textproduct: Gray - Portland

WHAT HAS CHANGED

Little change to the short term portion of the forecast as latest guidance has shown good run to run consistency with relenting cold today and Thursday along with some light snow tonight.

Confidence continues to increase for a arctic blast this weekend bringing dangerously cold windchill and air temperatures.

KEY MESSAGES

1. Very cold morning this morning with wind chill values near zero many areas, to well below zero in the mountains.

2. Low pressure passes north of the area tonight bringing a period of generally light accumulating snow. Accumulations will be light and snow is forecast to end before the Thursday morning commute. A few snow showers and possible squalls will be possible with cold front Thursday late morning and afternoon, especially across New Hampshire.

3. Arctic blast will bring dangerously cold weather to the region this weekend. The coldest air of the season thus far is looking likely with sub-zero wind chills Friday night into Saturday followed by will below zero low temperatures Sunday morning. Frostbite onset will occur quickly for those not dressed properly.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... We will see a bit of a moderation in temperatures today as winds go southwesterly. However, early this morning will be quite cold with most low temperatures in the single numbers. In the mountains and other outlying areas, temperatures will be below zero around sunrise. Bundle up.

Highs will "rebound" today, with them getting close to 30 at the coast and across southeastern NH. Clouds will increase as the afternoon progresses in advance of a warm front.

KEY MESSAGE 2 DESCRIPTION... A low pressure system moves northeastward out of the Great Lakes tonight bringing a warm air advection regime to our forecast area. This will aid in the development of mainly light snow early this evening in the west, then eastward from there during the evening hours. It's a quick-hitting system that should be gone by 12z Thursday. BUFKIT soundings show a fairly deep DGZ, so with this favorable lift and cold temperatures bumping snow ratios higher than 10:1 much of the area receiving measurable snow is in the cards. Looks like 1-2" for most locations with potential for 2-4" on the Midcoast with some ocean enhancement. Some leftover slippery travel possible for the Thursday morning commute.

A cold front will approach from the west on Thursday with a chance for snow showers and perhaps a few squalls, especially across NH.

KEY MESSAGE 3 DESCRIPTION...At the end of the week, a negative phase of the North Atlantic Oscillation will allow for a very weak polar vortex across the northern hemisphere, opening us up for an invasion of arctic air. The strongest of this airmass will gyrate around eastern Canada this week and make a southerly swing into the Great Lakes and New England by the weekend. Ensemble guidance is relatively locked in already for an anomously cold airmass this weekend on the order of the 99th percentile of normal at 700mb temps, as a piece of the polar vortex moves overhead on Saturday.

AVIATION /02Z WEDNESDAY THROUGH SUNDAY/

Through Thursday...VFR prevailing at all terminals through the day today. Ceilings may trend toward MVFR late this afternoon at KLEB and KHIE.

Tonight...Widespread MVR to IFR in light snow expected for most of the night, with a trend toward MVFR as snow comes to an end near day break Thursday.

Thursday: Local MVFR or lower possible in snow showers. Otherwise widespread VFR.

Outlook...

Thursday Night: Widespread VFR, with local MVFR possible at HIE.

Friday: Widespread VFR, with local MVFR possible at HIE.

Friday Night: Widespread VFR, with local MVFR possible at HIE.

Saturday: VFR prevails at all terminals.

Sunday: light snow possible across southern TAF terminals by PM

Monday: MVFR becoming VFR as potential lights snow pulls away.

MARINE

SCA conditions persist through tonight. Conditions favorable for light freezing spray continue through this morning. Low-end gales possible Thursday.

Thursday night through Sunday night...High end SCA conditions are possible Thursday night as cold front swings through the coastal waters with offshore flow. Winds stay elevated on Friday and increase Friday night as an arctic front pushes through with a strong high pressure system moving into the region for the weekend. Gales are possible Friday night into Saturday morning along with freezing spray and sea smoke. Conditions improve by Saturday night as winds and seas subside.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 7 AM EST Thursday for ANZ150-152- 154. Small Craft Advisory from 4 PM Wednesday to 7 AM EST Thursday for ANZ151-153.