November 20, 2023

post made 6:00pm

Winter Weather Advisories up for portions of the Alleghenies. Not everyone under the advisory will see big impacts, but stay alert none the less.

NWS Ice Forecast(which can be viewed in the drop down menu under snowfall info, click the office you live in for the latest)

Likely overdone on ice amounts here. We shall see.

Not a long duration event, or one of major impacts. Many areas, even areas under the advisory will mainly see a mostly plain rain event. Elsewhere the ice event should last in most areas 2-5 hours with possibly up to 5-8 hours along the Allegheny Front from Spruce Knob north and extending back to Meadow Mt and Savage Mt in Garrett and points North and Northeast.

Precip begins to push in, south to north around daybreak give or take. HRRR modeled below

As this pushes in, there can be some post onset sleet or wet snow along and east of the Allegheny Front. Possibly even extending back to Cabin Mt briefly and continued northward Meadow Mt and east.

Lets see,…you got a high pressure off to the east, marginally cold enough, with dry air, driving the drier east winds back west, wedging under the incoming moisture and slightly milder air aloft. You got some lifting over the Allegheny Front and you are cooling with elevation yet as it drives up and over the east side. The wedge becomes shallower as you progress westbound. Near the Allegheny Front and points east the entire column may cool enough for some wet snow or be thick enough for some pings of sleet. Otherwise it’s primarily a freezing rain to rain event.

That High

Let’s see the East Flow in Motion off the HRRR

As you lift that up and over, look at the modeled 5000′ temps along and east of the Allegheny Front

First off the 3km Nam at 9am

Thats a process of the east flow, dry air, evaporational cooling.

closer in

This is the 850 temps modeled off the 3km Nam at 5000′ at 8am EST. That’s -2C(+28F) at the Allegheny Front at Bear Rocks. 1000′ above. So you got at least a thousand feet of below freezing air(if the model is correct) at 8am the 5000′ temps over Davis modeled at +7C or 45°F. That gives some idea of how great the variance can be east to west in the setup. A setup that is often repeated many times per winter and even transitional milder seasons without any frozen aspect.

At the surface at 8am the modeled temps off the 3km Nam are

Upper 20s Along the Allegheny Front, near freezing at Davis and I’d suspect those freezing temps which are iffy at Davis are short lived beyond this.

Let’s hop to 11am

modeled 850 temps(again around 5000′), near 0c or 32F at Bear Rocks and low to mid 40s Davis

Surface temps at 11am using the 3km Nam which for years has been good in these setups. It can run -1 or -2 too cold at times which can make a big difference

Let’s now hop to 1pm

850 temps, still holding on to some near freezing 5000′ temps , but most areas coming above. The wedge while there and the east winds still undercutting. Losing the ability to cool with the column moistened, and milder air working in

1pm Surface temps

Along the Allegheny Front Maybe a few holdouts yet at freezing.

Model detail on these features has become really good. From the 3km Nam, the HRRR is greatly improved this setup for details. Euro is good, over the years the GFS tends to have a warm bias and the Weather.us site has a mesoscale Swiss Model that through brief viewing has performed well in the setup. A quick look at 8,11,1 tomorrow

very similar to the 3km Nam

A jump north to Garrett County and surrounding counties.

8am off the 3km Nam

11am

for fun off the Swiss 8,11,1

Again this area early on, with those areas Meadow Mt and east , and especially Savage Mt and east, there can be a window of brief sleet and or wet snow.

check out the vertical temp profile off the HRRR for Garrett County Airport

Surface just below freezing but that warm tongue up around 4500-5000′ is there

9am

Surface has moistened up. Still just below freezing with no room for temps to fall. They should hold steady till late morning to midday back to 219 area above 2500′-2800′ + , later as you advance east.

come further east to Cumberland. Despite being much lower in elevation, this will show why you get that chance along and east of Meadow to Savage Mt and even the lower elevations that should be above freezing east can see a few wet flakes at times mixed in with rain or even some sleet pellets

5am, low levels dry, temps above freezing

that’s showing the upper air very close to freezing through the entire column with the lower surface temps mid 30s. So, that’s how you can get 29° at Garrett Airport and liquid falling and freezing on contact, and 36 and a wet flake mixed in in Cumberland a few thousand feet lower in elevation.

Thos strong winds tomorrow, which the NWS has wind advisories out. That should only aid through the morning hours of those east facing, eastern ridges getting aiding in ice accretion through the a.m hours. The ice itself likely wont be enough to cause lots of issues, but those exposed windy areas under freezing, use caution on roads , it only takes a trace on roads for a bad day.

Not a major event, but it’s always a setup that creates a unique division across the Allegheny topography and is often fascinating to watch play out. Everyone to rain tomorrow afternoon and rainfall amounts are quite hefty across the area

most areas in the .75 to 1.50 range with locally higher amounts possible. As the rain departs Wednesday a.m, colder air filters in and if enough moisture lingers a light coating of white is possible across the high ground by late day, night.

Review of November 20, 2023

Forest Service Cam offline since 6/24/21

Nov 20(Mon)

Cold , frosty Valley start, milder tops, east wind developing through the day with increasing cloud cover

Bittinger 2nw Valley

Bittinger 2nw Valley morning Experimental Spot

Bittinger 2nw Valley Experimental Spot evening

Garrett County Airport

Top of Wisp

Canaan Heights/Davis 3SE

Climate Reference Network

Atop Canaan Ski area

Cabin Mt at Bald Knob

Cabin Mt-Western Sods

Spruce Knob

Canaan Valley Refuge

Mt Davis

Snowshoe

Petersburg Grant County Airport

not reporting

Elkins Airport

SITE COMPARISON

Dy007-Canaan Valley Refuge 3150′, Dy002-Cabin Mt at Bald Knob 4350′, Dy003-Cabin Mt-Western Sods 4035′, Dy004-Spruce Knob 4820′, Cvpw2-Climate Reference Network Canaan 3380′, KW99-Petersburg Grant County Airport 961, K2G4 Garrett County Airport 2933′, KCBE Cumberland Airport 774′, KEKN Elkins Airport 1985′, KMGW Morgantown Airport 1227′, PMN16-Mt.Davis 3038′, KDCA-Reagan National 15′, G1472 Snowshoe 4500′, F0183 Burkes Garden 3050′