October 12-13th "Potential" Severe Outbreak

[patrick7032]

Figured I'd start this thread concerning the "general" setup for this weekend...especially since today's runs have come into better agreement...with a couple soundings below. Although this is a ways out...they're not bad soundings...especially considering the GFS typically under-estimates cape this time of year due to it's initialzation/parmaterzation scheme.

[patrick7032]

A few exerts from today's discussions:

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE AMARILLO TX

421 AM CDT MON OCT 8 2012

THE FRIDAY PATTERN LOOKS VERY SPRING-LIKE...AND THE PIECES WILL BE

THERE FOR A REGIONAL SVR WX EPISODE. HOWEVER...WHETHER THE PIECES

LINE UP WITH EACH OTHER AND AT A DIURNALLY FAVORABLE TIME REMAINS TO

BE SEEN. AS THE MODELS SHOW IT...FRI AFTERNOON AND EVENING WILL HOLD

THE BEST CHCS FOR SEVERE WEATHER FOR THE PANHANDLES. AS IS USUALLY

THE CASE THIS TIME OF YEAR...INSTABILITY WILL BE THE LIMITING

FACTOR...AND FORECASTING INSTABILITY AT THIS TIMEFRAME IS PLENTY

DIFFICULT. HOWEVER...STAY TUNED AS FRI NEARS IN CASE THE PIECES DO

LINE UP.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SAN ANGELO TX

347 PM CDT MON OCT 8 2012

BOTH THE GFS AND THE ECMWF SHOW AN INTENSE UPPER LOW OVER SOUTHERN

CALIFORNIA THURSDAY MORNING...WEAKENING AS IT SHIFTS INTO THE LEE

OF THE ROCKIES ON SATURDAY. AS THE UPPER LEVEL TROUGH AXIS MOVES

INTO NEW MEXICO LATE FRIDAY...APPEARS STAGE IS SETTING UP FOR AN

AREA OF INTENSE CONVECTION TO DEVELOP ACROSS THE PANHANDLE. HOW

FAR SOUTH AND EAST THIS MCS ROLLS FRIDAY NIGHT INTO SATURDAY IS

THE BIGGEST QUESTION IN THE LONG TERM. WILL CONTINUE THE CHANCE

POPS ACROSS THE NORTHWEST BIG COUNTRY FOR FRIDAY NIGHT AND

SATURDAY MORNING WITH THE TAIL END OF THE CONVECTION. FARTHER

SOUTH...WITH THE MAIN LIFT PASSING TO THE NORTH...GETTING ANY

SHOWERS AND STORMS WILL BE MORE DIFFICULTY. HOWEVER...SOME LIFT

FROM THE UPPER TROUGH AXIS...ALONG WITH WHAT LOOKS TO BE

RELATIVELY WEAK CONVERGENCE WITH A PACIFIC FRONT MAY BE ENOUGH TO

PRODUCE A FEW STORMS SATURDAY INTO SUNDAY.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE DODGE CITY KS

353 PM CDT MON OCT 8 2012

BY FRIDAY NIGHT, THE AFOREMENTIONED STORM SYSTEM WILL EJECT

NORTHEASTWARD INTO WESTERN NEBRASKA. THE ECMWF AND GFS ARE IN

EXCELLENT AGREEMENT WITH THIS SCENARIO, AND EVEN THE ECMWF YANKS THE

SURFACE FRONT OVER THE PANHANDLES FRIDAY AFTERNOON RAPIDLY NORTHWARD

INTO NEBRASKA BY SATURDAY MORNING. THIS SEEMS LIKE A REASONABLE

SOLUTION BASED ON THE STRENGTH OF THE SYSTEM. ANY THUNDERSTORMS THAT

DEVELOP FRIDAY AFTERNOON TO OUR SOUTHWEST OVER THE SOUTHERN HIGH

PLAINS WILL MOVE NORTHEASTWARD AND COULD AFFECT MUCH OF SOUTHWEST

KANSAS FRIDAY EVENING. GIVEN THAT THIS WILL BE OCCURRING OVER OUR

AREA AT NIGHT AFTER THE LOSS OF DAYTIME HEATING, TORNADIC ACTIVITY

IS NOT AS LIKELY. ALSO, THE GFS SHOWS A CAPPING INVERSION NORTH OF

THE FRONT AND IT IS NOT CLEAR HOW STORMS TO THE SOUTHWEST WILL

BEHAVE UPON MOVING OVER THE COOLER LOW LEVEL AIRMASS OVER SOUTHWEST

KANSAS. IF THE CAP IS NOT TOO STRONG, THERE COULD BE SOME ELEVATED

THUNDERSTORMS AT THE VERY LEAST THAT COULD CONTAIN HAIL. GIVEN THE

WARM FRONTAL PASSAGE FRIDAY NIGHT, EXPECT RISING TEMPERATURES

OVERNIGHT, WITH SATURDAY MORNING TEMPERATURES LIKELY STARTING OUT IN

