textproduct: Caribou

SYNOPSIS

High pressure will ridge across the area tonight into Tuesday. Low pressure will slide south of the region Tuesday night into Wednesday. High pressure will return Wednesday night. Weak low pressure will pass northeast of the area on Thursday. High pressure will then build over the area through Saturday.

NEAR TERM /THROUGH TUESDAY NIGHT/

Key Message: Snow is expected Tuesday night into Wednesday for all but far northeastern Maine. The greatest accumulation will be from Coastal Hancock County through southern Piscataquis County southwestward towards central and southern Maine.

Discussion: Tonight through Tuesday: High pressure will build over the area tonight, leading to decreasing winds and cold temperatures. Lowered temperatures across northwestern areas compared to the NBM due to more optimal radiational cooling conditions. Lows are expected to be around 0 to 10 below across the north and 0 to 10 above across the southern half of the area. Clear skies early will give way to increasing clouds in the afternoon on Tuesday with high temperatures slightly below average, ranging from the mid teens across the north to upper 20s along the coast.

Tuesday Night: A shortwave trough moving into southern New England will lead to the development of an inverted surface trough along the Maine coast Tuesday evening through Wednesday. Significant uncertainty remains in its exact placement, with solutions ranging from the GFS placement near Portland to the NAM placement just east of Mount Desert Island. Given that inverted troughs are highly mesoscale types of events, small shifts will significantly change snow amounts. A blended placement of the inverted trough near the Midcoast of Maine, similar to the ECMWF and RGEM, was favored, and also aligns with studies of where inverted troughs are climatologically most favored to be oriented along the Maine coast. The gradient of snowfall in the Penobscot Bay area could be significant, with potential for warning level snowfall prompting a Winter Storm Watch for Coastal Hancock County. Forecast soundings show more favorable lift within the dendritic growth zone further inland, so snow to liquid ratios may reach or exceed 20 to 1 over or northwest of Bangor into central and southern Piscataquis County. Winter Weather Advisories have been issued for these areas. Further east, QPF was lowered compared to the NBM due to uncertainty in the inverted trough positioning and potentially a sharper gradient in QPF than the NBM is forecasting. Far northeastern portions of the forecast area may see little to no accumulation.

SHORT TERM /WEDNESDAY THROUGH THURSDAY/

The storm discussed above tapers off Wednesday. A weak system moves through from NW to SE Wednesday night and Thursday, with the potential for light snow accumulation as much as an inch or two, but also potentially just a dusting or less. Only have a chance of snow in the forecast for now.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Key Message 1...Potential Significant Winter Storm Late Sunday/Monday Key Message 2...Bitter Cold Thursday Night to Saturday

Key Message 1... The main concern in the extended is the potential for a significant winter storm late Sunday/Monday. There is unusually good model agreement this far out for a system of at least decent strength around this time. Most models/ensembles have a vigorous upper trough moving through and rapidly strengthening a surface low pressure that moves east through the region. Models generally favor snow, but rain/snow or rain is possible especially Downeast if some of the warmer solutions pan out. Bottom line is this is still very far out and a lot can change, but we will need to keep a close eye on this, as some model solutions have heavy snow totals and significant winds.

Key Message 2... The other lesser concern is a very cold airmass especially Thursday night into Saturday. The cold air really moves in Thursday night, with lows around zero in the north with potential wind chills to around -20F. Not quite as cold Downeast, but still cold. Pretty high confidence that it stays cold Friday and Friday night, with highs Friday around 10 in the north and 15-20 Downeast, and lows Friday night 10 below to 5 above, with the potential of some colder readings if we clear out with high pressure moving in. Little/no precipitation Thursday night through Saturday, with a weather system likely missing us to the southwest as we will be too deep into the cold air. Can't rule out a little light snow getting as far NE as Bar Harbor/Bangor/Greenville, but more than likely it'll stay to our SW.

AVIATION /18Z MONDAY THROUGH SATURDAY/

NEAR TERM: Through Tonight: VFR. NW winds 10-15 kt with gusts up to 25 kt early, decreasing to 5-10 kt this evening.

Tuesday: VFR with light winds.

Tuesday Night: VFR, becoming MVFR with -SN for some eastern and northern terminals. IFR or lower possible in SN for BGR and BHB. Winds E at 5 to 10 kt with gusts to 15 kt.

SHORT TERM: Wednesday...Potential IFR/MVFR Downeast early Wed, with potential MVFR early Wed in the north, but confidence is low. Most places should become VFR by Wed afternoon regardless. N wind 5-10 kts.

Wednesday night-Thursday...VFR Downeast with possible MVFR, and mainly MVFR Aroostook terminals in potential snow showers and low cigs. Variable wind 5 kts becoming NW 10 kts.

Thursday night-Saturday...Mainly VFR. NW 5-15kts.

MARINE

NEAR TERM: Winds and seas will fall below advisory levels this evening before increasing to advisory levels again on Tuesday night. There is a chance (slightly below 50 percent) of localized gales later Tuesday night, but uncertainty remains on placement and timing of the strongest winds.

SHORT TERM: Potential NE gales Wed morning, but not enough confidence to issue gale watch. Next chance of gales is Thursday night, with potential freezing spray too.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory from 6 PM Tuesday to noon EST Wednesday for MEZ010-015-016-031. Winter Storm Watch from Tuesday evening through Wednesday morning for MEZ029. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ050- 051.