textproduct: Gray - Portland

SYNOPSIS

Low pressure to our west will continue to track through the Great Lakes and into Canada by this afternoon. This will bring a potential for mainly light rain and snow across most of the area. We only get a brief break from winter weather however as the next storm will quickly arrive Tuesday. This looks like it could be first widespread snowfall. Once that storm exits the region Wednesday, the rest of the week will be cool and breezy with mountain snow showers lingering.

NEAR TERM /THROUGH TODAY/

Strong warm air advection will ensue this morning as low pressure moves northeastward through the Great Lakes. Overall the forecast has not changed much at all over the last two days as the various models and associated thermal profiles have remained quite steady from run to run. Therefore, we continue to expect light precipitation to develop this morning, most likely in the form of light snow or flurries away from the immediate coast and southeastern NH with little accumulation expected. The next batch of stronger forcing will arrive during the afternoon hours and this is when any snow will turn to a cold rain south of the foothills as the low levels warm. The bulk of the accumulating snow will be in the mountains later today into this evening with several inches expected there.

Southerly winds will also become gusty with 20 to 25 MPH gusts likely. The coastline may see a brief period of 30-40 MPH gusts late in the afternoon and early evening, but a low level inversion should keep stronger winds aloft.

SHORT TERM /TONIGHT THROUGH MONDAY/

The main shield of rain and mountain snow will quickly depart this evening leaving behind some scattered rain and snow showers, especially across western zones. Mostly sunny skies are expected Monday except in the mountains near the Canadian border. Winds will be gusty with gusts around 30 MPH.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

Overview: High pressure crests over New England Monday night and quickly shifts east Tuesday morning. A progressive area of low pressure will track near southern New England Tuesday through Tuesday night bringing accumulating snow to much of the area. High pressure builds in late Wednesday followed by an Arctic cold front crossing Thursday.

Impacts:

*Slick travel due to accumulating snow is likely by early afternoon Tuesday and will likely become hazardous during the evening commute in moderate to heavy snow.

*Snow ends early Wednesday morning, while depending on track and resultant snow amounts travel impacts may linger into the Wednesday morning commute.

Details: High pressure crests over the area Monday night allowing temperatures to drop into the single digits north and teens south. High pressure quickly shifts east Tuesday morning as attention turns towards an area of low pressure tracking near southern New England Tuesday afternoon into Tuesday night.

Ensembles have generally held steady with loose clustering of low centers tracking near 40N/70W Tuesday evening and progressing ENE to south of Nova Scotia Wednesday morning. The envelope of solutions range from a deepening low pressure system tracking over southern New England into the Gulf of Maine to a weak low passing well SE of 40N/70W. The former solution would result in an axis of moderate to heavy snow across the interior and increased potential for snow changing to rain at times along the coastal plain. The latter scenario would result in light to moderate snow, mainly across the southern half of the area. As mentioned in the previous discussion, a minority of wetter solutions continue to skew the mean above the median with respect to QPF. The latest output from DESI shows that the spread between the 25th and 75th QPF percentiles is similar to the mean QPF highlighting the high variance in possible outcomes at this time range. However, incoming 00Z mesoscale models have trended higher on QPF so have stuck with the NBM which brings 0.7 to 1.0 inches along and south of the White Mountains and 0.25 to 0.5 inches north of the mountains. Temperatures along and south of I-95 and southeast NH may warm into the mid 30s Tuesday afternoon and act to limit snowfall amounts. Where precipitation stays all snow it is becoming increasingly likely for Warning level snowfall, while confidence in location is not high enough for a Watch at this time.

Low pressure quickly tracks east away from the Gulf of Maine Wednesday morning with precipitation ending by sunrise. High pressure builds in from the SW with little in the way of CAA behind the exiting system. This will allow for highs in the mid to upper 30s south of the mountains while northern areas stay in the 20s. High pressure shifts south Thursday as a strong cold front approaches. The timing and strength of this front look favorable for heavy snow showers and possibly squalls Thursday afternoon into Thursday night.

AVIATION /03Z SUNDAY THROUGH THURSDAY/

Short Term...MVFR ceilings become more likely by mid-morning as SHSN begin. Warming temperatures will bring RA to most of the region by noon except in the mountains and foothills where snow should continue much of the day. Occasional IFR conditions are then expected by late afternoon or early evening. Southerly winds may gust 20 to 35 MPH on the immediate coast late afternoon and early this evening. VFR gradually returns later tonight and for Monday except for occasionally lower conditions in the mountains. Westerly winds gust 20 to 30 kt Monday.

Long Term...Clouds thicken and lower Tuesday morning with snow likely by mid day across the south overspreading the area during the afternoon. A period of at least IFR is likely Tuesday afternoon through the first half of Tuesday night. Snow ends early Wednesday morning with VFR likely into Thursday.

MARINE

Short Term...Next system arriving today will bring a period of Gales to most of the coastal waters. Peak gusts may be short lived with a passing cold front, but low level jet supports Gales overnight and into early Mon morning. Expect a W wind shift this evening with this front, becoming NW Monday morning. With the added wind, wave heights increase quickly Sunday afternoon, building 8 to 10 ft towards the Midcoast coastal waters.

Long Term...Low pressure passes near the Gulf of Maine Tuesday into early Wednesday morning for building seas and possibly a period of northerly Gales. Winds drop below 25 kts briefly Wednesday afternoon before SW winds ramp up Wednesday night through Thursday ahead of a cold front.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning from 4 PM Sunday to 10 AM EST Monday for ANZ150- 152. Gale Warning from 4 PM to 10 PM EST Sunday for ANZ151. Small Craft Advisory from 8 AM Sunday to 7 PM EST Monday for ANZ153-154.