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October 12-13th "Potential" Severe Outbreak


patrick7032

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The overall synoptic pattern on Saturday also reminds me a bit of the 1012/05 event, where a localized tornado outbreak occurred over parts of Iowa, which included the damaging Woodward tornado.

Yea I can see that, expect it has potential to be a lot bigger of a severe weather outbreak than that. Right now I like the triple point, dryline/wf intersection in the Souix City, IA area for the best tornado potential, however that will change as the week progresses. Crapvection will change my target lol.

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Tony informed me that they have changed the parameters/thresholds on that (From 1000 J/kg MLCAPE to 500 and MLLCL heights from 1000 m to 1500 m, and looking at previous outbreak threads, that appears to be the case), which means seeing large numbers like this further out may be not as hard as it was in the past. Still, that is fairly impressive for 87 hours out.

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I've been busy installing the chase gear back in the car so I haven't been putting much out, but I will remind everyone we have the Texas/OU Game in Dallas on Saturday with around 100,000 people expected plus all the partying across the D/FW Metroplex.

Yes, I was going to mention that too. The DFW area should be way more congested than usual - but in the end maybe it'd take some people off the chase routes that otherwise would have been there. The game is at 11:00AM though, so the late afternoon timeframe could be a bit hectic.

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

That's what I'm starting to think too...and agree with what Forbes said in andyhb's post. The GFS and Euro both move the 500 and 250mb lows ashore around the same time and generally in the same location with very similar tracks...however the GFS really seems to accelerate the low after the 72-84 hour time frame from todays 12z run. The Euro maintains a fairly consistent wave speed with a slightly more amplified pattern...and ejects the low more slowly. If this solution was to verify...the eastern Texas Panhandle through western Oklahoma through the eastern Kansas where the 700...500...and 250 jets coincide

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That's what I'm starting to think too...and agree with what Forbes said in andyhb's post. The GFS and Euro both move the 500 and 250mb lows ashore around the same time and generally in the same location with very similar tracks...however the GFS really seems to accelerate the low after the 72-84 hour time frame from todays 12z run. The Euro maintains a fairly consistent wave speed with a slightly more amplified pattern...and ejects the low more slowly. If this solution was to verify...the eastern Texas Panhandle through western Oklahoma through the eastern Kansas where the 700...500...and 250 jets coincide

Yeah this was my concern that I mentioned to you yesterday that it could slow down a touch with the GFS being overtly progressive.

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Tony informed me that they have changed the parameters/thresholds on that (From 1000 J/kg MLCAPE to 500 and MLLCL heights from 1000 m to 1500 m, and looking at previous outbreak threads, that appears to be the case), which means seeing large numbers like this further out may be not as hard as it was in the past. Still, that is fairly impressive for 87 hours out.

That's highly annoying. Got pretty excited seeing that chart before I went to the next page and saw this -- I remember you posting a similar-looking SigTor map a few days before a certain event last fall. ;)

It was definitely tough to get more than 10-20% probs with the old method in the 2-3 day range, but that's kind of the point. I'm not sure how much value the new parameter set is. MLLCL of 1500 m is usually too high, and 500 J/kg may be a decent threshold in the Southeast, but not the Plains.

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That's highly annoying. Got pretty excited seeing that chart before I went to the next page and saw this -- I remember you posting a similar-looking SigTor map a few days before a certain event last fall. ;)

It was definitely tough to get more than 10-20% probs with the old method in the 2-3 day range, but that's kind of the point. I'm not sure how much value the new parameter set is. MLLCL of 1500 m is usually too high, and 500 J/kg may be a decent threshold in the Southeast, but not the Plains.

Yeah, I find it quite frustrating, it seems that they nerfed their own product doing that.

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Yeah this was my concern that I mentioned to you yesterday that it could slow down a touch with the GFS being overtly progressive.

If that's the case, then IMHO, this system will go to waste. Regarding Saturday, I've seen this song and dance far too many times before. It's just not going to work out, at least for chasers. The LLJ is sexy so no one can look away, but it's just not timed correctly -- plus, timing aside, I loathe such rapidly-lifting disturbances (as wxwatcher91 pointed out).

