textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes with this update. Have already seen some heavier bands of snow move onshore early this morning in the Seacoast area. This activity is expected to continue through today with the Maine coast seeing heavier bands later this morning.

KEY MESSAGES

1. Significant Nor'easter will bring blizzard conditions to coastal Maine and New Hampshire with decreasing snow/wind away from the coast.

2. Significant Nor'easter will bring coastal flooding to the coast of New Hampshire and southern Maine.

3. After a brief break Tuesday, the active pattern resumes with the region seeing another chance at wintry precipitation Wednesday with light snowfall and possible slick travel. Another system approaches late week but features more uncertainty.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...As of midnight, light snow is trickling northward into southern New Hampshire. Most recent ensemble guidance has still been waffling over how far north the snowfall makes it in northern New England, but the general trend appears to be a continued eastward trend in the low center. I remain very confident that substantial snowfall will occur across southern New Hampshire and York county. The Midcoast will probably see more significant totals as well. The current forecast and headlines are largely on track at this time. The adjustments to the snowfall forecast are mainly to incorporate more hi-res guidance, which decreased snow totals across the north and left totals mostly the same along the coast and in the south.

We continue to expect a sharp cutoff across the foothills region and into the mountains with advisory level snowfall and gusty winds still causing difficult travel. Still have no headlines further north where it is very possible very little snow falls.

Heavy winds with falling snow will create blizzard conditions, even if less snow falls than expected. Travel along the coast, especially along I-95, US-1 and NH-101 will be extremely dangerous. Winds may gust to 50mph along the coast for several hours during periods of moderate to heavy snow. This combination will lead to extreme reductions in visibility and the aforementioned blizzard conditions. Blizzard conditions will be most prevalent from late morning Monday until the late Monday evening. Snow will be dry, but snow ratios should not necessarily be high either. The drier character of the snow should help prevent snow from loading onto trees, and this storm poses a limited power outage threat.

KEY MESSAGE 2 DESCRIPTION...Coastal flood warning issued for Monday afternoon tide cycle with 2-3' storm surge combining with 10-15' nearshore waves for minor levels of inundation...beach erosion...and splashover. Water levels will be significantly lower than the events in January 2024...and wind direction / waves suggests greatest impacts south of Portland and esp along the NH Seacoast. Wild card is the presence of ice in bays/inlets given the cold winter we/ve experienced...and while we can/t model how this will impact the flooding...expect any dislodged ice to simply add to potential impacts with ice/rocks possible on coastal roadways.

KEY MESSAGE 3 DESCRIPTION...

The strong nor'easter will lift into the Maritimes by Tuesday with a northwest flow pattern across northern New England in its wake. This will bring the usual upslope snow showers and cloudy skies in the mountains, but there may be a couple of snow showers/flurries or at least more cloud cover downwind as a 500mb shortwave crosses through.

After the brief break, a clipper system brings another opportunity for wintry precipitation to the region late Tuesday and into Wednesday with slick travel possible to both commutes on the table. Precipitation type will be mostly snow, although can't rule out mixing with rain along the coast with winds being onshore. The progressive nature of this system and QPF from the ensembles favor a pretty light event with amounts on the order of 1-3", but hints of a secondary low near the Maine coast could produce a corridor of higher amounts upwards of 4" or more.

Once this system exits to the east, there will be a break, but it will again be brief with the next system quickly approaching later Thursday into Friday. Signs are pointing to this system to have more robust moisture to work with and higher potential QPF, but there is still a fair amount of spread in the track. So rain, snow, and even a mix are possible at this point.

Models are in fairly good agreement for the weekend with mostly dry weather. However, a wave moving across southern Canada and a cold front approaching the west could bring some light precipitation for northern areas.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Through 12Z Tuesday...Steady snow is impacting New Hampshire terminals this morning with 1-2 mile visibilities. This will begin to impact Maine terminals over the next hour or two. Winds will steadily increase, with gusts around 40KT+ for coastal and southern terminals today. Will need to monitor the need for LLWS despite some surface winds around 20-25kt. Snow rates will continue to pick up this morning, peaking in the afternoon with VSBY's dropping between 0.5-0.25 miles. Snow diminishes this evening into tonight with improvement to VFR expected. VFR then lasts into early Tuesday morning.

Outlook...

Tuesday: VFR expected, except MVFR ceilings and snow showers possible at HIE.

Tuesday night: Ceilings could lower to MVFR or IFR as low pressure approaches. Light snow may begin in NH between 06-12Z Wednesday.

Wednesday: Light snow and IFR restrictions likely.

Wednesday night: Improving conditions with a return to VFR.

Thursday: VFR early with restrictions possible later in the day.

Thursday night-Friday: Widespread restrictions possible. Precipitation type could be both rain and snow across the area depending on the track of the system.

MARINE

North to northeasterly Storm force winds are expected through the day today, with seas increasing through the day. Wave heights are expected to reach 10-18ft by the end of the day on today.

Northwest gales possible early in the morning Tuesday with more of a transition to SCA conditions the rest of the day.

The weather pattern remains active the rest of the week with a clipper system bringing another chance of SCA conditions on Wednesday into the first part of Thursday. A more potent low pressure could bring more SCA conditions and maybe a period of gales Thursday night into Friday, but the track is very uncertain. After a brief period of high pressure Friday night or early Saturday, another system looks to approach from the west.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory until 10 PM EST this evening for MEZ012>014-033. Winter Storm Warning until 10 PM EST this evening for MEZ018. Winter Storm Warning until 10 PM EST this evening for MEZ019>022. Blizzard Warning until 10 PM EST this evening for MEZ023>028. Coastal Flood Warning from 1 PM this afternoon to 6 PM EST this evening for MEZ023. NH...Winter Weather Advisory until 10 PM EST this evening for NHZ004-005-007. Winter Storm Warning until 10 PM EST this evening for NHZ006- 008>011-015. Coastal Flood Warning from 1 PM this afternoon to 6 PM EST this evening for NHZ014. Blizzard Warning until 10 PM EST this evening for NHZ012>014. MARINE...Storm Warning until 10 PM EST this evening for ANZ150>154.