December: Warm Days & Cool-Foggy Nights To End 2011

[srainhoutx]

SRAIN,EXPLAIN WHAT YOUR LAST POST SHOWS. FORGET WXMANS NEGATIVITY. HE MODEL HUGS RAW DATA FROM THE GFS.
WHAT DOES THOSE TWO MAPS SHOW THAT YOU POSTED? I DONT UNDERSTAND THEM

Now AZ, wxman57 isn't being negative and he certainly doesn't hug the models. What has been showing up for the past couple of days is another upper low diving S through the Great Basin/Intermountain West near Christmas. Guidance has been struggling with the exact details, but the charts I posted show a closed core upper low much further S into Mexico ejecting NE across Central Texas with some chilly air being pulled down from Central/Eastern Canada as the 3 jet streams (Arctic/Polar/Sub Tropical) merge, if you will. Right now it's just something to monitor, but there is a chance if we have some moisture to work with that things could get a bit interesting. We will see. Remember, the guidance still is not reliable beyond 3 days out in this active pattern. So, we will watch and see how it all plays out.

Edit to add the chart for the a week from Tuesday via the Euro (500mb)...

[biggerbyte]

An early season winter storm is brewing in the Southwest and is expected to bring blizzard conditions and heavy snow accumulations of over a foot to the southern High Plains on Monday, making travel across the region dangerous, if not impossible.

Winter storm watches were issued by the National Weather Service on Saturday for much of New Mexico, the panhandles of Texas and Oklahoma, extreme northwestern Oklahoma, southeastern Colorado, and southwestern and south-central Kansas.

Between 12 and 15 inches of snow is expected to fall on portions of the Texas and Oklahoma panhandles bringing near-blizzard-like conditions to the area Monday.

The heaviest snowfall and strongest winds are expected Monday morning through Monday night and Tuesday, the weather service said.

North winds of 20 to 30 mph will accompany the snow for much of the storm. Frequent wind gusts of 35 to 45 mph will also be possible, according to the weather service.

A blizzard watch or warning may be considered for the Texas and Oklahoma panhandles in future forecasts, the weather service said.

A blizzard watch is in effect for eastern New Mexico where as much as 8 inches of snow, combined with winds gusting to 45 mph, will likely cause whiteout conditions across the region Monday.

[srainhoutx]

i think the MODELS ARE UNDER ESTIMATING ANY COLD AIR AROUND CHRISTMAS. THERE IS ABOUT TO BE A HUGE SNOW DUMP TO OUR NORTH IN THE PLAINS.
IVE ALWAYS BEEN TOLD THAT MODELS UNDERESTIMATE COLD AIR WHEN THERE IS SNOWCOVER TO OUR NORTH BECAUSE THE SNOW COVER HELPS TO SOMEWHAT PREVENT AIR MODIFICATION. DO I MAKE ANY SENSE????? AND HOW DOES THIS UPCOMING BLIZZARD SNOW DUMP,PLAY INTO AND COLDER AIR LATER AROUND CHRISTMAS-POST CHRISTMAS?

It actually does (the blizzrard) 'play a part' in the pattern and that snowfall isn't going to melt anytime too soon with the totals expected. Additional snow is expected mid week across the Colorado Rockies and possibly out into the Plains just prior to the Christmas Holiday weekend. While we down here in SE TX will be watching a coastal trough/low next Thursday in our neck of the woods, bringing showers to some of the area. Needless to say, we have an active period ahead and a lot to chat about. As I stated, we'll just have to see how it all plays out. Stay Tuned!

[Andrew]

I just checked in on the 12z models and the canadian and Euro show some very interesting runs. It is interesting because a couple of weeks ago the models were hinting at the cold air in Canada shifting to the East and the orientation of this trough COULD dump the cold air straight towards Texas. Also multiple models are showing some sort of moisture to work with as disturbances continue to cross through. There is a good amount to watch once we get towards Christmas and hopefully we will get some cold air Also it is interesting to see the EURO indicate possible negative NAO values towards the end of the run. Could be a sign of things to come?

[biggerbyte]

It will be interesting to see if any of this comes to fruition. Due to the fact that we keep getting these consistent hints of winter weather, we certainly need to pay attention. There will not be a problem with snowpack to the north and northwest with this winter storm brewing. I can hardly wait too look at it on Friday.