THE 60S.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE FORT WORTH TX

327 PM CDT MON OCT 8 2012

OUR NEXT WEATHER SYSTEM THAT LOOKS TO BRING RAIN CHANCES BACK TO

THE REGION WILL BE A LOW PRESSURE SYSTEM THAT IS CURRENTLY OFF THE

COAST OF CALIFORNIA. THIS SYSTEM IS EXPECTED TO SLOWLY MEANDER

SOUTH/SOUTHEAST THROUGH THURSDAY BEFORE KICKING OUT TO THE

NORTHEAST FRIDAY. THIS TROUGH WILL PROVIDE SUFFICIENT LIFT...AND

WITH A WEAKER CAP...SCATTERED STORMS ARE LIKELY THIS WEEKEND. CAPE

VALUES ARE EXPECTED TO BE AROUND 1000 J/KG...BUT 0-6 KM SHEAR

VALUES OF 35 KNOTS COULD LEAD TO STRONG STORMS. THE WEAKER CAPE

VALUES SHOULD LIMIT THE SEVERE WEATHER POTENTIAL...BUT THIS IS

SOMETHING WORTH WATCHING OVER THE NEXT SEVERAL DAYS.

[patrick7032]

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0355 AM CDT MON OCT 08 2012

VALID 111200Z - 161200Z

...DISCUSSION...

MEDIUM RANGE MODELS CONTINUE TO INDICATE THE TRANSITION TO A MORE

ZONAL/PROGRESSIVE UPPER FLOW REGIME LATE THIS COMING WORK WEEK INTO

NEXT WEEKEND. AS THIS OCCURS...A CLOSED LOW...MIGRATING INLAND

ACROSS THE CALIFORNIA COAST BY MID WEEK...APPEARS LIKELY TO RAPIDLY

ACCELERATE EAST NORTHEASTWARD OUT OF THE SOUTHWESTERN STATES. AND

IT IS APPEARING INCREASINGLY LIKELY THAT THIS WILL BE ACCOMPANIED BY

SIGNIFICANT SURFACE CYCLOGENESIS FROM THE LEE OF THE CENTRAL ROCKIES

THROUGH THE GREAT LAKES AND EASTERN CANADA. GUIDANCE HAS BEEN

SUGGESTIVE THAT UPWARD VERTICAL MOTION...DEEP LAYER FLOW FIELDS AND

VERTICAL SHEAR WILL BE MOST SUPPORTIVE OF SEVERE WEATHER POTENTIAL

IN THE WARM SECTOR OF THIS SYSTEM ON SATURDAY. THIS SEEMS MOST

PROBABLE ACROSS PARTS OF EASTERN NEBRASKA AND KANSAS...NORTHEAST

OKLAHOMA...THE NORTHWESTERN THIRDS OF MISSOURI...IOWA AND ADJACENT

NORTHWEST ILLINOIS...SOUTHWESTERN WISCONSIN AND SOUTHERN MINNESOTA.

HOWEVER...THIS TIME FRAME ALSO COINCIDES WITH A SIGNIFICANT INCREASE

IN SPREAD AMONG MODEL ENSEMBLE DATA...PARTICULARLY CONCERNING THE

SPEED OF THE UPPER IMPULSE. QUESTIONS ALSO LINGER CONCERNING THE

DEGREE OF WARM SECTOR BOUNDARY LAYER DESTABILIZATION...WHICH COULD

BE IMPACTED SIGNIFICANTLY BY PRIOR CONVECTION. TOO MUCH UNCERTAINTY

STILL EXISTS TO CONFIDENTLY ASSESS THE POTENTIAL FOR A REGIONAL

SEVERE WEATHER EVENT.

..KERR.. 10/08/2012

[andyhb]

Pretty beefy discussion from EAX:

Medium Range (Thursday through Sunday)...

The main concern through this period focuses on a very strong

upper-level storm system and its potential to bring severe weather

to the Eastern Plains.

Models are in good agreement in bringing a closed upper low ashore

across southern California during the day Thursday and tracking it

across the Four Corners region Friday. Guidance agreement loses a

little steam by Saturday morning, mainly as the GFS ensembles show a

rather large standard deviation in the 500mb height fields across

the Eastern Plains. But there is very good clustering of the GFS

ensemble mean, GFS operational and the ECMWF showing the upper low

moving into western Nebraska Saturday morning. Even the GEM is in

the vicinity of the aforementioned cluster, although it appears to

be a slow outlier at this point. Given the agreement of the models,

confidence is high that an anomalously strong upper-level wave will

affect the region from Friday night through Saturday night.

