Severe Weather Discussion - October '09

[venture]

This is going to be a general thread for October, unless we see a ton of severe weather start stacking up - this should be good enough.

NWS Norman, Oklahoma - Enhanced Weather Page

Storm Prediction Center

[Thunder]

We might have some rotations later on Thursday.

[venture]

Preface to this. We are still several days out, but will start discussing this. Historically, we normally always have a secondary severe weather season as we transition into Winter. We've had several large outbreaks in October, one of the largest tornado outbreaks occurred in 1998, and can get some really interesting setups when wintry and liquid precip types start mixing. With that said, here are the thoughts coming up...

October 1st

Right now looks like any severe weather this day will be restricted well east and south of the area. There will be some rain and storms around from mid day through the evening, but instabilities aren't showing any signs of being too out of control right now. The biggest story on this day will likely be the strong shot of cold air coming in behind the front, with temps falling into the 50s in the afternoon and strong NNW winds.

Main Risk: Damaging Wind
Other Risks: Hail

October 3rd
Strong surface low develops in the Oklahoma Panhandle where CO & KS both meet and touch OK. Moisture from the Gulf returns and instability will increase over the western half of the state. Temps rebound fast from the previous strong cold front, getting back into the 70s across most of the state. Most development will be in Kansas or Northern Oklahoma. It appears that the area of strongest instability will have some isolated or scattered development, even though models aren't developing any precip right now. There will be a dryline that sets up in the TX panhandle that should be the focus of that activity.

Main Risk: Damaging Wind, Large Hail
Other Risks: Very slight chance of a tornado or two.

October 4th
Surface low is less defined here, so may need to wait for later runs to determine how next Sunday will evolve. Temps continue to rise will into the upper 70s and 90s across most of the state. Dryline feature will setup in Western OK from Waynoka to Clinton to Altus. Deep moisture will be present ahead of this feature. Also strong front will be plowing down from Kansas and will be through NW Oklahoma by late afternoon. Concerns are around existing precrip from Saturday on how they'll come into play here - and any outflow boundaries from those. Greatest risk area appears be NE, NC and Central Oklahoma. We'll see how things evolve as we get closer, but could be an interesting day into evening. As the front passes Sunday night into Monday morning, winds will be very strong out of the N or NW and temps will fall into the low 50s.

[MikeOKC]

I'm not sure I've ever said this before, but thank you for these threads and posts of yours. It's clear you have a passion and thanks for sharing it with us.

[venture]

Thanks for the feedback Mike, always welcome to hear it.

[venture]

Thursday is obviously getting the main focus right now. Not a lot of variety to go off of model wise since it is just outside the time frame of the other short term models. Timing may also be off some as the primary model used is speeding things up quite a bit...something it is known for.

Thursday - Oct 1

Surface low will pull out into Central Plains, with a secondary low drop down into KS but weaken as it does. Thursday morning cold front will stretch from Central NE through north central KS to SW KS. Dryline will start to establish itself from far NW Oklahoma through the TX Panhandle. By mid Afternoon, the cold front (in this model run) will be pushing through NC Oklahoma into Central sections and SW Oklahoma. The dryline will be just ahead of this but quickly getting over taken by the front. By early evening, the front is in SE Oklahoma already - which may be too fast. There will be some instability ahead of the front, and really if it takes this faster speed - the main severe risk will be WELL east of the area. Right now models do not forecast much if any precip west of I-35. There is some development in NC Oklahoma along the cold front early in the afternoon spreading down as it moves southeast. This could be a setup where we see initiation east of the OKC metro like we do in early spring events. As the front moves out, temps will fall into the 60s with some areas getting into the low 70s where the sun comes back out (western OK). Temps at night will drop in the mid 40s, as it is projected right now which might be too low if this system doesn't push through as fast.

No change to the risks right now until we get closer.

[venture]

Time frame is now with in a couple models that I feel are usually pretty reliable, so going to update this.

Thursday - Oct 1

Models coming together on agreement with timing. Front/Dryline will be racing east during the earlier part of the day. Looks like by noon-2pm the front will be either right on top of the I-35 corridor or just to the west. Moisture content ahead of the front will be pretty good with some decent instabilities. Setup seems to really point to a squall line event that will setup very quickly once initiation starts. Models leave most of the heavy precip well east and south of OKC. It does seem the front may slow a bit and only be from a Tulsa to Shawnee to Ardmore line by 6-7PM. Heavy rain, strong-severe storms will be east of that line at the time. Front will pick up a bit and be out of Oklahoma, except for extreme SE parts, by Midnight-1AM.

