textproduct: Gray - Portland

WHAT HAS CHANGED

The Gale Watch for this evening and Tuesday has been upgraded to a Gale Warning with this update.

No major changes needed otherwise as light snow continues to fall over much of the area.

KEY MESSAGES

1. Light snowfall through day break will bring slick travel this morning. Snowfall will taper off from NW to SE while an inverted trough may continue accumulating snow across southeast New Hampshire and coastal Maine through late morning.

2. A clipper system may bring a period of light snowfall Wednesday night before an Arctic airmass arrives for the remainder of the week through the upcoming weekend.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... Low pressure is roughly 200 miles ESE of Cape Cod as of this writing and is now pulling away towards Nova Scotia. Latest available NWP guidance has continued a downward trend in QPF and resultant snowfall as the heaviest snowfall has remained offshore. The back edge of the light snowfall is now moving across the CT Valley and light snowfall will continue to taper off from NW to SE during the pre dawn hours.

As low pressure offshore continues to pull away the final short wave is this busy upper air pattern slides across the eastern Great Lakes. Mesoscale and global models continue to suggest this short wave will result in an inverted trough extending northwestward from the low that will continue chances for snow across southeast NH and coastal Maine through late morning. Latest storm total snowfall calls for 1-2 inches along and south of the mountains and 1-3 inches across interior Maine and south-central NH. Where Advisories remain in tack snowfall amounts will range from 3-5 inches with slick travel here likely through the morning. Chances for snow will come to an end by this afternoon with the exception being snow snow showers in the mountains.

KEY MESSAGE 2 DESCRIPTION...

Geopotential heights will gradually rise Tuesday night into Wednesday with H8 temperatures warming to around -15C by Wednesday afternoon. Mainly clear skies and light winds combined with the snowpack will allow low temperatures Tuesday night to fall into the single digits either side of zero. Wednesday will feature increasing clouds with highs into the teens across the north with 20s in most other locations. A clipper system may bring a period of light snow or snow showers Wednesday night, which may result in some slippery travel conditions persisting into the Thursday morning commute.

Flow will briefly become SSW on Thursday, allowing for a warmer day with high temperatures into the 30s to near 40 degrees south of the mountains. Arctic air will then move into the region Friday through the upcoming weekend with well below average temperatures and a high likelihood for cold weather advisories/warnings. High temperatures on Saturday and Sunday may only be single digits for many areas with lows well below zero. Windchill values may approach 30 below in some locations.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Through 12Z Tuesday.. MVFR/IFR expected this morning and early afternoon as -SN continues to fall. There may be brief improvement before another period of deteriorating conditions later this morning. This begins to exit northeast after 18z, with VFR trend into this evening. West to southwest winds become breezy this evening and tonight with gusts to around 20 kt, possibly 25 kt at times.

Tuesday: VFR prevails at all terminals. Westerly wind gusts 20-25 kts possible in the afternoon.

Tuesday night/Wednesday: VFR conditions with winds generally less than 20 kts.

Wednesday night: Some restrictions possible due to -SN. Forecast confidence is low.

Thursday: VFR conditions with SSW winds prevailing.

Friday: VFR conditions with W wind gusts up to 25 kts possible.

MARINE

Winds and seas will be on a brief downward trend into day break as low pressure pulls away from the Gulf of Maine. An inverted trough extending from the low may continue snow over the waters through mid day. Winds then increase Monday afternoon as a cold front approaches from the west. The passing front will bring potential for westerly Gales Monday night through Tuesday.

SCA to near gale force winds will persist Tuesday night through the upcoming weekend along with elevated seas. Freezing spray is also likely as very cold air moves across the waters.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory until 1 PM EST this afternoon for MEZ018-023>028. NH...Winter Weather Advisory until 1 PM EST this afternoon for NHZ010-012>015. MARINE...Gale Warning from 7 PM this evening to 1 AM EST Wednesday for ANZ150-152-154. Small Craft Advisory from 7 PM this evening to 1 AM EST Wednesday for ANZ151-153.