Winter Storm Lorraine/Valentine's Day Nor'easter Update One

10:01 PM AST Sunday 11 February 2024

Winter storm forecast to pass south of Nova Scotia late Tuesday and early Wednesday.

Potential snowfall accumulations: 20 to 30 cm by noon Wednesday.

Maximum wind gusts: northerly 60 to 70 km/h giving areas of blowing snow.

Location: most of Nova Scotia.

Time frame: spreading across the province from Tuesday afternoon to Tuesday evening. Conditions improving from west to east on Wednesday.

Remarks: Forecast guidance is beginning to give a clearer picture regarding a nor'easter passing south of the province mid-week. At this time, the most likely scenario appears to be 20 to 30 cm of snowfall accumulation for most of the province by noon Wednesday. Any fresh snow from this system has the potential to combine with strengthening northerly winds to reduce visibilities in blowing snow.

As with all nor'easters, small changes in the storm track can result in large changes in the snowfall forecast, and this alert will be updated periodically to reflect the latest information.

Behind this system, a prolonged period of onshore flurries and snow squalls looks likely develop over portions of northeastern mainland Nova Scotia and northern Cape Breton, and these areas could continue to see accumulating snow into Thursday night.

Rapidly accumulating snow could make travel difficult over some locations.

Public Safety Canada encourages everyone to make an emergency plan and get an emergency kit with drinking water, food, medicine, a first-aid kit and a flashlight. For information on emergency plans and kits go to getprepared.gc.ca.

Please continue to monitor alerts and forecasts issued by Environment Canada. To report severe weather, send an email to NSstorm@ec.gc.ca or tweet reports using #NSStorm.

000

FXUS61 KCAR 120220

AFDCAR

Area Forecast Discussion

National Weather Service Caribou ME

920 PM EST Sun Feb 11 2024

.SYNOPSIS...

A cold front will cross the region through tonight. Low

pressure will organize along the Mid-Atlantic on Monday, move

south of the area on Tuesday, and exit into the North Atlantic

on Wednesday. High pressure builds in Thursday through Friday.

&&

.NEAR TERM /THROUGH TODAY/...

9:20PM Update...There is a cold front now entering the St. John

Valley and pushing SE. Cold air advection is developing in the

wake of the front. Webcams and observations indicate 1 mile

moderate wet snow falling in Frenchville and other areas of the

St. John Valley. Expecting snow showers to continue developing

along and ahead of this front as it drifts south. Temperatures

will begin falling below freezing, this combined with very cold

subsurface temperatures...frost depth 13 inches here at the

office...will result in slick conditions in Northern Aroostook

County. Have issued an SPS to handle the concern of slick travel

conditions developing tonight. Otherwise, mainly low clouds

across the North, mainly north of Baxter region. Higher clouds

passing through across southern zones with some areas of clear

skies. Expecting a general trend of partly cloudy skies south

and mainly cloud north. Minor tweaks to the temps and dew points

based on the observational trends.

Previous Discussion...

Deep layered westerly flow aloft will persist tonight through

Monday. A cold front will cross northern areas tonight, and then

cross the remainder of the region early Monday.

The guidance for the past many cycles has been suggesting a

northwest to southeast oriented band of snow showers developing in

the wake of the cold front for northern areas. The CMC regional has

led the way highlighting this. Have been monitoring the latest

several runs of the HRRR today and it continues to suggest a

band developing across northern Aroostook county through early

this evening before waning overnight. This could result in

localized accumulations of an inch or two in some parts of the

county into this evening.

The modest cold advection behind the front should still allow

overnight lows across the north to drop a good 10 degrees colder

that last nights, but still several degrees above the normals

for this time of year.

West to northwest flow persists on Monday with mainly cloudy

skies north along with isolated to scattered snow showers, and

partly cloudy for Bangor and Downeast. Afternoon highs on Monday

will be a good 5 to 10 degrees cooler than those of todays.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...

Synoptic: A low pressure system will move up through the Mid-

Atlantic states and track off the southern New England coast

Monday night into early Tuesday morning. This low will deepen as

it travels eastward, continuing to strengthen as it crosses

south of the Gulf of Maine and Nova Scotia and pushes out into

the North Atlantic.

Model Guidance: Recent guidance has come into better agreement

with the northern extent of the precip shield, with the ECMWF

trending southwards slightly and the last couple runs of the CMC

moving steadily northwards to meet the GFS solution in the

middle. This agreement has only just been realized with the 12z

runs, but gives better confidence (50 to 60%) of where will

receive measurable snowfall (primarily the Downeast region,

especially along the immediate coast).

Threats:

-Most snowfall is expected along the immediate coast, with

 current forecast being a chance (50%) of around 3 to 5 inches.

 This accumulation is largely dependent on the exact low track,

 as there is a steep gradient to the north where snowfall drops

 to zero, so any shifts in low track by a few miles could lead

 to amounts increasing or decreasing from here. Measurable

 snowfall will likely not begin until Tuesday afternoon, as a

 layer of mid-level dry air between 800 and 600 mb will need to

 saturate prior to accumulating snowfall onset.

-Winds will remain breezy during the event itself, but will

 rapidly increase behind the low passage Tuesday night into

 Wednesday, where gusty winds up to 30 mph will persist. Since

 snow will be of fluffier consistency, especially through the

 second half of the event with SLRs approaching 20:1, there

 could be some patches of blowing and drifting snow through the

 day on Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...

A ridge of high pressure will return through the end of the

week, with a tight pressure gradient aloft Wednesday night

persisting gusty winds, but this gradient will relax into the

day on Thursday as the high pressure continues to further

establish. A weak warm front may lift across the area on Friday,

bringing a few snow showers across the area, but there remains

timing and strength uncertainty across guidance at this time

with this feature........

Hazardous Weather Outlook

National Weather Service Caribou ME

342 PM EST Sun Feb 11 2024

MEZ029-030-122045-

Coastal Hancock-Coastal Washington-

342 PM EST Sun Feb 11 2024

This Hazardous Weather Outlook is for Coastal DownEast Maine.

.DAY ONE...This afternoon and tonight.

Hazardous weather is not expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

A coastal storm may bring light to moderate accumulating snow to

Coastal Downeast Tuesday into Tuesday night.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather

conditions according to Standard Operating Procedures.

$$