Right now, definitely not an end of the world scenario at all. Rain, wind, and maybe some hail. I wouldn't rule out a quick spin up - but that is not going to be the main hazard with this. Think early spring (March) type event here.

Extended

Friday...will be dry with highs in the 60-70 range.

Saturday...slight risk of a storm/shower in south central OK, otherwise dry and cool. Temps in the mid 50s to mid 60s.

Sunday...Warm front will move north through the state starting very early Sunday morning. Storms/Showers will increase and move north through out the state for most of the day - though scattered. Atmosphere could moderately unstable during this which will pose the risk for severe weather. Temps quickly rise into 80s early and will cool back to the 70s with the rain cooled air.

Monday 10/5...System gets better organized in Kansas and the warm front will change to a cold front and start moving south. Low will move out of CO into KS through the day. Deep gulf moisture will continue to pump into the area over this time. Front enters NW Oklahoma very late in the day. Models indicate a complex of storms development over SW Oklahoma and moving NE through OKC into NE OK and into AR. Atmosphere will be somewhat unstable and additional severe weather could be possible.

Tuesday 10/6-Thurs 10/8...Front drops down and enters central OK around morning rush. Very strong N/NE winds will be behind the front as it plows deep into Texas by Wednesday. Temps will be around 70 early and fall into the mid 50s after late afternoon/evening. Additional rain is likely to develop behind the front as it passes. Precip amounts are pretty high over the end of this period, but I think they are too exaggerated right now, but the potential could be there for some rain. Weds temps will range in the mid 50s to low 60s. Thursday is temps starting around 60 falling into the low 50s to the upper 40s later in the day. All in all it should be a relatively cool and dry period coming up at the end of next week as the High Pressure settles in and dries things out.

Key point in all this...forecast confidence falls as you go out farther. So near term next few days is pretty good...but going into next week it is pretty low right now. Needless to say, we are getting into that time of the year to expect these strong systems to come through with storms, and colder weather behind and eventually that will bring snow.

[Thunder]

It appears that the NWS shifted the Greatest Risk area a bit more to the west, much more west from the I-35 line. The cold front may not move that fast as once predicted earlier and the dryline may be able to keep up with the cold front. Venture?

[bretthexum]

Do you mean east Thunder? OKC will be lucky to get anything out of this now. Almost looks like Tulsa to the east now...

[Karried]

As long as it atays away from Journey concert tonight I'm good!

I too appreciate all the weather information!! Thanks Venture and all of the other weather buffs!

[venture]

It appears that the NWS shifted the Greatest Risk area a bit more to the west, much more west from the I-35 line. The cold front may not move that fast as once predicted earlier and the dryline may be able to keep up with the cold front. Venture?

Not exactly sure where you saw that, but it wasn't the weather service. They have everything well east. Morning models are all in agreement with the faster solution that the GFS has been kicking out the last few days. New Day 2 outlook will be out in a couple hours.

[venture]

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1201 PM CDT WED SEP 30 2009

VALID 011200Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE OZARK
PLATEAU/ERN SRN PLNS EWD INTO THE MID-MS RVR VLY/MID-SOUTH...

...SYNOPSIS...
STRONG WRN STATES MID-LVL WAVE WILL TRANSLATE EWD INTO THE PLNS AND
CLOSE INTO A LOW OVER THE CORN BELT BY THU EVE. A 70-90 KT H5 JET
WILL EVOLVE FROM THE GRT BASIN INTO THE SRN PLNS/OZARKS DURING THE
PD. IN THE LWR-LVLS...A LOW OVER THE MID-MO RVR VLY WILL DEEPEN
OVER NWRN IA/SWRN MN THU AFTN/NIGHT. A STRONG CDFNT TRAILING THIS
LOW WILL SWEEP ESE ACROSS THE CNTRL/SRN PLNS AND THE OZARKS REGION
DURING THE DAY AND EVENTUALLY INTO THE LWR OH RVR VLY...MID-SOUTH
AND CNTRL TX BY THE END OF THE PD. THE FRONT WILL SERVE AS A FOCUS
FOR PSBL SVR TSTMS THU AFTN/NIGHT.

