January Weather Discussion: Slight Chance Severe Storms

[srainhoutx]

The GFS suggests a big dump of Arctic air in the 192 time frame into Canada and CONUS. Several feature worth watching in the days ahead. Moisture mid week has increased and although light, it is on shore versus offshore. Although the 00ZGFS backs off the 'cold' for next weekend, the storm is still there. What is note worthy via the medium range is a 1060mb High in Western Canada and a 1050+ in the N Rockies. Some mighty cold air is poised to spill S beginning with a frontal passage on Friday, if the GFS is correct with reinforcing shots of colder air. Infact the GFS suggests a prolonged period of wintry precip in the longer range. All in all a very interesting pattern is unfolding and certainly bears watching, IMO.

[skidog40]

so what i gather from this is more than 2 days of snowing in houston?

[biggerbyte]

That much cold air would just fall way south with nothing being able to stop it. This type of scenario is always exciting for folks in Texas, because with upper air support or not, it would pay us a visit. Just a few more days to verify. I sure hope we don't get left empty handed. It is important for the newbies to understand that, even though it looks promising and exciting, this is more than three days out, with likely alterations as we close in.

[skidog40]

myforecast.com has 6 days of snow in dallas. if things happen the way the models say, more than 2 days of snow in houston?

[Andrew]

WOW! 00z GFS does open some eyes:



Not as much moisture but that is some cold air! Lets see if the trend continues.

[sambucol]

The model runs have been consistent with this, right?

[Andrew]

The model runs have been consistent with this, right?

For the past couple of days it has showed a 1050+ high come out of western Canada, so yes

[redneckweather]

Wxman will be on here bright and early in the morning to bring everyone back to reality. lol

[srainhoutx]

Looks like an interesting week or two ahead. The 00Z Euro (Canadian as well) is in agreement regarding to Arctic Air spilling S into the lower 48 later next weekend and the following week. Here are some discussions from various NWS offices concerning the mid week rains, next weekend storm and beyond...

HGX:

THIS WILL LEAD TO
AN ONSHORE FLOW RETURNING AND AN INCREASE IN MOISTURE. LOW LEVEL
CONVERGENCE WILL INCREASE AS COASTAL TROUGHING DEVELOPS. FCST
SOUNDINGS SHOW PW VALUES INCREASING TO BETWEEN 1.2 AND 1.4 INCHES
BY TUESDAY NIGHT. JET DYNAMICS LOOK WEAK AND SOUNDINGS SUGGEST
CAPPING WILL REMAIN IN PLACE. THE LOW LEVEL CONVERGENCE AND
DEEPENING MOISTURE BENEATH THE CAP SHOULD YIELD SCATTERED SHOWERS
TUESDAY AFTERNOON AND TUESDAY NIGHT. A WEAK COLD FRONT WILL CROSS
SOUTHEAST TEXAS ON WEDNESDAY AND THIS FEATURE WILL ALSO TRIGGER
SHOWERS. DRIER AIR WILL WORK INTO THE REGION ON THURSDAY BUT SKIES
WILL BE SLOW TO CLEAR. HIGH PRESSURE WILL AGAIN SETTLE OVER THE
SOUTHERN PLAINS AND BRING ANOTHER COOL MORNING ON FRIDAY. LONG
RANGE MODELS ARE PRETTY GOOD AGREEMENT WITH BRINGING A POTENT
SHORT WAVE ACROSS TEXAS ON SATURDAY NIGHT. JET STRUCTURE IS
IMPRESSIVE WITH THIS SYSTEM AND RAIN CHANCES WILL INCREASE AGAIN
LATE SATURDAY OR SATURDAY NIGHT. THE SYSTEM IS PROGRESSIVE AND
WILL EXIT THE REGION EARLY SUNDAY.

