textproduct: Gray - Portland

WHAT HAS CHANGED

Allowed SCA to expire in the bays. Otherwise, forecast remains largely the same for the overnight hours.

KEY MESSAGES

1. Several weak shortwaves will move through the region this afternoon through Tuesday, bringing low to medium chances of snow showers mainly to the far north.

2. Remaining warm but mostly cloudy on Wednesday with a few rain showers.

3. The pattern stays active late week and into the weekend with colder temperatures and multiple chances for wintry precipitation.

DISCUSSION

Key Message 1 Description...

As a low continues to move off to the northeast from the Canadian Maritimes, the flow will deamplify through the day becoming nearly zonal by this evening. A couple of weak shortwaves will then ripple through the flow this afternoon and evening. This will mean another round of snow showers, mainly across the far north and mountains. Overall, accumulations should be light. A low amplitude ridge axis crosses the forecast area Tuesday afternoon, transitioning us back into southwest flow aloft. A stronger wave then approaches Tuesday evening as a surface low deepens near the Ontario/Quebec border. While most of the large scale forcing will remain north of the International border, we should see enough lift for at least some light snow showers across our northern zones and the higher terrain. Farther south, we are likely to see rain mixing in or rain from the onset.

Temperatures will be on a warming trend through the first part of the week as well. Highs today are forecast to range from the mid 20s north, to the mid to upper 30s south. Then on Tuesday, highs are forecast to mainly range from the lower 30s north, to the lower 40s south.

Key Message 2 Description...

Weakening low pressure continues to trek across Quebec Wednesday with a frontal boundary approaching New England from the west. Ongoing southerly flow out ahead of the front will result in another day of above normal temperatures with most seeing highs in the 40s. A few rain showers are possible, except snow showers in the higher elevations.

Key Message 3 Description...

There has been more of a trend in the model guidance for Wednesday night and Thursday depicting the frontal boundary or what's left of it stalling out somewhere over the area with broad low pressure developing at the surface. Multiple waves aloft riding along the boundary will result in chances for precipitation with mostly snow across the north where up to a few inches of snow are possible based on latest ensemble mean QPF. To the south, more of a rain/snow mix or even plain rain are both possible, although where the mix occurs could fluctuate a bit depending on where the boundary hangs up. There may be periods of drizzle as there hints of dry air in the DGZ.

The surface low begins to exit into the Maritimes Thursday night into Friday, and northwest winds will begin to bring in colder air, which should transition ptype to mostly snow with lift still present from an upper low approaching. This may result in slick travel on Friday morning in some areas, but details are still uncertain. Any lingering precipitation should come to an end by Friday afternoon as shortwave ridging begins to build in, but the rest of the day will be chilly with highs only in the 20s.

Saturday will be the dry day with high pressure overhead, but this will quickly give way to another system that could bring more wintry weather on Sunday, although there is quite a bit of spread in the guidance. There is good support in the ensembles for drying going into next Monday other than some lingering upslope snow showers in the mountains.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

Expect mainly VFR conditions outside of the mountains through Tuesday, while MVFR ceilings remain possible at HIE. There's an outside shot for some MVFR ceilings at LEB, but they should mainly see low VFR ceilings. MVFR conditions may hang around at HIE until sometime Tuesday morning.

The next wave then approaches Tuesday evening, leading to more IFR to MVFR conditions in snow/rain showers overnight.

Outlook:

Wednesday: MVFR ceilings possible with tempo MVFR visibility in rain showers.

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 if rain transitions to snow.

Thurs night and Friday: More widespread wintry precipitation (mostly snow) and IFR flight restrictions possible.

Saturday: Mostly VFR except MVFR ceilings and snow showers possible at HIE.

MARINE

SCA conditions should continue through tonight before diminishing during the day on Tuesday and then returning on Tuesday night as low pressure crosses through the Gulf of Maine.

Wednesday-Monday...SCA conditions likely continue into the first part of Wednesday with low pressure passing well north of the waters and a frontal boundary approaching from the west. Low pressure moves across or near the waters (track is still uncertain) Thursday and Friday with SCA conditions at times and possibly a period of gales. High pressure builds across the waters Friday night into early Saturday and then quickly shifts east as another low pressure system approaches and crosses the region around Sunday.

GYX WATCHES/WARNINGS/ADVISORIES

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