12/07 - WINTER STORM: SRN PLAINS

[Robert Dewey]

Looks like a decent overrunning snowstorm setting up for parts of TX, OK, and KS... A high pressure builds in from the north, dropping arctic air southward - 12Z NAM shows daytime highs not getting much above 10F across the Southern Plains (and further north, struggling to even hit 10F!). The SFC flow is northwesterly across a very strong baroclinic zone located across southern TX, with a strong southeasterly flow aloft at 850MB. This creates a good overrunning/isentropic upglide situation, and the NAM outputs roughly .50 to .75 inches of QPF across northern TX, and another bullseye around the KS/OK boarder (yes, missing Norman).

I also included the Midwest (more towards the Great Lakes) since the shortwave heads in that general direction once it begins developing.

The exact placement of all these features is crucial, and with it being +60HRS out - things are subject to significant changes. I still thought it was interesting though.

 

[Gabe Garfield]

I was a little bit skeptical of the snowfall probs looking at the 6z ETA, not only because it was one run, but it's also an off-hour run (with no benefit of soundings). However, the 12z run of the ETA is much more compelling.

As Robert mentioned, liquid equivalents are forecast to be in the .50-.75 range across parts of the southern plains. As far as the bullseye of precip is concerned, the dprog/dt of the vort max is markedly southward (comparing the 0 and 6 UTC NAM vs. the 12 UTC NAM). This could bring about a fortuitous combination of lifting mechanisms with differential positive vorticity advection juxtaposed with the left exit region of a cyclonically curved jet along with strong warm air advection. If this scenario were to pan out, I believe that parts of Oklahoma and north Texas could receive as much as a foot of snow.

I believe the main caveat to the above scenario will be moisture return. The southern plains have been in a serious drought, so I'm a bit skeptical about whether there will be enough moisture to support heavy snowfall. Regardless, I believe that at least a couple of inches of snow is likely.

Gabe

 

[David Brookshier]

Originally posted by Gabe Garfield
I was a little bit skeptical of the snowfall probs looking at the 6z ETA, not only because it was one run, but it's also an off-hour run (with no benefit of soundings). However, the 12z run of the ETA is much more compelling.

As Robert mentioned, liquid equivalents are forecast to be in the .50-.75 range across parts of the southern plains. As far as the bullseye of precip is concerned, the dprog/dt of the vort max is markedly southward (comparing the 0 and 6 UTC NAM vs. the 12 UTC NAM). This could bring about a fortuitous combination of lifting mechanisms with differential positive vorticity advection juxtaposed with the left exit region of a cyclonically curved jet along with strong warm air advection. If this scenario were to pan out, I believe that parts of Oklahoma and north Texas could receive as much as a foot of snow.

I believe the main caveat to the above scenario will be moisture return. The southern plains have been in a serious drought, so I'm a bit skeptical about whether there will be enough moisture to support heavy snowfall. Regardless, I believe that at least a couple of inches of snow is likely.

Gabe

Even if the foot of snow scenario does not pan out at least those of us suffering in north Texas from the drought and extreme stability aloft might get something. I'll take anything at this point.

 

[Jay McCoy]

I dont look for near that much snow in Texas. We are just too damn dry. DP's are miserable. In amarillo we are 43/-2 right now and its 45/15 in DFW. The DP's are in the teens to low 20s all the way to the coast and I dont see anyting that will pull them up much between now and wednesday. Just some light snow and some serious cold air.At least for Texas and Oklahoma its serious cold

 

[Karen Politte]

WFO OUN are getting confused with the Norman Pit signature currently proposed by this winter storm. It will be interesting to see how the National Weather Center's pre-existing weather deflectors hold up with winter weather - but I have a fairly good idea that they will keep the city safe once again.

WFO OUN evidently do, too - as despite the whole area being blanketed in a Winter Storm Watch as of 4.30pm CDT Monday Dec 5th, Norman's Point Forecast page remains at a 20% chance of "wintry mix". :lol: I'm wondering how that wording can possibly jive with us being under a Winter Storm Watch. :roll:

Long live the Norman Pit effect - blessed by thy hallowed protective circle keeping us Normanites safe and dry!!!

KR

 

[Aaron Kennedy]

I was also curious to why they have wintry mix when the high is progged to be 18F AND temps at 850/700 should be well below 0.

Hmmmm

Bring on the snow! I'm gathering a party to hunt down and destroy the primary OUN deflector shield.

Aaron

 

[Robert Dewey]

Originally posted by Aaron Kennedy
I was also curious to why they have wintry mix when the high is progged to be 18F AND temps at 850/700 should be well below 0.

It is interesting... At first, I thought that freezing drizzle would be the big "mix" threat. Typically, when you have a profile that is 0 to -10C through the cloud layer with a significant dry air intrusion directly above the cloud top / saturation level, freezing drizzle is likely.

In this case, temperatures through the cloud layer are in the -10C to -20C, which seems slightly too cold for a "perfect" freezing drizzle situation, but I still wouldn't rule it out completely.

Also, I'm not liking the 18Z NAM forecast soundings out of OUN, in terms of heavy snow. The saturated layer barely reaches the -15C isotherm, and the majority of the strongest vertical velocities are located at the very top of the saturation layer. Definitely not good for snow flake growth, and I have seen small flake size kill plenty of good setups (mostly over my area, LOL).

