textproduct: Gray - Portland

WHAT HAS CHANGED

Snowfall amounts have increased slightly for areas south of the foothills for this afternoon and evening.

KEY MESSAGES

1. A wave of low pressure will cross this afternoon into tonight, bringing a period of snow to much of western ME and northern NH with mainly rain in south-central NH and extreme southwestern ME.

2. A colder and more active pattern is expected next week with multiple rounds of precipitation expected.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... Another H5 s/wv trof axis and weak wave of low pressure will cross the region this afternoon and evening before exiting by early Saturday morning. Precipitation looks to begin across northern areas between 12pm-2pm before spreading south between 3-6pm. Ahead of the precipitation from this system temperatures will warm into the middle to upper 30s across northern areas with 40s to lower 50s further to the south.

This will likely allow for a rain/snow mix at onset across the mountains and towards the Canadian Border with primarily rain south of the mountains. A fairly quick transition to mainly snow is then likely as a result of wet bulbing and dynamical cooling for most areas from a line roughly between Auburn/Lewiston up through Augusta and Waterville and points north. Across NH, mainly rain is likely from the Lakes Region and points south with snow to the north.

Snowfall accumulations of between 2-5" are expected for the mountains and points north with a slushy coating to 2" for Auburn/Lewiston to Waterville up through the foothills. This may result in slippery travel conditions for the evening commute. Snow and rain will quickly end between 8pm-11pm with some clearing overnight. A brief period of freezing drizzle is possible as drier air moves in aloft but this is currently anticipated to be isolated should it occur. Lows will fall into the 20s to middle 30s from north to south.

Saturday will feature warmer temperatures into the 40s and 50s along with partly cloudy skies and dry conditions.

KEY MESSAGE 2 DESCRIPTION...Strong mid-level ridging over the western US will allow for a trough to deepen over the region this weekend, allowing for generally colder weather to take place. Sunday night, a surface low will move along this pattern and arrive in New England. Mostly snow is expected with this system, as below-freezing air remains overhead. Wintry mix and rain can not be ruled out in southern New Hampshire, and roads could be slick during the Sunday evening and Monday morning commutes. Models still show a lot of uncertainty on snowfall amounts, but widespread measurable snowfall is likely. Upslope enhancement is also possible in the White Mountains and may allow for locally significant snowfall amounts at higher elevations. The system moves out of the area by the end of the day on Monday.

The remainder of the week looks colder and active, with model guidance trying to hint at more rain and snow through the remainder of next week. While models are confident in the pattern, they are struggling to piece together the timing on any subsequent system.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Through 12Z Saturday: Mainly VFR conditions are expected until this afternoon. Precip moves in from the west and conditions in the mtns will drop quickly to IFR or lower in snow. South of the mtns a period of VFR or MVFR in light rain is expected, but eventually areas of IFR or lower develop in low CIGs and perhaps some drizzle. Those IFR conditions likely extend into Sat morning before clearing out.

OUTLOOK:

Saturday...VFR expected. Westerly surface wind gusts up to 30 kt possible.

Sunday...IFR expected with snow.

Monday...Restrictions return to VFR as snow exits the region.

Tuesday...VFR expected.

MARINE

SCA conditions are expected outside of the bays beginning this afternoon with southerly winds and increased seas before becoming northwesterly by early Saturday while remaining at SCA criteria through Saturday afternoon.

OUTLOOK:

Saturday Night...Sub-SCA northwesterlies, with 3-6ft seas.

Sunday...Sub-SCA and variable winds, with 3-6ft seas.

Monday...SCA level northeasterlies, with 5-7ft seas.

Tuesday...Sub-SCA and westerlies, with 5-7ft seas.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory from 5 PM this afternoon to 8 PM EDT Saturday for ANZ150-152-154.