This setup will be enhanced by broad surface high pressure over the

eastern CONUS which will allow for strong moisture return. Indeed,

with several days of favorable flow over the Gulf of Mexico,

dewpoints by Friday should be in the low 60s across the Southern

Plains. As the upper wave approaches from the west, it will induce

strong surface cyclogenesis in the High Plains allowing a front that

moved into the region Thursday/Thursday night to lift back northward

as a warm front Friday/Friday night placing the region squarely in

the warm sector of this powerful synoptic system come Saturday.

Aided by anomalously strong low to mid-level winds, strong warm and

moist advection is expected which destabilize this region leading

potentially to SBCAPE values in the 1000 to 1500 J/kg range.

The upper-level jet streak will be seasonal but it`s the low and

mid-level flow that looks to dominate this system. 925mb to 850mb

flow is some +3 to +4 standardized anomalies and as a result

low-level shear is forecast to be quite high, on the order of 50+

kts in the 0-3km layer. While surface winds may be veered in our

region, the strong low to mid-level winds will result in very high

helicity values. And, while the upper-level jet is not all that

robust for this time of year, the flow becomes largely diffluent as

the upper wave becomes negatively tilted during the day Saturday. So

given the strong kinematics and marginal thermodynamics of this

system, there is an increasing potential for at least strong storms

and quite possibly severe storms affecting the region during the day

Saturday. There are still uncertainties with the timing and

ultimately the location of critical elements, but the large-scale

pattern itself favors some strong to severe convection in the

Eastern Plains given today`s suite of models.

In the wake of this system, temperatures are expected to rebound

quickly back into the 70s as westerly downslope flow and warm

advection aloft develop over the region.

[patrick7032]

FWIW...if things continue to look good by Thursday for the weekend...and someone wouldn't mind a chase partner in the Texas or Oklahoma area...send me a message. I get off shift at the NWS office Friday afternoon and can meet you somewhere Friday evening or Saturday morning. I'm also an experienced chaser of many years...but would prefer not to chase solo until I get to know the area better...as I just transferred to the area a few months ago.

[patrick7032]

Here are the 18Z forecasts for a few levels and the Midland sounding.

[MnWeatherman]

There's looks to be a good setup for cold air funnels/ tornadoes in the upper plains along the warm front, on Saturday. Crazy to see models showing 60°F+ dewpoints in southern MN for this time of year. GFS showing a nice "dry punch" pushing into SW MN and Western Iowa in order to steepen the lapse rates.

For Saturday's regional potential, I'm not sold, till higher resolution models come into play. Precip. maps are way to boisterous for any destabilization predictability.

[patrick7032]

There's looks to be a good setup for cold air funnels/ tornadoes in the upper plains along the warm front, on Saturday. Crazy to see models showing 60°F+ dewpoints in southern MN for this time of year. GFS showing a nice "dry punch" pushing into SW MN and Western Iowa in order to steepen the lapse rates.

For Saturday's regional potential, I'm not sold, till higher resolution models come into play. Precip. maps are way to boisterous for any destabilization predictability.

Very true on the destabalazation issue...I'm mainly going off what I expect to play out...but certainly the entire I-35 corridor will have the chance. It'll be interesting to see if the lower 60 dew points make it that far north as the potential convection will likely limit some of the moisture return. FWIW...I think the "best areas" would be between DFW and TUL...and perhaps even more so in a MSN-MKX-DVN- just west of DMX "box". Obviously later runs will tell more.

[patrick7032]

Think Topeka has the right idea...as does the KC AFD posted earlier:

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE TOPEKA KS

346 PM CDT MON OCT 8 2012

THURSDAY AND FRIDAY...THE CLOSED UPPER LOW...EMBEDDED WITHIN THE

SOUTHERN STREAM JET...WILL SLOWLY MOVE EAST ACROSS THE DESERT

SOUTHWEST. SOUTHWESTERLY MID LEVEL FLOW WILL LEAD TO THE

AMPLIFICATION OF A LEE SFC TROUGH ACROSS THE SOUTHERN HIGH PLAINS.

THE LOW LEVEL FLOW WILL BECOME SOUTHERLY AND ADVECT DEEPER GULF

MOISTURE NORTHWARD INTO SOUTHERN KS BY THURSDAY AFTERNOON.

