November Weather Discussion. Rollercoaster Pattern.

[srainhoutx]

Checking some GFS forecasts for the Northern Rockies Region, I noticed Great Falls, MT is forecast to see a couple of -20 readings...

http://wxweb.meteostar.com/sample/sampl ... ?text=KGTF

[biggerbyte]

Brrrr!

[Andrew]

Not as cold for the GFS:

[srainhoutx]

Good Morning. Well the models have flipped back to a Wednesday frontal passage of the Arctic Boundary. There are some new details concerning an Upper Air feature rotating across TX under the base of the trough that will need to be watched. While the GFS is not as cold, the Euro has come in colder which is a 180 degree flip from what that model has been depicting. This should make for some interesting model watching as we get a bit closer to the event...

00Z GFS for Thansgiving...2 meter temps



Euro for Wednesday before Thanksgiving...850mb temp anomalies...



Euro 500mb Height Anomalies...



Finally, the GFS/Euro Upper Air comparison for hour 168...

[srainhoutx]

Also the HPC Prelim discussion gives an idea that things are far from set in stone regarding which model has the right idea...

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
320 AM EST THU NOV 18 2010

VALID 12Z MON NOV 22 2010 - 12Z THU NOV 25 2010

UPPER FLOW OVER THE CONUS EARLY NEXT WEEK GENERALLY FEATURES A
TROUGH IN THE WEST WITH RIDGING IN THE EAST... THANKS TO A
PERSISTENT/STRONG UPPER RIDGE NEAR THE GULF OF ALASKA. HOWEVER...
AS THE PATTERN BREAKS DOWN IN THE PACIFIC BY MIDWEEK... THE MODELS
SHOW SOME WAVERING AS TO HOW MUCH ADDITIONAL ENERGY DROPS DOWN
FROM THE CANADIAN VORTEX AND THROUGH THE INTERIOR PAC NORTHWEST...
IF AT ALL... BY TUE/D6. THE 00Z ECMWF/GFS BRIEFLY PUSH THE ARCTIC
AIRMASS THROUGH THE NORTHERN ROCKIES BEFORE SHUNTING IT EASTWARD
INTO THE PLAINS AND TOWARD THE GREAT LAKES/NORTHEAST BY THU/D7...
THANKSGIVING DAY. THE 00Z CANADIAN/UKMET... LIKE THE PREVIOUS TWO
RUNS OF THE ECMWF... DIVE THE ENERGY SOUTHWARD INTO THE GREAT
BASIN BEFORE SLIDING IT EASTWARD. BOTH THE 00Z GEFS AND 12Z ECMWF
ENSEMBLE MEANS SHOW A MUCH TEMPERED VERSION OF THE 00Z
CANADIAN/UKMET BY MIDWEEK... WITH THE RIDGE AXIS NEAR 130W AND
TOWARDS SE ALASKA AND THE DOWNSTREAM POSITIVELY TILTED TROUGH FROM
THE UPPER MIDWEST SOUTHWESTWARD TOWARD THE LEE OF THE ROCKIES.
THIS ALSO FOLLOWS CONTINUITY AND WAS THE PREFERRED PRELIM
SOLUTION. FOLLOWED THE 12Z ECMWF ENSEMBLE MEAN ALMOST EXCLUSIVELY
FOR THE MEDIUM RANGE PERIOD THOUGH THE 00Z GEFS MEAN WAS A CLOSE
SOLUTION AS WELL.



FRACASSO

Euro Ensemble 500mb...




GGEM (Canadian) Ensemble 500mb...





00Z Canadian...and snowcover charts...

[srainhoutx]

Updated HPC Prelim discussion is painting an interesting scenario regarding the models and the Upper Air feature lagging in the SW next week...

...UPDATED MORNING PRELIMS...
A CHANGE IN CONTINUITY IS PREFERRED FROM THE OVERNIGHT PROGS AS
06Z GFS HAS BECOME MORE SIMILAR TO THE 00Z ECMWF AND PRIOR MODEL
RUNS HOLDING THE SOUTHWESTERN TROF WESTWARD OF OVERNIGHT MODEL
PROGRESSION. CONTINUITY AND A LAGGED AVERAGE FORECAST WOULD ALSO
SLOW THE TROF DOWN. LATEST MODEL RUNS AT ANY TIME FROM DAY 6 AND
ONWARD ARE NOT NECESSARILLY CORRECT AND A LAGGED AVERAGE FORECAST
PERFORMS BETTER. IN THIS CASE THEY HOLD THE TROF WESTWARD AND
SLOWER. IN ADDITION A PATTERN CHANGE IS UNDER WAY WITH
RETROGRESSION OF THE EPAC STRONG POSITIVE ANOMALY AND PROGRESSION
OF HIGHER HTS INTO GREENLAND AND DAVIS STRAITS AND EVENTUALLY NRN
CANADA. THIS MORE OFTEN THAN NOT OCCURS WITH A CORRESPONDING SFC
WEATHER REFLECTION. IN THIS CASE ENOUGH ENERGY IS SWINGING
EASTWARD WITH THE TROF TO INDUCE A FRONTAL WAVE EJECTING NEWD
ALONG THE SFC FRONT INTO THE LOWER OH VALLEY EARLY WEDNESDAY WITH
A SIGNIFICANT LOW IN THE EASTERN GREAT LAKES THURSDAY.