I'd almost put money down that the ECMWF is not progressive enough on Saturday, and that it will snap back to something closer to the GFS over the next 24 h. And even if it's dead accurate, the LLJ still veers too much along the dryline, especially if the dryline stays so far west. (The farther west you go, the less veering you can afford, because you're higher elevation and you've got the desert/Mexican plateau nearby to the SW).

The only thing staving off total depression right now in my eyes is that even with the slow EC soln, Friday still looks doable in NM. It would have to slow down a TON not to get good deep-layer shear to the TX/NM border by 00z Sat.

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I've been busy installing the chase gear back in the car so I haven't been putting much out, but I will remind everyone we have the Texas/OU Game in Dallas on Saturday with around 100,000 people expected plus all the partying across the D/FW Metroplex.

Do you think a whole lot of anything will really happen in DFW? I've been gathering that all the good stuff will stay west and then north of us, and the most we might get would be an overnight MCS.

I sure wish I could drive out ahead of this thing but the intricacies of my schedule only allow me to chase on Sundays and Mondays.

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I'll preface my comment with this, just to keep myself out of trouble and out of my flame suit: I won't pretend to be a decent severe weather forecaster. I am a student so I have a general but ever-growing, meteorological background and a keen sense of observation, and that is what I most commonly do here, I just read and try and learn from those smarter than I.

With that being said, Friday appears to me to be the more favorable day for tornadoes in E NM / W TX panhandle / SW OK and panhandle / SE CO / SW KS based on shear profiles and generated forecast soundings from twisterdata. Anti cyclone positioned over MS will allow moisture to be transported northward throughout the day, resultant 850/700/500mb temps aren't exceptionally cold but UVVs and Vorticity associated with the transient low will provide enough divergence aloft to overcome this. My issue with Saturday is the plethora of Vorticity and UVVs as the low deepens, which leads me to believe that anything that goes up discretely on Saturday will soon be followed by other convection and quickly congeal into a convective line. That and storm motions look like they'd be difficult to deal with in an area of the country that isn't as friendly to chasing as the SW is.

Comments, corrections appreciated.

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I'll preface my comment with this, just to keep myself out of trouble and out of my flame suit: I won't pretend to be a decent severe weather forecaster. I am a student so I have a general but ever-growing, meteorological background and a keen sense of observation, and that is what I most commonly do here, I just read and try and learn from those smarter than I.

With that being said, Friday appears to me to be the more favorable day for tornadoes in E NM / W TX panhandle / SW OK and panhandle / SE CO / SW KS based on shear profiles and generated forecast soundings from twisterdata. Anti cyclone positioned over MS will allow moisture to be transported northward throughout the day, resultant 850/700/500mb temps aren't exceptionally cold but UVVs and Vorticity associated with the transient low will provide enough divergence aloft to overcome this. My issue with Saturday is the plethora of Vorticity and UVVs as the low deepens, which leads me to believe that anything that goes up discretely on Saturday will soon be followed by other convection and quickly congeal into a convective line. That and storm motions look like they'd be difficult to deal with in an area of the country that isn't as friendly to chasing as the SW is.

Comments, corrections appreciated.

Agree mostly. Friday has looked like the better chase day for a while now.. only looking moreso that way as we close in. I see people talking about trying for both on Twitter etc (plus wishcasting a lot). If things stay as is looks like a waste of gas and missed sleep for frustration.

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It was definitely tough to get more than 10-20% probs with the old method in the 2-3 day range, but that's kind of the point. I'm not sure how much value the new parameter set is. MLLCL of 1500 m is usually too high, and 500 J/kg may be a decent threshold in the Southeast, but not the Plains.

And, to add on to that when we saw a 50 area on hour 87 prior to 4/27, we knew all hell could break loose....

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FWIW... 12z GGEM much more in the line with the GFS timing.