MEANWHILE...ANOTHER H5 TROUGH WILL DIG AND AMPLIFY ACROSS THE GREAT

LAKES STATES. ONCE AGAIN LOW-LEVEL CAA ACROSS THE NORTHERN PLAINS

AND THE UPPER MIDWEST WILL CAUSE A FRONT TO DROP SOUTHWARD ACROSS

THE CWA TUESDAY AFTERNOON. AS THE FRONT PUSHES SOUTH OF

I-70...THE MOISTURE MAY BE DEEP ENOUGH FOR SHOWERS AND

THUNDERSTORMS TO DEVELOP THURSDAY AFTERNOON. MOST OF THE ASCENT AHEAD OF

THE SOUTHERN STREAM UPPER LOW WILL BE ACROSS NM INTO WEST TX. THE

FRONT WILL SLOWLY PUSH SOUTH THURSDAY NIGHT AND BECOME STATIONARY

ALONG THE OK AND KS BORDER. THE SHOWERS AHEAD OF THE FRONT MAY

LINGER INTO THURSDAY EVENING ACROSS THE SOUTHEAST COUNTIES...BUT

MOST OF THE CWA WILL REMAIN DRY THURSDAY NIGHT.

DURING THE DAY FRIDAY THE LEE SURFACE TROUGH ACROSS THE SOUTHERN

PLAINS WILL DEEPEN AS A STRONG MID LEVEL JET LIFTS NORTHEAST

ACROSS NM DURING THE DAY AHEAD OF THE SOUTHERN STREAM UPPER LEVEL

LOW. STRONG SOUTHERLY LOW-LEVEL FLOW WILL TRANSPORT DEEPER

MOISTURE NORTH OF THE SURFACE BOUNDARY. THE RESULTING ISENTROPIC

LIFT WILL CAUSE SHOWERS AND THUNDERSTORMS TO REDEVELOP ACROSS THE

SOUTHERN COUNTIES OF THE CWA DURING THE DAY ON FRIDAY.

TEMPERATURES WILL BE COOLER ON FRIDAY WITH CLOUDY SKIES AND

NORTHEAST TO EAST SURFACE WINDS. HIGHS WILL ONLY REACH THE MID

60S.

FRIDAY NIGHT THROUGH SATURDAY NIGHT...THE SOUTHERN STREAM UPPER

LEVEL LOW OVER THE FOUR CORNERS AREA WILL LIFT NORTHEAST INTO

WESTERN NE...THEN EASTERN SD. INCREASING ASCENT AHEAD OF THE H5

TROUGH ALONG WITH A DEVELOPING LLJ...WHICH WILL TRANSPORT GULF

MOISTURE NORTH...WILL INCREASE CHANCES FOR SHOWERS AND THUNDERSTORMS

ACROSS THE CWA DURING FRIDAY NIGHT INTO SATURDAY MORNING. THE

STRONGER WAA WILL SHIFT NORTHEAST OF THE CWA BY NOON SATURDAY AND

WE COULD SEE A BREAK IN THE SHOWERS AND THUNDERSTORMS DURING THE

EARLY AFTERNOON HOURS. SHOWERS AND THUNDERSTORMS WILL REDEVELOP

ALONG AND AHEAD OF THE PACIFIC COLD FRONT ACROSS THE EASTERN HALF

OF THE CWA SATURDAY AFTERNOON. THE BEST CHANCE FOR SEVERE WEATHER WILL BE

ACROSS SOUTHEAST CO...SOUTHWEST KS AND THE TX PNHDL FRIDAY

AFTERNOON AND EVENING. THESE STRONGER STORMS MAY REACH THE CWA

AROUND OR AFTER MIDNIGHT...BUT AT THIS TIME THE STRONGER STORMS

WILL BE ELEVATED AND SOME OF THE STRONGER STORMS MAY PRODUCE MARBLE

TO NICKEL SIZE HAIL

IF WE SEE ANY CLEARING LATE SATURDAY MORNING AND THROUGH THE EARLY

AFTERNOON HOURS THE INSTABILITY WILL INCREASE...PROVIDING THE POTENTIAL

FOR SEVERE THUNDERSTORMS ACROSS NORTHEAST AND EAST CENTRAL KS

SATURDAY AFTERNOON INTO SATURDAY EVENING.

[Stebo]

Been watching this potential evolve over the last few days, i do agree with your thoughts on the GFS underdoing the instability. A better representation of the thermodynamic profile for this event would be seen on the Euro, a bit more realistic temp/dewpoint profile.

[patrick7032]

Been watching this potential evolve over the last few days, i do agree with your thoughts on the GFS underdoing the instability. A better representation of the thermodynamic profile for this event would be seen on the Euro, a bit more realistic temp/dewpoint profile.

This is true...but the GFS has just been more consistent. Today they trended towards each other...and the 00Z runs will be interesting.

[andyhb]

00z GFS looking pretty good for the High Plains on Friday, 30-40+ kt southerly LLJ and sfc winds backing east of the dryline, with 60s dews in place and a 60 kt H5 jet streak ejecting into the OK Panhandle by 00z.

Saturday looks like a more MO/IA/N AR deal on this run though, possibly even into IL.

