Thanksgiving Week Severe Weather

[Thundersnow12]

Just as an FYI, the last time there were two months in a row that had significant tornadoes in the LOT CWA was April and May 2004. The last time two significant tornado events occurred within a month of each other in the CWA was 8/5 and 8/18/79.

And who would of thought the next time it happened was Oct/Nov....simply amazing. Also wouldn't of guess that for the two tornado warnings issued this year for my county would of been in Oct/Nov.

[Thundersnow12]

Going to wait until the 0z runs to say more about tomorrow but think there could be some nice tornadic supercells in eastern OK/southern MO/western AR. Same strength of mid-level jet nearing 85kts, nice looking theta-e axis nosing into the area after 18z with dew points in the low/mid 60's across the warm sector. Bulk shear and low-level shear will be pretty impressive tomorrow.

[JoMo]

Going to wait until the 0z runs to say more about tomorrow but think there could be some nice tornadic supercells in eastern OK/southern MO/western AR. Same strength of mid-level jet nearing 85kts, nice looking theta-e axis nosing into the area after 18z with dew points in the low/mid 60's across the warm sector. Bulk shear and low-level shear will be pretty impressive tomorrow.

Yeah, I haven't been paying much attention since I am in winter weather mode. But it looks like there could be some big storms here tomorrow if we can get enough instability. The cold front should undercut any storms along the actual front, but I'm not sure about earlier in the day.

[Thundersnow12]

0z NAM showing even more instablity and dew points in the upper 60's in eastern OK..

[Thundersnow12]

[Stebo]

I'd certainly be watching Eastern OK, SW MO, and W AR tomorrow evening. Things kind of coming together nicely for a decent potential.

[JoMo]

I'd certainly be watching Eastern OK, SW MO, and W AR tomorrow evening. Things kind of coming together nicely for a decent potential.

Severe T-storms, followed by a bit of ice and snow as it ends. Sounds about right for here

[tornadotony]

Yeah, if the NAM instability trends are correct, ern OK and wrn AR could be in a world of hurt tomorrow...looks like a long, sustained period of threat that could last into the night...will have to reevaluate in the morning...FWIW, GFS has the main threat lesser and further S, while the SPC WRF paints some decent updraft helicities in cells in ern KS and SW MO, so yeah, precision from our lovely models is out the window...oh and there are 68F Td to I-20 at this hour...

[Fred Gossage]

Yeah, if the NAM instability trends are correct, ern OK and wrn AR could be in a world of hurt tomorrow...looks like a long, sustained period of threat that could last into the night...will have to reevaluate in the morning...FWIW, GFS has the main threat lesser and further S, while the SPC WRF paints some decent updraft helicities in cells in ern KS and SW MO, so yeah, precision from our lovely models is out the window...oh and there are 68F Td to I-20 at this hour...

We're already talking about this personally, but given how far north those high dewpoints are already, the fact that we are dealing with a straight WSW jet from the higher elevations to advect that EML overtop the moisture axis... and the general performance of the NAM and SPC WRF, in comparison to the GFS, with yesterday's event.... I'm willing to lean toward their solution as well.

[Stebo]

Yeah I would have to agree that the NAM is going to have a better handle on this, GFS is just bias towards climo too much. I would be hard pressed to believe its going to be only near 60 tomorrow at 00z in a major portion of E/NE OK. Again look at how well the NAM handled the event yesterday.

[David Reimer]

This is what I just posted over on my website. Keep in mind this was specifically written for those who live in the Oklahoma/Texas region. I'll be out tomorrow chasing what looks to be adding up as a possible tornado outbreak.

Thus is fall in the southern plains... We're talking about a potential severe weather event in late November, on the busiest travel day of the year. Welcome to La Nina folks! We've been watching tomorrow on the models now for several days. Beginning yesterday the models began hinting on increased amounts of instability being present for Wednesday's event, and tonight's 0Z NAM really spiked up the values. Lets take a detailed look into what might be a considerable severe weather threat tomorrow.

The two maps above, each from 6 PM Central tonight, show the rapidly changing weather conditions across the United States. A very deep trough is digging into the Western US. This is allowing for very cold air bottled up in Canada and the Arctic Circle to invade the Untied States. At the time of posting, Salt Lake City had broken a one hour snow record with a major blizzard was underway. Temperatures in South Dakota will be hard-pressed to reach zero for the next few days. Although the winter affects won't be nearly as severe here in the south, we'll be dealing with our own issues as this very cold airmass collides with the unseasonably warm and moist environment in place over Texas and the deep-south tonight.

