textproduct: Gray - Portland

SYNOPSIS

Afternoon clouds and a few rain and snow showers are once again expected today. Low pressure moves in from Canada on Sunday, with wintry precipitation expected across interior NH and Maine Saturday night into Sunday. Behind the storm, breezy winds and upslope snow are possible Monday afternoon. High pressure moves in for the second half of next week.

NEAR TERM /THROUGH TODAY/

One more short wave trough associated with larger parent low pressure moving out to sea will move across New England today. As a result clouds will fill in again by afternoon with widely scattered snow and rain showers expected. Most locations will probably remain dry. Highs should top out in the 40s at lower elevations with 30s likely in the mountain valleys. NW winds will be a bit breezy with 20 MPH gusts likely today.

SHORT TERM /TONIGHT THROUGH SATURDAY/

We'll get a break in between systems Friday night and Saturday with fair weather (but still some upslope clouds in the mountains tonight). The next short wave trough will approach from the west Saturday afternoon allowing for some increasing high clouds from west to east but any precipitation should hold off until Saturday night.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Evening Update...

Worked to incorporate cooler high res guidance for the cold air damming set up for Saturday night and Sunday. Low pressure moves in from the west, with pressure falls in the Gulf of Maine. This should hold the cooler air across the interior through the majority of the event, with temps then rising behind the cold front Sunday afternoon. This brings some freezing rain, especially to central New Hampshire Saturday night, with light ice accretion likely. Further north and east into Maine, a few inches of snow looks likely. Mainly rain is expected across the coastal plain, but the MidCoast may start as a little snow Saturday night before a changeover to rain.

Full Discussion...

Saturday night, a low moves in from the northwest. The low looks to interact with the cold surface air over the northeast, overrunning at least some of the colder air. This will allow for some snow and wintry mix north of the mountains and across western NH. However, models are much more uncertain how long the cold air dam over northern New England holds. Models have always struggled with this, and tend to have a warmer bias in these overrunning low situations. This time around, models are generally latching onto two distinct solutions. The first (GFS/CMC) bring more rain and wintry mix to the area, and completely overrun the cold air overhead. The second (ECMWF/NAM) bring the low further south, with secondary redevelopment over the Gulf of Maine. The development of the secondary low would disrupt the circulation advecting the warm air, allowing for rain across the coastal plain, but more consistent heavy, wet snow in the mountains.

Both solutions agree that precipitation should be light. Liquid accumulations of about 0.5-1" are possible. A few inches of snow is possible across the interior, as well as a light glaze of ice in western New Hampshire.

By Monday morning, the mentioned low will move offshore. A pressure gradient appears to form, potentially bringing breezy northwest winds early next week. Otherwise, next week looks cooler as a broad trough remains over the Northeast.

MARINE

Short Term...Coastal waters remain in NW cyclonic flow into Saturday as high pressure nears but passes to the south. Expect conditions to remain below SCA for winds and waves, but could see a few gusts to 25 kt on the outer waters.

Long Term...Low pressure approaches from the west Saturday evening, with a warm front lifting over the waters Sunday morning, then low/cold front that afternoon. SCA to gales are possible in northerly winds Sunday night through Monday night. SCA conditions are possible into Tuesday, with high pressure building across the water for midweek.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.