Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 060105 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 905 PM EDT Mon Jun 5 2023 .SYNOPSIS...
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Low pressure south of Nova Scotia will slowly move northward overnight and will gradually move north into the Maritimes Tuesday. The low will remain stalled over the Maritimes through Friday and move east of the region Saturday.
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&& .NEAR TERM /THROUGH TUESDAY/...
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9:05 PM Update: The forecast remains on track with only minor adjustments to account for the current and expected conditions for the remainder of the night. The water vapor satellite channel shows a mid level circulation to the south of Nova Scotia that will lift north overnight. Area radars and observations indicate manly dry conditions as of 9 PM with a bit of light rain in spots across the North Woods and an isolated shower in spots Downeast. The main area of rain is moving out of Nova Scotia and into eastern New Brunswick. The rain will continue to back toward eastern Maine overnight. Previous discussion: The vertically stacked low pressure south of Nova Scotia will deepen tonight into early Tuesday as it drifts northward into Nova Scotia. Blocking will prevent much movement of this system and the entire closed low circulation will become much broader tonight into Tuesday as a powerful upper jet moves southward on the backside of the upper trough. A shortwave rotating around the low was responsible for the band of rain that lifted north across the area today and is currently weakening/stalling in Aroostook County. This band should dissipate in place this evening as upper level support disappears. A strong shortwave is currently rounding the base of the offshore low with deep Atlantic moisture and strong lift moving into western Nova Scotia. While some models such as the HRRR suggest the southeastern corner of Washington County could be clipped by this heavier precip, will go with a maximum of one half inch tonight near Lubec and Eastport...and much less further inland. As the cut-off low lifts north into Nova Scotia, this moisture will eventually wrap cyclonically around the closed circulation and approach the rest of eastern Maine from the east after midnight. This wrap-around occlusion will cause rain across the area all of Tuesday. Although there is decent moisture transport westward into the area on Tuesday, helped by an emerging H850 jet, lift will be weak and PWs will be less than an inch. Therefore, QPF tonight into Tuesday will be limited to between a quarter inch to one half inch...in spite of somewhat continuous rainfall on Tuesday. The tight pressure gradient will lead to fairly gusty northerly winds, but a low mixing depth and extensive cloud cover will keep gusts maxed out around 25 mph. The clouds, rain and cool air aloft will produce another day with high temps limited to the low to mid 50s...only several degrees above record low high temps and some 15 to 20 degrees below normal readings.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... Vertically stacked low pressure trough remains centered over eastern Maine into the Canadian Maritimes through the mid-week time period. This will persist the cool, cloudy, rainy pattern that we have seen across the forecast area over the next several days. With the blocking pattern in place, there is good model consistency in this pattern remaining in place through the short term. Wednesday will be cool with highs in the lower 50s across the north. Northwest to north winds will descend from the higher terrain across the north into the lower terrain Downeast, and this downsloping will help Downeast areas remain a bit milder with highs in the upper 50s. Flow will shift more northerly across the forecast area on Thursday, though more breaks in the clouds are likely as the low begins to weaken overhead, so temperatures will be warmer on Thursday with highs in the mid to upper 50s across the north and around 60 Downeast. Low temperatures each night will fall into the 40s and overcast skies and lingering rain will limit how far temperatures fall, limiting the threat for frost. Downsloping will lead to a lesser chance of precip Downeast through midweek as the air mass dries over higher terrain, with a greater chance of consistent light to moderate rainfall over the northern half of the forecast area. That said, enough mid level moisture will fill this low pressure system such that rain is expected to continue Downeast, just in lesser amounts than across the north. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... The trough of low pressure will begin to slowly break down and exit the region through the end of the weak, allowing for a narrow ridge of high pressure to build in across northern and eastern Maine by Saturday, lasting through the weekend. Under the high pressure, though there remains a chance for rain showers each day (mostly diurnally driven), partly cloudy skies will return and temperatures will lift back into the 70s for daily highs across the forecast area. Unfortunately, the warmer and quieter weather pattern under the ridge of high pressure will not last long, as another low pressure system approaches from the west. Better model agreement now exists on the front for Sunday night into Monday among the global models. This front will bring another round of rain through the entire forecast area. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/...
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NEAR TERM: Generally MVFR ceilings this evening, although VFR at times north of KHUL. The trend will be towards IFR cigs for all sites later tonight through Tuesday. Ceilings may lift a bit to low end MVFR later in the day Tuesday. LLWS is possible during Tuesday, but it is borderline at this time and was left out of the 00z Tafs. N wind 5 to 10 knots the remainder of tonight, becoming N 10 to 15 knots on Tuesday. SHORT TERM: Tues night - Thurs night: MVFR cigs, with potential for cigs to lift to VFR each afternoon. Winds NW 10 to 15 kts Tues night, shifting N at 5 to 10 kts Wed through Thurs night. Fri - Sat: Mainly VFR, though MVFR possible in scattered showers. Winds N at 5 to 10 kts, becoming light and variable on Saturday.
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&& .MARINE... NEAR TERM: Will continue the ongoing SCA into Tuesday morning. The offshore low is deepening with a tightening pressure gradient, but the cold waters will enhance stability and limit mixing. Cannot rule out some fog tonight into Tuesday morning as dew points creep above water temperatures, but confidence was not high enough to include in the forecast. North winds will slowly shift to northwest by Tuesday afternoon. There will be some decrease in wind speeds on Tuesday and saw no need to extend the SCA. SHORT TERM: Winds and seas will remain below SCA levels Tuesday night through the end of the week. NW winds will briefly gust near 20 kts on the coastal waters Tuesday night, but will decrease and remain well below advisory criteria through the end of the week. Seas will sit around 2 to 4 ft. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory until 8 AM EDT Tuesday for ANZ050-051. && $$ Near Term...CB/MCW Short Term...AStrauser Long Term...AStrauser Aviation...CB/MCW/AStrauser Marine...CB/MCW/AStrauser

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