The GGEM doesnt do well with southern events during the summer from what most of the guys at the office has told me. We really don't use it....we look at it but really rely on the GFS and EURO for long range events. In a day 4-5 range forecast usually all models are fast by 12 hours on average. We'll see.235_100.gif

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I'd argue that the GGEM is much much closer to the Euro on timing and evolution of the system.

Just going by the 00z Sun position of the ULL:

GFS - just E of Sioux Falls

GGEM - along the MO River west of Yankton

ECMWF - between Hastings and Holdrege NE

By that measure, the GGEM is about 60% GFS and 40% EC, I guess.

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I'd argue that the GGEM is much much closer to the Euro on timing and evolution of the system.

True...I just don't have much faith in the GGEM. Most seem to go with the Euro over the GFS at the office...and since I'm still learning the models in this area...figured will follow the advice from work.

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE LUBBOCK TX

347 PM CDT TUE OCT 9 2012

MUCH STRONGER DYNAMICS WILL COME INTO PLAY ON FRIDAY AS THE UPPER

CLOSED LOW DRAWS NEAR. A 100KT JET WILL BE ROUNDING THE BASE OF THE

UPPER TROUGH ALONG WITH GOOD DIVERGENCE ON THE EAST SIDE OF THIS

TROUGH AXIS. LOW LEVEL FLOW WILL BACK ON FRIDAY BRINGING IN AN

ABUNDANCE OF MOISTURE. IN FACT...MODEL PRECIPITABLE WATER INDICATE

AROUND 225 PERCENT OF NORMAL BY FRIDAY EVENING. THESE MOIST

CONDITIONS WILL LEAD TO HIGH INSTABILITY FOR THIS TIME OF YEAR. THIS

WILL ALL LEAD TO A POSSIBLE SEVERE WEATHER EPISODE ON FRIDAY

EVENING. AREAS GENERALLY LUBBOCK AND NORTH WOULD SEE THE HIGHEST

CHANCES FOR THUNDER AND SEVERE WEATHER. OBJECTIVE ANALOG GUIDANCE

NOW SUGGESTS OCT 21 2010 IS A STRONG CANDIDATE FOR AN ANALOG AS

MENTIONED IN A PREVIOUS DISCUSSION.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE WICHITA KS

349 PM CDT TUE OCT 9 2012

FRIDAY NIGHT-SATURDAY EVENING WILL BE THE MAIN FOCUS FOR THIS

FORECAST PACKAGE...AS A POWERFUL STORM SYSTEM APPROACHES FROM THE

SOUTHWEST. OTHER THAN MINOR VARIATIONS...MODELS ARE IN GOOD

AGREEMENT SURROUNDING THE TIMING OF THIS SYSTEM. THE NEW ECMWF CAME

IN A BIT SLOWER THAN THE OPERATIONAL GFS...WHICH WOULD SHIFT THE

HIGHEST SEVERE WEATHER POTENTIAL A BIT FURTHER WEST (POSSIBLY WEST

OF THE FLINT HILLS) FOR SATURDAY AFTERNOON/EVENING. SEVERAL GFS

ENSEMBLE MEMBERS SUPPORT THIS SCENARIO. ADDITIONALLY...A SLOWER

SOLUTION TENDS TO BE FAVORED WITH STALLED WEST/SOUTHWEST CONUS UPPER

LOWS. ALL-IN-ALL...SATURDAY AFTERNOON/EVENING WILL NEED TO BE

WATCHED FOR SEVERE WEATHER POTENTIAL...SOME OF WHICH COULD BE ON THE

HIGHER END...DUE TO STRONG FORCING AND 60-70 KTS OF DEEP LAYER

SHEAR...ALONG WITH THE POTENTIAL FOR MODEST INSTABILITY.