THE MORE EXTREME SOLUTIONS OF DROPING LOWER HTS OR EVEN A CLOSED
LOW INTO THE GREAT BASIN TUES-WED ALTHOUGH EARLIER DISCOUNTED HERE
YTDA AND TDA BASED ON ENS MEANS AND OVERALL MODEL CONSENSUS MUST
STILL BE CONSIDERED AND WATCHED AS PER LAGGED AVERAGES AND LATEST
06Z GFS. THE EXTREME SOLUTION OF THE 00Z CMC IS NOT DISSIMILAR TO
THAT OF YTDAS 00Z AND 12Z ECMWF. THE RESULT OF THESE SOLUTIONS
WOULD BE NEAR OR RECORD COLD TEMPS WITH DEPARTURES OF BELOW 40
DEGREES FROM NORMAL WITH MID LEVEL HT STANDARDIZED HT ANOMALIES IN
THE 3.5 TO 4.5 FROM NORMAL RANGE. THIS THREAT IS ALSO SEEN BY THE
06Z GFS WHICH IS OUR PREFERRED SOLUTION FOR TODAY.


...OVERALL WEDNESDAY TRAVEL DAY AND THANKSGIVING DAY OUTLOOK...

MILD AND BREEZY WITH EASTERN CONUS WITH FRONTAL SHOWERS WED.
STRONG COLD FRONT WILL MOVE OFF GULF COAST WED NIGHT WITH COOLER
DRIER CONDITIONS WHILE CONTINUED MILD AND BREEZY WITH SHOWERS
ALONG THE EAST COAST THANKSGIVING DAY. THE FRONT WILL MOVE OFF THE
EASTERN SEABOARD LATE THURSDAY CLEARING SOUTH FLORIDA BY EARLY
FRIDAY WITH MUCH COOLER CONDITIONS.

SNOW...MAINLY LIGHT IS POSSIBLE ACROSS THE WESTERN GREAT LAKES
REGION AND UPPER MS VALLEY WEDNESDAY. QUITE COLD THROUGH THE
PLAINS INTO THE ROCKIES AND GREAT BASIN WEDNESDAY. WINDY AND COLD
BEHIND THE FRONT FROM THE UPPER MS VALLEY SOUTHWARD THRU THE SRN
PLAINS. SNOW MAY CONTINUE ON THE BACKSIDE OF THE SURFACE LOW
ACROSS THE GREAT LAKES REGION THURSDAY. SOME LIGHT SNOW OR SNOW
SHOWERS POSSIBLE ACROSS TEH UPPER MS VALLY/MIDWEST FRIDAY
OTHERWISE BASICALLY DRY AND QUITE COOL EAST OF THE ROCKIES
BECOMING WARMER OVER THE WEST AS MID LEVEL RIDGING RETURNS.
FRACASSO/ROSENSTEIN
±

[snowman65]

What about Tennessee now?? I am getting conflicting forecasts from weather.com, accuweather.com, Knoxville local news,,,,,Still too far out to know about mid week or turkey day?

[srainhoutx]

What about Tennessee now?? I am getting conflicting forecasts from weather.com, accuweather.com, Knoxville local news,,,,,Still too far out to know about mid week or turkey day?

Still too far out to know just yet.

[srainhoutx]

The differences in the 500mb pattern are really starting to show now. It will be interesting to see how all this unfolds...

12Z NAM...



06Z GFS...

[wxman57]

12Z GFS still brings the front through Wednesday evening. Cool/cold and dry on Thursday:

[srainhoutx]

Still some differences in the Upper Air Pattern at hour 144. The GEM (Canadian) holds enery back to our W a bit longer while the GFS is a bit faster and more progressive via 12Z guidance. We'll see what the Euro offers later...

[srainhoutx]

The 12Z GFS does suggest with some of the members that the Upper Air energy may hold back W just a bit...

[srainhoutx]

The 12Z CMC (Canadian Operational) is much slower with the Upper Air Feature, for what it's worth...

[srainhoutx]

The 12Z Euro has come in much different than we have seen from that model. It suggests a positive tilted trough passing our area with a robust Upper Air Feature deepening to our N (N TX) and is much colder looking as well...

[sambucol]

The 12Z Euro has come in much different than we have seen from that model. It suggests a positive tilted trough passing our area with a robust Upper Air Feature deepening to our N (N TX) and is much colder looking as well...