Corpus Christi:

LONG TERM (MONDAY NIGHT THROUGH SATURDAY)...THE PERIOD BEGINS WITH
SURFACE HIGH PRESSURE ACROSS THE SOUTHEAST... WITH ONSHORE FLOW AND
MOISTURE RETURNING TO SOUTH TEXAS. A WARM FRONT IS EXPECTED TO LIFT
NORTH ACROSS SOUTH TEXAS LATE MONDAY INTO TUESDAY AND ISENTROPIC
LIFT WILL CAUSE AN INCREASE IN CLOUD COVER. THE INVERSION WILL LIFT
TO 800-850MB BY TUESDAY MORNING SO MAY GET A FEW SPRINKLES OR LIGHT
RAIN. LEFT THE 20 POPS IN ALONG THE COASTAL BEND AFTER MIDNIGHT.
RAISED OVERNIGHT LOWS INTO THE 50S TO AROUND 60 FOR THE EXPECTED
CLOUD COVER. INVERSION HEIGHTS LIFT TO AROUND 750MB DURING THE DAY
ON TUESDAY AS ISENTROPIC ASCENT CONTINUES...SO LIGHT RAIN AND
SPRINKLES ARE EXPECTED ACROSS THE EASTERN TWO-THIRDS OF SOUTH TEXAS.
THEREFORE...BUMPED UP POPS TO CHANCE CATEGORY. OVERALL PRECIPITATION
AMOUNTS ARE ONLY EXPECTED TO BE A TRACE TO AROUND 1/10 OF AN INCH.
HIGHS WILL BE IN THE 60S TO LOWER 70S ON TUESDAY.

A WEAK SHORTWAVE WILL SLIDE ACROSS THE FOUR CORNERS REGION AND BEGIN
TO SHEAR OUT AS IT MOVES INTO THE SOUTHERN PLAINS ON WEDNESDAY. THIS
WILL HELP PUSH A FRONTAL BOUNDARY THROUGH THE REGION WEDNESDAY
AFTERNOON OR EVENING. INTRODUCED SLIGHT CHANCE POPS FOR TUESDAY
NIGHT AND WEDNESDAY TO ACCOUNT FOR THIS. DRIER AIR IS THEN EXPECTED
TO FILTER INTO THE REGION THROUGH THE END OF THE WEEK. WITH MORE
SUNSHINE ON WEDNESDAY DUE TO THE BOUNDARY...TEMPERATURES WILL LIKELY
WARM INTO THE 70S TO AROUND 80.

MODELS DIVERGE FOR NEXT WEEKEND...WITH THE GFS MUCH WETTER THAN THE
ECMWF. THE GFS MOVES A BAGGY TROUGH ACROSS SOUTH TEXAS ON
SATURDAY...WITH GOOD DYNAMICS OVER THE REGION...WHICH WOULD PRODUCE
WIDESPREAD RAINFALL. THE ECMWF HAS MORE OF A CLOSED UPPER LOW AND IS
FURTHER NORTH...AND RAIN CHANCES WOULD BE MINIMAL FOR MOST OF THE
AREA AS WINDS ALOFT VEER SOUTHWESTERLY AHEAD OF THE SHORTWAVE. LEFT
SLIGHT CHANCE AND CHANCE POPS IN FOR SATURDAY AND SATURDAY NIGHT.



Austin/San Antonio:

LOWER CLOUDS ARE
EXPECTED TO BEGIN IN THE DAYTIME MONDAY WITH A FEW SPRINKLES
EXPECTED TO DEVELOP BY TUESDAY. LIGHT SHOWERS TUESDAY NIGHT AND
WEDNESDAY SHOULD END WITH A CLIPPER STYLE FRONT LATE WEDNESDAY.
THIS FRONT SHOWS INCREASING STRENGTH IN THE RUN-TO-RUN MODEL
TRENDS OF THE GFS...SO HAVE MADE SOME COOLER ADJUSTMENTS TO TEMPS
IN THE THURSDAY-FRIDAY TIME FRAME. MODELS ARE COMING INTO SLIGHTLY
BETTER AGREEMENT ON THE SOUTHERN US STORM TRACK FOR NEXT
WEEKEND...BUT THERE REMAINS CONSIDERABLE VARIATIONS IN STRENGTH
AND TIMING. WILL KEEP WITH THE GFS TIMING BUT CAP RAIN CHANCES AT
20-30 PERCENT LATE SATURDAY.