HOWEVER...MAGNITUDE OF SEVERE WEATHER WILL DEPEND ON EXTENT OF

LOW-CLOUDS AND ASSOCIATED DESTABILIZATION.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE TOPEKA KS

337 PM CDT TUE OCT 9 2012

FRIDAY NIGHT THROUGH SATURDAY NIGHT...THE H5 LOW OVER THE DESERT

SOUTHWEST WILL LIFT NORTHEAST INTO EASTERN NE. A LEE CYCLONE SHOULD

FORM ACROSS EASTERN CO INTO THE NORTHERN TX PNHDL THROUGH THE

EVENING HOURS OF FRIDAY IN RESPONSE TO THE INTENSE H5 TROUGH

LIFTING NORTHEAST INTO THE SOUTHERN HIGH PLAINS. THE DEEPENING LEE

SURFACE CYCLONE WILL CAUSE THE LOW-LEVEL WINDS TO BECOME SOUTHERLY AND

TRANSPORT DEEPER GULF MOISTURE NORTHWARD ACROSS THE STATE OF KS.

THE COMBINATION OF ISENTROPIC LIFT AND INCREASING ASCENT AHEAD OF

THE H5 LOW WILL CAUSE NUMEROUS SHOWERS AND THUNDERSTORMS TO

DEVELOP. VERTICAL WINDSHEAR PROFILES AND THE POTENTIAL FOR

MODERATE INSTABILITY MAY ALLOW FOR SUPERCELL THUNDERSTORMS TO

DEVELOP ALONG THE SFC DRYLINE/PACIFIC FRONT DURING THE LATE

AFTERNOON AND EVENING HOURS OF FRIDAY ACROSS SOUTHWEST KS AND THE TX

PNHDL. THESE SCATTERED SEVERE THUNDERSTORMS WILL PROBABLY CONGEAL

INTO A QLCS AND LIFT NORTHEAST ACROSS CENTRAL KS AFTER MIDNIGHT.

THESE STORMS WILL BECOME ELEVATED AND SOME OF THE STRONGER STORMS

MAY PRODUCE SMALL HAIL EARLY SATURDAY MORNING ACROSS THE WESTERN

COUNTIES OF THE CWA.

AS THE H5 TROUGH LIFTS NORTHEAST ACROSS WESTERN KS INTO EASTERN NE

DURING THE AFTERNOON AND EVENING HOURS...THUNDERSTORMS WILL

REDEVELOP ALONG THE PACIFIC COLD FRONT ACROSS CENTRAL OR EASTERN KS.

THE 12Z RUN OF THE ECMWF IS ABOUT 4 TO 5 HOURS SLOWER THAN THE NAM

AND GFS AND MAY INCREASE THE POTENTIAL FOR THUNDERSTORMS ACROSS THE

ENTIRE CWA DURING THE AFTERNOON AND EVENING HOURS OF SATURDAY. THE

ECMWF SOLUTION ALSO TRACKS THE UPPER LOW A BIT FARTHER SOUTH THAN THE

OTHER OPERATIONAL MODEL SOLUTIONS.

Waiting to see what AMA says.

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Impressive discussion from DMX, and mentions the 11/12/05 analog I did earlier:

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...

MAIN FORECAST ISSUE TODAY WILL FOCUS ON TRANSITION IN UPPER PATTERN

FROM A BROAD NORTHWEST FLOW REGIME TO A MORE ZONAL PATTERN INTO NEXT

WEEK. DURING THIS TIME...A STRONG UPPER LOW CURRENTLY OFF THE

CALIFORNIA COAST WILL PASS THROUGH THE FOUR CORNERS AREA AND THEN

LIFT NORTHEAST THROUGH THE MIDWEST. PRIOR TO THE ARRIVAL OF THIS

SYSTEM...ONE MORE SHORTWAVE WILL DROP DOWN INTO THE NORTHERN PART OF

THE REGION. THE BULK OF THIS SYSTEM IS FORECAST TO REMAIN WELL TO

THE NORTH ACRS THE GREAT LAKES WHERE THE FORCING WILL BE MAXIMIZED.