...LWR MO/MID-MS RVR VLYS SWD TO THE WRN GULF CSTL AREA...
STRONG LOW/MID-LVL THETA-E ADVECTION COURTESY OF A 40-50 KT SSWLY
LLJ WILL LIKELY DRIVE A CONSIDERABLE AMOUNT OF CLOUDS AND ELEVATED
CONVECTION EARLY THU MORNING FROM SWRN MN SWD INTO THE OZARK
PLATEAU. THIS ACTIVITY WILL TRANSLATE ENE DURING THE AFTN INTO THE
UPR MS VLY AND MIDWEST.

ATTENTION WILL THEN FOCUS FARTHER W FOR SVR POTENTIAL AFT 18Z.
STRONG WARM ADVECTION WILL PROBABLY DRIVE A CONSIDERABLE AMOUNT OF
MULTI-LAYERED CLOUDS EAST OF THE CDFNT...ESP FROM THE OZARKS NWD.
THIS WILL LIMIT DESTABILIZATION ACROSS IA AND NRN MO WITH STRONGER
INSTABILITY FROM CNTRL/SRN MO SWWD INTO ERN OK...AR AND NERN TX. BY
MID-AFTN...MLCAPES SHOULD RANGE FROM A FEW HUNDRED J/KG IN SRN IA TO
2000 J/KG OVER ERN OK...WRN AR AND NERN TX.

SFC-BASED TSTM INITIATION IS LIKELY ALONG AND IMMEDIATELY AHEAD OF
THE CDFNT EARLY IN THE AFTN FROM SRN IA INTO NRN MO. A SUBSEQUENT
BACKBUILDING/AND OR NEW DEVELOPMENT IS EXPECTED SW INTO THE WRN
OZARK PLATEAU AND CNTRL OK 18-21Z AS THE SRN PERIPHERY OF LARGER
SCALE HEIGHT FALLS SPREADS EWD. WHILE STORMS ALONG THE NRN PORTIONS
OF THE FRONT MAY PRODUCE ISOLD HAIL/DMGG WINDS...HIGHEST SVR
POTENTIAL WILL EVOLVE FROM SRN MO SWWD INTO AR...ERN OK AND NERN TX.
HERE...MORE ROBUST SFC-BASED INSTABILITY AND DECENT MID-LVL LAPSE
RATES COUPLED WITH INCREASING DEEP-LAYER SHEAR /40-50 KTS/ WILL BE
FAVORABLE FOR ORGANIZED SVR STORMS. INITIAL STORMS MAY BE
SUPERCELLS WITH LARGE HAIL AND ISOLD TORNADOES...BUT ANTICIPATED
SPEED OF FRONT...THE TEMPORAL BACKING OF THE MID-LVL FLOW AND
MAGNITUDE OF FORCING WILL RESULT IN A TRANSITION TO A COMPLEX LINEAR
MCS AS STORMS MATURE. DMGG WINDS WILL BECOME MORE OF A THREAT WITH
TIME DURING THE EVENING ACROSS THE MID-SOUTH AS MAIN PORTIONS OF THE
70-90 KT WLY MID-LVL JET PUNCHES EWD ACROSS THE FRONT.

SVR THREATS SHOULD GRADUALLY DECREASE OVERNIGHT. INSTABILITY WILL
BECOME LESS WITH EWD EXTENT. LLVL MOISTURE RETURN WILL BE STRONGEST
ACROSS ERN TX INTO THE MS DELTA REGION. BUT...SURGING NATURE TO THE
CDFNT AND THE FACT THAT STRONGER LARGE SCALE ASCENT WILL BEGIN TO
TURN MORE NE TOWARD THE LWR OH VLY ARGUE THAT STORMS ALONG WRN
PORTIONS OF THE FRONT MAY BECOME UNDERCUT AND LIMIT SVR THREATS TO
ISOLD HAIL AND/OR DMGG WIND GUSTS.

[venture]

Looks like everything is sticking to the forecast as outlined the last 4 days with no major surprises.



DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1251 AM CDT THU OCT 01 2009

VALID 011200Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SERN/N-CENTRAL TX AND
SWRN LA TO AR/MO OZARKS...

...SYNOPSIS...
UPPER-AIR PATTERN WILL REMAIN HIGHLY AMPLIFIED ACROSS CONUS THROUGH
PERIOD. CYCLONE INITIALLY CENTERED OVER SRN QUE IS FCST TO MOVE
SLOWLY IN CYCLONICALLY CURVING LOOP -- MAINLY N OF ST LAWRENCE
RIVER. MEANWHILE STG SHORTWAVE TROUGH -- NOW ANALYZED OVER
CENTRAL/NRN ROCKIES STATES -- IS FCST TO EVOLVE INTO CLOSED LOW BY
EARLY THIS PERIOD OVER NEB...MOVING EWD TO IA BY 2/12Z.

