textproduct: Gray - Portland

WHAT HAS CHANGED

Winter Storm Watches have been upgraded to Winter Storm Warnings. A Blizzard Warning has been issued for coastal Rockingham County. A coastal flood watch has been issued for the Monday afternoon high tide for coastal York and Rockingham counties.

KEY MESSAGES

1. Nor'easter will track just southeast across Southern New England, bringing snow, wind, and potentially coastal flooding on Monday.

2. Strong winds are possible on Monday through Monday night as a Nor'easter tracks just to the south of the area.

3. Minor coastal flooding is possible Sunday night, and then more flooding impacts from large waves are possible during the Monday afternoon high tide.

4. After a brief break Tuesday, the region will see another chance at wintry precipitation Wednesday, and perhaps again late week. Should the systems remain progressive and move through northern New England quickly, light snowfall accumulations would result causing slick travel conditions.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...Sunday night, a Nor'easter will arrive in New England and will move northeastward across the Gulf of Maine on Monday. Compared to yesterday, guidance has generally trended a little to the east. Colder temperatures and high low-level winds associated with the storm will allow for varied snowfall ratios. Ratios may be less than 10:1 in more exposed areas, with perhaps even higher than 15:1 along areas with more vegetation. This could allow for very localized and uneven snow totals, especially along the coast. Snowfall looks to be the most significant in the Seacoast, where 10-14 inches of snow is expected. Higher snowfall totals are likely to bleed across most of southern NH and coastal Maine. I have upgraded the Winter Storm Watch to a Warning for these areas.

High winds and heavy snow will allow for periods of whiteout conditions, especially along the coast south of Portland. With frequent gusts exceeding 35mph likely in coastal Rockingham county, I opted to issue a Blizzard Warning here. Travel along I-95 on Monday will be extremely dangerous with the heavy snow and very low visibility forecast.

Across the interior, moderate snowfall is expected, with generally 4- 8 inches expected south of the mountains, 1-4 inches north of the mountains. Winter Storm Warnings and Winter Weather Advisories were issued across the interior.

KEY MESSAGE 2 DESCRIPTION...Strong winds are expected on Monday as the low moves across the Gulf of Maine. This will allow for substantially reduced visibility in periods of heavy snow along the coast. Winds may gust to 50mph along the coast Monday, with gusts to 40mph likely as far inland as Keene and Augusta. Overall this will lead to a limited power outage threat for coastal areas.

KEY MESSAGE 3 DESCRIPTION... Minor coastal flooding is possible during the Sunday night high tide as winds increase, surge rises, and waves build. Water levels may reach flood stage from Portland south, but there is still some question as to if enough surge builds up in time for high tide to bring minor flooding as the storm is just ramping up. Waves will also just be building up, so wave impacts are expected to remain minor during this tide cycle.

The tide of more concern is the Monday afternoon high tide, which is the one the coastal flood watch has been issued for. By Monday afternoon, surge values of up to 3ft are expected to be in place, and large breaking waves of 15-20ft just offshore. The greatest impacts will be found along coastal York and Rockingham counties, with impacts progressively increasing moving southward. Debris on shoreline roads, significant splashover, and beach erosion are all possible.

Minor flooding is then possible again during the Monday night high tide, but surge values and wave heights are likely to be decreasing during this time period.

KEY MESSAGE 4 DESCRIPTION... Behind the exiting low pressure system Monday night, a tight pressure gradient remains with dry air arriving from the NW. This will make Tuesday breezy, particularly through the morning hours. General gusts 20 to 25 mph are forecast, and the shift in wind direction compared to during the prior storm may again relocate freshly fallen snow.

The wind and cooler temperatures will make for less pleasant clean-up conditions than Saturday of this week. Wind chill values will generally hover in the single digits to teens above zero, but raw temps do climb into the mid 20s to around 30.

The next system to impact the area will quickly approach early Wednesday morning. There still remains spread on how this system evolves across the Northeast. Generally, low pressure clipper system moves across the Great Lakes Tuesday night and enters northern New England Wednesday morning. There are some differences how south the main low tracks, whether across the northern LP of MI, or staying north of the Great Lakes. Consolidation or second development could then organize somewhere along the Maine coast into the afternoon.

This would bring a region of light accumulating snow to the area based on its quick track, but local enhancements will be possible depending on how strengthening takes place near the Gulf of Maine. Resulting snow could impact the Wednesday afternoon and evening commute.

The second system late week (Thurs night - Fri) features even more spread, but amid the guidance envelop is well represented. The two main outcomes look to be either a Colorado Low ejecting out of the Plains (with varying latitude) and intensifying over the Northeast, or remaining flatter on the Plains exit and staying south off the Mid-Atlantic coast. Better feel for this and its potential impacts to area will be sorted once we get through disturbances 1 and 2!

AVIATION /06Z SUNDAY THROUGH THURSDAY/

06Z Sunday through Monday night...VFR will persist through most of the day Sunday. Restrictions arrive with a coastal low Sunday night, and will move in from south to north. Visibility along the coast could be very low, with gusty winds and heavy snow allowing for LIFR conditions Sunday night, through Monday and into Monday night. The most impactful restrictions as mentioned will be on the coast, but places across the interior could see periods of IFR and lower visibility with snowfall moving in as well.

Outlook...

Tuesday: VFR. NW winds gust 20 to 25 kts. MVFR cigs may be in vicinity of HIE.

Tuesday night and Wednesday: Skies thicken and lower with MVFR/IFR cigs by Wed morning across NH. This moves east into ME along with SN.

Wednesday Night: SN tapers with trend to MVFR/VFR.

Thursday: Brief period of VFR possible, but there is a lot of uncertainty on arrival time of next potential storm system late week and resulting aviation impacts.

MARINE

A developing storm tracks south of Nantucket and through the Gulf of Maine on Monday. Storm force winds and hazardous seas up to 18-23 ft are likely across the outer waters, with Gales in Casco Bay. The storm then slowly moves into the Canadian Maritimes Monday night.

Seas will take a day or so to become less agitated from the exiting storm Monday, thus wave heights may remain 4 to 7 ft into Tuesday night. Additional low pressure may pass near or north of the waters Wednesday, potentially redeveloping over the Gulf of Maine in the evening. This could bring a period of SCA conditions. Otherwise would need to look towards late week for next chance of passing storm to increase seas/winds over the waters.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory from 1 AM to 10 PM EST Monday for MEZ012>014-033. Winter Storm Warning from 7 PM this evening to 10 PM EST Monday for MEZ018-019-023-024. Winter Storm Warning from 1 AM Monday to 1 AM EST Tuesday for MEZ020>022-025>028. Coastal Flood Watch Monday afternoon for MEZ023. NH...Winter Weather Advisory from 1 AM to 10 PM EST Monday for NHZ004-007. Winter Storm Warning from 7 PM this evening to 10 PM EST Monday for NHZ006-008>013-015. Coastal Flood Watch Monday afternoon for NHZ014. Blizzard Warning from 7 PM this evening to 10 PM EST Monday for NHZ014. MARINE...Storm Warning from 7 AM to 10 PM EST Monday for ANZ150>152-154. Gale Warning from 7 AM to 10 PM EST Monday for ANZ153.