January: Calmer Pattern To End The Month

[srainhoutx]

The updated QPF for Thursday into Saturday as increased. It is also noteworthy that the updated 12Z MEX text data is now suggesting some form of potential light frozen precip Friday afternoon into early Saturday for locations N of I-10 including IAH, DW Hooks and College Station. This also includes Austin and the Dallas/Ft Worth Metroplex.

[Portastorm]

Lots of comments about the late-week "weather" from this afternoon's AFDs out of Texas/Louisiana-based NWFSOs:

Austin/San Antonio:
MODELS ARE COMING INTO BETTER ALIGNMENT ON THE INCREASE OF PACIFIC
AND GULF MOISTURE AND THE ARRIVAL OF AN ARCTIC FRONT EARLY
THURSDAY. THE TEMPERATURE TRENDS ARE HEADING LOWER WITH EACH
RUN...BUT SOUNDING DATA FROM THE GFS INDICATES A DEEP AND WARM
LAYER CAPABLE OF MODIFYING THE INVERSION FROM PERSISTENT SHOWERS
TO HOLD TEMPERATURES ABOVE FREEZING THROUGH FRIDAY MORNING. LATER
SHIFTS WILL NEED TO WATCH THE TRENDS AND POSSIBLY ACCOUNT FOR
MIXED PRECIPITATION CHANCES FOR EARLY FRIDAY. POPS AND QPF AS WELL
AS WARMER THURSDAY MIN TEMPS FAVOR THE ECMWF MODEL THROUGH THIS
COLD AND DAMP PERIOD. RAIN CHANCES ARE EXPECTED TO DIMINISH
SATURDAY WITH A WARMING TREND EXPECTED FOR NEXT SUNDAY.

Dallas/Fort Worth:
THE THURSDAY FRONT WILL BE FAIRLY STRONG...AS THE HIGH PRESSURE
SYSTEM WILL ORIGINATE IN THE ARCTIC AND DROP RAPIDLY SOUTH INTO
THE NORTHERN PLAINS BY WEDNESDAY. THE COLDEST OF THE AIR WILL HEAD
PRIMARILY INTO THE MIDWEST AND EASTERN PART OF THE CONTINENT AS
THE MAIN UPPER TROUGH PULLS OFF TO THE EAST. BUT NORTH TEXAS WILL
STILL SEE TEMPS TUMBLE THURSDAY TO BELOW NORMAL AS WE GET A
GLANCING BLOW OF THIS SHALLOW ARCTIC AIRMASS. THE FRONT SHOULD
CROSS THE RED RIVER AROUND SUNRISE THURSDAY MORNING. THIS WONT BE
ONE OF THOSE FRONTS WITH A SHARP TEMPERATURE GRADIENT...BUT RATHER
A SUSTAINED BOUT OF STRONG COLD ADVECTION THAT WILL SEND TEMPS
INTO THE 20S BY THURSDAY NIGHT. MEANWHILE WE WILL BE EXPERIENCING
A SUBTLE SHIFT IN THE UPPER LEVEL PATTERN BY THURSDAY AS A PIECE
OF UPPER LEVEL ENERGY FROM THE PACIFIC RIDES OVER THE TOP OF THE
WEST COAST RIDGE AND DROPS INTO THE WESTERN US. WINDS IN THE MID
AND UPPER LEVELS WILL BACK FROM NORTHWEST TO WEST...WHICH WILL
HAVE THE EFFECT OF BRINGING IN MORE PACIFIC MOISTURE ALOFT IN THE
FORM OF MID TO HIGH LEVEL CLOUDS THURSDAY. THESE CLOUDS WILL LIMIT
MODIFICATION OF THE SHALLOW ARCTIC AIRMASS...BUT ALSO HELP KEEP
OVERNIGHT LOWS FROM GETTING TOO COLD.

