Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 160400 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 1200 AM EDT Mon Apr 16 2018 .SYNOPSIS... Cold Canadian high pressure will remain in place into tonight. Low pressure will approach from the Midwest Monday and slowly cross the area Tuesday into Wednesday. && .NEAR TERM /THROUGH MONDAY/...
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Midnight update: No significant changes at this time. Will update with the latest observations and expected conditions overnight. Light mixed precipitation is falling across much of northern MA and southern NH, and will lift into the southwest corner of the CWA as well as across the Downeast Region after 3 or 4 am. The morning commute looks to be a slick one for many areas across the southern portions of the CWA. Previous discussion: An unusually cold 1047mb high centered over Quebec is the dominant feature in area weather through Monday. The cold and dry air will provide one last chilly night...most notably in Aroostook County where teens are expected. Further south, clouds will be too thick for radiational cooling. Overrunning high clouds will thicken and overspread the entire area as the night progresses and lows will be posted well before dawn. The warm advection aloft will feature a warm nose at H700 that will ensure precip begins as mostly sleet later in the night. An initial band of sleet...and some freezing rain...will advect into southwestern portions of the forecast area early in the morning. While most of the precip should be sleet, some freezing rain could mix. As a result, have issued a Winter Weather Advisory for southern Piscataquis, southern Penobscot, and Hancock counties. The concern is for slick roads for the early morning commute before road surfaces warm. It`s possible that the advisory could need to be extended towards Washington and central Penobscot counties, but the general thinking is that the initial precip band will dissipate as it moves northeastward into the drier air...and any remaining precip will be just sleet. The cold air damming and frontal inversion will last all day with highs mostly in the low 30s except the immediate coast. It`s conceivable that sleet and freezing rain could be the dominant P-types much of the day with resultant extension of advisories. However, due to the time of year and surface temperatures near 32F, am hesitant to have any advisories beyond Monday morning for now. Warming aloft will increase such that H850 temps will become 10C by afternoon and any sleet will gradually change to rain and freezing rain. This thermal ridge could also serve as a base for some elevated instability on Monday afternoon, but will hold off any mention of convection in the forecast at this point. Pops will increase through the day as the low level dry air is wiped out from west to east. Upslope and coastal front precip will develop in the afternoon, but the real significant precip will arrive late day as a potent shortwave rotates around the closed Great Lakes upper low with a triple point low moving into southern New England...aided by strong upper jet support. Besides the mixed precip, the other concern during Monday will be high winds along the coast. A 60-kt easterly H925 LLJ is expected to develop in the afternoon along the coast. Expect a deep enough mixed layer to cause some strong gusts and have issued the wind advisory for this event as well as the stronger LLJ that arrives Monday night.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... An occluded front will cross the region Monday night through Tuesday. A mix of sleet, freezing rain and rain will change to mostly rain across northern and central areas Monday night, with mostly rain Downeast. A strong low level jet will cross the region Monday night, with the strongest winds along the Downeast coast where gusts up to 50 mph are expected. A Wind Advisory is in effect for the Downeast coast Monday night. Rain will persist in advance of the occlusion Tuesday then diminish during the afternoon. Vertically stacked surface/upper level low pressure will slowly cross the region Tuesday night through Wednesday. With cooling temperatures, expect precipitation will transition back to snow showers or a rain/snow shower mix across northern areas later Tuesday night, with rain showers transitioning to a rain/snow shower mix Downeast. Expect a chance of rain/snow showers across the north and mountains Wednesday, with a chance of rain showers Downeast. Temperatures will remain at below normal levels Tuesday/Wednesday. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Snow showers north, with a slight chance of rain/snow showers Downeast will persist Wednesday night. Uncertainty then exists regarding the track of low pressure Thursday into Friday. Precipitation amounts Thursday/Friday will be dependent on the eventual track of the low. Precipitation types will be largely tied to diurnal temperature trends, with snow or a snow/rain mix overnight into the morning hours and mostly rain through the afternoon into the evening. Precipitation should taper to snow showers Friday night. High pressure should then build across the region Saturday into Sunday with generally partly cloudy skies. Temperatures will remain at below normal levels Thursday through Saturday, with near normal level temperatures Sunday. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... NEAR TERM: VFR conditions continue until late tonight. MVFR cigs/vis will start to affect BGR and BHB late tonight into Monday morning. The cause of the vis reduction will be sleet and freezing rain. This mixed precip will spread northward and affect all zones by late afternoon. LLWS will be a threat Monday afternoon for BHB and coastal airfields. BGR may also be affected. SHORT TERM: IFR/LIFR conditions are expected across the region Monday night through Tuesday. Low level wind shear is a concern Monday night with a strong low level jet crossing the region. East to southeast winds are expected to gust up to 50 mph along the Downeast coast Monday night. A mix of sleet, freezing rain and rain will change to mostly rain across central and northern areas Monday night, with generally rain Downeast. Rain is expected across the region Tuesday. MVFR/IFR conditions are expected across the region Tuesday night through early Wednesday, with occasional MVFR conditions later Wednesday. MVFR/IFR conditions are possible Thursday into Friday dependent on the eventual track of low pressure. && .MARINE... NEAR TERM: Gale conditions will develop Monday morning. Winds and seas will continue to increase through the day, but not quite to storm conditions. SHORT TERM: A Gale Warning is in effect for the waters Monday night. Small craft advisory conditions are then expected Tuesday into Wednesday, mostly for seas. Visibilities will be reduced in rain Monday night into Tuesday. && .HYDROLOGY... With cooler temperatures, along with less rainfall and snowmelt expected with this storm, the immediate flood threat has diminished. However, river levels will still rise. Temperatures through the remainder of the week should then allow for a controlled snowmelt. Across the Saint John, Aroostook and Allagash River basins along with their tributaries river levels will rise along with weakening ice. This could allow the ice to move with ice jams possible later this week. && .TIDES/COASTAL FLOODING... Minor coastal flooding is possible during Monday nights high tide due to wave run-up action causing coastal overwash and minor beach erosion. This isn`t a major storm by any means but almost perfect timing of the high tide, 1 to 1.3 foot storm surge and strong onshore flow creating 5 to 10 foot near shore waves. Total Water Level guidance is providing minor flood threat for most of the wave run-up impacted locations. Overall looks to be a relatively minor event. This should be the only tidal cycle that a flood threat exists for and not expecting any inundation flooding in coastal areas. && .CLIMATE... The low temperature of 12F at Caribou, Maine this morning broke the previous record low of 13F, set in 1981. Including today, Caribou has now had the 5th coldest first half of April on record. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Winter Weather Advisory from 5 AM to noon EDT Monday for MEZ010-015-016-029-031. Wind Advisory from 2 PM Monday to 5 AM EDT Tuesday for MEZ029- 030. Coastal Flood Advisory from 10 PM Monday to 2 AM EDT Tuesday for MEZ029-030. MARINE...Gale Warning from 8 AM Monday to 6 AM EDT Tuesday for ANZ050>052. && $$ Near Term...CB/MCW Short Term...Norcross Long Term...Norcross Aviation...CB/MCW/Norcross Marine...CB/MCW/Norcross Hydrology...Norcross Tides/Coastal Flooding...Dumont Climate...CB

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