textproduct: Caribou

SYNOPSIS

High pressure builds in through tonight, then exits to the east on Sunday,as low pressure approaches from the west. A warm front crosses Sunday evening, followed by a cold front crossing Maine late Sunday night. A secondary cold front crosses the area on Monday, followed by high pressure building in through Monday night. A coastal low approaches from the south on Tuesday, passes offshore Tuesday night, then exists into the southern Maritimes on Wednesday.

NEAR TERM /THROUGH SUNDAY/

Update...

See updated marine section.

Previous Discussion... A northern stream shortwave passes this morning, followed by northern stream shortwave ridging building in this afternoon. High resolution guidance suggests any snow showers with the shortwave should be confined to Northern Somerset county along the border with Quebec, so pops have been adjusted accordingly. Should see decreasing cloud cover, especially this afternoon with the passage of the shortwave ridge. Highs today will range from the upper 20s to upper 30s, this is a few degrees below normal.

Deep layered ridging builds in tonight, with associated subsidence keeping things dry. Should see increasing mid and high clouds after midnight with the advection in of mid-high level moisture ahead of the next system. The increase in cloud cover makes the low temperature forecast a bit tricky, as it should work to offset the winds becoming light and variable, if not calm overnight. There is some question how thick these clouds will be initially (especially if the ridge axis is a bit slower to move off to the east) - so you could still end up with some decent radiational cooling. To reflect this possibility blended 2 parts NBM with 1 part NBM 10th percentile then subtracting a degree for lows. If had full radiational cooling would lean much more towards the NBM 10th percentile for lows. As a result, expect lows to be from the lower teens to lower 20s, which is around 5 degrees below normal. With the winds diminishing tonight, there should be little if any in the way of wind chill.

The axis of the deep layered ridge exits to the northeast Sunday morning, allowing for precipitation to move in from SW to NE ahead of the leading edge of a northern stream trough extending down from a cutoff low over Hudson Bay. The precipitation should increase in intensity in the afternoon, with a southeast 30-35KT 950mb and southwest 50-55KT 850mb jets over the area by Sunday evening. The precipitation should start everywhere as snow, except near/south of a Bangor to Wesley line where it should start as a rain/snow mix. The increasing low level warm advection, should bring the precipitation to along and south of a Dover-Foxcroft to Howland to Topsfield line, a mix of rain and snow north of there to south of a Houlton to Katahdin to Moosehead Lake line with all snow from there on north. By evening expect 1-3 inches of snow along/north of a Monson to Millinocket to Hodgdon line.

The increasing low level winds should bring about gusty winds in the afternoon as well, especially in areas that have gone to all rain. So expect 35-40mph wind gusts over coastal Downeast by late Sunday afternoon, gusts up to 20-25 mph for the Bangor region and northern Downeast Maine, with little in the way of gusts farther north. For now not quite confident in exactly how much winds mix down, so have held off on a Wind Advisory for coastal Downeast at this time. Highs on Sunday should be near to slightly above normal across the North and around 5 degrees above normal elsewhere.

SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/

Key Messages... 1. Wintry precipitation ends in the north Sunday evening 2. Easily the coldest air of the season so far Monday night

1. Precipitation ends quickly from west to east Sunday evening. Sped up ending time just a bit based off model trends. Still expecting warmer air to work up into far Northern Maine with a brief change to rain, or at least mix of rain, before everything ends by about midnight. Overall confidence in the system is high, with the main item of uncertainty being how far north the change to rain gets and whether it can make it to the St John Valley. Don't anticipate any sleet or freezing rain. For storm total snow accumulations, adjusted totals down just a touch, with 1-4 inches from Houlton, Millinocket, and Dover-Foxcroft north, with the higher end of that 1-4 inch range generally being over north/northwest portions of Northern Maine. May end up reaching low end advisory criteria (4 inches) at a few places, but don't see it being widespread enough at this point to issue any advisories. Breezy from the south with a few gusts 35-45 mph possible mainly near the coast Sunday evening, then winds decreasing.