[Thundersnow12]

My prelim Friday target is CVN-LBB-HOB. Further north isn't going to cut it. Gotta be south of the sfc boundary. Still will have plenty of shear over the dryline down there and better heating.

More later.

[andyhb]

Pretty impressive looking Pacific Jet streak coming onshore near the end of the higher-res on the GFS as well.

Edit: All three models (GFS/Euro/GGEM) carve out a large trough across the central US with that jet streak, but I'm getting ahead of myself, the time for more discussion on that will come.

[andyhb]

We have a Day 5...

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0353 AM CDT TUE OCT 09 2012

VALID 121200Z - 171200Z

...DISCUSSION...

MEDIUM RANGE MODELS CONTINUE TO INDICATE THAT A REMNANT CLOSED

LOW...OVER THE SOUTHERN GREAT BASIN AT THE START OF THIS PERIOD...

WILL FINALLY ACCELERATE MORE RAPIDLY NORTHEASTWARD...ACROSS THE

CENTRAL ROCKIES AND PLAINS BY LATE SATURDAY...BEFORE DE-AMPLIFYING

OVER THE GREAT LAKES REGION. AND CONFIDENCE IS INCREASING THAT THIS

WILL BE ACCOMPANIED BY SIGNIFICANT LEE SURFACE CYCLOGENESIS

...INCLUDING A SUB-1000 MB SURFACE LOW CENTER. ALTHOUGH QUESTIONS

LINGER CONCERNING THE POTENTIAL MAGNITUDE OF DESTABILIZATION...

INSTABILITY...DEEP LAYER FLOW FIELDS/VERTICAL SHEAR AND FORCING FOR

UPWARD VERTICAL MOTION STILL APPEAR MOST SUPPORTIVE OF SEVERE

WEATHER POTENTIAL IN THE WARM SECTOR OF THIS SYSTEM ON SATURDAY.

THIS SEEMS MOST PROBABLE FROM PARTS OF EASTERN NEBRASKA AND KANSAS

NORTHEASTWARD ACROSS NORTHERN MISSOURI...IOWA...AND PARTS OF

SOUTHERN MINNESOTA...SOUTHWESTERN WISCONSIN...AND NORTHWESTERN

ILLINOIS. GIVEN THE SEVERE WIND AND TORNADO POTENTIAL POSSIBLE

WITHIN A KINEMATIC ENVIRONMENT NEAR A 70-90 KT SOUTHWESTERLY 500 MB

JET...AND 50-70 KT SOUTHERLY 850 MB JET...A REGIONAL SEVERE OUTLOOK

APPEARS WARRANTED...AS THE POTENTIAL EVENT BEGINS TO COME WITHIN A

MORE PREDICTABLE TIME FRAME.

..KERR.. 10/09/2012

[Minnesota Meso]

Strange to see MN painted for a day 5 regional threat in mid Oct. Just wondering how far north the warm sector will get. With rainfall commencing Sat morn and possibly heavy rain by 18z I wonder if it will each the TC metro.

[brettjrob]

My prelim Friday target is CVN-LBB-HOB. Further north isn't going to cut it. Gotta be south of the sfc boundary. Still will have plenty of shear over the dryline down there and better heating.

More later.

My thoughts exactly. No question at all which day chasers should be looking at now. GFS soundings from near I-40 down to CVN-LBB look pretty nice at 00z Sat, and I do favor S for now, as you noted. I do notice the NAM is slower to open up the H5 low at the end of its range, which gives more meridional flow over E NM. Either way, low-level backing should not be an issue, though it remains to be seen whether substantial low-level shear can develop before dark.

[Srain]

Good discussion out of AMA this morning regarding the potental and the primary issues that may hamper this event. My concern is the H5 disturbance may be a tad slower to eject out of the Great Basin. We will see.

THURSDAY-THURSDAY NIGHT: CLOSED UPPER LOW WILL SLOWLY MOVE ONSHORE.

IN RESPONSE TO THIS...LEE SIDE CYCLOGENESIS WILL CONTINUE TO PUMP

LOW-LEVEL MOISTURE INTO THE AREA. CAPPING SHOULD LIMIT THE COVERAGE

OF ANY THUNDERSTORM ACTIVITY FOR MOST OF THE DAY...BUT SOME ISOLATED

STORMS COULD DEVELOP ACROSS THE SOUTHWEST TEXAS PANHANDLE. IF ANY

STORMS DEVELOP DURING THE AFTERNOON AND EARLY EVENING...THEY COULD BE

STRONG TO MARGINALLY SEVERE. DAMAGING WINDS AND SMALL HAIL WILL BE THE

PRIMARY HAZARDS. BETTER CHANCES FOR THUNDERSTORMS WILL BE OVERNIGHT

AS THE INCREASING LOW-LEVEL JET INTERACTS WITH CONVERGENCE ALONG A

SURFACE WARM FRONT. THE OVERNIGHT THUNDERSTORMS WILL BE CAPABLE OF

PRODUCING SMALL TO MARGINALLY SEVERE HAIL.