Dallas/Ft Worth:

LATEST MODEL GUIDANCE IS COMING INTO BETTER AGREEMENT FOR THE LATE
WEEK AND NEXT WEEKEND FORECAST...HOWEVER IS STILL PRONE TO SOME
MAJOR CHANGES REGARDING STRENGTH/TIMING OF THE MAIN PLAYERS. OF
INTEREST IS AN UPPER LOW OFF THE CALIFORNIA COAST THAT SHOULD HEAD
EASTWARD AND ACROSS THE STATE NEXT WEEKEND. WILL INTRODUCE SOME
POPS SATURDAY...WITH BEST CHANCES COMING SATURDAY NIGHT. VARIOUS
OPERATIONAL RUNS OF THE GFS THE LAST 2 DAYS HAVE BEEN TRYING TO
INDICATE THE POTENTIAL FOR WINTRY PRECIP. GIVEN THE UPPER PATTERN
IT WILL BE TOUGH TO GET THE ENTIRE COLUMN BELOW FREEZING AND THIS
HYPOTHESIS IS VERIFIED BY LATEST MODELS ALL SUGGESTING WARM 850MB
TEMPS OF 2-4C AS THE SYSTEM MOVES ACROSS. OF COURSE IF THE UPPER
LOW IS STRONGER THAN FORECAST...THERE MAY BE SOME DYNAMIC COOLING
TO ALLOW FOR SUBFREEZING TEMPS OR SNOW POTENTIAL...BUT THERE IS
LITTLE ENSEMBLE OR OPERATIONAL SUPPORT FOR THIS SCENARIO NOW. ANY
WINTER PRECIP THREAT WOULD LIKELY BE IN THE FORM OF FREEZING RAIN.
THE KEY TO THIS POTENTIAL IS GOING TO BE THE POSITIONING OF THE
EAST COAST UPPER TROUGH AND THE STRENGTH OF THE SURFACE HIGH
MOVING INTO THE MIDWEST FRIDAY/SATURDAY. THIS WILL CONTROL JUST
HOW MUCH COLD/DRY AIR IS ABLE TO BLEED INTO THE REGION FROM THE
NORTHEAST BEFORE THE UPPER DISTURBANCE ARRIVES. LATEST ECMWF IS
THE WEAKEST WITH THIS HIGH...HAS LITTLE TO NO COLD AIR IN PLACE
AND TEMPS WELL INTO THE 60S SATURDAY WHEN THE PRECIP IS FALLING.
THE CANADIAN/UKMET HAS THE STRONGEST HIGH AND THUS COLDEST TEMPS.
THE GFS OFFERS THE COMPROMISE WITH MOST OF THE COLD AIR REMAINING
NORTHEAST...BUT EVAPORATIVE COOLING RESULTING IN TEMPS FALLING
INTO THE 30S WHEN PRECIP ARRIVES. WILL SIDE WITH THE 0Z GFS AND
PUT LOWS SAT NIGHT JUST ABOVE FREEZING AND THUS GET TO KEEP PRECIP
TYPE AS ALL RAIN. OBVIOUSLY WILL CONTINUE TO WATCH CLOSELY.

AND FINALLY WE HAVE BEEN SEEING SOME CONSISTENCY TAKE HOLD IN ALL
THE MODELS BEYOND 7 DAYS WITH RESPECT TO A PERIOD OF COLDER THAN
NORMAL WEATHER FOR THE SECOND WEEK OF JANUARY. AN UPPER LEVEL REX
BLOCK OFF GREENLAND/NEWFOUNDLAND HAS BEEN A STAPLE OF THIS
WINTER/S UPPER PATTERN AND HAS RESULTED IN BELOW NORMAL TEMPS IN
THE EASTERN US. THIS BLOCKING FEATURE IS FORECAST TO GRADUALLY
HEAD WESTWARD DURING THE NEXT COUPLE WEEKS...REACHING ALASKA AND
WESTERN CANADA BY 10 DAYS. THIS SHOULD RESULT IN A PROLONGED FETCH
OF CANADIAN AND PERHAPS EVENTUALLY TRUE ARCTIC AIR INTO MUCH OF
THE COUNTRY. TOO EARLY TO OFFER ANY EXACT NUMBERS...BUT THIS MAY
END UP BEING OUR BIGGEST COLD SPELL OF THE 2010-11 WINTER.


