November 20, 2023

November 20, 2023November 23, 2023 / alleghenymountainsweather / Leave a comment

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′

The Valley vs Cabin Mt

Canaan area temps

High Ground Comparison

Up High and Down Low

Up High, High Valley, Low Valley

The Valleys

Wv High Ground Cold Spots vs DCA

RTMA

Radar

https://mesonet.agron.iastate.edu/GIS/apps/rview/warnings.phtml?osite=RLX&tzoff=0&layers%5B%5D=nexrad&layers%5B%5D=warnings&layers%5B%5D=cwas&layers%5B%5D=uscounties&layers%5B%5D=watches&layers%5B%5D=blank&site=RLX&tz=EST&archive=yes&year=2023&month=11&day=20&hour=23&minute=55&warngeo=both&zoom=250&imgsize=640×480&loop=1&frames=90&interval=15&filter=0&cu=0&sortcol=fcster&sortdir=DESC&lsrlook=%2B&lsrwindow=0

Satellite

Flow

Current Surface Features and 500mb Height Anomalies and Flow

Town Hill

Polish Mt

Martins Mt

Cumberland

Lavale

Grantsville

November 19, 2023

November 19, 2023November 20, 2023 / alleghenymountainsweather / Leave a comment

November 19, 2023

Outlook:

Heading out this morning a fairly uniform chill across the area. Temps mainly mid 20s to low 30s. Some of those deeper valleys in the south east side of the Alleghenies where winds died are running a bit colder.

Cold enough for Snowshoe to have the guns on all night in to this morning

A pleasant Sunday on tap and overall a pleasant and a pleasant Monday albeit a touch chilly. Nothing bad though considering we are entering late November. The chilly, and dry air mass than in part to a high pressure skirting to our north that will influence our Tuesday as a low pressure system pushes northward.

That high pressure will help wedge some cold air back to the Alleghenies. The dry air/cold enough air will cause some evaporational cooling in addition at the precip onset as well. This should create a period of freezing rain initially over the Alleghenies and rapidly limiting itself in the classic ice zones before temps mild up enough for plain rain everywhere. Not a major winter event, but enough to create some ice on objects Tuesday. Finer details will come as we close in.

That Southeast Flow Tuesday off the ECMWF, and winds will be gusty along the ridges out of the SE.

off the Ventusky site

A look at precip type Tuesday off various modeling

Initially after onset a bit more widespread in the frozen department across the Alleghenies but rapidly limiting the location Cabin Mt and east to the Allegheny Front, northward to central and northern Garrett, especially Meadow Mt, Savage Mt, Dan’s Mt and points North around and above 2000′. There could also be some patchy sleet or even wet flakes early along the Allegheny Front and even the lower elevations east, where surface temps will be above freezing there. Not the classic freezing air trapped in those deep valley setup, simply because the air mass in front is not that cold. But a case of ingredients coming together thanks to the dry air and marginally cold air with the moisture coming in to create a window for that scenario.

All a fairly brief event winter weather wise, as it all turns to rain everywhere and it’s a fairly moisture laden system. .75 to 1.5″ of moisture looks possible across the region. The old timers say the creeks need full before it can snow. Precip amounts off the models.

As we head towards Thanksgiving, it’s yet possible we get a touch of white pre Thanksgiving. Light coatings are possible, and whatever if any falls melts off Thanksgiving day. Except shady areas perhaps.