Texas Winter 2012-2013

[dhweather]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
315 PM CST TUE JAN 15 2013

.DISCUSSION...
MOST OF THE DRIZZLE HAS ENDED ACROSS NORTH TEXAS AND TEMPERATURES
HAVE WARMED ABOVE FREEZING. CALLS INDICATE THAT AREA ROADWAYS ARE
CLEAR OF ICE AND THUS WE HAVE LET THE ADVISORY EXPIRE AT 2 PM.

THE QUESTION ON EVERYONES MIND TODAY HAS BEEN WHAT HAPPENED THAT
ALLOWED THE HIGH COVERAGE OF SLEET/SNOW TO DEVELOP THIS MORNING.
YESTERDAY AFTERNOON IT WAS APPARENT THAT THERE WOULD BE SUFFICIENT
LIFT FOR PRECIPITATION ACROSS NORTH TEXAS AS AN UPPER LEVEL
DISTURBANCE EMBEDDED IN THE SOUTHWEST FLOW MOVED ACROSS THE AREA.
THIS LIFT WAS SEEN WELL IN ADVANCE ON ISENTROPIC CHARTS. IT WAS
ALSO APPARENT THAT TEMPERATURES WOULD BE EASILY COLD ENOUGH TO
SUPPORT FROZEN PRECIPITATION. THE QUESTION...AS IT HAS BEEN WITH
THE PAST SEVERAL DAYS...WAS WHETHER OR NOT THERE WOULD BE SUFFICIENT
MOISTURE FOR PRECIPITATION AS FAR NORTH AS THE METROPLEX. THE
HIGHEST MOISTURE CONTENT WAS SET UP ACROSS THE SOUTHEASTERN ZONES
AND THE THOUGHT WAS THIS IS WHERE THE BEST CHANCES FOR
PRECIPITATION WOULD BE. ALTHOUGH THE MODELS HAVE NOT EXPLICITLY
SHOWN WINTER PRECIPITATION FOR OUR FORECAST AREA THE PAST COUPLE
OF NIGHTS...ONE COULD INFER AFTER INTERROGATING THE DATA THAT WE
HAD TWO OUT OF THE THREE NECESSARY INGREDIENTS FOR
PRECIPITATION...WHICH IS WHY WE HAD SOME MENTION OF SLEET/FREEZING
RAIN IN THE FORECAST. STEEP MID-LEVEL LAPSE RATES PLAYED A
PIVITAL ROLE IN MANUFACTURING MOISTURE. ISENTROPIC LIFT FROM THE
850-700 MB REGION ON THETA SURFACES ACCELERATED CONVECTIVELY WHEN
IT REACHED THE LEVEL OF INSTABILITY LOCATED ABOVE 700 MB. THIS WAS
EVIDENT AT THE ONSET OF THE EVENT WHEN THUNDERSLEET WAS REPORTED
ACROSS MANY LOCATIONS. AFTER THE ONSET OF THE INITIAL SLEET...THE
COLUMN CONTINUED TO SATURATE TOP-DOWN FROM THE MID-LEVELS TO THE
SURFACE.

THIS BRINGS US TO THE FORECAST FOR TONIGHT AND WHETHER OR NOT THE
APPROACHING UPPER LOW CAN BRING US ANOTHER ROUND OF WINTER PRECIP.
THE TWO MAIN CAUSES FOR PRECIP LAST NIGHT WERE THE STEEP LAPSE
RATES AND LOW-LEVEL LIFT DUE TO ISENTROPIC LIFT/WARM-AIR
ADVECTION. THE POSITIVELY TILTED UPPER TROUGH IS CURRENTLY IN
EASTERN NEW MEXICO AND MOVING EAST. AHEAD OF THE TROUGH...THE 850 MB
TROUGH IS BEING FORCED SOUTH...AND WE NOW HAVE ISENTROPIC
DOWNGLIDE/COLD ADVECTION IN THE LOWER LEVELS. THIS CAN BE VERIFIED ON
AREA VAD WIND PROFILES. THIS MORNING...NORTH WINDS EXTENDED UP TO
4KFT...AND THAT HAS INCREASED TO 6KFT. THIS IS EXPECTED TO
CONTINUE TO KEEP INCREASING THROUGH THE EVENING. AS THE TROUGH
MOVES CLOSER THE POSITIVE TILT WILL CAUSE THE STEEP LAPSE RATES
TO BECOME MORE STABLE. THERE IS A SMALL WINDOW FOR PRECIPITATION
FOR OUR EXTREME SOUTHEASTERN ZONES NEAR DAYBREAK BEFORE THE 700
FRONT SLIDES SOUTH OF THE CWA. FORECAST SOUNDINGS SHOW A SMALL
LAYER OF MOISTURE AROUND 600 MB WITH VERY DRY AIR BELOW. THIS
WOULD ONLY ALLOW FOR FLURRIES AND WILL MENTION FLURRIES MAINLY IN
ANDERSON...LEON AND HENDERSON COUNTY. AGAIN...THE MECHANICS IN
PLACE LAST NIGHT WILL BE SHIFTED WELL EAST OF THE FORECAST AREA.