THE MAIN FORECAST UNCERTAINTY IS JUST HOW STRONG THIS PIECE OF
PACIFIC ENERGY IS...AND THE EXACT TRACK IT WILL TAKE. THE 12Z GFS
MADE A SUDDEN CHANGE BY DIGGING THIS UPPER SYSTEM SOUTH OF LAS
VEGAS BEFORE EJECTING IT EASTWARD TOWARD TEXAS. THE ECMWF...UKMET
AND CANADIAN KEEP THIS SYSTEM FARTHER NORTH AND MUCH WEAKER. THE
12Z GFS ENSEMBLE SHOWS ABOUT HALF OF THE MEMBERS INDICATING THE
DEEPER/STRONGER TRACK. ALL FORECAST MODELS SHOW THIS SYSTEM
ENTERING A REGION OF CONFLUENT FLOW ALOFT WHICH WILL HAVE THE
AFFECT OF SQUASHING/SHEARING OUT THE SYSTEM...WHICH MEANS THE
SYSTEM WILL WEAKENING AS IT APPROACHES THE REGION.

THE QUESTION WILL BE JUST HOW MUCH RETURN FLOW NEAR 850MB THE
SYSTEM CAN GENERATE OVER THE REGION. THE STRONGER THIS RETURN FLOW
IS...THE BETTER THE LOW LEVEL MOISTURE/ISENTROPIC LIFT WILL BE
FOR PRECIPITATION. THE LOW LEVEL AIRMASS WILL CERTAINLY BE COLD
ENOUGH FOR FREEZING RAIN OR SLEET BY THURSDAY NIGHT AND FRIDAY
MORNING...AND THE MAIN UNCERTAINTY IS THE PRECIPITATION COVERAGE
WHICH HINGES ON AN ACCURATE 500MB FORECAST OF A SMALL SCALE
FEATURE 100 HOURS OUT. WHAT WE CAN SAY IS THAT THE BEST CHANCE OF
PRECIP IS ACROSS CENTRAL AND SOUTHEAST TEXAS...WHERE GULF MOISTURE
IS MOST LIKELY TO RETURN EVEN WITH A WEAKER SYSTEM. RIGHT NOW WE
WOULD ESTIMATE BASED ON ALL MODEL FORECASTS THERE IS ABOUT A 1 IN
5 CHANCE OF WINTER PRECIP IN OUR CWA THURSDAY NIGHT AND FRIDAY
MORNING. UNFORTUNATELY THE PUBLIC RESPONSE TO A MERE MENTION OF A
20 PERCENT CHANCE OF WINTER PRECIP ON DAY 5 SEEMS TO IGNORE THE
FACT THAT IT MEANS THERE IS AN 80 PERCENT CHANCE OF NOTHING
OCCURRING. THEREFORE...THERE IS JUST NOT ENOUGH CONFIDENCE YET TO
ADVERTISE FREEZING RAIN IN THE OFFICIAL FORECAST...AND WE WILL
NEED TO SEE SOME RUN TO RUN CONSISTENCY FROM THE GFS AND/OR
ANOTHER MODEL TO JUMP ON BOARD BEFORE FIRING UP THE WINTER WEATHER
PANIC MACHINE. HOWEVER...WILL ADD IN A 20 PERCENT CHANCE OF LIQUID
RAIN THURSDAY AFTERNOON AND EVENING OVER THE SOUTHERN PARTS OF
THE AREA...BUT END PRECIP CHANCES BEFORE TEMPS DROP BELOW FREEZING
TO AVOID THE ISSUE. HIGHS FRIDAY LOOK TO BE COLD WITH CLOUD COVER
AND POSSIBLE PRECIPITATION AND HAVE UNDERCUT GUIDANCE BY SHOWING
MOST OF THE ENTIRE AREA ONLY IN THE LOW 40S. AGAIN THIS PART OF
THE FORECAST BEARS CLOSE WATCH.

CLEARING SKIES SHOULD OCCUR BY FRIDAY NIGHT AS NORTHWEST FLOW
ALOFT RETURNS. WESTERLY LOW LEVEL FLOW WILL RESULT IN A RAPID
MODERATION OF TEMPS SATURDAY AND SUNDAY WITH HIGHS REBOUNDING INTO
THE MID 50S TO MID 60S.

