textproduct: Gray - Portland

WHAT HAS CHANGED

No major changes were made at this time but did increase PoPs across southern areas for this morning based on latest radar trends and surface observations to our west.

KEY MESSAGES

1. A weak short wave trough will move across the forecast area today aiding in the development of a little light snow. Trends have been for a drier system with weaker forcing for ascent, so have lowered PoPs across the board. The best chances for a coating will be across southern NH, with much lower chances north of there. Otherwise, turning colder tonight and Monday.

2. Low pressure brings the next chance for more widespread precip late Tuesday and Wednesday.

3. Mild conditions follow the system for late week, but another system is then increasingly likely for Friday.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Trends have been for a drier system with weaker forcing for ascent for today's system, so have lowered PoPs across the board. The best chances for a coating will be across southern NH, with much lesser chances north of there. Otherwise, turning colder tonight and Monday. Cold weather advisories possible in the mountains late tonight.

KEY MESSAGE 2 DESCRIPTION...

Low pressure rides eastward during the daytime on Tuesday, spreading moisture into southern areas by the late afternoon hours. Dry air will be in place ahead of the system from the departing Arctic high pressure. After some daytime warming of temperatures, temps will fall as snow begins and wet bulbing occurs. This snow then spreads northward overnight Tuesday, but likely diminishes as it reaches far northern areas.

Some mixing is possible across southern areas as warmer air nudges in from the south, but overall the trend on the models for the last few runs has been to keep the cooler air more established, limiting mixing. The precip then mostly moves out by late morning on Wednesday.

KEY MESSAGE 3 DESCRIPTION...

Mild air likely nudges northward behind the system for Thursday, but just how far northward remains to be seen as a front lingers through New England. Late winter warm ups in northern New England have a tendency to be more suppressed as they approach, so we'll watch for this trend over the coming days.

The next low pressure system approaches on Friday, and has the potential to bring more widespread mixed precipitation. Overall the system looks warmer than the Tuesday night one, but how much cool air remains at the surface will be the determining factor for the precip type outcome from this system. We'll also continue to monitor these trends over the coming days, as they'll largely be influenced by the events that preceded them.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Through 12Z Monday...Some light snow is possible at CON/MHT/PSM/PWM for a period today with localized MVFR-IFR visibilities possible. Otherwise, VFR tonight and Monday. NW wind gusts up to 25 kts are possible late morning through early this evening.

Outlook...

Monday night: VFR as high pressure settles overhead.

Tuesday-Tuesday night: VFR initially, but conditions are expected to deteriorate to IFR or lower as widespread light snowfall overspreads the area from west to east during the afternoon and evening. Snow should gradually end overnight Tuesday night. Also can't rule out a brief period of -PL/-FZRA or even RA at MHT, CON, PSM, and PWM.

Wednesday - Wednesday night: Improving conditions with any leftover precip coming to an end in the morning. Mainly VFR otherwise.

Thursday - Friday: Several rounds of mixed precip and IFR are possible through this time period.

MARINE

SCA conditions are likely on the outer waters, and possibly on the bays today and tonight as high pressure builds in from the west and the pressure gradient tightens. Moderate freezing spray is also likely. SCA conditions are then possible in southwesterly flow on Tuesday, with a front crossing late Tuesday night. High pressure briefly crosses through late Wednesday, and then a front lingers near the waters Thursday and Friday with SCA conditions in northeasterly flow possible north of the front.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 5 AM EST Monday for ANZ150>152-154. Freezing Spray Advisory from 9 PM this evening to 1 PM EST Monday for ANZ150>154.