[wxman57]

12Z Euro does end the precip well before temps get very cold late in Christmas Day. It has our temps in the mid 40s during the day on Christmas, falling to the upper 30s next Monday and 30-32 in northern to central Harris County on the 27th. Though there will be some snow to the north, it will only be a narrow band across the northern TX panhandle to eastern KS. North of that is no snow from northern KS to South Dakota. This airmass across TX next weekend doesn't appear to be as cold as a few weeks ago.

[srainhoutx]

Various Winter Weather Watches/Warnings issued for the Southern Rockies/Southern Plains. A Blizzard Warning is in effect for NE New Mexico/Texas/Oklahoma Panhandles/SE Colorado and SW and S Central Kansas...

[JackCruz]

wxman57 » Sun Dec 18, 2011 6:15 pm
how CAN HE SAY THAT WHEN YOU YOURSELF SAID THAT GUIDANCE ISNT RELIABLE 3 DAYS OUT,WITH THIS PATTERN? AND THE SNOW THATS ABOUT TO FALL DOESNT LOOK LIKE A NARROW BAND TO ME

Don't worry dear, everything will happen with time. It's coming...eventually.

[srainhoutx]

Well looky here for Christmas Day...

12192011 12Z GFS f162.gif

12192011 00Z GFS f168.gif

[sambucol]

Well looky here for Christmas Day...

Please explain!!

[srainhoutx]

What the GFS suggests is a coastal low forms near Corpus late Saturday (Christmas Eve). As the low heads NE along the coast, cold air is pulled S with over running precip. Areas inland could see some wintry mischief if that model is correct. Remember the Euro (12Z) showed earlier that things were coming together for a surprise or two near or just after Christmas. There is an upper air disturbance diving S along the Great Basin/Intermountain West into N Mexico. That feature provides additional lift over the cold air at the surface. Then add any coastal low/trough activity, then Central and E Texas has the ingredient for making things rather interesting. We will see.

[don]

looking at the more detailed version of the 12z Euro it doesn't look that much different than the gfs itll be interesting to see what the 0z Euro shows...

[srainhoutx]

The 00Z Canadian has the same idea...

[singlemom]

srain WHAT DO THOSE MAPS MEAN WE CANT READ THAT STUFF ,WE ARE AMATEURS, I REQUEST THAT WHEN U POST MAPS,,PLEASE EXPLAIN THEM

If you read under the picture in the bottom right corner, you'll see that it says "precip." That means the darker the colors the more rain is forecast to fall. The bottom right picture shows a black line. That's the freeze line. It shows it going below Houston at the same time the "precip" is forecast to fall. Please correct me if I'm wrong, 'srain, and I could hug you for posting that.

May I request that you please....pretty please....turn your all caps off? That is screaming in netiquette. Thanks.

[srainhoutx]

Just for grins, here is the twisterdata clown maps of the GFS...

[srainhoutx]

The 00Z GFS ensembles are onboard as well...

[srainhoutx]

We need to focus a bit more on tomorrow right now as we have a Slight Risk for severe weather from the SPC via the update. Damaging winds and hail will be the primary threat, but an isolated tornado or two is not out of the question for Central and SE TX...

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1137 PM CST SUN DEC 18 2011

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS CNTRL AND EAST TX...

...CNTRL AND EAST TX...
AN UPPER-LEVEL LOW IN SE AZ WILL MOVE QUICKLY EAST TO NEWD ACROSS
WEST TX TODAY. TO THE EAST OF THE SYSTEM...A 45 TO 60 KT LOW-LEVEL
JET WILL STRENGTHEN...RAPIDLY TRANSPORTING MOISTURE NWD INTO CNTRL
TX THIS AFTERNOON. SFC-BASED THUNDERSTORM DEVELOPMENT IS FORECAST
THIS AFTERNOON ALONG THE WRN EDGE OF THE MOIST AXIS WHERE A LINE OF
THUNDERSTORMS IS LIKELY TO ORGANIZE AND MOVE EWD ACROSS THE I-35
CORRIDOR FROM NEAR DALLAS/FORTH WORTH SWD TO NEAR BRIAN-COLLEGE
STATION. THIS LINE SHOULD PERSIST EWD ACROSS THE SLIGHT RISK AREA
EVENTUALLY AFFECTING THE HOUSTON AREA DURING THE EVENING.

