Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 221647 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 1247 PM EDT Tue May 22 2018 .SYNOPSIS... Low pressure approaches today and then crosses the region tonight through Wednesday. A cold front will cross the region on Wednesday. Canadian high pressure builds in Wednesday night into Thursday. && .NEAR TERM /THROUGH TONIGHT/...
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1250 pm update... Just minor tweaks to temps/dew points at this hour. Prev discussion blo.. Sfc low sitting acrs cntrl Ontario as of 08z this mrng with wmfnt extending fm low ewd twd the St. Lawrence River. Lgt showers being picked up on MRMS radar data acrs portions of Quebec this mrng and as sfc low and assoc wv appchs the CWA tda. Convection currently entering NY fm PA wl be fighting against dry air per 00z GYX raob and wl lkly not saturate down ovr western areas until late this aftn. At the same time, sfc front wl be dropping south out of Canada and spreading showers acrs the north. Max temps this aftn expected to be warmest acrs the north and east where last of the thicker clds wl mv in, allowing temps to rise into the l/m 70s. Elsewhere temps wl rise thru the 60s and appch 70F, except for higher terrain and coastal areas. Frontal bndry expected to enter into the St. John Vly after and slipping south thru daybreak. Mins wl stay up arnd 50F for most of the region, tho cold advection in wake of fropa may dip temps into the l/m 40s acrs the far north.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... The short-term will begin with a front pushing into the Crown of Maine Wed AM, then pushing south to the coast by the mid to late afternoon hours. The previous forecast`s idea of having a chance of thunderstorms with the highest POPs was maintained with this update, with t-storms added around and ahead of the front between 16z and 21z. This represents the best chance of when there may be some CAPE present in the warm sector, though even MUCAPE values are likely to be capped at around 1000 J/kg given the limited surface heating due to some AM cloud cover. That said, any thunderstorms or squall lines that form could tap into some strong unidirectional mid- and upper-level winds, but it is very much a `conditional` threat. As the front approaches the coast in the later afternoon, it will likely run into some more stable air and precipitation should diminish. High pressure will build into the state overnight, allowing for some clearing skies and light winds. Frost and freeze conditions will likely be common Wed night across central and northern areas. SW-W`ly winds and early sunshine should allow for highs Thu to be a bit warmer for the northern half of the CWA, while a developing afternoon seabreeze may keep highs to the south similar to Wed. Low pressure moving across interior Quebec later Thu into Thu night will push a warm front across the region, and some showers are possible, especially across northern and eastern parts of the CWA. && .LONG TERM /FRIDAY THROUGH MONDAY/... At the start of the long-term period, there is some disagreement on the timing of the southward progression of a cold front across the CWA as low pressure moves across the Canadian Maritimes. As of now, it appears the best chance for precip will be Fri night, though POPs may need to be increased Fri afternoon and evening in future forecasts. Thunderstorm potential doesn`t look to be as strong with this one, due to the overnight timing of the precip, but an earlier frontal passage could increase that chance. The front may then stall over southern New England, with precip possible over southern Maine. Chance POPs were put along the GYX border for Sat thru Sun, though the ECMWF was the only model showing precip over any part of our CWA. A shortwave may then approach early next week, but currently looks to keep precip out of the CWA through the end of the long-term on Mon. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... NEAR TERM: VFR expected to persist into this evening, before diminishing to MVFR after 08z acrs northern terminals and after 06z at BGR and BHB. Potential IFR cigs toward end of TAF valid time in low level moisture. Expect light showers toward daybreak at all terminals. SHORT TERM: Widespread shower and rain activity expected Wed AM and afternoon, generally progressing from northwest to southeast through the day, with localized MVFR CIGs and VIS possible. Afternoon TSTMs are possible at all TAF sites, with the highest risk currently appearing to be KHUL and KBGR. Precip diminishes quickly after 21z. VFR conditions expected overnight, except some localized fog possible, mainly in valleys. Some showers possible Thu night for KHUL to KFVE, with some clearing likely on Friday before more showers Fri night. && .MARINE... NEAR TERM: Winds and seas will remain well below SCA levels through tonight. SHORT TERM: Onshore breezes during the day Wed will turn offshore and freshen in the evening and overnight hours. As high pressure slides offshore Thu AM, winds will briefly drop, then shift back onshore Thu PM through Fri and increase once again. Gusts appear likely to remain below 25kts, but Seas Fri into Fri night may exceed SCA criteria, and reach 6-8 feet in the outer waters. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Duda/Farrar Short Term...Kredensor Long Term...Kredensor Aviation...Duda/Farrar/Kredensor Marine...Duda/Farrar/Kredensor

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