Winter 2010-11 for the Southern Plains

[srainhoutx]

Some shifts in guidance for the Christmas Eve Storm have occurred overnight. A very complex and complicated forecast is ahead and expect some changes. The Euro, Canadian and UKMET has trended further S and stronger with an Upper Air feature (closed low) tracking across Southern California, Desert SW into the TX Panhandle and dropping ESE into LA, while the GFS keeps an open wave/trough further N exiting CO into KS and heading E. Now what does that mean? It appears more moisture may be involved with the Christmas Eve front and perhaps a 6-12 hours slower arriving Friday afternoon/evening versus the faster GFS solution. Also of note with the Euro solution is the chance of rain and possibly elevated storms across the TX Panhandle, W TX, N TX/OK along and N of the Upper Low track, should it verify. Christmas Day still looks cold and dry for now, but if the Euro solution is correct, there may well be some wrap around cloudiness/very light moisture and stiff northerly winds as a surface low pressure deepens over LA. The Euro solution also opens the door to a Major Christmas Weekend Winter Storm along the East Coast as well with very heavy snowfall totals and even a 'hint' of an Archambualt Signature for that area. In the longer range the pattern as well as guidance suggests a bonified chance at some much needed rain in Southern, SE TX as a coastal low/trough develops during the pre New Years Eve time frame. We have been hoping for some sort of pattern change and this may well be it.

Forecaster Roth in the HPC morning Prelim Update...

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
757 AM EST MON DEC 20 2010

VALID 12Z FRI DEC 24 2010 - 12Z MON DEC 27 2010

...SIGNIFICANT PRECIPITATION EXPECTED TO CONTINUE ALONG AND JUST
INLAND OF THE WEST COAST FOR ANOTHER 5 TO 6 DAYS...

TELECONNECTIONS WITH A RIDGE MOVING SLOWLY ACROSS THE PRAIRIE
PROVINCES OF CANADA FAVORS NEARLY CLOSED CYCLONES ALOFT MOVING
UNDER ITS BASE THROUGH THE NORTHERN ROCKIES/NORTHERN PLAINS LATER
THIS WEEK...A SOLUTION BEST INDICATED BY THE 00Z CANADIAN AND 00Z
GEFS AND ECMWF ENSEMBLE MEAN GUIDANCE. OTHERWISE...ENERGY MOVING
OUT INTO THE MIDWEST EARLY ON IS EXPECTED TO SCOOP UP SOME
SHORTWAVE ENERGY MOVING OUT OF THE SOUTHWEST AND SOUTHERN PLAINS
BEFORE LOSING LATITUDE AS IT MOVES THROUGH THE EAST UNDER THE BASE
OF A PORTION OF THE POLAR VORTEX DESCENDING THROUGH EASTERN
CANADA. THIS SOLUTION IS BEST REPRESENTED BY THE 06Z GFS/00Z
CANADIAN/00Z ECMWF AND GEFS MEAN GUIDANCE. OVERALL...USED A
COMPROMISE OF THE 00Z CANADIAN/00Z ECMWF ENSEMBLE MEAN...AS THE
06Z GFS MIGHT BE A TOUCH TOO QUICK PER ITS OCCASIONAL QUICK BIAS
WITH SYSTEMS IN THE WESTERLIES...WHICH LED TO GOOD CONTINUITY WITH
THE PRESSURES FROM SUNDAY AFTERNOON. THIS PATTERN SHOULD REMAIN
MOIST ALONG THE WEST COAST...AND COLD ACROSS THE NORTHERN
PLAINS/MIDWEST/MUCH OF THE EAST.

WEST AND PLAINS THIS WEEKEND INTO EARLY NEXT WEEK...
WITH STRONG RIDGING PERSISTING ACROSS WESTERN AND CENTRAL CANADA
THROUGH THE PERIOD...A PACIFIC SYSTEM IS EXPECTED TO MOVE THROUGH
THE REGION UNDERCUTTING THE RIDGE. TIMING ISSUES EXIST...WITH THE
06Z GFS THE QUICKEST. SINCE THE RIDGING ACROSS WESTERN AND
CENTRAL CANADA IS SHOWING SOME PROGRESSION IN THE NORTHERN
STREAM...A SLOWER PROGRESSION IS LIKELY IN THE SOUTHERN
STREAM...SO WENT WITH THE NON-06Z GFS GUIDANCE HERE.
OVERALL...THE 00Z CANADIAN HAD THE BEST ENSEMBLE MEAN SUPPORT...SO
WENT WITH A 00Z CANADIAN/00Z ECMWF ENSEMBLE MEAN COMPROMISE WITH
THIS SYSTEM. SIGNIFICANT PRECIPITATION ACROSS THE WEST IS
EXPECTED FOR ANOTHER 5 TO 6 DAYS...WITH LOCAL LIQUID EQUIVALENT
AMOUNTS OF 10 INCHES POSSIBLE ACROSS THE OLYMPIC
PENINSULA...NORTHERN COASTAL RANGES OF CALIFORNIA AND SISKIYOU
RANGE...AS WELL AS THE COASTAL RANGES OF SOUTHERN CALIFORNIA AND
SOUTHERN WASATCH DURING THIS TIME FRAME.

