textproduct: Gray - Portland

WHAT HAS CHANGED

As of 715 PM...Have utilized latest guidance trends to make a few changes to headlines. Have added a couple of zones in northern NH to the winter weather advisory since there will be the possibility of a period of light freezing rain or light freezing drizzle before the precipitation comes to an end Sunday. Have also cancelled the advisory for coastal Cumberland County ME as temperatures are currently in the mid 30s with dews in the lower 30s. Not much room for low level cooling and the latest CAMS reflect that. No other changes at this time, but will continue to monitor.

KEY MESSAGES

1) Rain, snow, and a wintry mix impact the region tonight and on Sunday.

2) Above normal temperatures return Tuesday and Wednesday while a couple of weak clippers move through. Precipitation chances potentially linger into the end of the week.

DISCUSSION

Key Message 1 Discussion...

Low pressure moves through the Great Lakes tonight and tomorrow, as a second low pressure center develops and deepens in the Gulf of Maine. With temperatures in the 40s during the daytime today, the system has limited cold air to work with, and will have to rely on wet bulbing for cooling tonight, and cold air advection on Sunday as the coastal low deepens.

With the given set up, precip overspreads the area from south to north this evening and into the overnight hours. Precip likely starts as rain across southern NH and the southwest coast of Maine. As precip intensity increases, a flip to snow is expected across coastal Maine, and then a switch back to rain after a few hours of snow as the wet bulb cooling is maxed out and warmer air continues to work in off the ocean. Across the Seacoast of NH, precip likely remains mostly rain through the overnight hours.

North of these areas, a period of freezing rain and sleet is expected as temperatures remain at of just below freezing at the surface, and warmer air moves in aloft. Generally around a tenth of an inch of ice is expected. A flip back to snow is then expected in these areas and along the Maine coastal around sunrise tomorrow as the coastal low deepens and draws cooler air southward. Through the NH Seacoast, precip likely ends before the cold air arrives, so little more than a few snowflakes are expected tomorrow morning.

Across the north, mainly snow is expected as the column remains cold. A brief period of sleet is possible even into the mountains as the warm air aloft reaches its northernmost extent. Cooler air then drains in as the coastal low deepens, and the low also provides sufficient moisture to keep light snow ongoing much of the day on Sunday.

Elsewhere, precip comes to an end through the morning hours. Mainly cloudy skies and cold air advection from the deepening low keep highs confined to the low to mid 30s, while 20s are expected across the north. Scattered snow showers will be possible in the afternoon hours as the cold front from the parent low crosses northern New England.

Temperatures then fall tomorrow night, freezing up any remaining slush or standing water. Lows fall into the teens to low 20s across the area, with a gusty west wind of around 30 mph through the overnight.

Key Message 2 Discussion...

Temperatures will be around normal for this time of year on Monday with highs forecast to mainly range from lower 20s north, to the low to mid 30s south. A low amplitude ridge axis moves through the region Monday afternoon and we transition back into southwest flow aloft Monday night as a weak wave approaches. Moisture will be limited with this wave so we only expect some low chances for mountain snow showers at the moment Monday night.

Steady warm air advection will lead to above normal temperatures on Tuesday with highs forecast to range from the upper 20s and lower 30s north, to the lower 40s south. Another progressive ridge axis moves through on Tuesday afternoon, which will keep most of the area dry but the next shortwave approaches Tuesday night into Wednesday. Expect on and off low to medium chances of rain and snow through at least Thursday night as multiple waves cross the region. Highs on Wednesday will be even warmer, ranging from the low to mid 30s north, to the low to mid 40s south. Snow will mainly be confined to the higher terrain and across the north Tuesday night through Wednesday evening as rain should remain the dominant precipitation type south. That being said, a cold front will cross the area Wednesday night into Thursday, which will promote falling temperatures through the day and any lingering precipitation should transition to all snow. When all is said and done, QPF and snow amounts appear to generally be light at this time, but we will be keeping a close eye on these waves as we move closer.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

VFR quickly drop to IFR as precip spreads from south to north through the evening hours. Mainly rain is expected at MHT and PSM, periods of rain, snow, and pellets are likely at CON, LEB, PWM, and RKD. Snow and pellets are likely at HIE and AUG, with freezing rain also possible at AUG and CON. Precip ends as snow Sunday morning at most terminals, with IFR continuing through midday. Light snow continues at HIE and AUG into the afternoon. Improvement to MVFR is likely by late tomorrow afternoon, with VFR returning tomorrow night. HIE and LEB likely hold on to MVFR ceilings through Sunday night.

Outlook:

Monday: Any lingering MVFR improves to VFR as the day goes on. Westerly wind gusts 20-30 kts possible at all terminals, easing into Monday evening.

Monday night: VFR prevails at most terminals. MVFR possible at HIE.

Tuesday: VFR prevails at most terminals. MVFR possible at HIE.

Tuesday night: IFR possible in snow showers at LEB and HIE.

Wednesday: LEB and HIE gradually improve to MVFR as snow tapers off. MVFR prevails at all other terminals.

Wednesday night: IFR possible in snow showers at LEB and HIE. MVFR restrictions more likely at other terminals in light rain early but could lower to IFR overnight as rain transitions to snow.

Thursday: IFR possibly lifts to MVFR at LEB and HIE. MVFR elsewhere as light precipitation lingers.

MARINE

Low pressure deepens across the Gulf of Maine tonight and tomorrow, bringing SCA conditions in northeasterly flow tonight and Sunday. Winds shift to westerly late Sunday, and strengthen to gales across the outer waters as the low deepens across the Canadian Maritimes Sunday night.

The threat for gales tapers off by Monday afternoon, but SCA conditions may continue through much of next week as the weather pattern remains active.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory from midnight tonight to 7 PM EST Sunday for MEZ007>009-012>014-018>022-025>028-033. NH...Winter Weather Advisory from midnight tonight to 7 PM EST Sunday for NHZ004-006. Winter Weather Advisory until 7 PM EST Sunday for NHZ003-005- 007>011-015. MARINE...Small Craft Advisory until 10 PM EST Sunday for ANZ150-152-154. Gale Warning from 10 PM Sunday to 1 PM EST Monday for ANZ150- 152-154. Small Craft Advisory from 1 AM Sunday to 1 PM EST Monday for ANZ151-153.