textproduct: Gray - Portland

WHAT HAS CHANGED

Chances for accumulating snowfall across extreme southern NH this afternoon and tonight continues to trend downward with little to no accumulation now expected.

KEY MESSAGES

1. A coating of snow is possible across extreme southern NH this afternoon and tonight, which may result in a few slippery spots.

2. Plowable snow for much of the region is looking more likely Friday night into Saturday with impacts also likely to the Friday evening commute.

3. A coastal low will bring another chance of snow Sunday night and Monday, and although there is still time for changes, latest guidance favors keeping the highest amounts offshore to the south and east.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... Latest forecast guidance continues to trend drier across southern NH for this afternoon and tonight as the frontal boundary now looks to remain too far south for accumulating snowfall. Despite this, there is still a chance for some snow flurries or snow showers towards the Massachusetts state line with a coating to perhaps a few tenths of an inch of accumulation possible. Some rain may even mix in as temperatures are well above freezing as of this afternoon. Despite these minor amounts, a few slick spots are possible across untreated and elevated surfaces. Lows tonight will range from the teens and 20s across the region.

KEY MESSAGE 2 DESCRIPTION... 500mb trough swings across the Great Lakes Friday with primary surface low occluding and giving way to a new low developing off the Mid-Atlantic Coast Friday night. Favorable lift and moisture will allow widespread accumulating snowfall for New Hampshire and most of western ME with latest guidance showing snow overspreading the region from southwest to northeast Friday afternoon and evening with impacts to the afternoon and evening commute likely across much of NH and southwest ME. There is some uncertainty to the how quickly or even how far the snow progresses toward central ME as there will be more dry air to battle. Snow is expected to continue Friday night and then mostly taper off Saturday morning, but some guidance suggests light snow may hold across NH through much of the day, especially the southern half.

Highest amounts are currently expected to be across central and southern NH and into southwest ME with ensembles having high probabilities (>60%) for over 3" with lesser probabilities for over 6", although still worth watching. So it's reasonable for these areas to see a swath of 3-6" with locally higher amounts.

KEY MESSAGE 3 DESCRIPTION... A coastal low will bring another chance of snow Sunday night and Monday, and although there is still time for changes, latest guidance favors keeping the highest amounts offshore to the south and east.

High pressure brings a mostly dry day on Sunday before a coastal low develops off the coast of the Carolinas in response to a 500mb trough digging into the Mid-Atlantic. Guidance is in very good agreement in showing this low developing and deepening as it lifts northeast, but the latest ensembles are pretty tightly clustered in the low tracking far enough to the south and east to keep the highest QPF offshore but still potentially close enough to bring light snow and maybe gusty winds to coastal and southern areas.

Beyond this, temperatures look fairly seasonal for early next week with generally dry conditions expected Tuesday-Wednesday other than upslope snow showers.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Through 18Z Thursday...VFR conditions are expected across the region with NW winds diminishing to 5-10 kts by 00Z Thu through 00Z Fri. No LLWS is anticipated through the period.

Outlook...

Friday-Saturday: IFR or lower restrictions with widespread snow is looking more likely.

Saturday night = Sunday: General improvement to VFR expected, although there is some potential for light snow/restrictions to continue for the southern NH terminals.

Sunday night and Monday: A coastal low could bring restrictions and more snow if the track of the low is close enough.

MARINE

N-NW wind gusts up to 25 kts with seas of 3-5 ft across the outer waters are expected through early Thu morning. SCA conditions are possible as northeast winds increase Friday night and Saturday with low pressure passing south of the waters. Conditions generally improve Sunday as high pressure builds in from the north, but another period of SCA conditions and possible gales is looking likely Sunday night and Monday as a coastal low lifts northeastward from offshore of the Mid- Atlantic. These conditions could last into Tuesday as winds turn northwesterly.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 7 AM EST Thursday for ANZ150-152- 154.