textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes to the forecast at this time.

KEY MESSAGES

1. Seasonable highs and cool nighttime lows continue through midweek. A shortwave brings some scattered snow showers on Wednesday, with cooler air returning behind this system for late week.

2. Light snow is possible Friday night into Saturday and could create slippery travel.

3. Becoming bitterly cold and breezy this weekend with Cold Weather Headlines increasingly likely centered around Saturday night. Dangerous wind chills of -20F to -30F possible from Saturday late evening through Sunday morning.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A shortwave approaches from the west overnight, and brings some scattered snow showers to the area on Wednesday. These will mostly be focused across the higher terrain, but may also spill into central Maine during the daytime. Any accumulations would remain light, with no more than a coating expected.

Clouds move in ahead of this system tonight, but ideal radiational cooling conditions are expected again tonight before these clouds arrive. With clouds arriving in the west first, northern valleys see temps fall quickly through the evening, but then level off overnight as the clouds arrive. This leaves valley locations east of the mountains, particularly from Fryeburg through Waterville as having the best potential to see the coldest temps tonight before the clouds arrive.

The system swings through during the day tomorrow, with temps falling on a northwesterly wind behind the front tomorrow night. The front does weaken as it crosses through, so there won't be as cold of an airmass with wind as we've seen behind some other fronts lately. With this set up, radiational cooling will be possible again late tomorrow night, but doesn't look as good of a set up as the last few nights.

KEY MESSAGE 2 DESCRIPTION...

A shortwave trough will bring more cloud cover and a chance of snow showers on Thursday, but this looks to be primarily in the mountains. Otherwise, fairly benign weather is expected through Friday with highs in the 20s for both Thursday and Friday. Thursday night still looks cold with temperatures below zero for much of the region.

A more potent shortwave bring a better chance for light snow and slippery travel Friday into Saturday with ensembles suggesting a coating-2" possible, although a fluff factor may bring slightly higher totals.

KEY MESSAGE 3 DESCRIPTION...

Of more impact will be the Arctic airmass that invades the region from Saturday afternoon through Sunday night. An upper low will continue to drop to the south and east out of northern Canada the rest of the weekend with a strong front crossing the region on Saturday. At the same time, the shortwave that brings the chance for light snow will take on a negative tilt with a surface low quickly developing and deepening south and east of the Gulf of Maine. This and the high building in from the west will bring a tight pressure gradient across the area, and as the arctic air spills into the region, winds will also pickup Saturday afternoon through Saturday night, creating dangerous wind chills.

Based on the latest forecast, it looks like most of the area will be experiencing wind chills below zero by Saturday afternoon, double digits below by early Saturday evening, and between -20F and -30F Saturday night into Sunday morning. Cold Weather headlines will likely be needed.

A few snow showers could last into Sunday as the upper low crosses, but mainly it remain a cold day with wind chills potentially staying below zero with winds remaining breezy and temperatures struggling to reach the 10s. Winds will not be as breezy going into Sunday night but still enough to possibly bring wind chills in the double digits below zero once again (but not as cold as Saturday night).

Temperatures remain below normal but start to recover Monday, and by Tuesday guidance favors returning to near or even slightly above normal temps.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

VFR prevails at southern terminals through tomorrow night. Elsewhere, VFR continues into tonight, then HIE and LEB likely, and AUG and RKD possibly, see periods of MVFR ceilings and some scattered snow showers late tonight and Wednesday. MVFR ceilings likely then lingering at HIE Wednesday night, and possibly lingering at LEB.

Outlook:

Thursday-Friday: A few snow showers and possible MVFR on Thursday, mainly HIE and AUG, but otherwise VFR prevails.

Friday night - Saturday: Light snow and IFR restrictions possible. Northwest gusts of 25-35kt possible Saturday afternoon and evening.

Saturday night - Sunday: There could be a few snow showers but mainly VFR is expected, except MVFR possible at HIE. Northwest gusts of 25-35kt possible Saturday night and around 25 kt on Sunday.

MARINE

A weak low pressure system crosses New England on Wednesday, with a cold front crossing the waters late in the day. Some marginal SCA conditions are possible across the outer waters with the passage of the front late Wednesday afternoon and evening.

SCA conditions possible late Thursday and Thursday night with improving conditions Friday.

Low pressure slides across New England Friday night and is expected to strengthen south and east of the coastal waters over the weekend. North to northwest gales are likely, including the bays, and it's possible there will be a period of storm-force gusts over the outer waters. Moderate freezing spray is likely over the weekend with heavy freezing spray possible from late Saturday through Sunday morning.

Gales might linger into Monday with gradually improving conditions Monday night and Tuesday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.