Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 260112 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 912 PM EDT Wed May 25 2022 .SYNOPSIS...
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High pressure continues to slide further offshore overnight, followed by a warm front lifting to the north on Thursday. A cold front then slowly approaches from the west through Friday night, then crosses the area Saturday and Saturday evening. Weak high pressure then builds in through Sunday night, followed by a warm front lifting north on Monday.
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&& .NEAR TERM /THROUGH THURSDAY/...
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9:12 PM Update: High pressure in the Gulf of Maine will slowly retreat to the east through Thursday with an increasing return flow across the region. Satellite pictures show high clouds streaming toward the region from the west. A mainly clear sky is expected late this evening with increasing high clouds overnight. Temperatures are now in the upper 40s/low 50s along the coast with mid 50s to low 60s for most inland locations. The 00z Caribou sounding was fairly dry like last night. Very minor tweaks were made to the hourly temps and dew points based on the latest observations and expected conditions, but overall changes were minor. Previous discussion: High pressure centered over the Gulf of Maine will remain in the area tonight. 850-300mb RH models show clear skies early tonight, but the approaching warm front will push high level clouds in before midnight, then mid and low level clouds after midnight. Early clear skies will help with radiational cooling, but the late cloud cover should even temps out to upper 40s across the region. QPF models and SREF are pointing to the development of the marine layer tonight over the waters due to high pressure sitting over the waters. With SW flow, it is possible for some fog/low stratus to make it onshore. Decided to add patchy fog to the coastal Downeast regions. By Thursday, the approaching warm front will start to lift N across Quebec in the morning. Increasing cloud cover will help keep temps slightly below normal throughout the day. 925Mb indicates warm air overrunning cold air, which will help increase moisture in the afternoon with the S flow. Rain is expected to begin once the warm front settle to the north of the state. Upper air model soundings indicate fairly dry air in the low and mid levels for the south, thus decided to keep the rain north of the Bangor Region. As the front moves north, the high pressure over the waters will slowly make its way E. This will tighten the pressure gradients as the low level jet moves S. Winds will increase across the region, but especially along the coast where gusts could reach up to 25 mph.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... This time frame will feature a battle between deep layered ridging centered off the mid-Atlantic Coast and northern stream shortwaves going over the top of the ridge over SE Canada. The trend in the models is showing less flattening of the ridge by these shortwaves, this will help keep the surface frontal boundary up in Canada for longer than previously expected. While the surface warm front is to the north to start Thursday evening, the 850 hPa warm front is still catching up and should lift through northern portions of the CWA through the night. As a result have chance pops and higher mainly to the N of the Bangor Region with areas from on around Bangor on South likely staying dry. Pops should diminish from S to N through the night, with any precipitation likely confined to the Crown of Maine by Friday morning (if not totally into New Brunswick). Lows Thursday night should run 5-10 degrees above normal. Patchy to areas of fog is probable over at least coastal Downeast Maine with a strong marine layer with onshore flow. Friday morning should be mainly dry, except for possibly around the Crown of Maine. A passing northern stream shortwave Friday afternoon should bring some showers to the region, and possibly a rumble of thunder, with the best chance for any precipitation across the North. Downeast Maine, especially nearer the coast could end up dry through the day. However, with strong onshore flow, the marine layer will be rather strong, so low clouds and patchy fog could still be in play there, even with no precipitation. Highs on Friday could be quite mild, especially in the Central Highlands/Upper Penobscot Valley (depending on exact strength/orientation of the Marine layer and the exact areas impacted by the passing shortwave). Highs should run 5-10 degrees above normal, except possibly up to 15 degrees above normal in the Central Highlands/Upper Penobscot Valley. Another passing northern stream shortwave, coupled with the upper trough and surface trough creeping ever closer from the west should bring more widespread precipitation over the area Friday night than during