnight to speeds of 15 kts w/gusts to 20 kts over the outer zones. Wave heights will begin to build later tonight to 4 to 5 ft. SHORT TERM: Small Craft Advisory conditions are expected Wednesday afternoon into Friday. There`s a chance of a brief gale depending on the exact track of low pressure in the Gulf of Maine on Wednesday. Towards Saturday night into Sunday, there`s a significant risk of a more prolonged period of gale conditions. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Winter Weather Advisory from midnight tonight to 2 AM EDT Thursday for MEZ001>006-010. MARINE...None. && $$ Near Term...Hewitt Short Term...MCW Long Term...MCW Aviation...Hewitt/MCW Marine...Hewitt/MCW is the U.S. government's official web portal to all federal, state and local government web resources and services.