SOUTH AND EAST...
THE 00Z ECMWF IS SLOW/MORE CLOSED THAN THE OTHER DETERMINISTIC
GUIDANCE WITH ENERGY MOVING THROUGH THE SOUTHWEST AND SOUTHERN
PLAINS...WITH LESS THAN ONE-QUARTER OF THE OVERALL 00Z GLOBAL
ENSEMBLE GUIDANCE SUPPORTING ITS SOLUTION...IMPLYING IT IS TOO
SLOW. TELECONNECTIONS FARTHER NORTH IMPLY STRONGER ENERGY SHOULD
BE MOVING THROUGH THE NORTHERN TIER OF THE COUNTRY...WHICH SHOULD
ABSORB THE SOUTHWESTERN ENERGY AS IT MOVES INTO THE
PLAINS/MIDWEST. EITHER WAY...A SURFACE LOW IS EXPECTED TO MOVE
THROUGH THE SOUTHERN PLAINS INTO THE DEEP SOUTH OR TENNESSEE
VALLEY OFFSHORE THE VIRGINIA CAPES. THE BIGGER QUESTION IS HOW
CLOSE TO THE COAST THIS CYCLONE WILL TRACK. THE ECMWF BECOMES THE
MOST NORTHWESTERLY OF THE GUIDANCE AT THE SURFACE...AND IF THIS
SURFACE LOW WERE MOVING UP THE EAST SIDE OF AN AMPLIFIED TROUGH
RATHER THAN A PROGRESSIVE CLOSED CYCLONE A MORE COASTAL TRACK FOR
NEW ENGLAND WOULD MAKE SENSE. SINCE THIS DOES NOT APPEAR TO BE
THE CASE...AND THE 00Z ECMWF ALSO APPEARS TOO FAR NORTH WITH ITS
CYCLONE IN CANADA...ITS CYCLONE TRACK ALONG THE EAST COAST IS
PROBABLY TOO FAR NORTH/TOO CLOSE TO THE COAST. THE OTHER
GUIDANCE...INCLUDING THE ENSEMBLE MEAN SOLUTIONS...MOVE THIS
SYSTEM CLOSER TO THE GULF STREAM...A NATURAL BAROCLINIC ZONE/AREA
OF TEMPERATURE GRADIENT OFFSHORE THE EAST COAST...WHICH APPEARS
MORE LIKELY CONSIDERING THE FLOW PATTERN ALOFT. DUE TO
PREFERENCES ACROSS THE PLAINS AND WEST LATE IN THE PERIOD...CHOSE
THE 00Z CANADIAN HERE...ALTHOUGH THE 00Z ECMWF OR 00Z GEFS MEAN
ARE REASONABLE ALTERNATIVES. EITHER WAY...WINTER WEATHER SHOULD
SPREAD FROM THE CENTRAL PLAINS EASTWARD ACROSS THE TENNESSEE
VALLEY THROUGH THE MID-ATLANTIC STATES...AS WELL AS SNOW SHOWERS
UNDER THE BASE OF THIS SYSTEM ACROSS THE GREAT LAKES AND
NORTHEAST. THE IMPACT OF THIS SYSTEM ACROSS THE NORTHEAST REMAINS
SOMEWHAT OF A QUESTION MARK...BUT FOR THE TIME BEING...THE 00Z
ECMWF LOOKS LIKE A LOWER PROBABILITY ALTERNATIVE SCENARIO.

ROTH

[Portastorm]

Great post and information, srainhoutx! Thanks much. To your credit, you have been banging the pattern change drum for a while now.

I'm growing more optimistic that we'll see some desperately needed rainfall here in south central Texas as well as southeast Texas.

[Ntxw]

After seeing all the overnight runs, I would say the Euro is the outlier, and is a bit extreme with the energy digging in the southwest (usually does). However, the EC currently has some support from both it's own ensembles and the GFS ensembles. My guess from this is that the GFS will eventually correct itself to slower and perhaps suppressed track than where it is currently standing.

Either way it does look like OKC and Dallas would get much needed rain. How far south this thing goes has huge implications moisture wise for the rest of Texas.

Pacific looks quite active.

[TwisterFanatic]

12 GFS now much further south on the OK/TX border.

[wx247]

Seems everyone went further south with the 12z run. Now I feel the need to stay up for the 00z Euro tonight.

[wx247]

The NWS out of Kansas City has a great afternoon write up.

http://forecast.weather.gov/product.php ... glossary=1

[Ntxw]

0z GFS tonight is looking more like the Euro. The low cuts itself off (on and off but I'll assume it maintains that in the SW for our optimism) and digs a bit further south tracking along the red river. If this were to verify you could possibly have a winter storm in the making for OK/KS/MO/TX Christmas Eve.

