Winter Storm February 19-21

[Wxmidatlantic]

Winter Storm watches are up from NW North Carolina, western Virginia, all of Maryland.

 

Heavy Snow followed by heavy sleet and freezing rain. Buy candles, lots of candles. Plenty of time yet.

 

All models are in agreement. I will start with the O6Z ICON. Not because I'm a big fan of that model. I just never seen it forecast that much snow before.

 

 

 

[Wxmidatlantic]

Modified Arctic air that will fuel CAD is heading south across Great lakes.

 

[Phil]

Wind gust to 41mph here as the cool, dry air rushes over and down the mountains.

[Wxmidatlantic]

Just got back with storm supplies, ready to hunker down. Last storm I had to go shopping for a flashlight battery with ice laden tree branches overhead. Every now and then you would hear a branch break in the distance, sounds like a riffle shot. Very uncomfortable.

 

I have peeked at 12Z, NAM is relaxing from 06Z. Low level jet trying to kink precip band. GFS most consistent, slight migration NE. Will be looking at Euro...

 

[Wxmidatlantic]

Euro no Change synopticly. Snowfall totals have been the lowest last 48hrs. Maximums look orograghic. Atlantic moisture not reflected in precip fields. No convective signals.

 

Snow coverage in agreement with all models. CAD stronger, 850mb temps in accordance. Surface high more NE.

 

Once upon a time, it was the King..

[Phil]

The trees here have been darwinized pretty good by high winds in recent years (March 2nd of last year cleared out a lot of weak wood..24hrs of 60-75mph gusts). So hopefully if we end up with a lot of freezing rain, it won’t be too bad.

 

Then again, we haven’t had a bad ice storm in a very long time..1999 was the last one, and that sucker knocked out our power for almost a week IIRC. Also, the weighing down of branches is a different type of force than wind, so it might not matter.

 

Who knows..this doesn’t look like a setup for a truly destructive freezing rain event of old times, but you never know with CAD.

[Wxmidatlantic]

If I was in western Virginia, I would be shaking in my boots. Expect Ice Storm advisories.

 

18Z NAM dives CAD SW into upstate SC. CAD stronger.

 

Tropical tidbits algorithms leave much too be desired. Posting only to note

SE movement. In the end for Baltimore, Washington. 4-8 inches of snow. 1 inch of sleet. .25 to .35 of freezing rain.

 

Early call, things could change, yada yada yada...

 

[Wxmidatlantic]

Love to see that push...

 

[Andie]

Texas will be enjoying 33* to 40* Rain.

10-15 mph winds.

See you guys at the coffee-bar!

[Wxmidatlantic]

When I drink the music flows...

[Phil]

Winter storm warming for 4-6” of snow and 0.1”+ of ZR.

 

Nice. Hopefully the surface cold overperforms and we stay all frozen Wednesday night.

[Wxmidatlantic]

Precip fields are off. Light rain, sleet to up state SC. Thunder rolls in Miss.

 

It begins...

 

[Wxmidatlantic]

[Wxmidatlantic]

12Z runs shift 4" line further south. Heavy snow band should follow. NAM insist on .5" ice accretion NW Baltimore suburbs, including my place. Ugly...

 

Sleet in Charlotte NC, reports of snow in Morganton, jut west.

 

[Wxmidatlantic]

Awesome convective precip band. Thunder from central Texas to Atlanta. Snow reports NE Georgia.

 

[Wxmidatlantic]

18Z NAM continues heavy snow march to the coast.

 

 

 

[Phil]

38.1*F/12*F in my backyard with a light N/NW wind still blowing as of 520pm.

 

https://www.wunderground.com/personal-weather-station/dashboard?ID=KMDBETHE62&cm_ven=localwx_pwsdash#history

[Phil]

Down to 34.3*F, winds veering N/NW, dewpoint 13*F.

 

The HRRR dumps a lot of precipitation into the inversion during the midday hours tomorrow which keeps the profile cooler..not sure about that, but we’ll see.

 

FWIW, I’m leaning towards the wedge overperforming a bit because it becomes more of an in-situ inversion, which models actually struggle more with than a classic CAD with a legitimate NErly low level cold air feed.

[Phil]

Watching the wetbulb temperature. Down to 27.6*F now and I suspect it will fall bottom out around 25*F before the WAA and low level easterly component begins depositing moisture overnight.

 

The NWS point and click has us bottoming out at 29*F tomorrow morning..I’m almost certain that is too warm and that we will end up 1-2 degrees colder underneath the frontogenic band.

 

[Phil]

..Mid-Atlantic through the Northeast...

Days 1-2...

 

Surface low moving through the OH VLY into the Great Lakes will be accompanied by deep and moist warm advection on southerly winds pushing plumes of high RH from the Mid-Atlantic into the Northeast. As this occurs, a cold high pressure will be anchored over New England before only slowly retreating to the east, maintaining a wedge of cold high pressure down the coast east of

the Appalachians. Robust 290-300K isentropic lift will produce widespread and heavy precipitation from North Carolina all the way into Maine, with synoptic ascent aided by diffluence within a jet streak to the north.

