Southern Plains winter wx thread (2008-2009)

[Extremeweatherguy]

The 12z GFS does have OKC below freezing for 48 hours, but it just doesn't deliver precipitation during that period. With a SW flow aloft though, I am not so sure if I believe that will really happen. Also, the GFS pulling the air well back north on Wednesday and beyond seems like an error. As we all know, the GFS is notoriously bad with shallow cold airmasses, and tends to retreat them northward way too fast. In all likelihood, the cold air will retreat north much more slowly.

[Extremeweatherguy]

12z ECMWF looks pretty cold and wet, with a battleground between rain, frz. rain, sleet and snow setting up over North Texas and Oklahoma next week...

http://www.meteo.psu.edu/~gadomski/ECMW ... floop.html

[Ed Mahmoud]

The front itself stays semi-parked near the coast around here.


I wish the Euros would put more data out for free.

But a first guesstimate of the edge of the freezing/frozen near Dallas seems in the ballpark.

In a couple more days, we'll be inside the WRF's range, and get a better idea where the WRF is guessing the extent of the icing to be.

I will say, the WRF yesterday did not do a very good job on the snow overnight in Houston. The GFS seemed to do best. Not perfect, but better than the WRF or Canadian.

[jinftl]

PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS, MD
300 PM EST THU DEC 11 2008

6-10 DAY OUTLOOK FOR DEC 17 - 21 2008

TODAY’S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE EXPECTED 500-HPA
HEIGHT PATTERN DEPICTING A STRONG RIDGE OVER WESTERN ALASKA, A HIGHLY AMPLIFIED
AND POSITIVELY TILTED TROUGH ACROSS THE WESTERN CONUS, AND A RIDGE OVER THE
SOUTHEAST. THE OPERATIONAL 0Z GFS AND ECMWF MODEL RUNS INDICATE A RETROGRESSION
OF THE WESTERN ALASKA RIDGE, AND THESE OPERATIONAL RUNS MAY IDENTIFY A GRADUAL
LONGWAVE PATTERN CHANGE.

THE POLAR VORTEX CENTERED OVER HUDSON BAY WILL LIKELY
MAINTAIN BELOW NORMAL TEMPERATURES ALONG AND TO THE NORTH OF THE POLAR JET, IN
THE NORTHERN ROCKIES, NORTHERN PLAINS, AND UPPER MIDWEST. SOUTHWARD PENETRATION
OF A SHALLOW, ARCTIC AIR MASS COULD SPREAD BELOW NORMAL TEMPERATURES AS FAR
SOUTH AS OKLAHOMA AND MISSOURI.

BELOW NORMAL 500-HPA HEIGHTS FAVOR BELOW NORMAL
TEMPERATURES ACROSS THE WESTERN CONUS, WHILE ABOVE NORMAL 500-HPA HEIGHTS FAVOR
ABOVE NORMAL TEMPERATURES ACROSS THE SOUTHEASTERN CONUS.

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 ON A SCALE OF 1
TO 5, DUE TO GOOD AGREEMENT AMONG THE MODEL SOLUTIONS AND TOOLS.

[Extremeweatherguy]

Here is the latest from Norman...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
315 PM CST THU DEC 11 2008

.DISCUSSION...
WE CONT TO MODIFY THE LATEST CANADIAN AIRMASS ACROSS THE REGION.
STILL SOME SNOWPACK ACROSS PORTIONS OF NW OK AND THIS WILL PROBABLY
LINGER INTO PARTS OF THE DAY ON FRIDAY. THIS WILL LIKELY HINDER WARM
UP A LITTLE UP THERE ON FRIDAY. OTHERWISE WARM UP WILL CONT TOMORROW
INTO THE WEEKEND. STRONG SOUTH WINDS WILL DEVELOP LATE TOMORROW AND
CONT THROUGH THE WEEKEND. THIS WILL CREATE SOME FIRE WX CONCERNS...
ESPECIALLY ACROSS WESTERN SECTIONS WHERE MOISTURE RETURN WILL NOT BE
AS GREAT. EVEN THERE RH VALUES ARE NOT FORECAST AT THIS TIME TO MEET
RED FLAG CRITERIA.

STRONG COLD FRONT IS STILL PROGGED TO MOVE THROUGH OKLAHOMA AND
NORTH TEXAS SUN AFTN AND SUN NIGHT. COULD SEE SOME PRECIP SUN NIGHT
ASSOCIATED WITH THE FRONT AND AS LAYER COOLS SOME OF THIS COULD FALL
AS LIGHT FREEZING RAIN/FREEZING DRIZZLE LATE SUNDAY NIGHT... ALTHOUGH
BETTER PRECIP CHANCES LOOK TO SHIFT EAST OF THE AREA RATHER QUICKLY
MONDAY MORNING.

COULD SEE PERIODS OF LIGHT FREEZING DRIZZLE MON NIGHT AND TUESDAY AS
ANOTHER BOUT OF WAA OCCURS. AGAIN IT DOES NOT APPEAR THAT AMOUNTS
WILL BE MUCH MORE THAN TRACE AMOUNTS... BUT ANY ICING CAN BE
SIGNIFICANT...ESPECIALLY FOR THE ROADWAYS AND TRAVELERS.