FRIDAY-FRIDAY NIGHT: THIS COULD BE A VERY INTERESTING DAY

WEATHER WISE...BUT THERE REMAINS QUITE A BIT OF UNCERTAINTY. THE

CLOSED UPPER LOW WILL EJECT FROM THE FOUR CORNERS INTO THE SOUTHERN

ROCKIES THROUGH THE DAY. THE DYNAMICS ASSOCIATED WITH THIS UPPER

SYSTEM WILL LEAD TO LARGE SCALE FORCING FOR ASCENT OVER THE REGION.

WITH ABUNDANT MOISTURE AND LIFT INCREASING...THE STAGE WILL BE SET

FOR GOOD CHANCES FOR SHOWERS AND THUNDERSTORMS.

THERE ARE A FEW QUESTION MARKS WE HAVE AT THIS POINT.

1. OVERNIGHT CONVECTION AND EXTENSIVE LOW CLOUDS WILL LIKELY KEEP

TEMPERATURES FROM WARMING VERY MUCH DURING THE DAY. IF ANY BREAKS IN

THE CLOUDS DEVELOP...THE ATMOSPHERE WILL BECOME MORE UNSTABLE. IF

THIS SCENARIO PANS OUT...THE SEVERE WEATHER THREAT WILL BECOME

INCREASINGLY HIGHER.

2. THE DEGREE OF CAPPING SEEN ON FORECAST SOUNDINGS COULD LIMIT THE

COVERAGE OF AFTERNOON THUNDERSTORMS.

3. A WARM FRONT WILL BE LOCATED ACROSS THE PANHANDLES FOR MUCH OF THE

DAY. EXACTLY WHERE THIS WARM FRONT SETS UP...IT COULD ENHANCE

CONVERGENCE ALONG THE FRONT FOR THUNDERSTORMS TO DEVELOP.

DESPITE THESE QUESTION MARKS...IT APPEARS THAT SUFFICIENT INSTABILITY

WILL DEVELOP DURING THE AFTERNOON WITH MIXED LAYER CAPE VALUES UP TO

1500 J/KG. DEEP LAYER WIND SHEAR VALUES UP TO 55 KT WILL DEVELOP BY

THE EVENING AS THE DYNAMICS ASSOCIATED WITH THE UPPER SYSTEM

APPROACH. SUPERCELL THUNDERSTORMS ARE EXPECTED TO DEVELOP BY THE

MID-AFTERNOON HOURS WITH THE HIGHEST CHANCES WEST OF A CLAUDE TO

BEAVER LINE. SEVERE WEATHER LOOKS TO BE A DECENT BET WITH LARGE HAIL

AND DAMAGING WINDS BEING THE PRIMARY CONCERNS INITIALLY.

HOWEVER...ISOLATED TORNADOES CANNOT BE RULED OUT...ESPECIALLY ALONG

AND JUST NORTH OF THE SURFACE WARM FRONT WHERE LOW-LEVEL SHEAR WILL

BE MAXIMIZED. THE TORNADO THREAT COULD BE FURTHER ENHANCED IF

DISCRETE SUPERCELLS DEVELOP. WE WILL LEAVE MENTION OF TORNADOES OUT

OF THE HWO FOR NOW AS WE ARE NOT CONFIDENT ON WHERE THE WARM FRONT

WILL BE LOCATED. THE SUPERCELL THUNDERSTORMS AND ADDITIONALLY

THUNDERSTORMS WILL CONGEAL INTO A SQUALL LINE BY LATE FRIDAY EVENING

AND MARCH EASTWARD ACROSS THE FORECAST AREA. WHEN THE SQUALL LINE

DEVELOPS...DAMAGING WINDS WILL BE THE PRIMARY HAZARD...BUT AN

ISOLATED TORNADO STILL CANNOT BE COMPLETELY RULED OUT...ESPECIALLY IF

THE ENVIRONMENT AHEAD OF THE LINE CAN REMAIN SURFACE-BASED. LOCALLY

HEAVY RAIN WILL ALSO BE A CONCERN...AND THERE COULD BE SOME ISOLATED

FLASH FLOODING ISSUES.

[patrick7032]

My thoughts exactly. No question at all which day chasers should be looking at now. GFS soundings from near I-40 down to CVN-LBB look pretty nice at 00z Sat, and I do favor S for now, as you noted. I do notice the NAM is slower to open up the H5 low at the end of its range, which gives more meridional flow over E NM. Either way, low-level backing should not be an issue, though it remains to be seen whether substantial low-level shear can develop before dark.

