February 1-5, 2011 Arctic Blast/Winter Storm Discussion

[weatherguy425]

It's kind of sad, I mean the colder air is already starting to creep across the border, with temps nearing -50 in east central canada.

[wxman57]

12Z Canadian is in on the ewall site:
http://www.meteo.psu.edu/~gadomski/CMC_12z/cmcloop.html

It has strong low-level warm advection across SE TX on Thu/Fri. That would mean cold rain if it's right, not snow. It does indicate snow for west-central TX - north of the Hill Country where the cold air will be deeper. And if it's right, it has 850 mb temps about 15-20C warmer than the GFS, so no hard freeze. I am skeptical about the Canadian, though.

[srainhoutx]

Concern grows for the Lower Rio Grande Valley if the 12Z GFS ensembles are correct...

[ronyan]

12Z Canadian is in on the ewall site:
http://www.meteo.psu.edu/~gadomski/CMC_12z/cmcloop.html

It has strong low-level warm advection across SE TX on Thu/Fri. That would mean cold rain if it's right, not snow. It does indicate snow for west-central TX - north of the Hill Country where the cold air will be deeper. And if it's right, it has 850 mb temps about 15-20C warmer than the GFS, so no hard freeze. I am skeptical about the Canadian, though.

If it's varying by that much in one run why should we give it any validity? It still has the 1060+ mb high entering the US.

[ronyan]

Why did it double my post after editing?
Sorry about that.

[srainhoutx]

It happens sometimes royan. I deleted the double post for you.

[ronyan]

It happens sometimes royan. I deleted the double post for you.

Thanks srain.
Is there a site where the euro can be viewed as it's coming out?

[srainhoutx]

It happens sometimes royan. I deleted the double post for you.

Thanks srain.
Is there a site where the euro can be viewed as it's coming out?

It's going to be colder...

http://www.meteo.psu.edu/~gadomski/ECMW ... floop.html

01292011 12Z Euro f96.gif

01292011 12Z Euro f120.gif

01292011 12Z Euro f144.gif

01292011 12Z Euro f168.gif

[srainhoutx]

HPC:

...UPPER LOW MOVING FROM N. CALIFORNIA TO TEXAS THROUGH THE
PERIOD...

PREFERENCE: UKMET

EVOLUTION OF THIS SYSTEM IS ALMOST ENTIRELY DEPENDENT UPON
INFLUENCES FROM THE SHORTWAVE TROUGH OVER BRITISH COLUMBIA (SEE
SYSTEM ABOVE)...WITH THE 00Z ECMWF MORE PROGRESSIVE THAN THE GFS
WITH THE LOW CROSSING THE SOUTHERN ROCKIES...AND THE NAM LIKE THE
GFS EXCEPT MORE AMPLIFIED...WHICH MAY BE DUE TO INITIALIZING THE
CENTER OF THE LOW OFFSHORE SLIGHTLY WEST OF ITS ACTUAL
POSITION....BUT NOT UNREASONABLY SO AS TO RULE IT OUT. GIVEN
PREFERENCES FOR THE SYSTEM DESCRIBED ABOVE...THE MOST PREFERRED
SOLUTION IS BOUNDED BY FASTER ECMWF AND THE SLOWER GFS...WHICH IS
CLOSET TO THE UKMET. FINALLY...THE NEW CANADIAN HAS TRENDED EVEN
FASTER THAN THE UKMET...WHICH PLACES THE UKMET CLOSER TO THE MODEL
CONSENSUS.

...SHORTWAVE TROUGH MOVING FROM TEXAS TO FLORIDA TONIGHT THROUGH
MONDAY...

PREFERENCE: UKMET

[srainhoutx]

And so it begins...

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
1243 PM CST SAT JAN 29 2011

TXZ171>173-183>194-202>209-217>225-228-292145-
LLANO-BURNET-WILLIAMSON-VAL VERDE-EDWARDS-REAL-KERR-BANDERA-
GILLESPIE-KENDALL-BLANCO-HAYS-TRAVIS-BASTROP-LEE-KINNEY-UVALDE-
MEDINA-BEXAR-COMAL-GUADALUPE-CALDWELL-FAYETTE-MAVERICK-ZAVALA-
FRIO-ATASCOSA-WILSON-KARNES-GONZALES-DE WITT-LAVACA-DIMMIT-
INCLUDING THE CITIES OF...LLANO...BURNET...GEORGETOWN...DEL RIO...
ROCKSPRINGS...LEAKEY...KERRVILLE...BANDERA...FREDERICKSBURG...
BOERNE...BLANCO...SAN MARCOS...AUSTIN...BASTROP...GIDDINGS...
BRACKETTVILLE...UVALDE...HONDO...SAN ANTONIO...NEW BRAUNFELS...
SEGUIN...LOCKHART...LA GRANGE...EAGLE PASS...CRYSTAL CITY...
PEARSALL...PLEASANTON...FLORESVILLE...KARNES CITY...GONZALES...
CUERO...HALLETTSVILLE...CARRIZO SPRINGS
1243 PM CST SAT JAN 29 2011

...MUCH COLDER WEATHER COMING NEXT WEEK...