Houston/Galveston:
THE LAST HAZARD OF CONCERN WILL BE ASSOCIATED WITH A COASTAL
TROUGH THAT WILL FORM LATE IN THE WEEK. THE GFS AND ECMWF DIFFER
A BIT...BUT BOTH SHOW INCREASING ISENTROPIC LIFT LEADING TO LIGHT
RAIN OVER SPREADING THE FORECAST AREA ON THURSDAY. A VERY COLD
AIRMASS WILL THEN PUSH INTO THE PLAINS ON FRIDAY AND SATURDAY. THE
COLD AIR MAY ARRIVE IN TIME FOR FREEZING RAIN EARLY FRIDAY MORNING
AND THEN AGAIN EARLY SATURDAY MORNING OVER THE FAR NORTHERN
COUNTIES...MAINLY NORTH OF A LINE FROM MADISONVILLE TO COLDSPRING.
THERE IS A LOT OF UNCERTAINTY WITH TIMING AND WILL ONLY GO WITH A
SLIGHT CHANCE OF FREEZING RAIN MIXED WITH RAIN IN THESE LOCATIONS
FRIDAY AND SATURDAY MORNINGS. ONSHORE WINDS WILL THEN HELP BRING
WARMER CONDITIONS OVER THE WEEKEND AS THE COASTAL SYSTEM PUSHES
OFF TO THE EAST.

San Angelo:
END OF THE WEEK CONTINUES TO LOOK MUCH COLDER. HAVE CONTINUED TO
TREND DOWN TEMPERATURES.

BOTH THE GFS AND THE ECMWF SURGE A VERY COLD AIR MASS THROUGH THE
CENTRAL PLAINS AND INTO WEST CENTRAL TEXAS ON THURSDAY, AS A NEARLY
1050MB SURFACE HIGH PRESSURE MOVES INTO THE AREA. THE GFS IS NOW THE
COLDER OF THE MODELS FOR THURSDAY AND FRIDAY, AND ALTHOUGH GIVEN THE
MODEL UNCERTAINTY ON TEMPERATURES, WILL OP TO TAKE THE READINGS DOWN
FOR THURSDAY AND FRIDAY ANOTHER 5 DEGREES OR SO. STAYING SOMEWHERE
IN BETWEEN THE GFS AND ECMWF SEEMS TO HAVE BEEN A DECENT SOLUTION.

GFS IS ALSO BREAKING OUT SOME DECENT PRECIPITATION TOTALS, AS A WEAK
DISTURBANCE PASSES AND COMBINES WITH ISENTROPIC LIFT OVER THE
FRONTAL BOUNDARY. ECMWF IS DRIER, SURGING THE COLD AIR THROUGH THE
AREA QUICKER AND THUS ENDS UP WITH LESS CLOUDCOVER AND SLIGHTLY
WARMER TEMPERATURES. AT THIS POINT, OPTED TO INCLUDE A MENTION OF
LIGHT RAIN ACROSS THE I-10 CORRIDOR FOR THURSDAY ALONG AND JUST
BEHIND THE FRONT. KEPT IT DRY FARTHER NORTH FOR NOW, BUT WILL NEED
TO MONITOR AS ANY PRECIPITATION FARTHER NORTH COULD BE IN THE FORM
OF FREEZING RAIN. EXPERIENCE HERE SUGGESTS THAT WITHOUT A
SIGNIFICANT DISTURBANCE TO THE WEST, COLD AIR WILL SURGE SIMILARLY
TO WHAT THE ECMWF SHOWS AND MORE LIKELY TO CUT THE PRECIPITATION OFF
BEFORE THE FREEZING TEMPERATURES ARRIVE. WILL WATCH VERY CLOSELY
THOUGH.

Shreveport:
ARCTIC AIRMASS WILL DEFINITELY FOLLOW THE THURSDAY FRONT...WHICH
OPENS UP THE POSSIBILITY FOR WINTRY PRECIP THURSDAY NIGHT AND
AGAIN FRIDAY NIGHT. CURRENT THINKING IS THAT RAIN SHOULD END PRIOR
TO LOCATIONS FALLING BELOW FREEZING AS THE BEST CHANCES FOR PRECIP
SHOULD REMAIN ACROSS THE SRN ZONES. THUS...GRIDS DO DEPICT PRECIP
CHANCES WITH BELOW FREEZING MIN TEMPS...BUT POPS/WX TYPES MATCH
BETTER WITH THE HOURLY TRENDS. DO NOT HAVE VERY HIGH CONFIDENCE
FOR WINTRY PRECIP OCCURRING. HOWEVER...IT IS TOO CLOSE TO CALL
GIVEN THE TIME FRAME SO THE SITUATION WILL NEED TO BE MONITORED
CLOSELY. /09/

[unome]

great blog post from Conley Isom, Texas Storm Chasers

http://www.texasstormchasers.com/2014/0 ... -thursday/

a snippet:

the last four runs of the GFS model as of Sunday afternoon. The timing is Friday morning. On Saturday, the model showed only light rain in south Texas and cold, dry for everyone else. Then out of no where, it started showing all this moisture coming in from the west and widespread rain along with freezing rain, sleet, and snow. I don’t believe the winter weather scenarios and neither should you. Until it consistently shows it, very little weight is given. The rest of the computer models, including the European, have rain but no winter weather

Could we see winter weather in parts of the state by Friday? Sure but the odds are 10%, meaning there is a 90% chance it won’t even happen. Computer models will change over the next several days and we will be watching.

[srainhoutx]

Another chilly morning here in NW Harris County where temperatures have dropped to the mid 30's. Those temperatures will rebound nicely today ahead of a re inforcing cold front arriving tonight with an even colder front arriving Thursday as a fast progressive NW flow remain the theme this week. The Marathon weather still looks nice for the runners, but yet another front may arrive late Sunday into Monday continuing the dry weather pattern.

Changes are beginning to show up in the longer range computer guidance suggesting that a broad trough will develop across North America as the Western Ridge breaks down and that pesky -EPO/-WPO regime becomes re established and a strong Ridge develops across the Gulf of Alaska and noses all the way into the interior of our 49th State. The deterministic and ensemble guidance are once again developing a pattern that looks very similar to what we witnessed beginning in mid last November and continued into early January. While it is likely that we have seen the 'coldest' air of our Winter Season, it certainly does not mean winter is over. If such a pattern does in fact does develop toward the end of January/early February, climatology suggests our greatest threats for wintry weather are just ahead as upper air disturbances ride S along or just W of the Inter Mountain West into the base of the trough tapping Gulf moisture allowing precip albeit somewhat light to develop across our Region and strengthen as those storm systems organize over Colorado/New Mexico/Texas and Oklahoma and turn NE. Enjoy the relative warm/dry weather while it lasts. Changes may well be lurking in about a 7-10 days.

Actually the longer range GFS and Euro were 'sniffing' a disturbance and a trough to out W last week. So this 'out of nowhere' notion is not completely correct.

[skidog40]

get out the snow shovel. i can feel this one. i checked all forecast and you can tell their leaning towards some winter precip

[ronyan]

The 0z GFS has a 1043 mb high moving into TX Thursday night and has dropped temps for Houston a few degrees. The latest meteogram for 2m has IAH down to 26F Thursday night with a litle precip after we drop below freezing. Models still don't have a great handle on this situation yet and I expect to see further changes as we get closer to the 3-day time frame.

[srainhoutx]

A challenging weather week forecast continues to develop across our Region. A strong front will push through this afternoon and set the stage for at least a light freeze Tuesday night/early Wednesday.

Attention then turns to our NW where a rather strong upper air disturbance drops S over the Great Basin to near Las Vegas and taps into a piece of much colder Arctic air that will drop into the Great Lakes and the Mid West as a piece of the Polar Vortex once again heads very far S from its normal location NW of Hudson Bay in Canada. The GFS as well as the Euro are in agreement that the upper air feature is a bit stronger, but differ on the temperature profiles at the surface which lead to the forecasting challenges. What we do know is a secondary shot of Arctic air will begin to push S across Texas Wednesday night/Thursday morning. This Arctic boundary does appear to stall just offshore of Coastal Texas/Louisiana as the main trough and very cold air is to our NE. Both the GFS and the Euro suggest a Coastal trough/low will develop across the near shore Gulf waters of S Texas where over running precip will develop after the shallow Arctic air mass is in place. The GFS suggests a 1040mb + Arctic high pressure cell will keep cold air advecting into Central/SE Texas and Western Louisiana allowing sub freezing temperatures at the surface to develop during the over night hours of Thursday mainly N of I-10 while light precip in the form of drizzle or light rain would have time to freeze on elevated surfaces. There is a slight chance that temperatures could fall to 32 degrees in Houston proper which could create all kind of travel issues, if that where to occur. What we do not know as of Monday morning is exactly how all of this will actually unfold for a Thursday night/early Friday morning forecast. The best chance of any wintry mischief does appear to be a Southern half of Texas and Louisiana event, so it is worth monitoring. Meanwhile, stay tuned and we will keep a close eye on all this potential Winter Weather Worries over the next several days.

