textproduct: Gray - Portland

WHAT HAS CHANGED

As of 725 PM we have made some minor changes to PoPs and temperatures based on latest observed trends. Overall, no changes to the winter weather advisory at this time as mainly light icing remains a good possibility.

Previously...

Little changes needed to the going forecast for tonight into Friday based on today's model guidance. The Winter Weather Advisory remains in effect for interior western Maine and central to northern NH for light icing and slick travel into the Friday morning commute.

KEY MESSAGES

1. A wintry mix and slick travel remains likely tonight into Friday morning across interior western ME and central and northern NH. There is limited threat for power outages over portions of northern NH and the western ME mountains as winds could become gusty late tonight into Friday morning.

2. Temperatures remain above normal over the weekend with rain likely from Saturday night into Sunday night. A return to drier weather is then likely into the middle of next week with near to a little below normal temperatures.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Latest radar imagery is showing light returns moving across central and NH at this hour, and even though hi-res guidance isn't really picking up on this, it may move into western ME here before too long. Most of this will be light rain, but snow or sleet could mix in it at times. Precipitation chances further ramp up this evening and tonight as low pressure moves across the Great Lakes and a warm front lifts northward through the region. Increasing WAA and isentropic upglide aloft may allow for additional light precipitation to develop over portions of the area this evening, but the more widespread precipitation is expected overnight tonight and Friday morning when the better moisture and forcing arrive.

The low levels will remain cold, while forecast soundings show the warm nose aloft deepening, supporting a wintry mix of sleet and freezing rain (with FZRA expected to become the dominant type) generally from the foothills northward in western ME and then central and northern NH, where slick travel is possible into Friday morning. Can't rule out a brief mix to the south, but in general areas to the south should see just a cold rain with the exception of the higher elevations in SW NH. Those that do experience wintry precip should see a gradual transition to plain rain as the column slowly warms through the course of Friday morning, except the western ME mountains should stay cold enough a little longer.

Also, forecast soundings do show the potential for gusty winds of 25 to 30 mph late tonight into Friday morning over portions of the western ME mountains. On top of the freezing rain, this extra stress on tree limbs and small branches may bring a limited threat of power outages.

Rain will taper off from south to north through the course of Friday afternoon with mostly dry conditions south of the mountains the rest of the day. The sun should be able to make an appearance across NH during the afternoon as the lower clouds begin to mix out. As this occurs, it will get a bit breezy with winds gusting to around 25 mph, but temps will climb into the 50s to maybe low 60s. Over in western ME, some decrease in clouds may occur toward Portland by early evening, but for the most part I expect the marine layer/low clouds to hold through the day to keep temps in the lower to mid 40s, especially toward Augusta and the Midcoast. I have gone lower than the NBM temps in these areas, but it's possible it stays even cooler.

A cold front approaches Friday evening, and then crosses overnight, generally only bringing a few additional showers in the mountains. For the rest of the area, patchy fog is possible out ahead of the front, but this will clear out with the west to northwest winds behind the front.

KEY MESSAGE 2 DESCRIPTION...

A 500mb ridge continues to build through the weekend, allowing for above average temperatures to continue. This ridge will move eastward on Sunday, and a cold front attached to a low over Quebec will follow suit. This cold front is likely to bring a quick burst of rain to the area Sunday evening. Forecast soundings do not appear to be conducive for the development of convective storms, but a few rumbles of thunder can not be ruled out across southern New Hampshire. Only about a half inch of rainfall is forecast at this time. The cold front looks to be fairly progressive and with PWATS near 1 inch, this cold front does not appear to be a solid rain maker.

High pressure and a mid-level trough setup for the start of next week. This will allow for a much drier and cooler week ahead.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Most sites will deteriorate to IFR or LIFR tonight as ceilings lower. More widespread precipitation also moves in tonight and continues into Friday morning with rain expected for the coastal and southern NH terminals with a wintry mix possible for a brief period at LEB, AUG, and HIE. Fog is also possible outside of precipitation. Precipitation likely becomes all rain Friday morning with IFR to LIFR cigs continuing. NH terminals may see slight improvement to MVFR between 15-18Z Friday.

Outlook:

Rest of Friday: Improvement to MVFR and VFR across the NH terminals. IFR to LIFR may continue for PWM, AUG, and RKD.

Friday night: MVFR to IFR restrictions with fog and low stratus possible through 06Z especially in western ME. Conditions should improve after a cold front passes, except MVFR possible HIE.

Saturday: VFR in the morning, with lower restrictions expected Saturday night.

Sunday: MVFR expected with rain.

Monday: VFR likely, chance of a stray snow shower in northern New Hampshire.

Tuesday: Restrictions gradually lower as precipitation moves in through the day.

MARINE

SCA conditions continue over the waters into early this evening. E/ESE winds are expected to remain just shy of SCA criteria, but seas may quickly build back to around 5 ft either late tonight or Friday morning. South to southwest winds then increase ahead of a cold front late Friday with gusts likely exceeding SCA criteria. Winds become W/NW Friday night behind the front.

Variable SCA level winds are expected on Saturday and Sunday with 4-8ft seas likely through the weekend. Winds shift to easterlies and gradually simmer to sub-SCA levels by Monday night. 3-5ft seas are expected early next week.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory from 11 PM this evening to noon EDT Friday for MEZ007>009. Winter Weather Advisory from 11 PM this evening to 10 AM EDT Friday for MEZ012>014-020>022-033. NH...Winter Weather Advisory until 10 AM EDT Friday for NHZ001>006. MARINE...None.