CURRENTLY...THERE IS LIGHT SNOW OR FLURRIES BEING REPORTED NEAR
LUBBOCK...NEAR THE CENTER OF THE UPPER LOW. THESE SNOW SHOWERS
DEVELOPED IN THE AFTERNOON AS SURFACE BASED CONVECTIVE SNOW
SHOWERS. THESE ARE LIKE DAYTIME SHOWERS WE GET IN THE SUMMER AND
WILL DISSIPATE AFTER SUNSET.

THE UPPER LOW IS EXPECTED TO PASS EAST OF THE AREA WEDNESDAY
AFTERNOON AND NORTH FLOW WILL KEEP COLD TEMPERATURES IN PLACE
THROUGH FRIDAY MORNING. A BRIEF RETURN TO SOUTH FLOW WILL ALLOW
TEMPERATURES TO WARM INTO THE 50S FOR THE WEEKEND. THE GFS AND
ECMWF BRING A WEAK FRONT INTO THE AREA ON SUNDAY. THE ECMWF STALLS
THE FRONT NEAR THE RED RIVER WHILE THE GFS BRINGS IT THOUGH THE
CWA. FOR NOW...SIDE WITH THE GFS. BOTH MODELS BRING A STRONGER
FRONT THROUGH NORTH TEXAS MONDAY AFTERNOON...ALTHOUGH THE COLDEST
AIR WILL BE CONFINED TO THE EASTERN CONUS. SOUTHERLY FLOW WILL
RETURN TUESDAY. THIS FRONT WILL DROP HIGHS BACK INTO THE 40S WITH
A FREEZE FOR MOST OF THE AREA.

[jeff]

I remember christmas 04 when we were supposed to get 20 % chance flurries that night , and guess what ended up being a record breaking night where no meteorologist could describe what happened, 20 percent= 12 inches blizzard conditions, so nothings impossible

There was good model agreement for many days ahead of the Dec 04 snow event. It is just very hard for any forecaster to put out a foot of snow in S TX regardless if you have 100% model agreement...that event was extremely rare.

[Kludge]

Thanks for posting the FW AFD, dhweather. I saw that.

Here, let me fix it.... " THE QUESTION ON EVERYONES MIND TODAY HAS BEEN WHAT HAPPENED THAT
ALLOWED THE HIGH COVERAGE OF SLEET/SNOW TO DEVELOP THIS MORNING... even though our models told this wouldn't happen"

So they are doubling down, and saying it won't happen again tomorrow. Pretty bold.

They hedge their bets a little to say their SE zones could see a flurry. That's our N zones. Fingers crossed.

[Portastorm]

You guys need to re-read what the NWS forecaster wrote in that AFD. He explains quite well why the synoptics tonight are different than last night and why a winter "surprise" is a lot less likely.

Sorry. You got your snow and sleet today already! Alright ... whose next in line? Austin? San Antonio? Houston?

[Texas Snowman]

I see the 12Z Euro is in through next Thursday. It backed off on the cold for Texas again and now agrees with the GFS in no freeze for SE TX next week. Quiet a warm-up vs. the 00Z run.

Hence, never trust models beyond 3-4 days.


