textproduct: Gray - Portland

SYNOPSIS

An Alberta Clipper will track north of the area today, bringing a period of snow showers and a possible squall from the mountains north. A cold airmass follows this system to start the week. The next potential for accumulating snow arrives Tuesday and Tuesday night before somewhat quieter and seasonable weather returns for Christmas Eve and Christmas Day. Another system is then possible towards the end of next week.

NEAR TERM /THROUGH SUNDAY/

Key Messages:

-Snow showers and perhaps a snow squall is possible this morning across the mountains and towards the Canadian Border. These will be capable of producing locally dangerous travel conditions with near whiteout conditions.

-Westerly wind gusts up to 30 mph possible this afternoon into tonight behind a strong cold front.

Discussion:

Low pressure will continue to move across southern Quebec today, sending a sfc cold front southward through New England. This front is progged to be well offshore by early this afternoon. As the front crosses, modest pressure falls combined with increased moisture will likely allow for scattered snow showers across the mountains and towards the Canadian Border with an isolated snow squall possible. Further to the south, the vertical column looks to remain too dry but a flurry cannot be completely ruled out. High temperatures will range from the 30s across the north with lower 40s along the coast and in southern NH under partly cloudy skies. Westerly wind gusts between 25-30 mph are likely, which will make it feel a little cooler.

SHORT TERM /SUNDAY NIGHT/

High pressure will begin building to our west tonight, allowing for dry conditions and colder low temperatures into the single digits to teens from north to south. Northwesterly wind gusts up to 30 mph will send windchills into the single digits either side of zero.

LONG TERM /MONDAY THROUGH FRIDAY/

Key Messages:

-Increasing confidence for accumulating snowfall Tuesday into Tuesday night, bringing potential impacts to holiday travel.

-Dry and cold weather likely Christmas Eve and Christmas Day before additional snow chances arrive late week.

Discussion:

Canadian high pressure will allow for a dry but chilly Monday with high temperatures into the teens across the north with 20s/lower 30s south under partly cloudy skies. A weak H5 s/wv trof may then cross Monday evening, bringing with it additional clouds and perhaps a flurry or snow shower. Lows will be into the single digits across the north with teens south. Attention then turns towards Tuesday as an area of low pressure is progged to eject southeastward out of Quebec into New England as a potential secondary low develops over the Gulf of ME.

The ECMWF and its ensemble suite continues to be more bullish with this potential system than the GFS/GEFS, which suppresses the system mainly to our south while also showing weakening and little to no secondary development. The AI GEFS ensemble mean is closer to the ECMWF solution though and given the system will be traveling through a region of generally favorable jet dynamics, tend to side with the snowier solution. Snowfall amounts currently look to favor this system as a potential advisory level event with 3-5" the most likely outcome. The main takeaway though is that this has the potential to produce travel impacts on Tuesday for the Christmas Holiday, especially later in the day and during the evening. Some light snow may linger through Tuesday night with lows into the teens and 20s.

Christmas Eve and Christmas Day currently look mainly dry and cool with high temperatures into the 20s/30s and lows into the single digits and teens. Another system may bring additional snowfall on Friday and Friday night but significantly uncertainty exists at this time range.

AVIATION /04Z SUNDAY THROUGH THURSDAY/

Short Term...Mainly VFR conditions are expected through Monday night, with the possible exception being at KHIE this morning due to passing snow showers and lower viz. W winds will prevail at 10-15 kts, gusting to 25 kts. LLWS is likely through mid-day at WS020/21045KT. SN is likely to overspread all TAF sites on Tue and persist through Tue night, bringing possible IFR-LIFR restrictions with S-SW winds. Winds will become NW on Wed with gusts up to 25 kts possible.

Long Term...Mainly VFR conditions are likely both Wed and Thu. Snow is possible towards late week but confidence is low at this time range.

MARINE

Short Term...Westerly gales are expected through tonight before slowly diminishing on Tuesday. Seas of 6-10 ft are expected outside of the bays with 1-4 ft in the bays. Another period of gales and increased seas are then possible towards Wed.

Long Term...High pressure shifts east late in the week as another front approaches, bringing perhaps another period of increased winds and seas.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning until 7 AM EST Monday for ANZ150-152-154. Gale Warning until 7 PM EST Sunday for ANZ151-153.