ASSOCIATED SFC CYCLONE -- NOW ELONGATED ALONG ARCHING COLD FRONT
OVER NWRN KS AND S-CENTRAL NEB -- IS FCST TO MOVE EWD INVOF KS/NEB
BORDER EARLY IN PERIOD...THEN MOVE/REDEVELOP UNDER CYCLONE
ALOFT...OVER NRN IA/SRN MN. AS THIS OCCURS...COLD FRONT WILL SWEEP
SEWD FROM CENTRAL PLAINS...REACHING ERN MO...N-CENTRAL AR...SERN
OK...AND W-CENTRAL TX BY ABOUT 2/00Z. FRONT THEN SHOULD PROCEED
EWD/SEWD TO S-CENTRAL TX...W-CENTRAL/SWRN LA...CENTRAL MS...AND WRN
KY BY END OF PERIOD...AS PARENT CYCLONE OCCLUDES. OLDER FRONTAL
ZONE -- TRAILING FROM NWRN ATLANTIC AND DEMARCATING NRN EDGE OF
MOIST/RETURN-FLOW AIR -- IS EXPECTED TO LIFT SLOWLY ENEWD ACROSS
ARKLATEX AND WRN GULF COASTAL REGION THROUGH PERIOD...BUT WILL BE
OVERTAKEN BY COLD FRONT FROM N-S ACROSS LOWER MS VALLEY REGION.

...PORTIONS SERN/N-CENTRAL TX AND SWRN LA TO AR/MO OZARKS...
EARLY-PERIOD TSTMS IN CLUSTERS AND BANDS MAY BE ONGOING OVER
PORTIONS MO/IA...ROOTED IN LAYER OF ELEVATED BUOYANCY AND STG
ISENTROPIC ASCENT TO LFC. MAIN CONCERN WITH ANY SUCH ACTIVITY WILL
BE MRGL SVR HAIL...CARRYING OVER THREAT FROM PREVIOUS PERIOD. AS
LLJ WEAKENS THROUGH MID-LATE MORNING...SO SHOULD THIS
CONVECTION...CROSSING MID/UPPER MS VALLEY.

MAIN SVR CONCERN IS WITH DIURNAL CONVECTIVE INITIATION INVOF SFC
COLD FRONT...WHERE ROBUST LINE OF TSTMS PRODUCING DAMAGING GUSTS AND
MOSTLY LOW-END SVR HAIL IS EXPECTED TO FORM BY MID-LATE
AFTERNOON....THEN MOVE EWD ACROSS CATEGORICAL OUTLOOK AREA. SOME
INITIATION-TIMING UNCERTAINTIES STILL EXIST...COMPELLING LOOSER W-E
GRADIENT OF PROBABILITIES THAN ACTUAL SVR POTENTIAL IS LIKELY TO
EVOLVE ACROSS SWRN MO...ERN OK AND N TX. ONCE TSTMS DO
FORM...EXPECT RAPID UPSCALE GROWTH NEWD AND SWWD ALONG/AHEAD OF COLD
FRONT. CONVECTIVE MODE MAY TRANSITION THROUGH BRIEF MIX OF
MULTICELLS AND SUPERCELLS TO LINEAR...RESULTING IN LONG SQUALL LINE
AFTER DARK FROM SERN OZARKS REGION AT LEAST TO UPPER TX COASTAL
PLAIN. THIS LINE SHOULD SHIFT EWD ACROSS PORTIONS LOWER MS VALLEY
THEREAFTER...THREAT DIMINISHING WITH EWD EXTENT AFTER DARK AS
1. FOREGOING BOUNDARY LAYER COOLS DIABATICALLY...REDUCING AVAILABLE
SFC-BASED BUOYANCY...AND
2. CONVECTIVE BAND OUTRUNS HIGHEST THETAE BOUNDARY LAYER AIR MASS
FROM N-S AND INGESTS MORE STABLE AND INCOMPLETELY MODIFIED
CONTINENTAL TRAJECTORIES.