the day on Friday, though confidence is lowest in this over Downeast Maine, especially coastal areas. There is the potential for an area of locally heavy rainfall Friday night with any stronger convection. At this time, the best chance for this appears to be areas mainly from Mt Katahdin on North. Given the relatively dry antecedent conditions no hydrologic concerns are anticipated. Lows Friday night should be around 15 degrees above normal. The axis of a northern stream trough pushes into the area by Saturday afternoon, ahead of this axis (and its associated surface cold front) locally heavy rainfall is possible with any stronger convection. With 500-1000 J/kg of CAPE, surface dewpoints into the upper 50s-low 60s, the region in the right entrance region of a 100+KT 300 hPa jet, and 40-50KT of 0-6km Bulk Shear there is some potential for strong to possibly severe storms as well. With the flow in the low-mid levels becoming more parallel to the Maine Coast, the marine layer might not be much of an influence in keeping stronger convection at bay. At this time the confidence in any strong to severe storms is not high enough to reflect this threat in the HWO. For now highs on Saturday are forecast to be near normal. However depending on the strength of the warm push ahead of the cold front and its actual timing, they could be a bit higher especially for areas S/E of Mt Katahdin. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... While the CMC continues to show a cutoff low impacting the region Sunday and Monday, the GFS/ECMWF and their ensembles do not show much support for this, so followed a ECMWF/GFS blend in the long term. The northern stream trough axis exits to the east Saturday evening, bringing an end to any lingering showers with it over Downeast Maine. This is followed by WNW flow aloft through Sunday. With dry low levels it should be dry late Saturday night and Sunday. The region is then under WNW-NW flow aloft Sunday night - Wednesday with the region in between a deep layered ridge centered over the Ohio River Valley and a cutoff low over the Canadian Maritimes. While it should be mainly dry during this time frame, shortwaves coming down the front side of the ridge/backside of the cutoff low could bring bursts of showers and possibly a rumble of thunder as well. Historically this pattern is also favorable for severe weather if Mesoscale Convective Complex can develop over Quebec and then maintain itself as it advects ESE-SE into the area. While there are some signs this could occur in the models, there is far to much uncertainty to pick any one solution as being right or wrong. It is best at this time just to recognize the generic threat, and realize that for most, if not all locations this threat most likely will not materialize. Temperatures should be near normal Saturday night, then above normal Sunday- Wednesday. && .AVIATION /01Z THURSDAY THROUGH MONDAY/...
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NEAR TERM: Mainly VFR for all terminals with possible MVFR/IFR in patchy fog for Downeast terminals late tonight with light and variable winds. Confidence on fog was not high enough to include in the 00z Tafs. On Thursday, VFR for all terminals in the morning, then MVFR/IFR in the afternoon for the Aroostook terminals due to rain. S winds 5-10 kts in the morning, then 10-15 kts in the afternoon with gusts up to 25 kts. SHORT TERM: Thursday Night: MVFR or lower possible. S-SE Winds G15-25KT, LLWS possible. S-SSW Winds G15-20KT possible Thursday evening at northern terminals. LLWS possible southern terminals. Friday-Saturday: MVFR or lower possible. Thunderstorms possible Saturday. S-SW winds G15-20KT possible at northern terminals and LLWS possible at southern terminals into Saturday ahead of the surface cold front. NW winds G15KT possible behind the cold front. Saturday night-Monday: Becoming VFR Saturday evening.
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&& .MARINE...
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NEAR TERM: Winds and seas below SCA conditions tonight. Low visibilities possible in patchy fog. By Thursday, winds and seas will be below SCA in the morning, then winds increase quickly in the afternoon to 25 kts. Thus a Small Craft Advisory has been issued starting Thursday afternoon. SHORT TERM: SCA has been issued for all waters for Thursday night. This likely will need to ultimately be extended on all waters through at least Saturday. SCA conditions could linger on the coastal ocean waters east of Schoodic Point Saturday evening, other wise sub-SCA conditions are expected Saturday night-Monday.
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&& .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory from 2 PM Thursday to 6 AM EDT Friday for ANZ050>052. && $$ Near Term...CB/LaFlash Short Term...Maloit Long Term...Maloit Aviation...CB/LaFlash/Maloit Marine...CB/LaFlash/Maloit

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