I'm right there with you all for Friday. Once I get of shift at 3pm will be heading towards LBB myself.

[patrick7032]

One thing to keep an eye on is the frontal boundary which will be passing through my CWA as well as Lubbock's CWA...and may make it south into Midland's central CWA. It wouldn't surprise me if the front made it down to the I-10 corridor tomorrow which is further south than the models progg...however...as a meteorologist who works in the area I can tell you that the last several cold fronts...even the weak ones...HAVE ALL moved further south than model progs by an average of 150-200 miles. For instance...the last 3 or 4 fronts were shown to hang up in the northern Concho Valley or Big country in my area...basically on a Sterling City to Brownwood line...and when reality verified the fronts were on more of a Fort Stockton to San Antonio line. The current model progs take the front down to a Fort Stockton to Houston line. Obviously if this trend continued it would have significant implications on where to chase for Friday evening. Concerning that day...I VERY STRONGLY disagree with the panhandles not being mentioned for Friday. I could...perhaps...understand not having the catergorical risk since although instability is meager on the day 5 forecasts the shear would dynamically force the severe weather...but there is most definitely a thhreat after 21z on Friday evening. Even with capping...the moisture advection and incoming upper forcing would promote severe cells...and offices further west agree. Below are a couple mroe discussions in addition to the AMA one posted earlier.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE LUBBOCK TX

455 AM CDT TUE OCT 9 2012

HOWEVER...FRI AFTN/EVNG

APPEARS TO HOST THE BEST OPPORTUNITY OF WETTING RAINS AS THE UPPER

LOW LIFTS INTO ERN COLORADO AND DRAGS ITS TROUGH AXIS OVER THE

REGION COMPLETE WITH A DRYLINE AND PACIFIC COLD FRONT. ADDED WITH

UNSEASONABLY HIGH PWATS OF 1.3" TO NEARLY 2" AND STRONG KINEMATIC

PROFILES...THIS PATTERN IS BEGINNING TO EXHIBIT A STRIKING

RESEMBLANCE TO THE ONE WE SAW ON OCT 21 2010 WHEN NUMEROUS STRONG

AND SEVERE STORMS DEVELOPED. MANY MORE DETAILS WILL NEED TO BE

SORTED OUT IN THE DAYS AHEAD...BUT BASIC PATTERN RECOGNITION DOES

WARRANT A MENTION OF SEVERE STORMS IN THE HWO

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX

354 AM CDT TUE OCT 9 2012

FRIDAY LOOKS FAIRLY WINDY OVER THE EAST WITH A TIGHT

SURFACE GRADIENT EAST OF A SURFACE TROUGH EXTENDING DOWN ACROSS THE

AREA. COULD SEE DRYLINE STORMS FORM ALONG THIS BOUNDARY. COULD SEE

SOME SEVERE STORMS THURSDAY OR FRIDAY AND WILL CONTINUE TO MENTION

IN HWO.

[brettjrob]

One thing to keep an eye on is the frontal boundary which will be passing through my CWA as well as Lubbock's CWA...and may make it south into Midland's central CWA. It wouldn't surprise me if the front made it down to the I-10 corridor tomorrow which is further south than the models progg...however...as a meteorologist who works in the area I can tell you that the last several cold fronts...even the weak ones...HAVE ALL moved further south than model progs by an average of 150-200 miles. For instance...the last 3 or 4 fronts were shown to hang up in the northern Concho Valley or Big country in my area...basically on a Sterling City to Brownwood line...and when reality verified the fronts were on more of a Fort Stockton to San Antonio line. The current model progs take the front down to a Fort Stockton to Houston line. Obviously if this trend continued it would have significant implications on where to chase for Friday evening. Concerning that day...I VERY STRONGLY disagree with the panhandles not being mentioned for Friday. I could...perhaps...understand not haaving the catergorical risk since although instability is meager on the day 5 forecasts the shear would dynamically force the severe weather...but there is most definitely a thhreat after 21z on Friday evening. Even with capping...the moisture advection and incoming upper forcing would promote severe cells...and offices further west agree. Below are a couple mroe discussions in addition to the AMA one posted earlier.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE LUBBOCK TX