STRONGEST VERTICAL SHEAR PROFILES ARE FCST TO OCCUR ACROSS NRN
PORTION OF OUTLOOK AREA...ESPECIALLY OVER OZARKS IN ZONE WHERE
BUOYANT ZONE WILL BE NARROWING AND DIMINISHING IN MAGNITUDE...AS
COLD FRONT OVERTAKES RETURN-FLOW BOUNDARY. SFC DEW POINTS MID 60S F
OVER SRN MO...AND UPPER 60S/LOWER 70S ACROSS MUCH OF ERN OK...AR AND
NRN/ERN TX -- WILL COMBINE WITH DIABATIC HEATING TO SUPPORT MLCAPES
RANGING FROM LESS THAN 1000 J/KG NEAR MO RIVER TO AROUND 3000 J/KG
OVER PORTIONS N-CENTRAL/NE TX.

SWLY SFC WINDS ARE EXPECTED TO LIMIT SFC CONVERGENCE AND LOW LEVEL
SHEAR OVER MUCH OF AREA...WITH SIGNIFICANT COMPONENT OF MEAN FLOW
VECTOR BEING PARALLEL TO FRONTAL ZONE. FCST HODOGRAPHS ARE ENLARGED
ACROSS OZARKS REGION DUE TO COMBINATION OF CONSIDERABLE BOUNDARY
LAYER SPEED SHEAR AND SLGT VEERING WITH HEIGHT...HOWEVER CONCERNS
OVER CONVECTIVE MODE AND EXTENT OF FAVORABLE INSTABILITY PRECLUDE
MORE THAN MRGL TORNADO PROBABILITIES ATTM.

[Thunder]

Do you mean east Thunder? OKC will be lucky to get anything out of this now. Almost looks like Tulsa to the east now...

Not exactly sure where you saw that, but it wasn't the weather service. They have everything well east. Morning models are all in agreement with the faster solution that the GFS has been kicking out the last few days. New Day 2 outlook will be out in a couple hours.

I did see it on the NWS site. They shifted the greatest risk area a bit more back west, then now they changed their mind and moved it back to east.

[venture]

You were looking at an outdated graphic that showed their thinking before they started adjusting their forecast to compensate for the faster model solution that I was mentioning. I remember which one you were looking at. Sometimes they don't get the old graphics off the page in time.

[venture]

Cold front is blasting through the metro area now. Temps are around 80 with a moderately unstable atmosphere right now ahead of the front. If a storm could form along the front, it has the right conditions to let it go severe...but no indications of that happening right now.

[westsidesooner]

Cold front is blasting through the metro area now.

I was just watching that on radar. It's right along I-44 now and busting se. I kinda thought today was going to be a non-event for central Oklahoma. As fast as the front is moving it looks like anything would be in the far eastern part of the state.

Venture, Think we'll get much rain from that area of disturbed weather off Baja?

[venture]

Storms are developing rapidly now along the front from Tulsa to the SW. Front is just about out of the metro area totally.



MESOSCALE DISCUSSION 2052
NWS STORM PREDICTION CENTER NORMAN OK
1244 PM CDT THU OCT 01 2009

AREAS AFFECTED...EXTREME NERN TX...ERN OK...NWRN AR...SWRN/CNTRL MO

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 011744Z - 011915Z

1730Z MESOANALYSIS PLACES THE CDFNT FROM LAWRENCE KS-KTUL-DUNCAN
OK-SWEETWATER TX LINE. PRE-FRONTAL AIR MASS HAS CONTINUED TO
MOISTEN AND WITH BINOVC...SFC TEMPERATURES HAVE CLIMBED INTO THE
MID-70S TO LWR 80S. RECENT AIRCRAFT SOUNDINGS FROM KFSM...KOKC AND
KTUL SUGGEST THAT THE CAP WAS WEAKENING...OWING TO INCREASING LARGE
SCALE ASCENT/MOISTENING AND LLVL HEATING. EXPECT THAT TSTMS WILL
INITIATE EARLY THIS AFTN ALONG N END OF THE LLVL THERMAL AXIS NEAR
THE KS/MO/OK/AR BORDERS...THEN BACKBUILD SWWD WITH TIME. ACTIVITY
WILL THEN SPREAD ENE INTO SWRN/CNTRL MO...NWRN AR AND PERHAPS NERN
TX LATER THIS AFTN.