Amarillo:

A COLD FRONT THEN BACKS IN FROM THE NORTHEAST FRIDAY NIGHT...BUT HOW
FAR AND HOW QUICKLY SOUTHWEST THE COLD AIR PENETRATES WILL DEPEND
LARGELY ON THE TRACK AND TIMING OF THE SOUTHERN STREAM LOW WHICH
REMAINS QUITE UNCERTAIN ATTM. FOR NOW WILL PAINT A DECENT
NORTHEAST/SOUTHWEST TEMP GRADIENT ON SATURDAY...BASICALLY A BLEND
BETWEEN THE COLDER ECMWF AND WARMER GFS SOLUTION. SPEAKING OF THE
SOUTHERN STREAM LOW...THE 01/12Z ECMWF FEATURED A TRACK THAT KEPT
MOST IF NOT ALL OF THE PRECIP JUST SOUTH OF THE CWA SATURDAY/SATURDAY
NIGHT. THE LATEST 02/00Z RUN IS MUCH MORE PROGRESSIVE WITH THE
LOW...SWINGING IT THROUGH NOW FRIDAY NIGHT/EARLY SATURDAY...AND ISN/T
TAPPING ENOUGH DEEP MOISTURE TO GENERATE PRECIP UNTIL IT/S EAST OF
THE CWA GIVEN THE QUICKER SOLUTION. THE GFS ON THE OTHER HAND REMAINS
MUCH SLOWER AND WOULD BRING SOME PRECIP TO EASTERN PORTIONS OF THE
CWA SATURDAY AFTERNOON INTO SATURDAY NIGHT. NOT SURPRISINGLY
CONSIDERING THE CUTOFF NATURE OF THE LOW...GFS ENSEMBLES SHOW MUCH
VARIATION IN THE TIMING/TRACK OF THE LOW AT THIS POINT. CONSIDERING
THE POOR DISAGREEMENT IN SOLUTIONS AT THIS TIME AND THAT THE FORECAST
AREA LOOKS TO BE ON THE WEST/NORTHWEST EDGE OF THE PRECIP THREAT AT
LEAST THROUGH SATURDAY AT THIS POINT...DECIDED TO KEEP POPS SILENT
BUT WILL NEED TO KEEP A CLOSE EYE ON THIS TIMEFRAME. ALTHOUGH BEYOND
THE RANGE OF THIS FORECAST...MODELS CONTINUE TO SUGGEST THE
POSSIBILITY OF ANOTHER DUMP OF ARCTIC AIR INTO THE PANHANDLES EARLY
THE FOLLOWING WEEK AROUND THE JAN 10 TIMEFRAME.


Norman, OK:

WHILE ALL THIS TRANSPIRES... LARGE-SCALE CHANGES WILL TAKE PLACE
ELSEWHERE THAT MAY MOVE THE PIECES INTO PLACE TO SET UP A PERIOD OF
MORE SIGNIFICANT WINTER WEATHER EARLY NEXT WEEK... AND POSSIBLY AS
EARLY AS NEXT SATURDAY. POSITIVE HEIGHT ANOMALIES OVER S GREENLAND
BUILD W ACROSS N CANADA WHILE NEGATIVE ANOMALIES DO LIKEWISE FARTHER
S NEAR THE LATITUDE OF THE US-CANADA BORDER. LATTER LEADS TO AN
UPPER LOW ANCHORING OVER THE WA/BC AREA BY NEXT WEEKEND... AND
STRENGTHENING OF THE WESTERLIES ACROSS THE CONUS. MEANWHILE AN UPPER
LOW DEVELOPS OFF THE S CA COAST... IN THE S PART OF THE
AFOREMENTIONED W-COAST SPLIT FLOW PATTERN. THIS SYSTEM WILL MOVE E
LATER IN THE WEEK BUT TIMING DIFFERENCES EXIST AMONG THE MED-RANGE
MODELS. THE STRONGER WESTERLIES BY THEN MIGHT GIVE A NOD TO THE
FASTER ECMWF... IN WHICH CASE PRECIP WOULD ARRIVE HERE BY NEXT
SATURDAY. LOW POPS ARE THUS BEING INTRODUCED NEXT WEEKEND.