Moisture return is underway across south tonight as a warm front lifts northward, bringing very moist conditions to areas that have generally been dry the past few days. By tomorrow afternoon, dewpoints above 63F should be located from Tulsa, Oklahoma eastward to Little Rock, Arkansas. This is a moist environment for the springtime, and combining it with the volatility of a winter system will definitely bring the potential for severe weather issues.

This is undoubtly the strongest system we've faced so far this winter season here in the south. Winds at 500 MB will be over 75 knots from the southwest over most of Oklahoma, combine that with a 45 knot low level jet at 850 from the south-southwest, most storms tomorrow will rotate with ease. Winds at 925 MB are forecasted to be at 30 knots out of the due south, with a south to southeasterly surface wind. This is the classic direction change you look for rotating storms and possible tornadoes. Now in most cases, the low level wind fields are too weak to support any low level rotation.

This graphic shows the rotation potential in the lowest 1 KM of the atmosphere. Generally you'd look for numbers over 150 for possible tornadoes, with anything over 250-300 very significant. As noted in the graphic above, a maxima of 300+ is located over Eastern Oklahoma. Needless to say, the wind fields are supportive of tornadic activity tomorrow. In the winter time, the wind fields are usually favorable for tornadoes. It's just that there is no instability present and you're not able to get any organized convection. For the past several days it looked like tomorrow would be another one of those days with high shear but no instability, but that changed when the models began increasing the amount of instability present in the warm sector.

In this high shear environment, any surface based instability over 1,000 joules is considerable, with 2,000 joules being a very significant number. The 3 KM CAPE, a number we look for when determining the instability in the lowest 3 KM of the atmosphere, is over 200 joules. If these numbers were to materialize, there would be a very high probability of severe weather including tornadoes. In fact, with the numbers being presented tonight, I would not be surprised at all if we ended up seeing a stronger tornado (EF2+) tomorrow afternoon in Eastern Oklahoma. The numbers given above are from one model, and models can and are wrong in some cases. The fact at hand is the setup tomorrow is looking more and more like a classic fall severe weather outbreak, and residents in Eastern Oklahoma, Western Arkansas, Southwest Missouri should have a plan of action ready in the event a severe cell approaches your area. Not only do we have a severe weather threat, but the NWS in Tulsa is forecasting a change-over to sleet and/or snow for parts of their area by tomorrow night. Winter's coming folks! We're going to be chasing tomorrow and the Live Stream/GPS will be online. For the latest information, including updates from in-the-field while chasing, follow us on Twitter or Facebook. The links are at the top right portion of this page.

[David Reimer]

I should note that the NAM has over 300 J/Kg of 3 KM CAPE at 21Z. If a cell were to go up in that environment, we won't just be talking about a little EF1 tornado. I'm already having bells go off in my head with tomorrow. I really think we may end up ending the day wondering what the hell happened, kinda like yesterday.

[JoMo]

SPC is pretty meh about it. They don't think instability will be that high and shear will rip the storms apart.

[Thundersnow12]

I should note that the NAM has over 300 J/Kg of 3 KM CAPE at 21Z. If a cell were to go up in that environment, we won't just be talking about a little EF1 tornado. I'm already having bells go off in my head with tomorrow. I really think we may end up ending the day wondering what the hell happened, kinda like yesterday.

FWIW...think your better off using the 0-30mb Td map on our CoD site over the 2m Td map. Still a personal opinion on your part but Paul and others haven't liked that for awhile as its been wrong quite a few times and will likely be taken off the WRF page when we have our new CoD weather website in the near future.

[Thundersnow12]

SPC is pretty meh about it. They don't think instability will be that high and shear will rip the storms apart.

still 5% tor probs, they are aware of what happened yesterday...more instability with this setup then on mondays with the same mid-level jet strength, would think 0-6km shear would be close to the same.