THIS SYSTEM WILL PUSH A FRONT THROUGH THE STATE EARLY THURSDAY BUT

WITH LITTLE FORCING OR MOISTURE IN THE STATE...THE THREAT OF

PRECIPITATION WILL BE MINIMAL. THIS FRONT IS EXPECTED TO DROP INTO

NORTHERN OKLAHOMA AND SOUTHERN MISSOURI BEFORE STALLING IN ADVANCE

OF THE CALIFORNIA SYSTEM. AS THE UPPER LOW IN CALIFORNIA

EJECTS...THE STALLED FRONT WILL BEGIN MOVING BACK NORTHWARD ON

FRIDAY. INITIALLY...THERE WILL BE A THETA-E SURGE ON FRIDAY NIGHT

WITH INCREASING ELEVATED INSTABILITY AS THE LOW LEVEL JET

STRENGTHENS. CONVECTION IS EXPECTED TO BREAK OUT AS THE INSTABILITY

AND FORCING INCREASES DURING THE NIGHT AND LIKELY TO CATEGORICAL

POPS HAVE BEEN MAINTAINED. WIND PROFILES WILL BE STRONGLY VEERED

OVERNIGHT AND WOULD BE EASILY SUFFICIENT FOR SEVERE STORMS WITH THE

MAIN ISSUE FOR SEVERE OVERNIGHT LYING WITH THE AMOUNT OF

INSTABILITY. CERTAINLY AN ELEVATED HAIL STORM SEEMS POSSIBLE

ALTHOUGH THE HAIL SIZE MAY BE MARGINAL. SATURDAY COULD BE QUITE

INTERESTING AS WARM SECTOR OVERSPREADS THE STATE. ONGOING

CONVECTION IS EXPECTED IN THE MORNING BUT GRADUALLY PULLING

NORTHWARD INTO MINNESOTA AND WISCONSIN WITH TIME. BOTH THE 12Z GFS

AND 09.00Z EURO HAD A CLIMATOLOGICAL FAVORABLE SETUP FOR SEVERE

WEATHER ON SATURDAY AFTERNOON. THIS WOULD BRING A TROF AXIS/DRY

LINE INTO WESTERN IOWA AROUND PEAK HEATING WITH A STRONG WIND

PROFILE. HISTORICALLY...INSTABILITY OF 1000-1500 J/KG IS SUFFICIENT

IN THESE CASES FOR PRODUCING TORNADIC STORMS. NOVEMBER 12TH 2005

WAS SIMILAR TO THIS SYSTEM AND THAT SYSTEM EVENT HAD ONLY AN HOUR OR

TWO OF SUNSHINE AFTER THE LOW OVERCAST CLEARED BEFORE CONVECTION

DEVELOPED. THEREFORE...WILL WATCH THIS SYSTEM CLOSELY OVER THE NEXT

FEW DAYS TO SEE IF MODELS REMAIN CONSISTENT IN THEIR SOLUTIONS.

ALREADY...12Z EURO RUN IN SLOWER AND WOULD KEEP THE WORST CONDITIONS

WEST AND SOUTHWEST OF IOWA ON SATURDAY AFTERNOON. IN THE END...THE

SYSTEM BEARS CLOSE WATCHING FOR POTENTIAL OF SEVERE WEATHER AND

POSSIBLE TORNADOES ON SATURDAY AFTERNOON. THEREAFTER...TEMPERATURES

REMAIN RELATIVELY MILD WITH QUASI-ZONAL FLOW DEVELOPING.