455 AM CDT TUE OCT 9 2012

HOWEVER...FRI AFTN/EVNG

APPEARS TO HOST THE BEST OPPORTUNITY OF WETTING RAINS AS THE UPPER

LOW LIFTS INTO ERN COLORADO AND DRAGS ITS TROUGH AXIS OVER THE

REGION COMPLETE WITH A DRYLINE AND PACIFIC COLD FRONT. ADDED WITH

UNSEASONABLY HIGH PWATS OF 1.3" TO NEARLY 2" AND STRONG KINEMATIC

PROFILES...THIS PATTERN IS BEGINNING TO EXHIBIT A STRIKING

RESEMBLANCE TO THE ONE WE SAW ON OCT 21 2010 WHEN NUMEROUS STRONG

AND SEVERE STORMS DEVELOPED. MANY MORE DETAILS WILL NEED TO BE

SORTED OUT IN THE DAYS AHEAD...BUT BASIC PATTERN RECOGNITION DOES

WARRANT A MENTION OF SEVERE STORMS IN THE HWO

Good points. I am slightly concerned about the frontal intrusion, as you mentioned, and how it will affect moisture return for Friday. The upside is that it truly doesn't take much when you're talking about NM.

The analog mentioned by LBB piqued my interest. The pattern was somewhat similar (albeit with the mid-level low farther S than currently progged for 00z Sat), and moisture was downright pitiful, with low-mid 50s Td's across E NM. Nevertheless, this was the result:

Even if the less impressive moisture on the NAM is accurate, we should still manage 55-58 Td's in the area of interest. My biggest concerns are (1) sufficient clearing to realize 1500+ J/kg SBCAPE, and (2) a good balance of shear and instability (H5 winds will approach 60-70 kt by 00z unless the system slows further).

[patrick7032]

Good points. I am slightly concerned about the frontal intrusion, as you mentioned, and how it will affect moisture return for Friday. The upside is that it truly doesn't take much when you're talking about NM.

The analog mentioned by LBB piqued my interest. The pattern was somewhat similar (albeit with the mid-level low farther S than currently progged for 00z Sat), and moisture was downright pitiful, with low-mid 50s Td's across E NM. Nevertheless, this was the result:

Even if the less impressive moisture on the NAM is accurate, we should still manage 55-58 Td's in the area of interest. My biggest concerns are (1) sufficient clearing to realize 1500+ J/kg SBCAPE, and (2) a good balance of shear and instability (H5 winds will approach 60-70 kt by 00z unless the system slows further).

Nice video. I was gonna reserarch that later myself. I can tell you that as of late...at least when I was on shift...I used the NAM data for my short term discussions as it had less of an error margin when comparing model initialzations and raob data. I will post something to that effect on Thursday and Friday mornings if I remember to this week. The new NAM just came in and I'm LIKING THE PARMATERS. It's showing a 21z initation as I mentioned earlier...with -7 to -8 LI's and capes of 2300 j/kg from just north of Fort Stockton north the central part of the state line...then arcing northeast through AMA towards KGAG in western Oklahoma.

[patrick7032]

Here's a sounding from today's 12z NAM for Hobbs, New Mexico on the state line...to give an idea of the pre-convective conditions before the stronger forcing arrives. For whatever reason...bufkit is showing 300 j/kg and 2-3 less unstable LI's that what I see on my workstation data.

[patrick7032]

I like how the 12z GFS is trending stronger and slightly slower with the 500 and 250 jet maxes. Based on water vaper this looks reasonable as not only does the upper low off the California coast look stronger compared to yesterday, but it has a good deal of convection with the low...lots of positive and negative strikes around the center. There were no lightning strikes with the upper low yesterday. Looks like the Abilene, Texas area...through eastern Oklahoma...into southeastern Kansas (later in the afternoon here) will be a good spot for mid afternoon stuff Saturday....as this area will be in the right entrance region.

[andyhb]

Eastern OK, SE KS and SW MO also have a nasty 50-60 kt LLJ overlapping the warm sector at that same timeframe.

The result: Large looping, clockwise curved hodographs, although as mentioned before, we'll have to watch how much the LL winds veer, although that becomes a bit less of an issue east of I-35.

[JoMo]

You'll also have to watch out for crapvection lessening the instability up this way.

[OKpowdah]

Another issue to consider here is that the slower that this disturbance ejects eastward, the more latitude it will gain. There is more space put between it and the trough swinging out of Canada into the Great Lakes, and the background flow becomes more southwesterly ahead of a trough moving into the Pacific NW. This making it more prone to lifting northeastward.

Best bet in my mind is still a late Friday event, and hope for this to speed up.

[andyhb]

12z Euro looks to be a bit further south than previous runs, with the ULL taking a track through northern KS/southern NE rather than northern NE/southern SD.

It also has a pretty stout warm sector on Saturday.

[OKpowdah]

just as I say I'm more interested in Friday, some decent changes on the Euro to make Saturday more interesting.

[andyhb]

Forbes:

SATURDAY

Has the potential to be at least a limited severe thunderstorm outbreak with a few tornadoes in southeast SD, east NE, east KS, northeast and central OK, IA, south MN, west and north-central MO, possibly north-central TX. TORCON - 4 IA, east KS, west MO