We shall see, it's still a ways out.

 

[Simon Brewer]

Norman

I have to defend Mother Nature with respect to this storm and Norman, OK:

This setup is reminding me of January 2000; big snowstorm for Central Oklahoma. The "Norman Pit" filled up with 9 inches of white stuff on the OU Campus.

I'm hoping that shortwave digs a little further south and it is "SNOW TIME".

Just got a look at the 0z run of the models and it's not looking good for Oklahoma if you like snow; so this setup no longer reminds me of the Jan-2000 Norman Snow Storm.

Simon

 

[rdale]

Lawton is forecast to receive an inch or less per NWS, yet they are under a Winter Storm Watch. Do they really issue Winter Storm Warnings for an inch or less of snow in Oklahoma?

Not that OUN has the hold on bad snow forecasting - GRR called for 2 to 4" for Lansing last night and we picked up a flurry, they still think a half-foot could fall today and I'm going out on a limb by saying an inch or two ;>

- Rob

 

[Rob Satkus]

Originally posted by rdale
Lawton is forecast to receive an inch or less per NWS, yet they are under a Winter Storm Watch. Do they really issue Winter Storm Warnings for an inch or less of snow in Oklahoma?

- Rob

Well....seeing that it's a watch and not a warning, I guess not.
I think they issued a watch yesterday late when the computer models were showing heavy amounts possible ( Sunday night some models or at least a model showed 10"+ for northern Ok,(( comment based on a forecast discussion issued early Monday AM))). But as far as I know, a winter storm warning was never issued.I don't know what criteria they use down here for warnings or watches, but 2" or less of snow in Ok, merely a nuisance for you northern folks, can result in utter chaos for southerners. There is also a concern for some ice across southern areas, including Lawton.
Here is a quote from a winter weather statement issued around 4am from the NWS OUN:
A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY CREATE DANGEROUS AND LIFE-THREATENING CONDITIONS. ALTHOUGH SNOW AND ICE ACCUMULATIONS ARE NOT LIKELY TO BE HEAVY WITH THIS STORM...THE COMBINATION OF THE FIRST WINTER PRECIPITATION EVENT OF THE SEASON AND THE LIKELIHOOD OF A LIFE-THREATENING COMBINATION OF COLD AND WIND MAKES THIS DEVELOPING WINTER WEATHER EVENT A POTENTIALLY DANGEROUS ONE. CONTINUE TO MONITOR THE LATEST FORECASTS. RESIDENTS SHOULD PREPARE FOR THE CHANCE OF WINTER PRECIPITATION AS WELL AS THE COLDEST TEMPERATURES OF THE SEASON.

Rob2

 

[rdale]

"Well....seeing that it's a watch and not a warning, I guess not. "

I'm aware of that - but watches are issued when you have a 50% chance or greater of issuing a warning. So somehow they think it is better than even odds of the 1" or less snowfall resulting in some sort of warning, and I was wondering what warning would be valid for this type of event.

 

[Bill Hamilton]

Originally posted by rdale
I was wondering what warning would be valid for this type of event.

Considering that we haven't had a real snowstorm in years, they might issue one for all the bad drivers that get out when the slightest amount of snow hits the ground. :wink:
I personally hope we do get some snow down here. We need any moisture we can get right now.

 

[Aaron Kennedy]

Considering it is the first snowfall of the season... as long as it's above an inch or so it will warrant a winter weather watch.... this is OK we're talking about . A winter weather watch is much different than one say in Buffalo or Chicago. All it takes is an inch of snow to turn the streets into a frozen hell with OK drivers.

Sort of the same deal with heat advisories.... Temps of 90+ would warrent one in Seattle, yet in AZ you won't see them except for the most extreme of days (well above 100).

Aaron

 

[Shane Adams]

Originally posted by Aaron Kennedy
I'm gathering a party to hunt down and destroy the primary OUN deflector shield.

I'm heading up a small two-man squadron here in Dallas and will be searching for the deflecor as I trek my way back north either Wed or Thu. However, recent intelligence suggests the deflector maybe located along the gulf coast.

I'm awaiting an owl from the Ministry of Meteorology for further details. Godspeed.

 

[Karen Politte]

Originally posted by Shane Adams+--><div class='quotetop'>QUOTE(Shane Adams)</div>

<!--QuoteBegin-Aaron Kennedy

I'm gathering a party to hunt down and destroy the primary OUN deflector shield.

I'm heading up a small two-man squadron here in Dallas and will be searching for the deflecor as I trek my way back north either Wed or Thu. However, recent intelligence suggests the deflector maybe located along the gulf coast.

I'm awaiting an owl from the Ministry of Meteorology for further details. Godspeed.[/b]

Didn't you get the latest? Aaron's party was semi-successful last night. They personally scouted the grounds of the new Weather Center and found that the landscaping teams there had furtively woven deflector-strands into the lawns on the new site. Having seen the insane amount of cableage and man-hours that have gone into getting the new site up and running.......they were doing everything within their power to make sure that the next F-5 doesn't destroy their efforts!

Ahem - sorry, that's just too much. LOL.

But - for some reason - OUN's snow chances are now 60% chance of "Snow Likely" - so, something made the difference........a major victory for N.A.D.S. - Normanites Against Deflector Sheilds!!! :lol: :lol:

KR