They will probably do this 5-6 more times between now and then.

Right. Unless, that is, they predict snow for Texas 15 days from now.

Or a snowstorm in North Texas on Christmas. Hey, wait a minute...

[Texas Snowman]

:uarrow:

You guys need to re-read what the NWS forecaster wrote in that AFD. He explains quite well why the synoptics tonight are different than last night and why a winter "surprise" is a lot less likely.

Sorry. You got your snow and sleet today already! Alright ... whose next in line? Austin? San Antonio? Houston?

Sure, it's easy to say why something happened after the fact.

Not as easy before the fact.

And I think a number of folks find it hard to trust their before-the-fact reasoning when it's already proven to be less than perfect a couple of times this week.

[Tireman4]

:uarrow:

You guys need to re-read what the NWS forecaster wrote in that AFD. He explains quite well why the synoptics tonight are different than last night and why a winter "surprise" is a lot less likely.

Sorry. You got your snow and sleet today already! Alright ... whose next in line? Austin? San Antonio? Houston?

Ding Ding...winner winner Chicken Dinner.... There is the PWC we all know and love. No more Evil Death Star. No more Wxman57 and his "no snow for you, ever" quotes...

[Portastorm]

Alright then ... y'all can wait outside tonight for your surprise sleet/snow storm.

Instead of being Charlie Brown trying to kick the football ... you're gonna be Linus, waiting for the Great Pumpkin to show up.

[Texas Snowman]

Portastorm isn't as much fun now as he was in the old days!

And we're not waiting on the "Great Pumpkin" - we're waiting on the "Great Snowflake"!

[Tireman4]

Portastorm isn't as much fun now as he was in the old days!

He will come back. The force that is Wxman57 can only linger so long. It will fade my friend. In time, snow will be his only purpose (and the PWC) again. Their motto, "You want snow, you got it" will ring through every meteorological office again.

[Portastorm]

Y'all are pretty darn funny.

OK, I'll try and not be so grumpy.

[Texas Snowman]

Y'all are pretty darn funny.

OK, I'll try and not be so grumpy.

Wxman57 over lunch in Austin: "Portastorm Luke, come to the warm side - I am your father!"

Portastorm eating a bowl of vanilla snow cream: "Noooooo! Wait a minute, where's my bike?"

[Tireman4]

Y'all are pretty darn funny.

OK, I'll try and not be so grumpy.

Wxman57 over lunch in Austin: "Portastorm Luke, come to the warm side - I am your father!"

Portastorm eating a bowl of vanilla snow cream: "Noooooo! Wait a minute, where's my bike?"

Oh my gosh. I spit my Coke. LOL

[South Texas Storms]

:uarrow:

You guys need to re-read what the NWS forecaster wrote in that AFD. He explains quite well why the synoptics tonight are different than last night and why a winter "surprise" is a lot less likely.

Sorry. You got your snow and sleet today already! Alright ... whose next in line? Austin? San Antonio? Houston?

How about all of the above!

[Ntxw]

Portastorm will come around. He won't be able to resist the power when an arctic front delivers him frozen frosted flakes in vodka. And we know how much PWC mets love vodka! Seems like just yesterday our Porta got excited over 384hr GFS blizzards...

[Texas Snowman]

Seems like just yesterday our Porta got excited over 384hr GFS blizzards...

HA-HA-HA! Now I'm the one spitting out my Coke!!!!

[TeamPlayersBlue]

I'm in the surprise bandwagon for tonight.

[TeamPlayersBlue]

Heavy amount of moisture is now coming up from Mexico with the STJ. Should see some precip in SE TX from this within the next few hours.

[Kludge]

I'm in the surprise bandwagon for tonight.

Same here [ full disclosure: I just fell off the Texans bandwagon ]

It never got above 35 here today, and there's a new plume of moisture that just blossomed over the King ranch and might be heading this way as the ULL moves east overnight.

[Ntxw]

Looking ahead again (you knew it was coming ) Jan 28th-Feb 2nd ish, look for a potential major system. It should be associated with Arctic front number 2. Could be a phaser with a baja low and incoming low from Alaska and building heights behind it. Keep that in the back of our minds.