2. Slight cold advection begins later Sunday night, with stronger cold advection Monday afternoon/evening as the coolest airmass of the season so far arrives. May see some snow showers with the cold advection during the day Monday, and went above NBM PoPs in the north, going with about a 30 percent chance of snow showers. Can't totally rule out a couple snow squalls in the north, but the threat doesn't appear to be particularly high as instability is pretty limited. Looks quite breezy Monday with gusts 25-35 mph from the northwest. Winds ease Monday night as high pressure moves in. Looks very cold, easily the coldest of the season so far, with lows 5 below to 10 above in the north, and 10-15 above Downeast.

LONG TERM /TUESDAY THROUGH FRIDAY/

Key Messages... 3. Potential significant winter storm Tuesday/Tuesday night, but still substantial uncertainty 4. Very cold Thursday/Friday

3. Models have only come into slightly better agreement for the potential major Tue/Tue night storm, and confidence is still low. Models/ensembles continue to wobble, some shifting the low pressure track south/drier with the 0z cycle, and others shifting north. A more northerly track of the low closer to the coast would mean a foot of snow for portions of our area that could occur quite quickly, more likely central or Downeast. A more southerly track of the low further offshore means precipitation could miss the area entirely. Averaging all the current tracks brings the most likely snow over Downeast with the potential for over 6 inches, but this is just an average, and reality likely won't match this average. Bottom line is we need to be patient but continue to watch this system closely, as it has the potential to be a big one.

4. Models have come into better agreement on an Arctic front passing through roughly early Thursday, with very cold air behind it, even colder than what we will be seeing late Monday/Monday night. Snow showers or even snow squalls are a possibility Thursday with the Arctic front. Toward Friday, the consensus is for high temperatures only 15-20 in the north, but there's a realistic chance for highs to be closer to 10 in the north. Wind chills Thursday night should be below zero, perhaps even as cold as 20 below for some colder spots.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

NEAR TERM: Ceilings should flirt right below/above 3000ft this morning, otherwise it should be VFR through the TAF period. Winds becoming W 10-1520-25KT this morning. Wind gusts should abate by early this evening, with the winds becoming light and variable as the evening persists.

Sunday...VFR in the morning, becoming IFR or lower from SW to NE in the afternoon. SE winds G15-25KT possible in the morning. LLWS likely in the afternoon with a low end chance of SE winds G30-35KT in the afternoon at KBGR/KBHB.

SHORT TERM: Sunday night...IFR or lower Sunday evening, with snow or rain from PQI north, and rain from HUL south to the coast. Precipitation ends by about 6z, though IFR or lower is likely to continue through the night. S winds 10-20 kts in the evening with gusts 20-30 kts, strongest winds BHB/BGR, becoming SW 5-15 kts after midnight. LLWS likely.

Monday...VFR, except possible MVFR north. NW wind gusting 20-30 kts.

Monday Night...VFR with light wind.

Tuesday and Tuesday Night...MVFR or lower possible in snow, especially south. Confidence is increasing, but confidence in the details of this event, including location, is still low. N/NE wind 10-20 kts possible if the storm takes a snowier track.

Wednesday...Probably VFR with NW winds 10-15 kts.

MARINE

NEAR TERM: Have discontinued the current gale warning in favor of an SCA through midnight tonight. Have also issued a Gale Watch later Sunday afternoon through Monday afternoon. Low level 925mb jet increases Sunday evening followed by cold advection on Monday with the potential for gale force gusts much of the watch period.

SHORT TERM: Gales expected (greater than 90 percent chance) late Sunday through Monday morning, from the south at first, then switching to the west. Seas to around 10 ft. Much improved winds/seas Monday night/early Tuesday, but about a 50 percent chance of gales late Tuesday night/early Wednesday from a possible Nor'easter. Seas could also build back up to around 10 ft, depending on the track of the Nor'easter.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until midnight EST tonight for ANZ050>052. Gale Watch from Sunday afternoon through Monday afternoon for ANZ050>052.