THOUGH MODEST INSTABILITY SHOULD LIMIT OVERALL CONVECTIVE

COVERAGE/INTENSITY...STRENGTH OF DEEP-LAYER WIND FIELD WILL BE QUITE

SUFFICIENT FOR ORGANIZED/ROTATING STORMS.IN FACT...DEGREE OF SHEAR

MAY BE DETRIMENTAL ACROSS PARTS OF THE REGION -- TOO STRONG FOR THE

AVAILABLE INSTABILITY.NONETHELESS...EXPECT A FEW STRONGER

STORMS/SMALL-SCALE LINE SEGMENTS TO ORGANIZE THROUGH THE AFTERNOON

AND EVENING...WITH ACCOMPANYING POTENTIAL FOR DAMAGING WINDS AND

POSSIBLY HAIL.LOW-LEVEL SHEAR WILL ALSO BE SUPPORTIVE OF TORNADOES

-- ESPECIALLY ACROSS PARTS OF MO...THOUGH THREAT WILL REMAIN

ISOLATED DUE TO OVERALL LIMITED STORM COVERAGE/INTENSITY EXPECTED

ATTM.OVERNIGHT...A DECREASE IN THE ALREADY LIMITED CAPE SUGGESTS A

WANE IN CONVECTIVE INTENSITY AND ASSOCIATED SEVERE POTENTIAL.

[tornadotony]

Yeah, the SREF at 21z has CAPE levels, as a median, double what SPC says the max will be...good luck having the max be 500J/kg...

[Fred Gossage]

The GFS is the most stable out of the bunch... and it still has higher dewpoints than Goss' outlook is calling for. Considering the NAM, SREF, and SPC WRF did better, when compared to the GFS, with Monday.... I don't like this. The latest available SPC SREF run on their site, for a mean value has double the MLCAPE at 21Z tomorrow over eastern OK.... that the 06Z Day 1 outlook cites.... Given how high the dewpoints already are in the warm sector, and the advection of the drier air aloft with the low amplitude flow... to help with cloud cover concerns.... someone had better wake up.

[Thundersnow12]

The GFS is the most stable out of the bunch... and it still has higher dewpoints than Goss' outlook is calling for. Considering the NAM, SREF, and SPC WRF did better, when compared to the GFS, with Monday.... I don't like this. The latest available SPC SREF run on their site, for a mean value has double the MLCAPE at 21Z tomorrow over eastern OK.... that the 06Z Day 1 outlook cites.... Given how high the dewpoints already are in the warm sector, and the advection of the drier air aloft with the low amplitude flow... to help with cloud cover concerns.... someone had better wake up.

Would be nice to get a outlook written by Rich or Roger tomorrow, not to knock Goss at all, but those two are the best two severe weather forecasters IMO.

The one good thing about the terrain tomorrow in the jungles of eastern OK is most of the leaves should be off the trees by now.

[JoMo]

Would be nice to get a outlook written by Rich or Roger tomorrow, not to knock Goss at all, but those two are the best two severe weather forecasters IMO.

The one good thing about the terrain tomorrow in the jungles of eastern OK is most of the leaves should be off the trees by now.

I dunno, we still have a lot of leaves in SW MO.

[Thundersnow12]

a few obs showing low 60 dews in southern OK with a dew point of 37 in northeast OK, going to be some serious moisture return tomorrow.

[Fred Gossage]

a few obs showing low 60 dews in southern OK with a dew point of 37 in northeast OK, going to be some serious moisture return tomorrow.

Oklahoma always has to be so extreme with everything. They can't ever do anything like normal folk.

[Stebo]

Yeah I'm definitely not buying the conservativeness on this outlook, especially when no model is as low as he is stating...

[thewxmann]

Yeah I'm definitely not buying the conservativeness on this outlook, especially when no model is as low as he is stating...

Same. Although I do agree that shear might be a little strong. Bigger problems though should be the undercutting front and timing of initiation, which will be directly related to the timing of a morning disturbance that moves across the risk area.

IMO higher risk areas are N of I-40... S/SW MO maybe under the gun?