What does this mean for SE Texas?

[srainhoutx]

The main thing is frontal passage timing in our area. The Euro is about 12-16 hours slower with the front than the GFS. The HPC has noted this in the afternoon Final Update as it is somewhat similar to the Canadian with a deeper trough and slower frontal passage across TX. What is noteworthy regarding the Euro, is that it wants to hold some mighty chilly air in our part of the world longer as a big storm becomes wound up in th Ohio Valley Region.

[wxman57]

The 12Z Euro has come in much different than we have seen from that model. It suggests a positive tilted trough passing our area with a robust Upper Air Feature deepening to our N (N TX) and is much colder looking as well...

What does this mean for SE Texas?

Euro says quite windy and cold on Thanksgiving. Maybe temps holding in the mid to upper 40s with a 25-35 mph northerly wind (and higher gusts). Probably cloudy, too.

[helloitsb]

The 12Z Euro has come in much different than we have seen from that model. It suggests a positive tilted trough passing our area with a robust Upper Air Feature deepening to our N (N TX) and is much colder looking as well...

What does this mean for SE Texas?

Euro says quite windy and cold on Thanksgiving. Maybe temps holding in the mid to upper 40s with a 25-35 mph northerly wind (and higher gusts). Probably cloudy, too.

My favorite weather

[srainhoutx]

Some afternoon discussions from various NWS Offices in TX/OK/AR/LA...

Houston/Galveston...

GFS/ECMWF DIFFER A BIT WITH TIMING ON THE NEXT
COLD FRONT. THE GFS IS FASTER AND BRINGS THE FRONT THROUGH
WEDNESDAY EVENING WHILE THE ECMWF BRINGS THE COLD FRONT THROUGH
SOUTHEAST TEXAS THURSDAY MORNING. THE FRONT WILL TRIGGER SHOWERS
AS IT CROSSES THE AREA. PW VALUES INCREASE TO AROUND 1.5 INCHES BY
WEDNESDAY AFTERNOON. SOUTHEAST TEXAS WILL ALSO LIE IN A RIGHT REAR
QUAD OF A DEPARTING JET. HOWEVER...FORECAST SOUNDINGS SHOW A PESKY
CAP REMAINING IN PLACE SO CONFIDENCE IS LOW ON PRECIP COVERAGE.
LONG RANGE MODELS IN GOOD AGREEMENT WITH CLEARING BEHIND THE FRONT
AND CONSIDERABLY COLDER TEMPERATURES MOVING INTO THE REGION. LOWS
NEAR FREEZING WILL BE POSSIBLE BY NEXT FRIDAY MORNING.

Dallas/Ft Worth...

AS FOR THE COLD FRONT ARRIVING MID NEXT WEEK. TIMING IS HARD TO
PIN DOWN AT THE MOMENT...BUT SHOULD BECOME MORE CLEAR BY THE
BEGINNING OF THE NEXT WORK WEEK. THE AIRMASS WILL ORIGINATE AS A
COMBINATION OF ALASKAN AND NORTHERN CANADIAN AIR...WHICH IS
CURRENTLY RUNNING IN THE TEENS AND SINGLE DIGITS. OUR
EXPERIENCE...AND DETERMINISTIC MODEL BIAS WITH ARCTIC AIR
MASSES...INDICATE THAT THE ARCTIC FRONT WILL ARRIVE FASTER AND BE
COLDER THAN CURRENT GUIDANCE INDICATES. FOR THESE REASONS...WE/VE
DECIDED TO BRING THE ARCTIC FRONT THROUGH EARLY WEDNESDAY
FOLLOWING THE GFS TIMING...AND USE THE ECMWF THERMO PROFILE FOR
SURFACE TEMPERATURES AND WINDS ON THANKSGIVING DAY AND FRIDAY. WE
WILL ALSO LIMIT DIURNAL TEMP CHANGES BOTH DAYS WITH OVERNIGHT LOWS
FALLING INTO THE MID 20S TO LOWER/MID 30S...AND HIGHS ONLY IN THE
MID 40S TO MID 50S ON THURSDAY AND 50S ON FRIDAY. A WIDESPREAD
FREEZE IS EXPECTED ACROSS MUCH OF THE CWA BOTH MORNINGS.

SINCE THIS EVENT IS STILL A WAYS OUT...OUR CONFIDENCE IN
WEDNESDAYS FRONTAL TIMING IS MODERATE AT BEST AS IT COULD ARRIVE
TUESDAY NIGHT OR HANG UP UNTIL WEDNESDAY EVENING. AS FOR
TEMPERATURES BEHIND THE FRONT...OUR CONFIDENCE IS MUCH HIGHER THAT
THE AIR MASS WILL BE VERY COLD AND DENSE WHEN IT DOES ARRIVE.

