textproduct: Gray - Portland

WHAT HAS CHANGED

Trended down with ice amounts on Tuesday/Tuesday night as confidence for significant accumulations continues to be low. Otherwise, no major changes were needed other than to issue a new Small Craft Advisory for Tuesday morning through Tuesday evening.

KEY MESSAGES

1. A weak disturbance will lead to some accumulating snow Tuesday afternoon through early Wednesday morning. A wintry mix will be possible over southern New Hampshire and southwest Maine.

2. Mild air makes northward progress into New England mid to late week, with more chances for precip late week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

The center of high pressure will gradually move off into the Atlantic tonight but conditions should still be favorable for radiational cooling. Thus, we are looking at another cold night with below zero low temperatures expected over much of the northern valleys and vicinity. Lows will mainly be in the single digits above zero across much of southern New Hampshire and the Interior of Maine. Coastal areas could see some readings in the lower teens.

The next shortwave approaches in nearly zonal flow aloft on Tuesday afternoon. While CAMs are suggesting that we could see some precipitation making it into southern New Hampshire by mid afternoon, it may take some time to overcome dry air at the surface. When precipitation starts to fall, forecast soundings suggest we will mainly see snow as surface temps will generally be in the 32 to 35 degree range. Later in the evening, soundings suggest a warm nose aloft may nudge in and lead to some pockets of a wintry mix at times into the overnight hours across southern New Hampshire or southwest Maine. While some freezing rain is possible with this wintry mix (mainly at night), confidence in significant ice accretion is currently too low to issue any headlines at this point but trends will be important to watch over the next couple of forecast cycles. For central New Hampshire, the Interior of Maine, the Midcoast and points north, expect mainly snow with a general swath of 1 to 3 inches of accumulation with locally higher amounts possible. Precipitation should move out fairly quickly Wednesday morning.

High pressure nudges back in on Wednesday which should lead to plenty of sunshine and well above average temperatures. Highs are forecast to range from upper 30s and lower 40s north, to the lower 50s south.

KEY MESSAGE 2 DESCRIPTION...

500mb heights continue to increase and will allow for a little more upper-level warmth to advect into the region during the day on Wednesday. This may allow for wintry mix, and showers to develop over the area as a low moves across southern New England on Thursday. Chances of precipitation still look fairly uncertain with many ensemble members keeping precipitation in southern New England. Rain showers and perhaps some wintry mix are also possible as a warm front moves through the region from south to north over the weekend. Uncertainty still remains on precipitation type, amounts and timing of the warm front. Warmer temperatures look slated to remain in the forecast beyond the upcoming weekend.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Through 18Z Tuesday: Winds remain generally light and variable through tonight with VFR conditions continuing. We could see some breezier southwest winds at AUG and RKD by mid to late Tuesday morning or early afternoon.

Outlook:

Tuesday afternoon/night: Snow will overspread the region from southwest to northeast during the afternoon and evening before gradually ending overnight. Also can't rule out a brief period of -PL/-FZRA or even RA at MHT, CON, PSM, and PWM.

Wednesday: IFR or lower in the morning due to snow and wintry weather. Conditions improve by daybreak, with VFR by the end of the day.

Thursday: VFR in the morning, with conditions potentially degrading Thursday night due to rain and snow.

Friday and Saturday: IFR or lower expected due to snow, rain and wintry mix.

MARINE

SCA conditions are expected to develop Tuesday morning and last through the evening in the southerly flow regime. Conditions ease as high pressure crosses the waters on Wednesday.

Sub-SCA conditions are then expected to continue on Thursday. Northeasterly winds will pick up on Friday, reaching SCA levels Friday morning. SCA conditions continue through the day but could return to sub-SCA conditions Friday night.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory from 7 AM Tuesday to 1 AM EST Wednesday for ANZ150>154.