AS THE UPPER-LEVEL LOW MOVES OUT INTO THE SRN PLAINS...A 65 TO 80 KT
MID-LEVEL JET IN THE BASE OF THE TROUGH WILL CREATE STRONG DEEP
LAYER SHEAR PROFILES ACROSS THE SLIGHT RISK AREA. FORECAST SOUNDINGS
ALONG THE I-35 CORRIDOR AT 00Z SHOW 0-6 KM SHEAR VALUES IN THE 55 TO
65 KT RANGE. IN ADDITION...SFC DEWPOINTS MAY REACH THE LOWER 60S F
AS FAR NORTH AS DALLAS WITH UPPER 60S F LOCATED ALONG THE MIDDLE TX
COAST WHERE MODERATE INSTABILITY IS FORECAST. THIS ENVIRONMENT
SHOULD SUPPORT SEVERE STORMS WITH THE GREATEST POTENTIAL ACROSS THE
NRN HALF OF THE SLIGHT RISK AREA WHERE THUNDERSTORM DEVELOPMENT IS
MOST CERTAIN. AS THUNDERSTORMS INITIATE...SUPERCELL DEVELOPMENT WILL
BE POSSIBLE ACROSS THE WRN PART OF THE SLIGHT RISK AREA WHILE THE
CONVECTION REMAINS DISCRETE. AS STORMS INCREASE IN COVERAGE AND A
LINE ORGANIZES...A WIND DAMAGE THREAT MAY DEVELOP WITH THE GREATEST
POTENTIAL ACROSS THE CNTRL AND ERN PART OF THE SLIGHT RISK AREA. THE
MAGNITUDE OF THE SEVERE THREAT SHOULD DEPEND ON UPON HOW MUCH
DESTABILIZATION TAKES PLACE IN CNTRL AND EAST TX THIS AFTERNOON.
ALTHOUGH THE SRN END OF THE LINE SHOULD AFFECT THE HOUSTON AREA THIS
EVENING...LARGE-SCALE ASCENT WILL BE QUITE WEAK IN SE TX SUGGESTING
THE SEVERE THREAT COULD BE MORE ISOLATED THERE.

...NW TX/SW OK...
SCATTERED THUNDERSTORMS SHOULD BE ONGOING ACROSS WEST AND NORTHWEST
TX AT DAYBREAK. THIS ACTIVITY SHOULD BE FOCUSED ALONG THE NWRN EDGE
OF THE LOW-LEVEL JET AND ALONG THE LEADING EDGE OF LARGE-SCALE
ASCENT ASSOCIATED WITH AN APPROACHING UPPER-LEVEL LOW. FORECAST
SOUNDINGS ACROSS WEST AND NORTHWEST TX THIS MORNING SHOW SOME CAPE
IN THE 700 TO 500 MB LAYER WITH INSTABILITY INCREASING AS THE
AIRMASS WARMS THIS AFTERNOON. THIS ALONG WITH STEEP MID-LEVEL LAPSE
RATES SHOULD BE ENOUGH FOR AN ISOLATED HAIL THREAT AS CONVECTION
INITIATES JUST AHEAD OF THE UPPER-LEVEL LOW. THE HAIL THREAT APPEARS
MOST LIKELY TO AFFECT NW TX AND SW OK AS STORMS MOVE NEWD ACROSS THE
REGION LATE THIS AFTERNOON. THE POTENTIAL FOR HAIL IS EXPECTED TO
REMAIN MARGINAL WITH A 5 PERCENT HAIL PROBABILITY SUFFICIENT TO
COVER THE THREAT.

[biggerbyte]

Looky here, indeed. If those maps validate come Thursday or Friday...

Exciting prospects.. ( Oh, and folks, that is all it is right now)

[Andrew]

Euro for next week:

f120.gif

Coming in line with GFS and Canadian....

[srainhoutx]

Euro for next week:

f120.gif

Coming in line with GFS and Canadian....

Which means less cold air and a weaker northern stream short wave that would suggest just chilly temps and dry conditions except further N. The Euro is a bit progressive with the trough and has it right over SE TX while the GFS is slower with that trough and generates the precip. It is prudent that we focus our attention on the severe threat today/tonight and we'll see what the week ahead brings in model world...