textproduct: Gray - Portland

WHAT HAS CHANGED

Blizzard warnings extended to all coastal zones in Maine and then west to Manchester-Nashua area in NH. Converted coastal flood watches to warnings. Wind forecast has increased with snowfall forecast very similar to 12 hours ago.

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. Active pattern continues as we track a clipper on Wednesday and another more complex weather system late Thursday into Friday

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

12Z Guidance suite jogged just slightly east with surface low track over the past 12 hours...but no significant changes to overall expectation as we remain on northern edge of significant Nor'easter that passes along the southern edge of the Gulf of Maine through Monday.

Primary change today was to expand blizzard warnings as model soundings show 3-4kft of mixing as far west as ASH/MHT with 50kts of flow at the top of the mixed layer. This should be sufficient to allow for multiple hours of gusts to 40 mph during the afternoon hours Monday. Similar story along the ME coast with MOS showing sustained winds in excess of 25kts...a good indicator of 45mph+ gust potential and thus...the likelihood of blizzard conditions...regardless of whether snowfall totals are a bit lower or higher. In addition to the visibility impacts... the relatively dry nature of the snow will result in significant blowing and drifting.

We do 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. Did add southern Grafton to the advisory in collaboration with neighbors and most recent expected snowfall totals...with a bit of added impact from gusty winds.

Peak snowfall amounts of 10-14" are currently painted across southern NH with roughly 1" of liquid. Given that we/re on the periphery of this event...noting that the 25th/75th percentile ranges are still rather large given that even small deviations in storm track could result in meaningful snow amount changes. So...we do expect further adjustments in final totals...but the expected impacts of poor visibility and blowing/drifting are very likely.

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. Wildcard 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...

An Alberta Clipper is expected to move across the Great Lakes region Wednesday into New England brining a period of widespread snow resulting in minor accumulations. There could be a band of higher amounts (20-40%) of 4" or more of snow in southern ME, though most locations will be 2" or less. A stronger frontal system is forecast to move across the Ohio Valley into local area Thursday through Friday. This wetter system could introduce some rain/snow mix near the coast, but mainly a snow event. Probabilities of 4" or more are higher with this second feature (30-50%). The probabilities of 6" or more (20-30%) mainly inland across the mountains. While there is uncertainty with this system timing, guidance has high pressure building in behind it Friday and lingering into the weekend with above normal temperatures. The pattern suggests temperatures falling back to near or below normal into next week.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

18Z Sunday through Monday night...VFR/MVFR turning IFR/LIFR as light snow overspreads the region between 03-12Z from S to N. Ceiling will fall rapidly upon the arrival of the snow. Winds will steadily increase, with gusts around 35KT+ for coastal and southern terminals Monday. Will need to monitor the need for LLWS despite some surface winds around 20-25kt. Snow rates will pick up early Mon morning, peaking in the afternoon with VSBY's dropping between 0.5-0.25 miles.

Outlook...

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

Tuesday night and Wednesday: Ceilings 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 another system is project to impact the area late Thursday into Friday that could have widespread impacts to the terminals.

MARINE

No changes to headlines over the waters with storm force winds expected for all but Casco Bay where high end gale force winds will occur. Wave heights will near 20' in the outer waters...closer to 10-15' in the nearshore. Wave heights will remain elevated through Monday night and gradually diminish on Tuesday. A weaker system passing north of the region Wednesday and Wednesday night will bring the potential for renewed SCAs. Another...stronger storm system is by the end of the week.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Winter Weather Advisory from 7 AM to 10 PM EST Monday for MEZ012>014-033. Winter Storm Warning from midnight tonight to 10 PM EST Monday for MEZ018. Winter Storm Warning from 7 AM to 10 PM EST Monday for MEZ019>022. Blizzard Warning from 7 AM to 10 PM EST Monday for MEZ023>028. Coastal Flood Warning from 1 PM to 6 PM EST Monday for MEZ023. NH...Winter Weather Advisory from 7 AM to 10 PM EST Monday for NHZ004-005-007. Winter Storm Warning from midnight tonight to 10 PM EST Monday for NHZ006-008>011-015. Coastal Flood Warning from 1 PM to 6 PM EST Monday for NHZ014. Blizzard Warning from midnight tonight to 10 PM EST Monday for NHZ012>014. 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.