textproduct: Gray - Portland

WHAT HAS CHANGED

Very little has changed in the short term. We expect continued cold for today, slightly warmer Wednesday with some light snow possibly entering New Hampshire late in the afternoon.

KEY MESSAGES

1. Cold with daytime wind chills today in the single numbers at lower elevations and single numbers below zero in the mountain zones. Wind gusts 25 to 30 MPH.

2. Low pressure passes north of the area Wednesday night bringing a period of accumulating snow. Accumulations will be light and snow is forecast to end before the Thursday morning commute.

3. Coldest stretch of the season is likely late Friday into early next week. Gusty winds Friday night into Saturday will likely warrant Cold Weather Headlines. Low temperatures Saturday night likely dropping several degrees below zero across the entire area with -20F or lower possible within northern valleys.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... Cold air pours into New England today on westerly wind gusts of 25 to 30 MPH allowing for very cold wind chill values all day. While it should remain dry there could be a few snow showers, especially across western zones as the low level flow will be lined up with the Great Lakes. Very cold tonight with diminishing winds. Lows in the single numbers lower elevations and below zero mountains zones.

KEY MESSAGE 2 DESCRIPTION... The latest NBM has picked up on the signal for a period of snow Wednesday night as a clipper system tracks north of the area. PoPs are now in the 30 to 60 percent range across much of the area with higher PoPs in the mountains and near the Mid Coast where there will be added moisture. Latest available model soundings show a 3 to 6 hour window with decent lift and moisture through the dendritic growth zone Wednesday night. This should be enough to bring around 2-3 inches of snow in the mountains and across central Maine with a coating to 2 inches elsewhere. Accumulating snow should be exiting there area before the morning commute. While there will be potential for slick travel on snow covered roads, the timing of snowfall will be favorable for limiting impacts during the Thursday morning commute. Temperatures will climb into the upper 20s in the mountains and upper 30s near the coast Thursday before a cold front crosses Thursday night with temperatures dropping below freezing Thursday evening. Some snow showers may accompany the front, mainly in the mountains.

KEY MESSAGE 3 DESCRIPTION... Late this week is the climatological coldest time of the year and an Arctic airmass will be arriving right on schedule late Friday and will persist through the weekend. A lobe of the tropospheric polar vortex will swing across Quebec Friday with a stout Arctic high pressure system building into the Great Lakes region. Persistent WNW flow ahead of the high will usher in a bitter cold airmass with 850 mb temps dropping to -30C across much of the area by Friday night. The going forecast brings wind chills to around -30F along and north of the mountains and -15F south of the mountains by Saturday morning. If this forecast holds over the coming days then these wind chills will likely necessitate Extreme Cold Warnings across the north and Cold Weather Advisories across the south. High pressure will gradually build overhead late Saturday into Sunday allowing the winds to subside while the cold airmass remains in place. Highs on Saturday will potentially remain below zero across the north and struggle to get out of the single digits south of the mountains. Light winds Saturday night may allow lows to bottom to their full potential given the air mass with lows approaching -20F in north valleys and remaining below zero all the way to the coast. The core of the cold airmass will retreat to the north early next week while temperatures look to remain well below normal.

AVIATION /02Z TUESDAY THROUGH SATURDAY/

Through 06Z Wednesday...VFR conditions are expected to prevail today with westerly wind gusts around 25, perhaps 30 kt at times. VFR continues tonight with diminishing winds.

Outlook...

Wednesday: VFR with increasing high clouds in the afternoon. Southwesterly winds of only 5 to 10 kt expected.

Wednesday Night: Light snow is likely for all TAF sites through Thu morning with areas of IFR or lower.

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

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.

MARINE

Any gales diminish to SCA levels early this morning. SCA conditions continue through Wednesday.

Southwest winds will ramp up Wednesday night as low pressure tracks north of the waters. Winds may gust up to Gale force over the outer waters at times, otherwise SCA conditions will likely continue for all waters. Winds shift more westerly Thursday night with SCA conditions continuing into Friday. Strong high pressure builds in from the west Friday with winds increasing to Gale force and Arctic air moving over the waters will bring at least moderate freezing spray into Saturday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning until 10 AM EST Tuesday for ANZ150-152-154. Small Craft Advisory until 1 AM EST Wednesday for ANZ151-153.