 

As precipitation falls, it will first occur into a column cold

enough for snow throughout, and a burst of heavy WAA snow is likely from WV and points northeast into PA. This WAA thump of snow will be accompanied by a brief but intense period of 750-600mb frontogenesis which is collocated with the saturated DGZ in an environment with negative theta-e lapse rates. This suggests intense snowfall rates which may exceed 1"/hr at times during the

morning across the Mid-Atlantic. The duration of intense snow in the region will be limited as the warm nose will lift northward turning precipitation from snow to sleet/freezing rain and eventually rain by the evening. The guidance may be too quick to warm the column due to reinforcement of the wedge by falling precipitation, but eventually precipitation will changeover, leading to a prolonged period of freezing rain across the terrain of WV/VA and into PA. The heaviest snowfall in the Mid-Atlantic is likely from the Panhandle of WV across MD and into Southern PA, where WPC probabilities are high for 4 inches. The heaviest freezing rain is likely in the terrain mentioned above, where a risk exists for 0.5" of accretion even after the snowfall.

[Wxmidatlantic]

No anomalies at 5am. 5 miles S- in west Baltimore. Moderate to heavy snow band in Virginia.

 

[Phil]

Holy mama it’s unloading. Just picked up 0.5” in 10 mins.

 

Currently 29.8/26 and still cooling.

[Phil]

Passed 2” already.

 

Currently 28.5/26 and light snow. Another heavy band is approaching from the W/SW, though, so we should start adding quickly again.

[Wxmidatlantic]

Finally, 3S- temp tanking 29F, stiff breeze 0810....

[Wxmidatlantic]

1/2 SN

[Phil]

Another nuke band developing overhead.

 

~ 2.5” on the ground..28.7/26..warmed 0.2 degrees between bands. So dynamic cooling is the refrigeration mechanism here now.

[Wxmidatlantic]

Visibility 3/4S- 27.4F freezing line digging SW. Freezing rain last two hrs Greensboro NC.

 

Convective band in Ohio starting to bend SE. Nice convective showers complex running up ridge line east of Roanoke.

 

[Wxmidatlantic]

It dropped the hammer 1/4S+

[Phil]

Temp down to 28.2 here..3”+ and counting.

[Wxmidatlantic]

1/8S+ 2" on the ground...

[Wxmidatlantic]

1/2SN. 27.2F you win temp forecast..

[Wxmidatlantic]

Just looked at NAM 3hr forecast, bust. Snow line 50 miles too far north. That main convective band is digging SE. A lot more potent than prog.

 

3" on the ground...

 

[Wxmidatlantic]

I'm getting some wind gust to 20mph temp 28.7F 1/2SN blowing snow. 4.2 on the ground.

[Phil]

Picked up 5 quick inches before the changeover. Most of that fell in ~ 2 hours. No wind here though, since we’re sheltered from the east (unlike those W/NW winds which always destroy us, haha). Snow falling straight down the whole time.

 

Now freezing rain coming down fast and hard under the warm nose..getting nasty out there in a hurry.

[Wxmidatlantic]

Just went through the "Mother of all dry slots." Never saw it coming....

[weatherfan2012]

Picked up 5 quick inches before the changeover. Most of that fell in ~ 2 hours. No wind here though, since we’re sheltered from the east (unlike those W/NW winds which always destroy us, haha). Snow falling straight down the whole time.

Now freezing rain coming down fast and hard under the warm nose..getting nasty out there in a hurry.

pretty Comerica when some promets cancel winter and winter is now showing up fitting this winter

[Phil]

Just went through the "Mother of all dry slots." Never saw it coming....

Negative vorticity advection from the convection over the Gulf states. Can’t always see that stuff until it’s right on top of you.

 

Am hovering right around 32 degrees now with freezing mist/rain still accreting to trees, metal, and snow..not much pavement accretion though. Been ongoing since 2pm, so over 6hrs straight. Have seen and heard multiple transformers blow up in the distance (mostly over the last hour or so) but our lights have not even flickered. Trees are holding up just fine, as far as I can tell.

 

Should warm above freezing shortly, but that’s never a guarantee w/ in-situ CAD, especially here in the river gorge, which can become a cold air drain under some (seemingly random) circumstances. Haha.

[Wxmidatlantic]

Light Zl- most of the night. Just a light glaze on exposed surfaces. 31.8F could have been ugly. Others not so fortunate I suppose.

 

Hope to get a good visible satilite after sunrise. Low clouds may hang on for a while.

[Wxmidatlantic]

In summary: 4-6 inches of snow. Ice accretion here was around .15. I really could not tell until after venturing out. Temperature remained below freezing throughout event.

 

It was a great lesson in negative vorticity.

 

[Phil]

INSANE variations in the ice accumulation here. It never warmed above freezing here until after sunrise. Apparently we got got stuck in a cold pocket (l live in a gorge-like area that in-situ CAD drains cold air into).

 

Ended up with around 0.2-0.25” of ice accretion at my location, but just a half mile away (out of the creek valley) it was almost nothing. Then there was another pocket of heavier accretion just to the SW along the River Valley, but once you crossed over (near the One Lane Bridge and the Clara Barton Parkway) it again diminished to almost nothing, over a distance of just a few hundred feet. Incredible.

 

So it was ~ 5” of snow, 1/3” of sleet (maybe a bit more since it compacted into the snowpack) and 0.25” of ZR.