Midland/Odessa...

TEMPERATURES ARE EXPECTED TO DROP
DURING THE MIDDLE OF NEXT WEEK AS A STRONG COLD FRONT MOVES
THROUGH THE AREA. THE OPERATIONAL MODELS ARE SHOWING SOME
DIFFERENCES WITH REGARDS TO THE TIMING OF THE NEXT COLD
FRONT...WITH THE ECMWF PERHAPS SHOWING A LITTLE MORE RUN-TO-RUN
CONTINUITY. FOR NOW...LITTLE CHANGES WERE MADE TO THE INHERITED
FORECAST AND PREFER TO WAIT FOR BETTER MODEL CONSISTENCY BEFORE
MAKING LARGE CHANGES TO THE FORECAST.



Tulsa...

ANOTHER COLD FRONT WILL MOVE INTO THE REGION MONDAY
NIGHT INTO TUESDAY AS A MID-LEVEL SHORTWAVE SWEEPS
ACROSS THE NORTHERN PLAINS. WILL KEEP CHANCES OF SHOWERS
AND THUNDERSTORMS IN THE FORECAST IN ASSOCIATION WITH
THIS FRONT MONDAY INTO TUESDAY. A MORE SIGNIFICANT COLD
FRONT IS EXPECTED TO MOVE THROUGH THE AREA WEDNESDAY
INTO WEDNESDAY NIGHT WITH THE PRECIPITATION ENDING
BEFORE THE TRULY COLD AIR INFILTRATES THE AREA LATE
WEDNESDAY NIGHT INTO THANKSGIVING MORNING.



Little Rock...

SEVERAL DISTURBANCES WILL MOVE THROUGH IN THE MEAN FLOW...AND
INTERACT WITH THE FRONT. THESE WILL PRODUCE SEVERAL WAVES OF
PRECIPITATION MONDAY NIGHT THROUGH LATE WEDNESDAY/EARLY THURSDAY. BY
LATE WEDNESDAY OR EARLY THURSDAY...FLATTENING OUT OF THE UPPER
RIDGE...ALONG WITH LOW PRESSURE DEVELOPING ALONG THE FRONT...WILL
ALLOW THE COLD FRONT TO PUSH THROUGH THE REMAINDER OF THE AREA.

BEHIND THE FRONT...COLD CANADIAN AIR WILL PUSH INTO THE REGION.
THURSDAY HIGHS WILL LIKELY STRUGGLE TO MAKE IT OUT OF THE 40S IN
MUCH OF THE AREA...WITH LOWS IN THE 20S TO NEAR FREEZING THURSDAY
AND FRIDAY MORNING.

WITH RESPECT TO THE FORECAST MODELS...THE GFS WAS A SLOWER SOLUTION
IN PREVIOUS RUNS...WITH THE EUROPEAN BEING MORE PROGRESSIVE. NOW...THE
TWO HAVE FLIP-FLOPPED...WITH THE EURO BEING MORE SLOW AND THE GFS
PUSHING EVERYTHING OUT OF THE AREA BY LATE WEDNESDAY AFTERNOON.
GIVEN THE STRENGHTH OF THE UPPER RIDGE OVER THE GULF...AM THINKING
THE GFS IS A BIT TOO QUICK IN BREAKING IT DOWN. THE SLOWER SOLUTION
SEEMS MORE PRACTICAL. AS SUCH...HAVE TRENDED THE FORECAST A LITTLE
SLOWER...WITH THE FRONT MOVING OUT WEDNESDAY NIGHT/EARLY THURSDAY
MORNING AS THE RIDGE FLATTENS OUT A BIT...AND A STRONG UPPER TROUGH
ENTERING THE PLAINS DIGS SOUTHWARD.

AS FAR AS ANY POTENTIAL FOR WINTER WEATHER BEHIND THE FRONT...CURRENT
THINKING IS THAT THE MOST SIGNIFICANT MOISTURE WILL BE EAST OF THE
AREA BY THE TIME THE COLDEST AIR REACHES NORTHWEST ARKANSAS. AS
SUCH...PRECIP WILL HAVE ENDED BY THEN...SO WE/RE NOT EXPECTING IT TO
BE A PROBLEM.

AS FOR THUNDERSTORMS MONDAY THROUGH WEDNESDAY...CLOUD COVER AHEAD OF
THE FRONTAL BOUNDARY WILL LIKELY INHIBIT ANY LARGE-SCALE SURFACE
BASED INSTABILITY. ALSO...UPPER SUPPORT WILL BE NEGLIGIBLE. THUS...
HAVE ONLY INCLUDED A MENTION OF ISOLATED THUNDERSTORMS IN THE
FORECAST AT THIS TIME.

[Mr. T]

Man, that Euro run is the coldest we've seen the model so far. Widespread 20s would certainly be possible...