[Texas Snowman]

Add in evacuations in California and an "epic" snowstorm in the making in Colorado (according to Grand Junction NWS statement) and this isn't your standard La Nina issue Christmas week of weather is it?

Interesting developments for sure...

I mean even discussing the possibility of a potential winter storm is exciting.

And I realize that this is going way out on a limb, but I can't help but wonder what the odds would be for TWO white Christmas events in consecutive years in portions of Oklahoma and/or Texas.

Astronomical, I'm sure.

[Ntxw]

Add in evacuations in California and an "epic" snowstorm in the making in Colorado (according to Grand Junction NWS statement) and this isn't your standard La Nina issue Christmas week of weather is it?

Interesting developments for sure...

I mean even discussing the possibility of a potential winter storm is exciting.

And I realize that this is going way out on a limb, but I can't help but wonder what the odds would be for TWO white Christmas events in consecutive years in portions of Oklahoma and/or Texas.

Astronomical, I'm sure.

It's too far out to really buy into anything, for all we know it could fall apart like the rest so far as it crosses the southern plains moisture deprived (I don't believe this is the case due to warmth and moisture return before hand, however temps might be an issue). The trend is better for us than previously since the GFS seems to be buckling to the Euro.

Dallas only saw it's third white Christmas ever I think last year, each being decades in between (correct me too lazy to find specific data lol). So a back to back would be unheard of. Keep your fingers crossed!

And I agree with you completely! We have something to discuss about potentially for Christmas which really is astronomical any year.

[Ntxw]

0z Euro has the cutoff low over north Texas before absorbing it into the northern stream and providing our friends in the southeast/east with some Christmas fun! I would still be very cautious at this point though as just 36 hours ago things were soley central plains-Tennessee Valley, they could very well swing the other way in 36 hours, we'll have a fairly clear idea by Friday evening Lol.

By the way tomorrow night should be the longest night of the year! Beginning of Winter.

[iorange55]

We're so used to being screwed that even if all the models agreed on something a day out we'd probably all say "we'll see"

[Ntxw]

We're so used to being screw that even if all the models agreed on something a day out we'd probably all say "we'll see"

It's never easy. Over the years I've compiled a list of things to notice.

1. Complex storms that requires a lot of things to come together almost never happens (this looks complex; lots of phasing required with perfect timing needed)
2. Unless both the GFS/Euro shows the same thing relatively, go by the Euro in short range
3. Lastly, qpf seems to be the issue this winter. Follow seasonal climatology.

So even if there is a low swinging by, it may just very well be one giant virga blizzard.

Longer range update: EC tonight breaks down the pesky GOA vortex after Christmas. This in turn allows for more southern stream storms to take shape off California and the Baja, something we see quite often during El Nino. Perhaps it's the time for weather to turn wetter here, which would be welcomed.

[TwisterFanatic]

This storm reminds me of one last year. It looked like a big Winter Storm in Kansas/Mizzou, and when it got about a week or a little less out it started trending southwards and before i knew it there were Winter Storm warnings for all of Oklahoma and Northern Texas.

Deja Vu?

[iorange55]

This storm reminds me of one last year. It looked like a big Winter Storm in Kansas/Mizzou, and when it got about a week or a little less out it started trending southwards and before i knew it there were Winter Storm warnings for all of Oklahoma and Northern Texas.

Deja Vu?

Yeah but the odds of it happening twice? I don't see it. Probably just some rain and cooler temps.

[Ntxw]

A key difference from last year was that the storm even this far out was predicted to be intense and was a matter of track. This one has wobbled from weak to decent to weak to ok again lol.

[Ntxw]

NAM this morning at 84hr.

[srainhoutx]

The 12Z NAM took a big step toward the Euro solution. A slower, less progressive and deeper short wave suggests a better chance at moisture...

[wx247]

The 12z NAM spits a lot of snow out in my area. I would be more confident if this was the model picture the morning of... deeper moisture is definitely evident on the NAM. The fact that it heads closer toward the Euro is also interesting.

[Ntxw]

Again my confidence in this system isn't moisture, it's quite warm (most of Texas is making a run at 80 today if not more) with a return flow from the gulf prior to it. I'm thinking much of the southern plains will get beneficial rain. Will it be cold enough for snow south of I-40? That is yet to be seen. That adds to consensus that yet another model is trending to the Euro.

[Portastorm]

The larger-scope atmospheric signals are somewhat encouraging for a pattern change to more possible "wetness" for us in the Southern Plains.

The MJO is headed into Phase 7 (and possibly later Phase 8) and that often means wetter than normal and cooler than normal for the Southern Plains. The AO and NAO are progged to remain negative so we'll have plenty of frosty air to our north. And the PNA is progged to get closer to neutral than currrently which should make for a more active southern jet.