MUCH COLDER WEATHER IS COMING TUESDAY THROUGH FRIDAY OF NEXT WEEK...
WITH A HARD FREEZE EXPECTED TUESDAY NIGHT...WEDNESDAY NIGHT...AND
THURSDAY NIGHT. AN ARCTIC COLD FRONT WILL MOVE ACROSS SOUTH
CENTRAL TEXAS ON TUESDAY. THE COLD AIR THAT AFFECTS THE AREA
TUESDAY THROUGH FRIDAY OF NEXT WEEK IS EXPECTED TO BE THE COLDEST
SO FAR THIS WINTER SEASON FOR SOUTH CENTRAL TEXAS.

BEFORE THE COLD WEATHER ARRIVES...A DISTURBANCE WILL BRING A
CHANCE OF RAIN LATER TODAY AND TONIGHT. SHOWERS AND THUNDERSTORMS
ARE POSSIBLE TONIGHT NEAR AND EAST OF A BURNET TO HONDO TO CATARINA
LINE. A FEW STRONG THUNDERSTORMS ARE POSSIBLE TONIGHT MAINLY IN
AN AREA EAST OF INTERSTATE 37 AND SOUTH OF INTERSTATE 10.

AFTER THE DISTURBANCE MOVES EAST OF SOUTH CENTRAL TEXAS SUNDAY
MORNING...SOME BRIEF PATCHY EARLY MORNING FOG WILL GIVE WAY TO
MOSTLY SUNNY AND WARM CONDITIONS SUNDAY AFTERNOON. THE BRIEF
WARMING TREND SUNDAY THROUGH MONDAY WILL END QUICKLY TUESDAY
AND TUESDAY NIGHT WITH THE ARCTIC COLD FRONT.

SEVERAL NIGHTS WITH HARD FREEZES ARE EXPECTED TUESDAY NIGHT...
WEDNESDAY NIGHT...AND THURSDAY NIGHT NEXT WEEK. INITIALLY ON
TUESDAY A CHANCE OF COLD RAIN AND SHOWERS IS EXPECTED FROM A
DISTURBANCE PASSING JUST NORTH OF SOUTH CENTRAL TEXAS. AS THE
DISTURBANCE MOVES EAST...MUCH COLDER AIR WILL SPILL ACROSS THE
REGION DURING THE DAY ON TUESDAY AND TUESDAY NIGHT. WINDY AND COLD
CONDITIONS WILL COME WITH THE COLD FRONT AND CONTINUE TUESDAY
NIGHT...WITH LOWS TUESDAY NIGHT BELOW FREEZING. FREEZING
TEMPERATURES WILL RETURN WEDNESDAY NIGHT AND THURSDAY NIGHT.

DAYTIME HIGHS ON WEDNESDAY ARE EXPECTED TO BE IN THE 30S ACROSS
THE HILL COUNTRY TO NEAR 40 AND LOW 40S OVER ADJACENT PARTS OF
SOUTH CENTRAL TEXAS. BY FRIDAY AFTERNOON HIGHS IN THE 40S TO
NEAR 50 ACROSS THE HILL COUNTRY AND NEAR 50 TO LOWER 50S ACROSS
ADJACENT PARTS OF SOUTH CENTRAL TEXAS ARE EXPECTED.

PRECAUTIONS TO PROVIDE PROTECTION FOR TENDER PLANTS...PIPES...AND
OUTDOOR PETS FOR NEXT WEEKS COLD TEMPERATURES BEGINNING TUESDAY
AND CONTINUING THROUGH THURSDAY AND FRIDAY IS ADVISED.

[srainhoutx]

The Euro and the GFS ensembles suggest another Arctic intrusion will follow our next week event.

[weatherguy425]

Srain- how long before the Euro's 2m temps can be looked at?

[TexasBreeze]

For grins:
http://www.srh.noaa.gov/data/Guidance/G ... KIAH.1.txt
19 degrees is low and it looks mighty cold to me!

[srainhoutx]

Srain- how long before the Euro's 2m temps can be looked at?

That data is restricted to pay pre view customers and is copyrighted. Someone that has access to that data may want to share a brief thumbnail sketch of what they show. Oh and here is our next Arctic Intrusion...

