Southern Plains winter wx thread (2008-2009)

[HarlequinBoy]

Forecasts in Little Rock and Memphis have a really tough forecast. I don't think things will be very certain until late Sunday.

Across the Mid South I think areas north of a Dyersburg to Jonesboro to Conway line could see some ice.

I'll watch it closely though. The front won't have to sag too far south to bring ice into the Little Rock and Memphis metro.

[Extremeweatherguy]

The NAM is much colder than the GFS for next week. Check out the differences shown at 1am Wednesday morning...

18z NAM = http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_084l.gif

18z GFS = http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_084l.gif

The NAM has the 0C 850mb line down near the red river, while the GFS has it way up in southern Kansas at the same time. That is a BIG difference!

[srainhoutx]

I suspect the 00Z's will look a bit different a well.

[ntxweatherwatcher]

I hope we get some good wintery precip here in DFW!! We missed out last time, it all went south!!

[iorange55]

I've been checking temps around the northern plains...WOW! Pretty dang cold just looking at those temps makes me want to put on a jacket.


I don't see how that arctic air would only bring us in the 40's and 30's for a day or two and then just leave. We shall see though!

[Extremeweatherguy]

The 00z NAM continues with its colder look. It is not quite as cold as the 18z NAM was, but it is definitely still much cooler than the 18z GFS. By Wednesday morning, the latest run of the NAM has the 0C 850mb line draped across North-central Oklahoma, with the surface 0C line likely further south than that.

loop of the 00z NAM: http://www.nco.ncep.noaa.gov/pmb/nwprod ... loop.shtml

[Extremeweatherguy]

According to the HPC, there is currently a 1055mb high up in NW Canada: http://www.hpc.ncep.noaa.gov/sfc/satsfcnps.gif

This is a few millibars stronger than what both the 00z NAM and the 00z GFS initialized it as...

00z NAM = http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_000l.gif

00z GFS = http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_000l.gif

Interesting.

[iorange55]

According to the HPC, there is currently a 1055mb high up in NW Canada: http://www.hpc.ncep.noaa.gov/sfc/satsfcnps.gif

This is a few millibars stronger than what both the 00z NAM and the 00z GFS initialized it as...

00z NAM = http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_000l.gif

00z GFS = http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_000l.gif

Interesting.

Would that make much of a difference in temps?

[Extremeweatherguy]

According to the HPC, there is currently a 1055mb high up in NW Canada: http://www.hpc.ncep.noaa.gov/sfc/satsfcnps.gif

This is a few millibars stronger than what both the 00z NAM and the 00z GFS initialized it as...

00z NAM = http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_000l.gif

00z GFS = http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_000l.gif

Interesting.

Would that make much of a difference in temps?

I do not know exactly what difference it will make, but a stronger high certainly does raise confidence in the idea that the cold air will spill further south and erode more slowly than what the models are currently showing.

[Extremeweatherguy]

Not surprisingly, the 00z GFS once again allows the cold air to be eroded out of the southern plains ahead of an approaching low next week. The main reason this happens is because the model decides to weaken the powerful high (currently 1055mb) down to 1035mb by 66 hours and also seems to still be having problems with the shallow cold air....

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_066l.gif

By Wednesday morning it warms temperatures to nearly 50F in OKC and into the 70s down in SE Texas...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_084l.gif



Here is a comparison to the 00z NAM at the same time (Wednesday morning)...

00z NAM (850mb temps) = http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_084l.gif

00z GFS (850mb temps) = http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_084l.gif

The GFS has the 0C line in north-central Kansas, while the NAM has the 0C line in north-central Oklahoma. This is a difference of hundreds of miles. An even greater difference though is the 10C line. The NAM has it placed in north-central Texas, while the GFS has it placed on the Oklahoma/Kansas border! No agreement what so ever!

[wxman22]

Interesting!! (Is GFS getting onboard with the European model!??)

[Extremeweatherguy]

It is interesting to look back at how the models busted with some of the cold snaps in years past. Back in November 2007, for example, the models were showing highs in the 40s for Dodge City, KS on the 30th. In reality, once the front arrived, temperatures only reached the 20s. That was a one day bust of 10+ degrees. Even a 9 hour forecast by the GFS busted with this event. The model was predicting 34F in Dodge city at a time when it really only ended up being 25F! The 3 day forecasts were definitely the worst though. Weather.com predicted 60s for that day...a 30+ degree bust!!! This is a perfect example of how the models are horrible with handling shallow arctic airmasses down the plains...

http://www.underthemeso.com/blog/?m=200711

^^Start midway down the page (Nov. 28th) and work your way up.^^

[Extremeweatherguy]

High pressure in NW Canada now up to 1056mb according to the HPC...

http://www.hpc.ncep.noaa.gov/sfc/satsfcnps.gif

Also the arctic front is entering northern Colorado and NW Nebraska at this time and is surging southward at an impressive clip. The leading edge should easily be through the OK and TX panhandles by noon tomorrow.