VEERING OF THE LLVL WINDS JUST AHEAD OF THE FRONT AND APPROACH OF A
NEARLY PARALLEL 50-60 KT WSW FLOW ALOFT WILL LIKELY RESULT IN
DEVELOPMENT OF A QLSC AND/OR MULTIPLE LINEAR SEGMENTS. EMBEDDED
BOWS/LEWPS WILL RESULT IN RISKS FOR DMGG WIND GUSTS...ALTHOUGH HAIL
WILL BE POSSIBLE GIVEN THE STEEP LAPSE RATE IN THE H7-H5 LAYER.
ATTM...IT APPEARS THAT THE HIGHEST SVR PROBABILITIES WILL EXIST FROM
EXTREME SWRN MO INTO ECNTRL OK AND NWRN AR THROUGH LATE AFTN.

[venture]

I was just watching that on radar. It's right along I-44 now and busting se. I kinda thought today was going to be a non-event for central Oklahoma. As fast as the front is moving it looks like anything would be in the far eastern part of the state.

Venture, Think we'll get much rain from that area of disturbed weather off Baja?

There will be some scattered rain around. GFS is showing some heavier rain middle of next week as a strong low goes through the Great Lakes (some chance for their first snow up there).

[venture]

Severe Weather is expected to return Monday. Will go into more detail when I have a bit more time.



DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0246 AM CDT SAT OCT 03 2009

VALID 051200Z - 061200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
PLAINS...

...SYNOPSIS...
WHILE AN UPPER LOW SHIFTS SLOWLY ACROSS NEW ENGLAND...A MORE
SIGNIFICANT FEATURE WITH RESPECT TO THE CONVECTIVE FORECAST IS
FORECAST TO SHIFT ACROSS THE ROCKIES AND INTO THE CENTRAL U.S. THIS
PERIOD. AS THIS OCCURS...A LEE LOW OVER ERN CO IS FORECAST TO MOVE
INTO THE SRN HIGH PLAINS DURING THE AFTERNOON...WHILE A SECOND AREA
OF CYCLOGENESIS EVOLVES OVER THE MID MO VALLEY. WITH TIME...THIS
NRN LOW WILL BECOME THE PRIMARY SURFACE CYCLONE...SHIFTING ENEWD
TOWARD THE UPPER MS VALLEY WHILE A TRAILING COLD FRONT DRIVES SEWD
ACROSS KS/OK INTO MO/AR/N TX THROUGH THE REST OF THE PERIOD.

...SRN PLAINS...
NWD RETURN OF A HIGHER THETA-E BOUNDARY LAYER INTO N TX/SRN OK IS
FORECAST THIS PERIOD...AS PERSISTENT SLY LOW-LEVEL FLOW ALLOWS A
LINGERING SURFACE BAROCLINIC ZONE ACROSS TX TO SHIFT NWD WITH TIME.

AS THE SURFACE LOW MOVES OUT OF ERN CO INTO SWRN KS AND THE TX/OK
PANHANDLE REGION DURING THE AFTERNOON...BOUNDARY-LAYER
HEATING/MOISTENING SHOULD RESULT IN AROUND 1000 J/KG MIXED-LAYER
CAPE FROM WRN OK SWD. THOUGH THE MAIN UPPER SYSTEM WILL REMAIN WELL
N OF THIS REGION...SUBTLE FEATURES EMBEDDED IN THE FAST WSWLY
MID-LEVEL FLOW ARE PROGGED TO MOVE INTO THIS REGION DURING THE
AFTERNOON...SUPPORTING THE DEVELOPMENT OF ISOLATED STORMS. WHILE
CONVECTION FROM NRN OK NWD SHOULD REMAIN ELEVATED...SURFACE-BASED
CONVECTION IS EXPECTED ACROSS WRN PORTIONS OF N TX AND POSSIBLY INTO
SWRN OK.

WITH 50 KT WSWLY MID-LEVEL FLOW PROGGED TO SPREAD ACROSS THIS REGION
ATOP LOW-LEVEL SLYS...SHEAR WILL SUPPORT ORGANIZED/SUPERCELL STORMS
-- AND ASSOCIATED SEVERE POTENTIAL. DURING THE EVENING...STORMS
SHOULD TAKE ON MORE OF A LINEAR CONFIGURATION INVOF THE SEWD-MOVING
COLD FRONT...WITH ASSOCIATED SEVERE POTENTIAL LIKELY TO SPREAD INTO
WRN AR/NERN AND CENTRAL TX THROUGH THE LATTER HALF OF THE PERIOD.