01292011 12Z f216.gif

01292011 12Z Euro f240.gif

[srainhoutx]

HPC Final Update:

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
129 PM EST SAT JAN 29 2011

VALID 12Z TUE FEB 01 2011 - 12Z SAT FEB 05 2011



..WIDESPREAD MAJOR WINTER STORM TO IMPACT THE PLAINS TO THE
NORTHEAST THIS WEEK...

LATEST MODELS AND ENSEMBLE MEANS MAINTAIN A STRONG MEAN RIDGE FROM
THE ERN PAC NWD THRU THE PERIOD ALTHOUGH SOME CHANGES IN SHAPE
OCCUR AS SHRTWVS ROUND THE RIDGE. ASSOC POSITIVE HGT ANOMALIES
ARE FCST TO BE STRONGEST OFF THE PAC NW COAST BY D+8. FAIRLY
CONSISTENT WITH TELECONNECTIONS RELATIVE TO THIS FEATURE...
GUIDANCE DISPLAYS AN ELONGATED MEAN TROF FROM ERN CANADA SWWD.
ONE OR MORE INSTANCES OF FLOW SEPARATION WITHIN THIS MEAN TROF
WILL CONTINUE TO ADD TO TYPICAL DETAIL UNCERTAINTIES.

WITH THE MAJOR STORM SYSTEM FCST TO TRACK NEWD FROM THE PLAINS TUE
ONWARD... MODELS AND ENSEMBLES HAD BEEN SHOWING SIGNIFICANT SPREAD
AND CONTINUITY CHANGES RECENTLY BUT OVER THE PAST 24 HRS APPEAR TO
BE STARTING TO CONVERGE TOWARD A COMMON SOLN THOUGH SOME
TRACK/TIMING DIFFS REMAIN. GFS RUNS HAVE STABILIZED OVER THE PAST
DAY WHILE THE 12Z AND NEW 00Z ECMWF RUNS HAVE ADJUSTED STEADILY
EWD FROM THE 00Z/28 RUN THAT HAD DEFINED THE WRN SIDE OF THE SOLN
ENVELOPE. MEANWHILE THE UKMET IS ON THE FASTER SIDE OF THE SPREAD
OVER THE ERN STATES AND BY EARLY THU THE CANADIAN BECOMES SLOWER
THAN THE GUIDANCE AVERAGE OFF THE NERN COAST. THE 00Z GEFS/12Z
ECMWF ENSEMBLE MEANS PROVIDE A GOOD COMPROMISE FOR TRACK/TIMING
AND ALSO FOLLOW PREVIOUS CONTINUITY EXTREMELY WELL... SO THEIR
SOLNS ARE RECOMMENDED FOR THIS SYSTEM.

WITH UPSTREAM FLOW THE GFS COMPARES LEAST FAVORABLY TO ENSEMBLE
CLUSTERING AND MOST OTHER MODELS. THE GFS FEEDS A LOW CONFIDENCE
WRN CANADA SHRTWV INTO THE MEAN TROF OVER THE WEST BY WED AND IS
RELATIVELY FAST/AMPLIFIED WITH ENERGY EJECTING ACROSS THE
CNTRL-ERN STATES BY DAYS 5-7 THU-SAT. BY LATE IN THE FCST THE
GEFS MEAN ALSO BECOMES RATHER AMPLIFIED WITH ITS ERN CONUS TROF.
TELECONNECTIONS RELATIVE TO THE ERN PAC MEAN RIDGE FAVOR HOLDING
DOWNSTREAM NEGATIVE HGT ANOMALIES FARTHER WWD THAN INDICATED BY
THE GEFS MEAN AT THAT TIME. MEANWHILE UNCERTAINTY WITH EXACTLY
HOW FLOW WILL EVOLVE OVER THE SWRN CONUS/NWRN MEXICO FAVORS
GREATER WEIGHTING OF ENSEMBLE MEANS VERSUS ONE INDIVIDUAL MODEL
RUN. THE 00Z ECMWF COMPARES BETTER TO ENSEMBLE MEANS THAN THE GFS
BUT THE ECMWF MAY BECOME TOO DEEP WITH ITS NWRN MEXICO CLOSED LOW
BY DAY 6 FRI IN LIGHT OF SOME FCST HGT ANOMALIES REACHING 3-4
STDEVS BELOW NORMAL.