^^Temperature loop^^

[iorange55]

High pressure in NW Canada now up to 1056mb according to the HPC...

http://www.hpc.ncep.noaa.gov/sfc/satsfcnps.gif

Also the arctic front is entering northern Colorado and NW Nebraska at this time and is surging southward at an impressive clip. The leading edge should easily be through the OK and TX panhandles by noon tomorrow.

I hope the models are making one of those mistakes again and it gets a lot colder here, looks like it could happen.


Btw thanks for all the info EWG.

[iorange55]

Looks like that high is now up to 1057mb


It can keep going up as far as i'm concerned.

[iorange55]

Dallas Noaa Discussion

STRONG COLD FRONT IS NOW BARRELING THROUGH THE PLAINS AND WILL
CROSS THE RED RIVER THIS EVENING. CURRENT SURFACE OBSERVATIONS
INDICATE TEMPS FROM 0 TO -20F ACROSS THE NORTHERN PLAINS AND INTO
MONTANA. GFS 6 HOUR FORECAST WAS 5 TO 15 DEGREES WARMER THAN
OBSERVATIONS AT 6Z...WITH THE NAM FORECASTS MARGINALLY BETTER.
THE STRENGTH OF THE ARCTIC AIRMASS IS PROBABLY UNDERESTIMATED BY
THE MODELS AND WILL SIDE WITH THE FASTER TIMING FOR FROPA TONIGHT.
WE HAVE FROPA IN THE METROPLEX AT 6Z AND CLEARING THE SOUTHERN
ZONES JUST AFTER SUNRISE. TEMPS WILL FALL INTO THE 30S WITH NORTH
WINDS OF 15 TO 25 MPH. WE HAVE SIDED WITH THE COLDEST AVAILABLE
GUIDANCE...BUT THERE STILL IS SOME CONCERN THAT WE HAVE NOT GONE
COLD ENOUGH. WE WILL GET A BETTER IDEA ON HOW COLD IT WILL GET
HERE BASED ON UPSTREAM OBS/TRENDS DURING THE NEXT 12 TO 24 HOURS.

THE FRONTAL LAYER WILL BE JUST A FEW THOUSAND FEET DEEP OVER NORTH
TEXAS WITH A CLOUD DECK LIKELY DEVELOPING AT THE INVERSION ZONE.
COLD ADVECTION WILL INITIALLY BE STRONG...BUT WANE BY AFTERNOON AS
NORTH WINDS WEAKEN. UPPER LEVEL SUPPORT FOR SOUTHWARD TRANSPORT OF
COLD AIR WILL END...AND PRESSURES WILL BEGIN TO FALL BY MONDAY
EVENING. THIS WILL BE IN RESPONSE TO A FAST MOVING SHORTWAVE WHICH
WILL CAUSE SOUTHERLY FLOW ABOVE THE COLD LAYER TO INTENSIFY WITH
ISENTROPIC LIFT OCCURRING THE REGION. -RA/DZ IS EXPECTED OVER MUCH
OF N TX MONDAY NIGHT AND TUESDAY. MOS/MODELS ARE IN REASONABLE
AGREEMENT THAT SUBFREEZING TEMPS WILL EXIST NORTH OF A LINE FROM
COMANCHE TO FORT WORTH TO PARIS TUESDAY MORNING. NOT EXPECTING A
MAJOR ICE EVENT...BUT COULD BE ENOUGH TO CAUSE SOME TRAVEL ISSUES.
EXACT LOCATION OF THE 32F LINE IS UNCERTAIN...AND IF THE INITIAL
SURGE IS COLDER THAN CURRENTLY FORECAST...WE WILL NEED TO BRING
FZRA FARTHER SOUTH TUESDAY MORNING.

I'm guessing the freezing line will be more south, they have already had to lower temps and I will bet they will have to again. Tuesday morning might be tricky here.

[Portastorm]

FWIW, JB said in his Sunday morning blog update that he sees the freezing line coming as far south as San Antonio to Shreveport by Tuesday. Apparently the upstream cold is blowing GFS grid predicted numbers out of the water in Kansas and Oklahoma already. Sounds a bit like this past week's situation here in Texas although the synoptics are different. We ended up a lot colder than the NWS thought. Not sure how much of that was the polar air mass or being underneath the core of an upper-level low. Maybe both.

[PTPatrick]

MAN what a temp gradient...currently -1 in Denver, Amarillo is sitting at low 50s! What even crazier Boise City, OK down to 17 while Amarillo still sits at low 50s...Not from the area but that cant be more than a 2 hour drive...

[ntxweatherwatcher]

Maybe there is hope in DFW for winter weather yet!! Sounds like it is much colder than the models predicted!

[Extremeweatherguy]

Wow, looks like the front is moving much faster than anyone anticipated! Yesterday the NWS in Norman didn't think it would arrive until this evening, but now they think it will arrive early this afternoon. They also think it will be much colder than originally predicted, and are now calling for a low of 18F tonight and 14F tomorrow night! If we do hit 14F, then that will definitely be our coldest low so far this season. BRR!



BTW, you can track the progress of the arctic front through the afternoon using the OK Mesonet: