textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes with this forecast package update. Temperatures have trended warmer today and Tuesday.

KEY MESSAGES

1. Mostly dry weather combined with temperatures climbing into the upper 50s to 60s will act to significantly reduce snowpack through Tuesday, with modest dewpoints keeping melt controlled. Shifts in river ice will have to be monitored, but the flood risk remains low at this time.

2. The pattern turns more unsettled by midweek as cooler air begins to work back into Northern New England. A battle between warm and cool air then continues through the end of the week and into the weekend with more chances for precip.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... Deep west-southwest flow will allow for high temperatures to climb +20F or more degrees above normal today through Wednesday. Temperatures will rise to around +10C at 925 mb with favorable mixing allowing highs this afternoon to push well into the 60s south of the mountains. An onshore component of surface winds will limit the warmth near the mid coast. Dewpoints will rise above freezing after day break but will mainly remain at or below 40F through this afternoon. A mix of sun and clouds will transition to mostly sunny skies this afternoon with the combination of these elements resulting in controlled snowmelt.

Temperatures and dewpoints remain mild tonight leading to even warmer conditions during the day Tuesday. Deep southwest flow along with mostly sunny skies will bring high temperatures into the mid to upper 60s across much of the area. The exceptions will be near the Canadian Border with a sagging cold front will keep temperatures cooler and near the Mid Coast where a light seabreeze will develop. Dewpoints will be higher than today reaching the low 40s that will continue to allow for significant, but controlled snowmelt with the lack of precipitation. During this melt period will continue to keep a close eye on river rises due to snowmelt and ice movement while the flood risk remains low.

KEY MESSAGE 2 DESCRIPTION...

The cold tries to make its return on Wednesday in the form of a backdoor cold front pressing in from the northeast. Southwest New Hampshire stands a chance to eek out one more warm day, but the forecast is steadily trending colder for the rest of the forecast area. As the NBM gradually catches up to the back door front and cold air damming pattern, the forecast is likely to continue to trend colder over the coming days.

At the same time, a wave of low pressure rides eastward on Wednesday, bringing the potential for a wintry mix across at least northern areas. Freezing rain and sleet would be the most likely forms of precip, with more scattered shower activity further south. The best forcing looks to be on the north side of the front, focusing the higher QPF amounts across northern locations.

The low likely crosses New England on Thursday, with a brief chance to break into the warm sector for a few hours Thursday morning, before the cold front crosses in the afternoon hours. Cooler air then returns behind the front for Friday and the weekend, with attention then turning to the next potential system on Friday night and Saturday.

AVIATION /06Z MONDAY THROUGH FRIDAY/

Through 00Z Tuesday...VFR is expected across all TAF sites through tonight. Around 40 kts of southwesterly low level wind shear will be present again at most terminals through early this morning. SW surface winds will increase later this morning through the afternoon with gusts to 25 kts. As surface winds diminish tonight there may be another period of low level wind shear tonight. VFR likely continues tonight through Tuesday

Outlook:

Tuesday Night: IFR possible from fog, low stratus, and drizzle.

Wednesday-Thursday: MVFR to IFR more likely across Maine, and possible in NH. Freezing rain and sleet possible at least at HIE and AUG.

Thursday night-Friday...Conditions return to VFR Thursday night with gusty west winds remaining possible. VFR most of Friday, but another low pressure will bring increasing chances for flight restrictions and precipitation later in the day.

Saturday: Snow and IFR conditions possible.

MARINE

South to southwest flow along with elevated seas will bring SCA conditions today with winds peaking this afternoon around 30 kts. Winds and seas diminish tonight into Tuesday morning.

A backdoor cold front crosses the waters Tuesday night and Wednesday, with northeasterly winds to SCA or low end gale strength. Low pressure tracks eastward Wednesday, shifting winds to south late Wednesday night. Westerly gales are then possible behind the system on Thursday into Thursday night. Another system is then possible by Saturday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 7 AM EDT Tuesday for ANZ150-152. Small Craft Advisory from 2 PM this afternoon to 2 AM EDT Tuesday for ANZ151-153. Small Craft Advisory until 2 AM EDT early this morning for ANZ153. Small Craft Advisory until 2 AM EDT Tuesday for ANZ154.