textproduct: Gray - Portland

WHAT HAS CHANGED

Have issued a Special Weather Statement for areas of locally dense fog across the coastal plain of Maine and portions of eastern and southern New Hampshire. Visibility restrictions of 1/2 to 1/4 mile are being reported in areas within the Special Weather Statement and will bring slow travel through the morning commute. Fog will dissipate with the passage of a cold front from west to east through morning.

KEY MESSAGES

1. Mild weather and rain continue through today.

2. Light snow is expected to move across the area Friday afternoon into the overnight.

3. Low pressure brings a round of light snow to most of the area Friday night into Saturday.

4. A stronger low pressure system looks increasingly likely to bring a period of rain and gusty winds early next week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Cold air dam is slowly giving way and temps are expected to continue to gradually rise thru the morning. The rise will be most pronounced as the frontal boundary arrives and helps to mix out the inversion. In the meantime low clouds and areas of fog will be present thru morning as the warmer air moves over the remnant snow cover. Also will be looking at more widespread rain showers moving into the forecast area from the southwest. I do think thunderstorms will miss us to the south, but some elevated convection and heavier downpours are possible. Overall the relatively high capacity for storage in the local river systems means that the forecast rainfall thru the afternoon should be manageable even with snow melt added to the mix. River ice continues to get flushed out as well. Despite a few break up jams occurring, the water levels are currently at or below action stage. We will continue to monitor river levels, but at this time do not anticipate a widespread flooding threat. Rain showers may linger along the coast today as the front takes its time to clear, but once colder air begins to work in from the northwest winds could get gusty thru the late evening.

KEY MESSAGE 2 DESCRIPTION...

A robust low pressure will move into the Great Lakes and send a warm front into New England Fri. A broad area of warm advection will lift thru the region and provide a period of ascent from Fri afternoon into the late evening hours. Temps should be cold enough for this to fall largely as snow. Current forecasts are a little moisture starved and snowfall brief/light. Some minor accumulations are possible for much of the forecast area, but farther north into the upper Kennebec River Valley a longer period of saturation could allow for 2 to 3 inches with locally higher amounts.

KEY MESSAGE 3 DESCRIPTION...

Low pressure tracks eastward into New England Friday night and Saturday. The best forcing with the system will be north of the warm front, across northern areas and the higher terrain. Up here, a few inches of snow are possible, with the best chance for the highest amounts closer to the Canadian border. Further south, a brief burst of snow followed by some scattered snow showers looks more likely, but accumulations would remain limited.

The leading edge of the snow may reach into New Hampshire and western Maine before dark on Friday afternoon. Any snow that falls during the daytime will have a hard time sticking to the roads following highs into the low 40s. But across the north, steadier periods of snow continue through the overnight hours and into the day on Saturday. Several inches of snow and slippery travel are more likely in these areas.

The system then moves out late in the afternoon on Saturday, with snow showers ending last across the northern mountains. High pressure quickly builds in and crosses Saturday night and Sunday. Clouds then begin to arrive by late Sunday afternoon ahead of the next system.

KEY MESSAGE 4 DESCRIPTION...

A strong low pressure system looks increasingly likely to track through the Great Lakes and then through Quebec Sunday night through Monday night. This will put New England solidly in the warm sector of the system. Rain and gusty southeast winds look increasingly likely from this system. How much rainfall materializes remains a major question as the forcing from this system looks to mostly be limited to the passing warm front and then cold front. Taping into deep moisture, upslope enhancement on the southern slopes is to be expected. A more significant rainfall would likely hinge on the development of a triple point low closer the New England, so we will be watching for signs of this over the next few days.

The main concern with this system will be the potential for river rises given the recent snow melt. These impacts will mainly be driven by the rainfall, while much of the snowpack has been lost this past week. Colder air then follows the system going into midweek next week.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Widespread LIFR CIGs and patchy fog continue south of the mtns thru morning. A pronounced inversion will also allow for LLWS at around 1000 ft across southern NH thru early morning, and coastal western Maine thru sunrise. A front crossing the area will allow low level moisture to mix out and CIGs to lift or scatter out to VFR by midday. Some showers are possible near the coast into the afternoon, and local MVFR or lower conditions could result.

Outlook:

Friday: Areas of IFR or lower conditions possible in light snow that quickly moves across the area during the afternoon and evening.

Friday Night and Saturday: IFR with snow likely across northern terminals, with MVFR to IFR possible across southern terminals. Gradual improvement likely through the day from south to north.

Saturday Night: VFR likely returns to all terminals, except HIE which may hold MVFR ceilings in upslope flow.

Sunday: VFR, no sig wx. Clouds thicken and lower in afternoon.

Sunday Night and Monday: MVFR to IFR cigs with any wintry mix transitioning to rain Monday morning. Rain and gusty southeast winds likely Monday.

Monday Night: IFR likely continues with periods of rain and breezy conditions.

MARINE

Southerly winds continue to increase thru morning with SCA conditions expected for all waters. In addition areas of fog will be possible thru sunrise. Winds will eventually turn westerly this afternoon and remain gusty until around midnight. After winds and seas briefly diminish tonight, southerly winds will increase again Fri and SCA conditions are expected again. Marginal southerly gales are possible Friday night ahead of an approaching low pressure system. Westerly gales are then more likely Saturday behind the passing system. High pressure crosses the waters Saturday night and Sunday. Southeasterly gales are then likely by late Sunday night and Monday as a strong low pressure system tracks through the Great Lakes.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ150>152-154. Small Craft Advisory until noon EDT today for ANZ153.