..GOSS.. 10/03/2009

[westsidesooner]

Venture....whats your thoughts on this cold air I keep hearing about in the 7-10 day period? Thoughts from the NWS:

"THE REAL ANCHOR IN THE DEVELOPING LONGWAVE PATTERN WILL BE AN
UPPER RIDGE SETTING UP UPSTREAM - INITIALLY OFF THE W COAST. AS
THE RIDGE BUILDS N TOWARD NW CANADA... THE INEVITABLE BUILDUP OF
CANADIAN/ARCTIC AIR WILL COMMENCE. HENCE THE 1050+ HIGH THAT THE
ECMWF PLACES OVER NW CANADA BY FRIDAY. IT REMAINS TO BE SEEN IF
THIS AIR WILL ROLL SE/S INTO THE S PLAINS BY LATE NEXT WEEKEND...
AS INDICATED BY THE ECMWF... OR IF THE LARGE-SCALE PATTERN WILL
DEAMPLIFY BY THEN AND WE GET ONLY A GLANCING BLOW OF COLD AIR...
LIKE THE 00Z GFS."

[venture]

Get the arks ready. First some severe weather business next couple of days.



AY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT WED OCT 07 2009

VALID 071200Z - 081200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
LARGE SCALE SPLIT FLOW REGIME WILL CONTINUE TO PREVAIL OVER THE
WESTERN STATES...WITH THE SOUTHERN STREAM UPPER LOW OVER SOUTHERN CA
EXPECTED TO MIGRATE EASTWARD OVER THE SOUTHWEST DESERTS/NORTHWEST
MEXICO THROUGH THE PERIOD. IN THE EAST...A SWIFT MOVING UPPER TROUGH
WILL CONTINUE TO STEADILY PROGRESS EAST-NORTHEASTWARD OVER THE
NORTHEAST STATES/NEW ENGLAND...WHILE A SUBTROPICAL RIDGE BUILDS OVER
FL AND THE ADJACENT SOUTHEAST STATES. PRIMARY SURFACE COLD FRONT
WILL QUICKLY RACE EASTWARD OFF MUCH OF THE ATLANTIC SEABOARD BY
AFTERNOON...WHILE THE WEST-SOUTHWEST PORTION OF THE FRONT
STALLS/ELONGATES GENERALLY EAST-WEST ACROSS THE GULF COAST STATES TO
TX.

...SOUTHERN HIGH PLAINS OF TX TO OK/LOWER MO VALLEY TONIGHT...
A STRENGTHENING NOCTURNAL LOW LEVEL JET /40-50 KT/ ACROSS THE
SOUTHERN PLAINS...AND ONSET OF LATE PERIOD HEIGHT FALLS...WILL
CONTRIBUTE TO THE NORTHEASTWARD TRANSPORT OF A MOIST/UNSTABLE
ELEVATED AIRMASS ATOP A COOL/STABLE NEAR-SURFACE LAYER LATE TONIGHT.
ACCORDINGLY...00Z DETERMINISTIC GUIDANCE/MAJORITY OF 21Z SREF
MEMBERS IMPLY AN INCREASE OF ELEVATED TSTMS TOWARD/AFTER 06Z FROM
PORTIONS OF WEST TX/OK TO THE LOWER MO VALLEY/OZARKS. WITH AN
UNSTABLE SOURCE REGION AIRMASS INITIALLY ACROSS THE SOUTH HALF OF
TX...WEAK TO MODERATE ELEVATED BUOYANCY /500-1500 J PER KG/ AND
AMPLE SHEAR THROUGH THE CLOUD BEARING LAYER IS SUGGESTIVE OF AT
LEAST ISOLATED BOUTS OF SEVERE HAIL INTO THE OVERNIGHT.



DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1156 PM CDT TUE OCT 06 2009

VALID 081200Z - 091200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM MUCH OF OK INTO PARTS OF
SOUTHERN MO AND NORTHWEST AR...

...SOUTHERN PLAINS INTO MID MS VALLEY...
MODEL GUIDANCE IS IN GOOD AGREEMENT THAT THE UPPER TROUGH CURRENTLY
DIGGING SOUTHWARD ACROSS ALBERTA WILL PHASE WITH THE UPPER LOW OVER
SOUTHERN CA BY THURSDAY AFTERNOON...AND ROTATE EASTWARD ACROSS THE
PLAINS STATES. AHEAD OF THESE UPPER FEATURES...STRONG SOUTHERLY LOW
LEVEL WINDS WILL TRANSPORT GULF MOISTURE RAPIDLY NORTHWARD WITH
UPPER 60S DEWPOINTS LIKELY TO REACH AS FAR NORTH AS SOUTHERN MO BY
09/00Z. THIS WILL DESTABILIZE THE AIRMASS FROM OK/AR/MO AND HELP TO
SUPPORT A RISK OF SEVERE STORMS.