THE DAYS 3-5 TUE-THU FCST STARTS WITH A BLEND OF THE 00Z GEFS/12Z
ECMWF ENSEMBLE MEANS TO REFLECT PREFERENCES WITH THE SYSTEM
AFFECTING THE ERN HALF OF THE CONUS. THIS SOLN COMPARES WELL TO
OTHER GUIDANCE IN PRINCIPLE WITH STRONG HIGH PRESSURE BUILDING
OVER THE CNTRL-WRN STATES. DAYS 6-7 FRI-SAT USE A 70/30 BLEND OF
THE 12Z ECMWF MEAN/00Z ECMWF AS THE ECMWF MEAN COMPARES BETTER TO
TELECONNECTIONS THAN THE GEFS MEAN. MINORITY WEIGHTING OF THE 00Z
ECMWF PROVIDES A LITTLE ADDED DETAIL WHILE DOWNPLAYING ITS LOWER
CONFIDENCE ATTRIBUTES.

MORNING PRELIM UPDATES BLEND EQUAL AMOUNTS OF 00Z GFS AND ECMWF
ENSEMBLE MEANS. THIS SIMPLIFICATION RESULTS IN THE SAME PATTERNS
OF THE PREVIOUS OVERNIGHT BLENDS.

...AFTERNOON UPDATE...
NEW 12Z GFS IS MORE PROGRESSIVE WITH THE MID LEVEL TROF AFTER DAY
4 WED THAN PRIOR RUNS AND OTHER MODELS AND ITS ENS MEAN. 12Z
CMC/UKMET AND ENS MEANS REMAIN PREFERRED. NO CHANGES TO AFTERNOON
FINALS FROM PRIOR HPC PRELIM PROGS.

EXPECT A BROAD HEAVY SNOW SWATH FROM THE CENTRAL PLAINS EAST AND
NORTHEAST NORTH OF THE OH RIVER AND MASON DIXON LINE TUESDAY INTO
WEDNESDAY WITH VERY FAVORABLE UPPER LEVEL JET COUPLING. HEAVY
RAINS SOUTHWARD ACROSS THE LOWER MS AND TN VALLEYS TUESDAY AND
WEDNESDAY.

WITH MASSIVE HIGH PRESSURE PUSHING DOWN THRU THE PLAINS WITH TEH
COLDEST AIR DAMMED AGAINST THE ROCKIES EXTREME COLD WILL SET INTO
THE PLAINS WITH NEGATIVE ANOMALIES NEAR OR BELOW 30 DEGREE
DEPARTURES FROM NORMAL YIELDING A HUGE AREA OF NEAR AND BELOW ZERO
TEMPERATURES READINGS DAY AND NIGHT TUESDAY AND WEDNESDAY.
CONSIDERABLE COLD AIR WILL SPILL OVER THE ROCKIES INTO THE GREAT
BASIN AND TO THE WEST COAST WITH TEMPERATURES WELL BELOW NORMAL
INTO LATE WEEK.
RAUSCH/ROSENSTEIN

[Andrew]

Srain- how long before the Euro's 2m temps can be looked at?

That data is restricted to pay pre view customers and is copyrighted. Someone that has access to that data may want to share a brief thumbnail sketch of what they show. Oh and here is our next Arctic Intrusion...

01292011 12Z f216.gif

01292011 12Z Euro f240.gif

Euro is showing around 27 or so for lows

[srainhoutx]

The 18Z NAM continues to advertize a rather suppressed solution of the Upper Low deep into N MX and is still running much colder than normal for that typically warm biased model...off for an evening of much needed R and R...I'm sure the evening/night crew will be active with severe chances ahead over night and all this cold marching S...

01292011 18Z nam_pcp_066l.gif

01292011 18Z NAM_221_2011012918_F75_SNOWIN_SURFACE.png

[Mr. T]

12z GFS MOS has a low of 19 degrees friday morning, which is a number geared towards climatology... Wow!

It'll be interesting to see what the NWS does with its favorite guidance now indicating teens across the area.

[Mr. T]

This airmass looks several degrees colder on the 12z GFS than the Jan 2010 arctic outbreak. Recall IAH reached 20 degrees with Hooks and Sugar Land reaching 16 degrees.

http://www.meteo.psu.edu/~gadomski/NARR/2010/us0109.php

During that outbreak, the 850 temp only dropped to -6, while the GFS is now forecasting a minimum 850 temperature of -11 for next week...

If you want to take the 12z GFS verbatim (and it might be too cold), then low to mid teens would be possible across the area with dewpoints expected to be in the single digits.

[Andrew]

Interesting to note on the CMC that with the overriding of the gulf moisture creating moisture while the 850mb temps back off we are still not to far off from ground level being at freezing. If the cmc was too warm in shifting the brunt of the energy out west but was right on the coastal low developing, well we could have some wintry weather.. That would be pretty cool.