textproduct: Gray - Portland

WHAT HAS CHANGED

All Winter Headlines have been allowed to expire as of 10PM. Light snow lingering in western ME will continue to taper off through this evening, but blowing snow/reduced visibility remains possible overnight as winds remain gusty.

KEY MESSAGES

1. Nor'Easter impacts continue through the afternoon and evening before conditions improve rapidly tonight.

2. Light snow arrives Wednesday morning and may impact the commute for parts of the area.

3. Another storm is possible Friday but confidence is low as the storm track could range from through the forecast area to well south.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Impressive ~970 mb low southeast of ACK as of 18Z is moving ENE with multiple snow bands lifting north and west of the low. While the heaviest band has remained over the Gulf of Maine and across southeastern New England...locally heavy snow and very strong winds continue across the NWS Gray forecast area. We/re at the peak of the event along the coast with multiple reports and webcam images confirming blizzard conditions for many areas. It has been a slow go to move snowfall further inland with dry northeasterly flow keeping snow at bay north of the Lakes region in NH atn IZG-WVL in ME...but as of this hour some snow has started to push into this region. Snow will reach it/s furthest inland extent in the next 1-2 hours before the low pressure moves east with snow eroding from the west and snowfall rates dropping off rapidly into the evening. Winds will shift to the northwest and remain gusty enough to continue some blowing snow through the evening hours along the coast. After this...there should be rapidly improving conditions after midnight with lows generally in the teens.

No changes to the headlines this afternoon and near term model trends suggest these should be able to be taken down on schedule this evening.

We/re still awaiting the afternoon high tide /330pm/ with roughly 2' of surge observed over the past few hours. This...combined with 15'+ nearshore waves along the NH seacoast will result in minor coastal flooding impacts...particularly splashover as water levels likely remain just below flood stage. Coastal flood warning remains in effect for York and Rockingham counties through the afternoon tide cycle.

KEY MESSAGE 2 DESCRIPTION...

Wed morning a clipper will pass north of the region, but a wind of warm advection crosses the forecast area. Any consequential lift is about 4 hours at most, but that will be sufficient to produce a light to occasionally moderate snowfall. Snow growth zone is well placed in the column to produce dendritic growth and snowfall ratios should be at least climatology if not a little better. The vast majority of guidance is an inch or two either side of 2 inches, which given the duration of forcing lines up pretty well. The biggest concern will be the timing, especially across the western half to two thirds of the forecast area. It is currently forecast to arrive during the morning commute. So travel during the morning hours may be hazardous for a time.

KEY MESSAGE 3 DESCRIPTION...

As high confidence as light snow Wed is, the storm Fri is low confidence. Storm tracks continue to vary widely run to run. Ensemble guidance is more or less evenly split between some precip or a miss. For that reason I feel the NBM PoP around 50 percent is a fair forecast for this range. I just do not have any confidence in the evolution of the storm system and resulting snowfall, or rain in the case for some of the southern zones is the more amplified ensemble members. In fact the 23.06z deterministic runs of the GFS and ECMWF highlight some of these drastic differences. The GFS would favor a warm advection driven laterally translating band of snow and potentially some mix/rain threat for southern zones, while the ECMWF would be more of a laterally quasi-stationary band that parallels storm track. One, the GFS, would bring a broad, evenly distributed wintry precip event to the forecast, while the ECMWF would be more straight snowfall confined to areas near the coast. More members would favor snow than not, so for now a chance of snow seems like the most reasonable forecast. Once again timing will be everything as this event could easily shift to align with the Thu evening commute or Fri morning.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

Through 00Z Wednesday...Winds remain gusty thru the night around 25 kt. As snow comes to an end a relatively quick return to VFR is expected for those still experiencing MVFR ceilings, though some occasional blowing snow may locally reduce visibility. HIE may see MVFR ceilings and a few snow showers through Tuesday afternoon with VFR prevailing elsewhere.

Outlook:

Tuesday Night: VFR conditions expected

Wednesday: Widespread IFR or lower conditions expected in light snow.

Wednesday Night: VFR conditions expected, with local MVFR possible in the mtns.

Thursday: VFR conditions expected.

Thursday Night: Areas of IFR possible in snow. Confidence is low.

Friday: Areas of IFR possible in snow. Confidence is low.

Friday Night: VFR conditions expected.

MARINE

Storm warnings continue for all waters into the evening which will need to transition to gales that will continue through the remainder of the overnight with lingering SCA waves through the day on Tuesday.

Wed southerly winds increase as a warm front crosses the waters. Some marginal SCA wind gusts are possible outside of the bays, and seas may build to near 5 ft Wed night into Thu as a result. Winds and seas diminish during the day Thu and then attention turns to Fri. Conditions will depend largely on storm track, which is low confidence at this time. At least some expectation for a period of SCA conditions Fri into the weekend, but a closer storm track could result in marginal gale force gusts for a time as well.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Storm Warning until midnight EST tonight for ANZ150. Gale Warning until 7 AM EST Tuesday for ANZ151-152. Gale Warning until 4 AM EST Tuesday for ANZ153-154.