THUNDERSTORMS WILL LIKELY BE ONGOING THURSDAY MORNING ALONG A COLD
FRONT FROM SOUTHERN KS INTO CENTRAL MO. OTHER SCATTERED SHOWERS AND
THUNDERSTORMS WILL LIKELY DEVELOP BY EARLY AFTERNOON ACROSS MUCH OF
TX/OK IN STRONG LOW LEVEL WARM ADVECTION REGIME. HOWEVER...THE
PRIMARY RISK OF SEVERE STORMS WILL LIKELY OCCUR DURING THE LATE
AFTERNOON AND EVENING HOURS AS A SURFACE LOW DEEPENS OVER NORTHERN
OK AND TRACKS ALONG THE FRONT INTO MO /PER GFS SOLUTION/. FORECAST
SOUNDINGS IN THIS REGION SHOW SUBSTANTIAL LOW LEVEL AND DEEP LAYER
VERTICAL SHEAR FAVORABLE FOR SUPERCELLS AND POSSIBLE TORNADOES. THE
MAIN UNCERTAINTY REGARDING COVERAGE OF SEVERE STORMS WILL INVOLVE
THE DEGREE OF INSTABILITY...WHICH COULD BE LIMITED GREATLY IF THE
WARM ADVECTION PRECIPITATION TO THE SOUTH SPREADS NORTHWARD FASTER
THAN FORECAST AND OVERSPREADS THE SLIGHT RISK AREA BEFORE MUCH
DAYTIME HEATING CAN OCCUR.


NAM Precip Forecast:



GFS:

[venture]

WRF 6 Hour Period Images Starting Thursday Morning

[Thunder]

I hope its not for Wednesday! Last I checked, dry weather, I better move quick!

[venture]

Flood watch
national weather service norman ok
1134 am cdt wed oct 7 2009

...thunderstorms with heavy rain thursday and thursday night...

.a tropical warm front in south texas will lift toward the red
river during the day thursday. Rich gulf moisture will overspread
the region north of the front...and an advancing upper level
trough will release that moisture in the form of thunderstorms
over northern oklahoma. Storms are expected to train from west to
east...with increasingly heavy rainfall. Later in the day...the
upper level trough will swing out across texas and into southern
and central oklahoma...resulting in new thunderstorm development.
These storms will become particularly widespread thursday
evening...when a strong cold front arrives to focus the activity.

Although the ground is not particularly close to saturation prior
to this rain event...it is likely that some of the thunderstorms
will produce exceptionally heavy rainfall. With several storms
moving over a given area...flooding will be possible within the
watch area.

Oklahoma-lincoln-mcclain-cleveland-pottawatomie-seminole-hughes-
stephens-garvin-murray-pontotoc-coal-jefferson-carter-johnston-
atoka-love-marshall-bryan-clay-
including the cities of...oklahoma city...chandler...purcell...
Norman...moore...shawnee...seminole...holdenville. ..duncan...
Pauls valley...sulphur...ada...coalgate...waurika...ardm ore...
Tishomingo...atoka...marietta...madill...durant... henrietta
1134 am cdt wed oct 7 2009

...flash flood watch in effect from thursday afternoon through
friday morning...

The national weather service in norman has issued a

* flash flood watch for portions of oklahoma and northern
texas...including the following areas...in oklahoma...atoka...
Bryan...carter...cleveland...coal...garvin...hughe s...
Jefferson...johnston...lincoln...love...marshall.. .mcclain...
Murray...oklahoma...pontotoc...pottawatomie...semi nole and
stephens. In northern texas...clay.

* from thursday afternoon through friday morning

* widespread thunderstorms...some with very heavy rain

* thunderstorms will increase thursday afternoon...becoming
widespread by the evening. A cold front will work with rich gulf
moisture to produce renewed thunderstorm development well into
thursday night. Prolonged heavy rain will produce accumulations
locally in excess of 3 inches. Given the intense rain rates that
are expected...isolated totals over 5 inches are possible...
Especially in southeast oklahoma. The rain will gradually end
late thursday night...as cool and dry air builds in from the
north.