Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 182227 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 627 PM EDT Fri May 18 2018 .SYNOPSIS... Frost tonight with high pressure moving to the east. A frontal system will lift across the region Saturday afternoon into Saturday night brining some rain to the region. A cold front will sweep across the region on Sunday with rain ending by the afternoon. && .NEAR TERM /THROUGH SATURDAY/...
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6:27 pm update: A nice evening across northern and eastern Maine with a clear sky aside from a bit of cirrus. The air mass is very dry with dew points mostly in the teens across far northern Maine to the 30s in most communities along the coast. The combination of a clear sky, light/calm wind, and dry air mass will allow temperatures to drop rapidly after sunset. The only concern for tonight is for frost and freezing temperatures. Tweaked a few of the normal cold spots in the northwest down a few degrees as Estcourt Station was 17F this morning, and will likely see similar lows tonight. Also, ended the frost advisory at 7 am based on how quickly temperatures in the cold spots recovered this morning. Even the coldest spots like Estcourt were well back into the 40s by 9 am. Otherwise the ongoing forecast is in fine shape, and only some minor tweaks based on the latest observations. Previous discussion: The main concern in the near term was the temperature forecast for tonight. Ultimately, not much was changed from the previous shift`s forecast, and we are still anticipating at least frost conditions across most of the CWA, with much of the northern half getting below freezing. Frost Advisory remains in effect for the southern two tiers of zones. Some debate was made over whether to go to a freeze warning for zones 15-16-17, but any below freezing areas will be brief, and likely localized to valleys. Otherwise, the end of the near-term involves the onset of rain as low pressure moves through Quebec and pushes a warm front toward the CWA. Onset of POPs were slowed down quite a bit, as all available guidance, both deterministic and ensemble, indicates it is more likely than not that rain will stay out of the CWA until at least 21z, and perhaps closer to 00z Sun. Given the trends in guidance, POPs on the western border were limited to chance for 21z Sat, and don`t get to likely until 23z/00z.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... A soaking rain expected Saturday night into Sunday. Rain will arrive in earnest Saturday night into Sunday as an occluded front lifts across the region. There is the possibility that a weak wave of low pres could develop along the boundary enhancing rainfall later Saturday night into Sunday morning. This latest suite of guidance appears to have pulled back on an organized area of low pres moving along the front. The GFS does hint at the potential of a weak low as does the 12Z ECMWF and its ensemble members. The GEFS showed a similar scenario. QPF was based on placement and strength of the mid level forcing which yields 0.75"-1.00" of rainfall for the Central Highlands and interior Downeast region. Elsewhere, rainfall amounts expected to be 0.50-0.75". Temps will be into in the upper 40s and 50s Saturday night. A lull in the action early Sunday as the occluded front lifts northward and forcing weakens. Another round of rainfall is expected as the associated cold front crosses the area by Sunday afternoon. There does appear to be sunshine returning by mid to late afternoon w/winds becoming wnw helping to bring drier air into the region. Afternoon temps will respond w/readings forecast to hit the 60s to even 70, especially central and downeast areas. Clearing Sunday night and cooler w/overnight temps dropping back to 40-45 across the northern and western areas while mid/upper 40s elsewhere. Sunday looks to be sunny and mild day w/daytime temps well into the 60s. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Looking ahead to mid and late week next week, the general pattern favors a longwave ridge across the nation`s midsection and an upper level trough in far eastern Canada. Cold fronts slipping south through the Canadian trough will come through on a couple occasions bringing chances for scattered showers and perhaps thunderstorms. Monday night into Tuesday morning will be dry as high pressure to our south slides east into the open Atlantic. A bit of moisture rounding the back side of the high and seeping north into our area will bring a chance for some spotty thundershowers Tuesday afternoon into Tuesday evening. A cold front pushing in from the north late Tuesday night into Wednesday morning will bring a chance of showers followed by drier cooler weather on Wednesday. High pressure will quickly build south of the area Wednesday night then another cold front will begin to press down from the north late Thursday. Some very warm air wrapping in behind the high to our south and ahead of the cold front may set the stage for some thunderstorms across northern and central areas late Thursday into Thursday evening. Drier air will again follow from eastern Canada on Friday. && .AVIATION /22Z FRIDAY THROUGH WEDNESDAY/... NEAR TERM: VFR conditions will persist through the period under mostly clear skies. Cloud deck will begin to move in Sat PM ahead of the next system, but should remain above MVFR through 00z Sun. SHORT TERM: MVFR to IFR conditions Saturday night into Sunday morning. Conditions to improve to MVFR by later morning especially for KBGR and KBHB. VFR by late afternoon for all terminals. Expecting VFR for Sunday night right into Tuesday as it looks attm. && .MARINE... NEAR TERM: Light and variable winds tonight will gradually freshen out of the S & SE during the day Sat. Seas will remain low through Sat AM, then begin an increasing trend later Sat afternoon. SHORT TERM: Winds and seas look like they will reach SCA thresholds later Saturday night into Sunday. Decided to increase the winds in collaboration w/GYX to 20-25 kt sustained and gusts to 30 kts. Seas are expected to climb to 7-8 ft and hold into Sunday w/a swell component. Winds shifting to the wnw and dropping to less than 15 kt will aid in knocking seas back by Sunday night to less than 5 ft. && .CAR WATCHES/WARNINGS/ADVISORIES...
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ME...Frost Advisory from midnight tonight to 7 AM EDT Saturday for MEZ015>017-029-030. MARINE...None.
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&& $$ Near Term...CB/Kredensor Short Term...Hewitt Long Term...Bloomer/Hewitt Aviation...CB/Kredensor/Hewitt Marine...CB/Kredensor/Hewitt is the U.S. government's official web portal to all federal, state and local government web resources and services.