THEN THERE IS THE ARCTIC AIR. MODELS CONTINUE TO BUILD A STRONG
HIGH-LATITUDE RIDGE AROUND 150-160W BY WEEKS END... WHICH IN TANDEM
WITH THE ABOVE-NORMAL HEIGHTS OVER N CANADA WILL SUPPORT A BUILDUP
OF COLD AIR OVER W CANADA BY NEXT WEEKEND. SOME OF THIS AIR WILL
OOZE/TRICKLE S INTO THE CENTRAL/EASTERN CONUS BY THE END OF THE
WEEK... LEADING TO A COOLING TREND FRIDAY AND BEYOND. IF ENOUGH OF
IT BECOMES ESTABLISHED THIS FAR S... WE COULD BE LOOKING AT A WINTER
PRECIP EVENT NEXT WEEKEND AS THE LATE-WEEK SYSTEM MOVES E ACROSS
TX/OK. MORE COLD AIR IS LIKELY TO MOVE S IN THE WAKE OF THIS
SYSTEM... AND THERE SHOULD BE PLENTY OF IT TO TAP INTO BY THEN TO
OUR N.

NOTE THAT BOTH THE 00Z GFS AND THE 00Z ECMWF HAVE A 500-MB HIGH OF
AROUND 580HPA OVER ALASKA BY TUE 11 JAN. NOT A GOOD SIGN - NASTY
THINGS USUALLY HAPPEN IN TERMS OF COLD AND SNOW/ICE IN PATTERNS LIKE
THIS... NOT ONLY AROUND HERE BUT IN MANY PARTS OF THE LOWER 48. NEXT
WEEK MAY BE INTERESTING IN A NUMBER OF WAYS.


Dodge City, KS:

NEXT WEEKEND THE PATTERN BECOMES A BIT MORE
INTERESTING AS BOTH 00Z GFS AND 00Z ECMWF INDICATE A FAIRLY STRONG
SHORTWAVE TROUGH MOVING ACROSS THE LONE STAR STATE. AS A RESULT,
HAVE INCREASED SILENT POPS IN THE GRIDS SATURDAY AND SUNDAY AND
LOWERED TEMPERATURES WITH ADDITIONAL CLOUD COVER EXPECTED. THE
ECMWF IS A BIT FASTER WITH THE UPPER AIR SYSTEM THAN COMPARED TO
THE GFS AND IT IS TOO SOON TO HAMMER OUT ALL THE DETAILS. THE
BOTTOM LINE IS THAT THERE PROBABLY IS A FAIR TO GOOD CHANCE AT
SEEING SOME FORM OF PRECIPITATION TOWARDS NEXT WEEKEND ACROSS
KANSAS.

JUST AS A SIDE NOTE, WEEK TWO LOOKS TO BE VERY INTERESTING ACROSS
THE PLAINS. THE GFS IS INDICATING A 1055-1060 (!) HPA HIGH SLIDING
DOWN THE LEE OF THE ROCKIES FROM NORTHERN CANADA. THE ECMWF IS
WEAKER (RELATIVELY SPEAKING - AROUND 1045 HPA) WITH THE HIGH AND THE
RESULTANT COLDER AIR SURGING DOWN THE PLAINS. ANYWAY, THERE ARE
SOME FAIRLY GOOD SIGNALS THAT TEMPERATURES WILL BECOME MUCH COLDER
AND FRIGID TOWARDS THE SECOND WEEK OF JANUARY. RIGHT NOW I AM
HEDGING TOWARDS THE FASTER GFS SINCE MODELS USUALLY HAVE A HARD TIME
BRINGING DOWN THE COLD ARCTIC AIR MASS WHEN IN REALITY THE ARCTIC
FRONT BEHAVES LIKE A DENSITY CURRENT AND GRAVITY TAKES OVER IN
BRINGING DOWN THE AIR MASS STRAIGHT SOUTH. THIS THINKING WAS CARRIED
TO THE GRIDS IN BRINGING DOWN TEMPS...PARTICULARLY TOWARDS THE END
OF THE EXTENDED PERIOD.

