Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 180110 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 910 PM EDT Mon Apr 17 2017 .SYNOPSIS... A frontal boundary will remain across the region through tonight with some snow possible. High pressure is expected to ridge down across the region on Tuesday into Tuesday night. && .NEAR TERM /THROUGH TUESDAY NIGHT/...
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9:10 PM Update...Areas of mostly light snow continue to fall from Caribou north through parts of the Saint John Valley as of 9 PM, with a mix of rain and snow from Caribou to Houlton, and mostly just rain showers to the south. There is an inverted surface trough across eastern Maine that the near term models shift to the west overnight. The latest couple runs of the HRRR and RAP continue to show at least some light areas of precipitation continuing much of the night, and shifting to the west with time. As the low levels continue to cool, snow will be favored over rain across the northern half of the CWA, with a mix possible south to Bangor after midnight. Any accumulation will likely be an inch or less, and mainly across far northern portions of the CWA. Another concern, as temperatures drop below freezing wet surfaces will likely become slick, and have addressed this with a special weather statement. Previous discussion... An inverted trof will be the focus for precipitation tonight and then drier wx in the offing for this term. The 18Z sfc analysis showed the inverted trof setting up across the region w/the best convergence residing across northern and eastern areas. Radar showed precip affecting basically northern and the eastern section in the form of some snow across the St. John Valley w/some accumulation occurring(around an inch so far). Further s, rain and drizzle w/patchy fog. Temps across the northern 1/2 of the CWA were in the 30s while further s down into the central and downeast region, temps were in the 50s and 60s thanks to some clearing. For tonight into Tuesday, the inverted trof will shift westward per the latest runs of the NAM and RAP which were matching up nicely w/the radar. 12Z UA showed an 700mb trof sitting back across Ontario set to swing across the region. This feature in conjunction w/ the inverted trof at the sfc will allow for an area of precip to set up say from northern Maine down into Washington County. Temps will be falling back as colder air filters down from Canada. It will be cold enough even into Washington County for some snow. The best chances for accumulations will be in the higher elevations. This cooldown w/cooling temps will lead to some icing possible on area roads. Things are expected to drier on on Tuesday as high pres to the n ridges down across the region. It will be a chilly day w/clouds hanging on across the region especially to the north and west. Daytime temps are forecast to be 5 to 10 degrees below normal for mid April Tuesday night will be a rather chilly night w/partial clearing late at night. Overnight temps look like they drop back into the mid/upper 20s for the northern 1/2 of the CWA w/downeast around 30 or so.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Return flow from the south expected by Wednesday as the surface high pressure pulls off into the Canadian Maritimes. Clouds will be on the increase during the day as a 500m shortwave trough approaches the state from Quebec province. Fairly good agreement that rain will spread from west to east during the day on Wednesday. Could be a few snowflakes mixed in across the higher hills at the onset. Rain showers will continue into Wednesday night, mixing with snow across the higher terrain. Overall QPF amounts look light with the wave, with most areas receiving between a tenth to quarter of an inch. Not expecting to much of a rise on any area rivers. Showers expected to end Thursday morning, with some partial clearing during the day on Thursday as weak ridging builds over the area. Temperatures will run near average for this period. && .LONG TERM /FRIDAY THROUGH MONDAY/... Active pattern continues Thursday night into Friday as an Ohio Valley low pressure system quickly tracks into New England. Still a lot of spread and run-to-run discontinuity with this system in regards to timing and track of the surface low. The ECMWF/GEM have trended north and more aggressive with the QPF compared to their previous runs and are closer to the GFS solution. We will have to watch this event in regards to how much rain falls due to elevated rivers and how much snow may fall across Northern Maine Friday night. The surface high due north over Quebec province and thermal profiles will support snow, especially after sunset on Friday night. Will watch how this evolves over the next few days. Partial clearing is expected by Saturday and all guidance is showing high pressure cresting over the region on Sunday. Very little agreement in the models by Monday next week. Overall temperatures will run near average for this period. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/...
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NEAR TERM: IFR/MVFR conditions tonight across the north w locally LIFR conditions in snow. VFR dropping to MVFR and perhaps IFR later tonight for KBHB & KBGR. IFR/MVFR for early Tuesday for all terminals w/a gradual improvement to VFR for KBHB & KBGR by 15z or so. VFR for all terminals for Tuesday night. SHORT TERM: MVFR conditions possible later in the day on Wednesday as rain showers and lower cigs move into the region as a weak area of low pressure approaches. Partial clearing on Thursday before rain and maybe some snow for the northern TAF terminals returns Friday into Friday night. IFR conditions or lower could be possible through the period at all TAF terminals.
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&& .MARINE... NEAR TERM: No headlines this term. Will see winds increase slightly tonight to 10 to 15 kts and turn more to the n and hold this direction and speed into Tuesday. Seas will average 3-5 ft w/an ese swell component. Winds will gradually drop back Tuesday night and turn more to the e. SHORT TERM: South winds off the waters on Wednesday will decrease and turn more easterly during the day on Thursday. Seas will generally run 3 to 5 through this period. More significant coastal low expected by Friday with buildings seas and prolonged period of easterly winds. && .HYDROLOGY...
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The mattawamkeag River at Mattawamkeag remains above flood stage this evening, and is expected to remain above flood stage this week with minor flooding. Other rivers across the HSA remain elevated and are running fast and cold, but are not expected to flood. A weather system late in the week will need to be watched closely for the potential of rain and snow that could cause additional rises.
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&& .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...CB/Hewitt Short Term...Dumont Long Term...Dumont Aviation...CB/Hewitt/Dumont Marine...CB/Hewitt/Dumont Hydrology...CB

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