Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 220201 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 1001 PM EDT Fri Apr 21 2017 .SYNOPSIS... Decaying low pressure in Quebec will slowly drift towards northern Maine while a new area of low pressure organizes south of Cape Cod tonight and intensifies south of the state on Saturday. The low will move south of Nova Scotia Saturday night and high pressure will build on Sunday. && .NEAR TERM /THROUGH SATURDAY/...
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935 PM Update: Precip has turned over to all sn a little faster then prev fcst, so we time shifted our fcst grids 1 hour forward and hand edited precip types slightly to shade to all sn a little faster and further S resulting in a 2 hour faster transition then the prev fcst. Fcst 6 hrly and stm total snfls were then updated to show a little more snfl over Nrn Penobscot and SE Aroostook counties. One concern that could reduce sn totals a little across the N is the potential of dry slotting which a few models indicate could sharply reduce sn rates aft mdngt across the region, with more intermittent lgt sn for the late ngt. To erly to make any decisions at this tm, but something to watch. Otherwise, fcst ovrngt hrly temps were updated to reflect a faster drop in temps into mid eve based on latest obs, but no chg in fcst ovrngt lows attm, thinking that temps will not fall much more with evaporational/ dynamic cooling processes mostly used up across areas that have transitioned to sn attm. Orgnl Disc: The big concern for this evening is a vigorous shortwave trough rotating around the closed upper low in Quebec. It will affect areas north of the Katahdin region and Houlton this evening into the overnight hours. There`s a lot of lift with this feature as evidenced by omega fields. There is some upper level instability and the LFQ of a strong upper jet will enter northern Maine later this evening. Although temperatures are currently in the upper 30s to lower 40s in northern zones, evaporative and dynamic cooling of the column will generate a fairly quick changeover from rain to snow as the warm boundary layer is eliminated. There is good omega in a rather high dendritic layer later this evening and snowfall rates over an inch an hour are possible as the shortwave crosses. The fact that the heavier snow will be falling at night with these snowfall rates means roads may become slippery at times overnight. Overall snowfall of 3-5 inches in northern Aroostook County and the potential for slick roads led to the decision to issue a winter weather advisory for zones one and two. Snow will linger in northern zones Saturday morning as the remnants of the Quebec low become an inverted trough connected to the offshore low. Further accumulation after daybreak Saturday is not likely with lower snowfall rates and snow will gradually change to rain as the boundary layer warms again. The snow will mostly be a factor for areas north of Greenville to Millinocket and Hodgdon. South of this line, snow may mix with the rain at times late tonight, but no accumulation is expected as lows will be 34 to 37F. Rain will fall tonight into Saturday morning and gradually taper off Saturday afternoon. It will be a chilly day for the entire region with highs only reaching the upper 30s to near 40F.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As the short term starts at 00z Mon/8PM Sun, the last remnants of the system should be departing, with most likely areas of rain and/or snow along the eastern border and also in the northern/western high terrain. As the system moves away, weak high pressure bringing calming winds could allow for some fog across the area through Sun AM. At least patchy sunshine is expected across the entire CWA Sun PM, and it may become mostly sunny or clear south of the Katahdin and Moosehead region. Temps will be near seasonal norms on Sunday. A weak cold front then looks to approach from the NW Sun evening, and bring some showers to the Crown of Maine. Precip appears likely to start as rain showers, then taper to a mix or snow showers. But all models show the precip associated with his front drying up before sunrise Mon, with the sfc boundary making it to the Bangor metro by 15z Mon, and off the coast shortly thereafter. Some clouds are likely to linger behind the front on Mon. The earlier passage of the front will lead to a cooler day Mon up north. But for Bangor metro and Downeast, it appears likely to be just as warm if not warmer thanks to SW`ly winds ahead of the front, but the timing of the front will be key to highs on Mon. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Medium range models are suggesting a moderating temperature trend by mid to late week with temperatures possibly rising to above normal levels late next week. But before that we will be dealing with the potential for some rain Tuesday into Wednesday as low pressure develops along the southeast coast of the United States and then tracks northeast and weakens through Wednesday. This would bring the potential for some rain to the region, especially across downeast areas. There could be a few showers around on Thursday as an upper trough swings across. Drier weather will return on Friday. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... NEAR TERM: Prevailing MVFR cigs will give way to LIFR vis in snow north of HUL and GNR later this evening. The snow will let up to IFR vis later in the night through Saturday morning. MVFR returns Saturday afternoon. For southern sites such as BGR and BHB, the trend will be towards IFR cigs later tonight in rain and drizzle. Once these cigs arrive, they will be very slow to depart on Saturday. SHORT TERM: MVFR to IFR conditions will be widespread Sat night as some low clouds are expected to persist, and areas of fog may develop in light winds. Clouds should break up and fog will dissipate Sun AM, allowing a return to VFR conditions, and remain clear thru Sun evening. Low to mid-level clouds and showers with a cold front may cause some MVFR to patchy IFR conditions for KHUL thru KFVE Sun night, while fog is possible for KBHB and KBGR ahead of the front Sun night and Mon AM. && .MARINE... NEAR TERM: 630 PM Update...we optd to go with an SCA for outer MZs050-051 for marginal wind gusts of 25 kt and wv hts upwards to 7 ft for a relatively narrow window between 4 and 11 am Sat morn. Orgnl Disc...There is a chance of SCA conditions ANZ051 from Schoodic Point to Stonington on Saturday morning as low pressure moves south of the waters. Confidence is higher in seas above 5 feet on Saturday than wind gusts over 25 kts. Will await 00Z guidance to get a better look and revisit the decision. SHORT TERM: Both winds and seas are forecast to remain below SCA criteria levels Sat night thru Mon. The biggest risk to safe navigation offshore may be some dense fog possible Sun night into Mon AM ahead of a cold front. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Winter Weather Advisory until 11 AM EDT Saturday for MEZ001- 002. MARINE...Small Craft Advisory from 4 AM to 11 AM EDT Saturday for ANZ050-051. && $$ Near Term...VJN Short Term...Kredensor Long Term...Duda Aviation...VJN/Kredensor Marine...VJN/Kredensor is the U.S. government's official web portal to all federal, state and local government web resources and services.