01022011 00Z Euro GFS 168-240 500mb test8.gif

01022011 00Z GGEM Day 11.gif

[wxman57]

It isn't uncommon for large masses of cold air to accumulate in Canada in a La Nina winter. Getting that Arctic air down to Texas is the hard part. To get snow down here requires getting that cold air to move south first. Then it's a matter of perfect timing and cold air depth. We have to get a disturbance moving across the cold air before the air modifies enough to produce only cold rain or sleet. There is usually only a very narrow window of opportunity. That's why we rarely see snow here.

Although the GFS did predict some snow across Texas in the past day or two, there appeared to be a problem with the airmass in place when the disturbance moved across next Saturday (to me, anyway). The cold air just didn't look cold enough for snow. Newer model runs are trending warmer, with temps in the mid 50s and rain next Saturday. Given that the large Arctic airmass will still be in Canada next weekend, that looks reasonable.

The 00Z GFS did predict a snow event for even the Texas coast 15 days out. Yeah, right. It does tend to do that quite often in winter, but it's rarely right. I'll concede that it's at least a possibility as long as we have that very cold air in Canada. But I sure wouldn't forecast snow here based on one 15-day GFS outlook.

[redneckweather]

You hit the nail on the head wxman. I don't know how many times ove the past 5 years models have showed a 50+ arctic high in the medium to long range coming straight south. As the time drew nearer not only did most of slide off to the east but it wasn't as cold of an arctic high. Don't get me wrong, I would love for us to get some solid butt whooping cold weather (with possible precip) but I've seen this song sung way too many times. As usual, I'm hoping for the best.

Thanks for the updates fellas.

[Portastorm]

This is more than a whim. We're going on two days now of consistent agreement with both the GFS and Euro that not only will there be "vodka cold" looming to our north but that it will be plowing south into the lower 48. There's "chatter" this morning from a number of NWS forecast offices across the Southern Plains about the impending airmass. I don't know about ice/snow ... but I think the case for the coldest air of the season (easily) impacting Texas starting late next weekend into the following week is growing.

[srainhoutx]

lol, a 1063mb Arctic High in Western Canada on the 12Z GFS...

[srainhoutx]

THE CMC (Canadian) agrees with a strong frontal passage around the 10th, +/- a day or so...

[srainhoutx]

Classic Arctic outbreak signature via the 12Z Euro...

[srainhoutx]

The Euro suggests an amazing bitter cold airmass settling in with reinforcing shots to follow. Wow!

[txsnowmaker]

The Euro suggests an amazing bitter cold airmass settling in with reinforcing shots to follow. Wow!

Srain, is this run depicting a December 1989-type setup temperature wise (or something even colder)?

[TexasMetBlake]

The Euro suggests an amazing bitter cold airmass settling in with reinforcing shots to follow. Wow!

Srain, is this run depicting a December 1989-type setup temperature wise (or something even colder)?

Same setup but not as cold. The high that dropped into Montana in 1989 was like a 1080mb high. It was 1052 over Amarillo. So this is bitter cold, but not to the likes of '89.

[srainhoutx]

The Euro suggests an amazing bitter cold airmass settling in with reinforcing shots to follow. Wow!

Srain, is this run depicting a December 1989-type setup temperature wise (or something even colder)?

A bit too soon to know with any certainty, but with the record cold building in Eurasia, it is certainly not out of the realm of possibilities. We will need to watch this very closely in the days ahead. The consistency via virtually all guidance lends credence to such an outbreak.

[txsnowmaker]

The Euro suggests an amazing bitter cold airmass settling in with reinforcing shots to follow. Wow!

Srain, is this run depicting a December 1989-type setup temperature wise (or something even colder)?

A bit too soon to know with any certainty, but with the record cold building in Eurasia, it is certainly not out of the realm of possibilities. We will need to watch this very closely in the days ahead. The consistency via virtually all guidance lends credence to such an outbreak.

Thank you very much for the prompt response (and yours as well Candy Cane) and keeping everyone informed. Will certainly be keeping an eye on this one. Happy New Year to all.