textproduct: Gray - Portland

WHAT HAS CHANGED

Minor update to reflect observed trends in the near term.

KEY MESSAGES

1.Warmer air continues to make a push into Northern New England, while a series of fronts begin to make southward progress by late Monday.

2. An active weather pattern sets up from Tuesday into next weekend, bringing multiple opportunities for widespread precipitation. Except for the possibility of a period of mixed precipitation in the mountains, mostly rain is expected Tuesday into Wednesday. The following system may feature a better chance for wintry precipitation for areas south of the mountains Thursday into Friday.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

The moderating trend continues through tomorrow as southwesterly flow brings warmer air into New England. Lows tonight will be notably warmer than the last few nights, with lows ranging from the mid 20s across the north, to upper 30s through the New Hampshire Seacoast.

Tomorrow looks to feature the most widespread warmth across the area for the week, with northern areas likely seeing their warmest readings of the week. Southern areas stand a better chance for higher temps Tuesday or Wednesday. But tomorrow, highs warm into the 60s across much of the area, with 50s more common across the north. Sunshine peaks midday after morning clouds move offshore, and before more clouds begin to move in during the afternoon hours.

However, the cooler air will already be making southward progress during the day tomorrow. A few showers are possible near the Canadian border tomorrow morning as a warm front lifts north of the area. Then by the afternoon, first a trough and then a cold front press into northern areas, bringing increasing clouds and scattered showers. Cooler air begins to move into northern areas overnight with lows in the 20s, while central and southern locations remain in the warm air mass with overnight temps in the 30s and 40s. The front likely stalls in our forecast area by early Tuesday, bringing increasing showers chances toward daybreak as more moisture rides along the front from the west.

KEY MESSAGE 2 DESCRIPTION...

Monday's backdoor cold front will lift back north as a warm front Tuesday into Tuesday night as a wave of low pressure ride along the boundary, bringing a round of widespread overrunning precip with strong isentropic lift. How fast the boundary lifts north is uncertain and whether a cold air dam sets up, which could result in a large spread in temps from southern NH to western ME, but regardless, temperatures do look to be warm enough to support mostly rain, even if end up being it's a cold rain in some areas. The exception may be in and around the mountains, where a period of freezing and sleet can't be ruled out if surface temps do trend colder. The column will likely continue to warm overnight, which will end any wintry precip in the mountains if it does occur. Ensemble means support 0.50" to 1.00" of QPF possible from the foothills northward and 0.25" to 0.50" to the south from Tuesday into Tuesday night.

Models are in good agreement with most of northern New England in the warm sector by Wednesday morning as low pressure tracks to the east across the Canadian Border and central Maine, which will send a cold front through in the afternoon. Despite mostly cloudy skies, the increasing west to southwest flow ahead of the front should bring a warm day for most areas south of the moutnains..well into the 50s and 60s possibly low 70s in southern NH if the front is a little slower. As the front moves through, there will be a chance of showers and maybe even a couple of storms (esp if the front is slower) across southern NH and southwest ME. However, convergence on the front may not be great with the southwest flow.

This front will come into play as it looks to stall out near or just south of the region going into late week with waves of low pressure riding along it. There's a better signal for CAD to lock in the colder air in the low levels north of wherever the boundary hangs up with high pressure to the north and east. There's also a strong signal in the ensembles for widespread precipitation (but not so much agreement on QPF) Thursday into Friday, but if this set up comes through, it could bring some wintry precip including freezing rain and/or sleet south of the mountains as well. So we'll have to monitor how things unfold.

For the weekend, Saturday might be dry, but there's already good model agreement with low tracking across Canada with a cold front approaching from the west increasing precip chances going into Sunday. There are a few colder ensemble members, but most currently favor rain as the ptype.

AVIATION /00Z MONDAY THROUGH FRIDAY/

VFR prevails at most terminals through Monday Night. Southwesterly wind sheer of around 30kt is likely at MHT, CON, and PSM overnight tonight. MVFR ceilings are then possible at HIE late tomorrow night.

Outlook:

Tuesday-Tuesday night: Widespread precip, mostly in the form of rain, is likely along with fog and low ceilings. Restrictions ranging from MVFR to LIFR possible. Mixed precipitation is possible at HIE.

Wednesday: VFR is possible, but there will be a chance of showers and maybe even a storm as a cold front approaches and crosses.

Thursday-Friday...Widespread precipitation and restrictions possible. There's potential for mixed precipitation to be a bit farther south to reach other terminals with this system.

MARINE

Increasing southwesterly winds ahead of a cold front bring SCA conditions to the outer waters through at least Monday evening. Some marginal gale force gusts are possible across the far eastern waters Monday afternoon.

Tuesday-Sunday...An active pattern will support several periods of SCA conditions across the waters as multiple fronts and low pressures trek across the region. The first is Tuesday into Wednesday as low pressure approaches from the west and sends a cold front through the waters on Wednesday. A period of gales may occur but confidence is low. Multiple waves of low pressure look to ride along this boundary through late week, which may lift back north or stall out just south of the waters. A cold front approaches from the west over the weekend with increasing southerly flow out ahead of it.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until midnight EDT Monday night for ANZ150-152-154.