BEYOND THIS CONFIDENCE IN ANY ONE SCENARIO IF VERY LOW. LATEST GFS
TRIES TO ERODE COLD AIR DURING THE DAY WITH WARMER TEMPS AND PRECIP
FALLING AND REMAINING IN A LIQUID FORM DURING LATTER PART OF THE
WEEK. HOWEVER 12Z ECMWF CONT TO TREND VERY COLD NEXT WEEK WITH
LINGERING CHANCES OF FREEZING PRECIP WITH WAA PATTERN OVER THE TOP
OF VERY COLD AIR AT THE SFC. UNFORTUNATELY THIS MODEL HAS DONE
BETTER LATELY AND CONT TO SHOW BETTER RUN-TO-RUN CONSISTENCY AND
WILL GO MORE IN LINE WITH THE ECMWF... WHICH PAINTS A NOT SO PRETTY
PICTURE FOR MUCH OF NEXT WEEK.

[Extremeweatherguy]

At least 4 days below freezing expected here in Oklahoma City...

Sunday Night: A chance of rain showers before midnight, then a chance of freezing rain. Cloudy, with a low around 21. Chance of precipitation is 30%.

Monday: A slight chance of freezing drizzle. Cloudy, with a high near 28.

Monday Night: A slight chance of freezing drizzle. Cloudy, with a low around 22.

Tuesday: A chance of freezing rain. Mostly cloudy, with a high near 28. Chance of precipitation is 30%.

Tuesday Night: A slight chance of freezing drizzle. Mostly cloudy, with a low around 23.

Wednesday: A slight chance of freezing rain. Cloudy, with a high near 27. Chance of precipitation is 20%.

Wednesday Night: A slight chance of freezing rain. Cloudy, with a low around 22. Chance of precipitation is 20%.

Thursday: A slight chance of freezing rain. Cloudy, with a high near 28. Chance of precipitation is 20%.

It has been many years since I have lived in a place that stayed below freezing for that long.

[iorange55]

It seems like all the new model runs are shifting towards warmer for us *moves up north*

[jinftl]

Looking more and more like what CPC Outlook has been saying for a week!

It seems like all the new model runs are shifting towards warmer for us *moves up north*

[mysterymachinebl]

It seems like all the new model runs are shifting towards warmer for us *moves up north*

I don't know...it's going to be close. The forecast for Sherman, just 60 miles to the north, shows being in the 30's all week. But, NWS has Dallas being in the 50's by Thursday. Hopefully, the front will push further south and not retreat northwards!

[jinftl]

Even with CPC Temp Outlook, go from below normal temps in OKC to above normal temps in Houston.....pretty big difference over a relatively small area....could be interesting in that stretch of the u.s. for sure

It seems like all the new model runs are shifting towards warmer for us *moves up north*

I don't know...it's going to be close. The forecast for Sherman, just 60 miles to the north, shows being in the 30's all week. But, NWS has Dallas being in the 50's by Thursday. Hopefully, the front will push further south and not retreat northwards!

[cheezyWXguy]

It seems like all the new model runs are shifting towards warmer for us *moves up north*

You mean that ONE gfs run? What other models are doing this? Not the ecmwf, and I cant remember the cmc ever showing it getting all the way thru dfw. The lee side low has always been a gfs error, and it has been showing this on and off ever since the beginning of this event. Who knows, it may be right...but I dont think so.

[iorange55]

Well I'm not sure most of the new GFS runs now seem to be warmer. I know ECMWF is still showing the cold but I don't think it's AS cold as what it was forecasting earlier, is it?

[Extremeweatherguy]

Here is a look at what the Ch. 4 news is calling for in OKC...



Hopefully they are right about that change to sleet. I would take sleet over freezing rain any day!

[iorange55]

Here is a look at what the Ch. 4 news is calling for in OKC...

Then if you drive down 4 hours we might be in the 50's? That sucks.

[Extremeweatherguy]

iorange55 - I still doubt Dallas will be in the 50s. I think, as I have thought all along, that the cold air will probably make it further south. Dallas, IMO, will probably be stuck below 45 for most of next week, with temperatures perhaps 5-10 degrees warmer than in OKC.

[cheezyWXguy]

Are there any pro mets who would like to express their opinions on this situation? Its been a couple days since Ive heard of any.

[amawea]

Come on guys! From this point on, you just need to look at good old meteorlogical sense. Quit watching the models and look at whats happening upstream. That way you will either be excited or totally disappointed.

The gfs is really underestimating this high right now. I see 10 degrees colder than it's forecast, but I don't pay any attention to the models at 96 hrs. Heh!
Arctic Cold front to Texas coast by tuesday I say. We shall see.

[jinftl]

That says alot right there...

Are there any pro mets who would like to express their opinions on this situation? Its been a couple days since Ive heard of any.

[Ed Mahmoud]

Cold in Siberia, but pressures aren't particularly high.




They didn't have all the cool stuff in the word wide interweb they do now back in 1989, so I don't know what kind of surface pressures and temps in Siberia I need to be looking at. Alaska doesn't seem particularly cold.


Looking around Wunderground, -65ºF (-54ºC) is coldest I can find in those parts, Yellowknife is below -30ºC.

[Ed Mahmoud]

WRF sees a 22ºF/6 hours drop in OKC temps Sunday night/Monday morning with frontal passage.

Precip breaking out in the Texas Panhandle at the end of the 84 hour run.


http://www.meteo.psu.edu/~gadomski/WRF_0z/wrfloop.html

Looked at the AccuWx PPV point soundings, and one can also see on the loop, the 850 freezing line isn't that far ahead of the 540 dm thickness line, and isn't too far behind the surface freezing line.


If the WRF is correct, the area of freezing as compared to frozen precip may be fairly narrow.