textproduct: Gray - Portland

WHAT HAS CHANGED

No major changes were made, and the current forecast remains on track.

KEY MESSAGES

1. Cold weather returns tonight with widespread lows below zero. The colder weather is short lived, however as we start to warm again by Tuesday.

2. An active pattern is expected in the second half of the week, with multiple systems moving through the area.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

As a cold front continues to move off into the Atlantic, high pressure will dominate the short term weather pattern, promoting colder temperatures and diminishing cloud cover. With a clear sky in place and diminishing winds, conditions should be favorable for radiational cooling and some frigid temperatures. To account for these conditions, the NBM 50th percentile was used for tonight's lows as it was significantly lower than the operational NBM. That being said, there is potential for even colder temperatures by Monday morning if winds relax a bit quicker than expected. Either way, there is high confidence that we will see widespread lows below zero with some double digits below possible north. Areas along the coast may even dip to around zero. While a few northern valleys could approach Cold Weather Advisory criteria, uncertainty regarding widespread impacts precludes the need for any headlines at the moment. Monday will then be a chilly day with plenty of sunshine. Highs will range from the low to mid teens north, to the low to mid 20s south. By Tuesday, we start to warm back up with above normal temperatures returning to the forecast mid-week.

KEY MESSAGE 2 DESCRIPTION...

A strong high pressure system over the northeast will breakup Monday night. This will allow for a disturbance to move northeastward, bringing rain and snow to northern New England Tuesday night and into Wednesday. Thermal profiles currently show snow as the dominant precipitation type over New Hampshire and Maine, with the rain/snow line positioning itself around the NH/MA border Wednesday night. Snow character will vary quite a bit within the region. Snow will likely be very heavy and wet across southern NH and coastal Maine (7:1 or so) with interior areas looking at a much drier snow (10- 12:1). Most areas across NH and ME should be looking at around 1-3 inches of snow, with precipitation moving out of the region by late morning on Wednesday.

After the exit of the aforementioned system, 500mb heights continue to increase and will allow for a little more upper- level warmth to advect into the region. This will allow for wintry mix, and showers to develop over the area at the end of the week. Ensemble guidance is still quite uncertain on amounts and timing but rain showers are possible Thursday through the weekend

AVIATION /18Z SUNDAY THROUGH FRIDAY/

VFR tonight Monday night. NW wind gusts up to 20 kts are possible through early this evening.

Outlook...

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 with southwesterly winds are expected Tuesday. Winds taper off by the end of the day, and sub-SCA conditions continue through the remainder of the week. Winds and seas do look to gradually increase towards the end of the week as active weather moves across the waters.

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.