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE AMARILLO TX

324 PM CDT TUE OCT 9 2012

FRIDAY THROUGH FRIDAY...THIS IS STILL THE PERIOD OF GREATEST CONCERN

WITH RESPECT TO SEVERE AND HEAVY RAIN POTENTIAL. STILL A CONCERN THAT

A MID LEVEL WARM LAYER WILL CONTRIBUTE TO CAPPING THAT COULD INHIBIT

CONVECTIVE INITIATION. HOWEVER...WITH SURFACE CONFLUENCE ALONG THE

PACIFIC COLD FRONT...ESPECIALLY LATE IN THE DAY...COMBINED WITH

SYNOPTIC SCALE LIFT FROM THE APPROACHING UPPER LEVEL LOW...SHOULD BE

ENOUGH TO OVERCOME ANY CAPPING. MODELS CONTINUE TO SHOW CAPE VALUES

NEAR OR JUST ABOVE 1000 J/KG AND BULK SHEAR VALUES 30 TO 40

KT...INDICATING A RISK OF SEVERE WEATHER. ADDITIONALLY PRECIPITABLE

WATER VALUES AT OR ABOVE AN INCH WILL INCREASE THE RISK OF HEAVY RAIN

AS WELL. AGREE WITH THE PREVIOUS SHIFT THAT THE MAIN HAZARDS WILL BE

HEAVY RAIN...HAIL...AND WIND AT THIS TIME AS THE CONVECTION SHOULD

LINE OUT BY THE TIME IT REACHES THE PANHANDLES. THUS THE POTENTIAL

FOR SUPERCELLS...AND THUS THE TORNADO THREAT...APPEARS VERY LOW AT

THIS TIME.

I think these cape values are WAY TOO LOW...and they are clearly going with the GFS cape forecasts. When compared to mesoanalysis...the GFS is usually 500 too low at 18z to over 1500 too low by 21z. This pattern has been seen many times this summer in my CWA.

post-767-0-39607500-1349819294_thumb.png

post-767-0-01004100-1349819308_thumb.png

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The GFS also has 60s sfc dews and H85 dews of 12-15+ degrees C across much of AMA's CWA by 00z Friday, if you were to adjust that to combine with the GFS' low boundary layer temp bias, you get a substantially different environment to what they are putting across there.

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE AMARILLO TX

324 PM CDT TUE OCT 9 2012

FRIDAY THROUGH FRIDAY...THIS IS STILL THE PERIOD OF GREATEST CONCERN

WITH RESPECT TO SEVERE AND HEAVY RAIN POTENTIAL. STILL A CONCERN THAT

A MID LEVEL WARM LAYER WILL CONTRIBUTE TO CAPPING THAT COULD INHIBIT

CONVECTIVE INITIATION. HOWEVER...WITH SURFACE CONFLUENCE ALONG THE

PACIFIC COLD FRONT...ESPECIALLY LATE IN THE DAY...COMBINED WITH

SYNOPTIC SCALE LIFT FROM THE APPROACHING UPPER LEVEL LOW...SHOULD BE

ENOUGH TO OVERCOME ANY CAPPING. MODELS CONTINUE TO SHOW CAPE VALUES

NEAR OR JUST ABOVE 1000 J/KG AND BULK SHEAR VALUES 30 TO 40

KT...INDICATING A RISK OF SEVERE WEATHER. ADDITIONALLY PRECIPITABLE

WATER VALUES AT OR ABOVE AN INCH WILL INCREASE THE RISK OF HEAVY RAIN

AS WELL. AGREE WITH THE PREVIOUS SHIFT THAT THE MAIN HAZARDS WILL BE

HEAVY RAIN...HAIL...AND WIND AT THIS TIME AS THE CONVECTION SHOULD

LINE OUT BY THE TIME IT REACHES THE PANHANDLES. THUS THE POTENTIAL

FOR SUPERCELLS...AND THUS THE TORNADO THREAT...APPEARS VERY LOW AT

THIS TIME.

I think these cape values are WAY TOO LOW...and they are clearly going with the GFS cape forecasts. When compared to mesoanalysis...the GFS is usually 500 too low at 18z to over 1500 too low by 21z. This pattern has been seen many times this summer in my CWA.

To be fair, I'm reading the wording to imply that a greater threat may exist, but it will be W of their CWA. That's certainly a possibility, although I think at least the westernmost column of Panhandle/South Plains counties will be in on it, too. Wouldn't be the most shocking thing in the world to see the "storm of the day" 50-75 mi. W of the state line, though.

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lol

"Reed Timmer: Meteorologist and Extreme Storm Chaser

MAJOR tornado outbreak likely on Saturday from Iowa/Illinois all the way southwest to the southern MS River Valley.

I would not be surprised if this Friday-Saturday goes down as one of the most significant tornado outbreaks in years in the central U.S."

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