textproduct: Gray - Portland

SYNOPSIS

Today will be another chilly day with gusty winds and mountain snow showers. A coastal storm passes well out to sea Saturday night into Sunday but may be close enough for a little light snow along the coast and southern NH. That will be followed up by another very cold and gusty Monday. Expect the wind chills to remain in the teens and single digits.

NEAR TERM /THROUGH TONIGHT/

Pressure gradient continues to relax as a shortwave ridge crosses the region tonight. So I anticipate winds will remain gusty into the evening...generally 30 to 35 mph with locally higher gusts...before decoupling boundary layer sees winds drop off sharply by midnight. Enough of a gradient will still exist that I do not think we will experience perfect radiational cooling conditions...but it will be another chilly night with lows around 5 to 10 degrees below normal. Along with the diminishing winds will also be a decrease in coverage and intensity of upslope snow showers.

SHORT TERM /SATURDAY/

Sat will be a transition day in the weather. A weak warm front will lift thru the region ahead of a low pressure crossing southern Quebec. Model guidance forecasts enough low to mid level warm advection that I could see a few snow showers squeezing out of the air mass. The NBM does show slight chance to chance PoP working its way thru the forecast area...so I did not see any need to alter that depiction. Otherwise winds will be more southwesterly and much lighter than previous days along with temps climbing above freezing for parts of southern NH and coastal western Maine.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/

A positively-tilted 500mb trough approaches the region Saturday night before crossing later in the day Sunday. This will induce a weak low pressure to form out to sea but still may be in close enough proximity for there to be enough moisture south of the foothills for some light snow Saturday night and/or Sunday morning...but the higher chances (30-40%) are along the coast and southern NH. Accumulations are generally expected to be less than an inch, but a few ensemble members suggest upwards of 3" could occur along the coast if the low tracks a bit farther north.

Once the low passes to the east, it's forecast to deepen over the Maritimes, which will bring more breezy and blustery conditions later Sunday through Monday as the gradient tightens with upslope mountain snow showers. Temperatures then remain below normal Monday night into Tuesday with another weak wave possibly bring light precip to parts of the area.

The global models are in good agreement from mid to late week on another couple of frontal systems moving across the region. The first will be around Wednesday, and the current forecast favors the low track well north us to maybe only bring light precip across northern areas as well as southerly flow bringing some warmer temperatures (maybe highs in the 40s Weds-Thurs?). The second system has a better signal for more widespread precip with less confidence in the track...so both rain and snow are possible Thursday night into next Friday.

AVIATION /17Z FRIDAY THROUGH TUESDAY/

Short Term...Mostly VFR conditions expected thru Sat. Upslope cloud cover are keeping MVFR CIGs in and around HIE...but is expected to scatter out overnight. Westerly surface gusts up to 30 kt are expected thru the evening hours at all TAF sites except HIE...where cloud cover will reduce mixing depths. Winds will turn more southwesterly Sat and will be much lighter. I cannot rule out a stray snow shower during the day Sat as a warm front passes thru the region...but confidence is too low to include in any TAF at this time.

Long Term...Low pressure passing south and east of the region may bring light snow and MVFR ceilings to the southern NH and coastal terminals Sat night and into Sunday morning. If the light snow does occur, MVFR to possibly IFR visibilities will also be possible. Otherwise, expecting VFR through Monday aside from upslope snow showers around HIE. Another couple of weak systems may bring light precipitation to parts of the region Mon night-Tuesday and again on Wednesday, but widespread restrictions look unlikely.

MARINE

Short Term...Gales continue for all waters into this evening but winds and seas will be gradually diminishing into Sat. The bays will drop to SCA conditions and eventually below this evening...and the outer waters will see gale force wind gusts until around midnight before SCA conditions linger into Sat.

Long Term...SCA conditions may occur Saturday night into early Sunday as weak low pressure passes nearby but are more likely late Sunday through Monday as northwest winds increases as the low deepens over the Canadian Maritimes. There may also be a period of gales as well. Conditions improve Tuesday before a cold front approaches and crosses around Wednesday, likely bring at least SCA conditions and possibly gales. Another frontal system is then possible toward late week.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning until 9 PM EST this evening for ANZ150-152-154. Gale Warning until 5 PM EST this afternoon for ANZ151-153.