[nuby3]

Just wanted to thank everyone in here for the quality of this forum. even paul Robison, although ridiculous as all get out, incredibly entertaining.

[srainhoutx]

While it is a bit too far out in time for my comfort level of the 12Z NAM/WRF, that short range meso model is suggesting a strong 1050mb+ Arctic High dropping S from Canada into Eastern Montana/Western N Dakota and heading S into the Plains. To its W our short wave or upper air disturbance is dropping S from British Columbia into the Great Basin.

[redneckweather]

Y'all do wxman will be in here shortly and totally squash any idea of cold weather and icy conditions for us here in Southeast, Texas correct?

Also, if the word SNOW enters the chatter, please ignore that completely. There is no such thing as snow in Southeast, Texas. It's merely a teaser word that has let us down time after time after time after time. I even got shafted in my neck of the woods during the Christmas Miracle in 2004. Didn't even see a snow grain out of that system.

[srainhoutx]

Y'all do wxman will be in here shortly and totally squash any idea of cold weather and icy conditions for us here in Southeast, Texas correct?

Also, if the word SNOW enters the chatter, please ignore that completely. There is no such thing as snow in Southeast, Texas. It's merely a teaser word that has let us down time after time after time after time. I even got shafted in my neck of the woods during the Christmas Miracle in 2004. Didn't even see a snow grain out of that system.

Actually wxman57 will be traveling starting tomorrow through Friday across the Central and NE Gulf Coast. That said I suspect he will be here shortly to tell us there is a chance of freezing rain in Houston early Friday...but snow chances even being mentioned would seem highly unlikely. This looks like an Freezing drizzle/freezing rain event as the primary wintry weather maker, if it even unfolds. The fly in the ointment will be just where and how close to the Coast the Coastal trough develops. Further off shore mean less precip further inland. Closer to the Coast with that trough would mean areas along and S of the I-35 Corridor may have a chance of the over running precip. We will see.

[redneckweather]

Yep, like I said...these arctic hp's are useless. Either they bring dry nose bleed cold weather or freezing rain events. Both totally useless and do nothing but harm. Oh well. Hopefully we can get this one out of the way quickly so Spring can get here sooner than later.

[wxman57]

The correct word is "quash" (meaning suppress) not "squash", by the way. No quashing here, except that I think that snow is pretty much out of the question. I think Houston could see temps near freezing with light rain on Friday morning. Maybe a light accumulation of ice on trees and other elevated surfaces. Streets should be OK.

[skidog40]

weather channel and intellicast has chances for snow posted

[srainhoutx]

weather channel and intellicast has chances for snow posted

The 12Z GFS suggests light freezing drizzle/rain with some sleet extending from Del Rio to Beaumont.

[wxman57]

12Z GFS has light freezing rain and sleet here Friday morning. Most precip to our west. Up to 1/2" freezing rain NW of Victoria. About 1/10 to 1/4" freezing rain into San Antonio/Austin. Snow west of there.

[Portastorm]

Should the 12z GFS verify, looks to me like a nasty weather day Friday here in Austin. Combined mix of light freezing rain and sleet. It won't take much to send traffic into chaos, even a 1/10th to 1/4 amt.

[ticka1]

what timeframe we looking at the freezing rain here in se texas?

[srainhoutx]

what timeframe we looking at the freezing rain here in se texas?

The most likely time frame would be during the overnight hours of Thursday into Friday morning. Perhaps a brief change to just rain before temperatures fall to near freezing Friday evening again. That said the MOS text data for IAH is suggest we may not get too much above 36F-38F on Friday, so a lot remains to be determined.

[MontgomeryCoWx]

If IAH will be hovering around Freezing, you can bet my area of Montgomery County will be 4-7 degrees colder. I may not be driving into the city on Friday.