[janetjanet998]

SPC has upped TOR prob to 10% and now says MLCAPE of up to 1000

SPG AFD hinted at this saying MLCAPE 800-1200 possible with dewpoints in the low 60;s but higher if dewpoints are higher

SPG was never buying SPC;s conservative outlook 06z outlook

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SPRINGFIELD MO

335 AM CST WED NOV 24 2010

DISCUSSION

A VERY ACTIVE 48 HOURS IS ON TAP AS A STRONG STORM SYSTEM TRACKS

ACROSS THE CENTRAL UNITED STATES. WE ARE GOING TO SEE ALL FOUR

SEASONS OF WEATHER THE NEXT FEW DAYS STARTING WITH A THREAT FOR

SEVERE STORMS LATER TODAY AND TONIGHT

MEANWHILE...MASSIVE CHANGES IN THE LOW LEVEL AIRMASS WILL TAKE

PLACE AS THAT WARM FRONT QUICKLY SURGES NORTH OF THE AREA. SEE NO

REASON WHY DEW POINTS WILL NOT MAKE IT INTO THE LOWER 60S...WITH

MID 60S NOT OUT OF THE QUESTION ACROSS SOUTHERN MISSOURI. THIS

QUICK MODIFICATION TO THE LOW LEVEL AIRMASS WILL SET THE STAGE FOR

WHAT COULD BE AN ACTIVE SEVERE WEATHER PERIOD. EVEN THOUGH LITTLE

IN THE WAY OF SUN IS EXPECTED TODAY...WARM ADVECTION SHOULD BOOST

TEMPERATURES INTO THE MIDDLE AND PERHAPS UPPER 60S ACROSS

SOUTHEAST KANSAS AND WESTERN MISSOURI THIS AFTERNOON. THIS WOULD

RESULT IN MLCAPES IN THE 700 TO 1200 J/KG RANGE...OR EVEN HIGHER

IF MID 60 DEW POINTS CAN MAKE IT IN HERE.

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0630 AM CST WED NOV 24 2010

VALID 241300Z - 251200Z

..THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF ERN OK

NWRN

AR...AND MUCH OF MO....

A LARGE UPPER TROUGH OVER THE WESTERN UNITED STATES WILL PROGRESS

EASTWARD TODAY INTO THE CENTRAL PLAINS. MEANWHILE...A STRONG COLD

FRONT WILL SURGE SOUTHEASTWARD THROUGH THE CENTRAL PLAINS AND INTO

MO/AR/OK BY THURSDAY MORNING. INCREASINGLY STRONG SOUTHERLY LOW

LEVEL WINDS TO THE SOUTH OF THE FRONT WILL TRANSPORT RICH GULF

MOISTURE NORTHWARD WITH DEWPOINTS IN THE MID 60S EXPECTED INTO

NORTHEAST OK BY AFTERNOON. A FEW BREAKS IN THE CLOUDS AND

STEEPENING MID LEVEL LAPSE RATES WILL HELP TO YIELD AFTERNOON MLCAPE

VALUES APPROACHING 1000 J/KG IN EASTERN OK/SOUTHWEST MO.

SCATTERED THUNDERSTORMS ARE ONGOING THIS MORNING OVER PORTIONS OF

EASTERN KS AND MUCH OF MO. THIS ACTIVITY WILL LIFT

NORTHEASTWARD...WITH MUCH OF OK/AR/MO RELATIVELY DRY FOR MUCH OF THE

DAY. BY LATE AFTERNOON...SCATTERED THUNDERSTORMS ARE EXPECTED TO

RE-FORM ALONG/AHEAD OF THE APPROACHING SURFACE COLD FRONT. FORECAST

SOUNDINGS SUGGEST LOW LEVEL AND DEEP LAYER VERTICAL SHEAR PROFILES

WILL BE VERY FAVORABLE FOR SUPERCELLS. INCREASING LARGE SCALE

FORCING FOR ASCENT OVER THE WARM SECTOR MAY RESULT IN A FEW DISCRETE

SUPERCELLS AHEAD OF THE FRONT OVER SOUTHWEST MO. THESE WOULD POSE

THE RISK OF A FEW TORNADOES DURING THE EVENING HOURS.

OTHERWISE...DAMAGING WINDS AND HAIL APPEAR POSSIBLE AS STORMS BECOME

MORE NUMEROUS ALONG THE COLD FRONT AND SAG SOUTHWARD ACROSS THE

SLIGHT RISK AREA.

[Ozarkwx]

Once again the tornado threat appears to be migrating to the I-44 corridor of SW MO. In fact the risk axis is almost directly aligned with I-44. The old weather joke in NW AR about this tendency is that "tornadoes are like everybody else, they like to take the interstate."

This might be one of those setups that escalates quickly if the instability can be realized. Probably be the time of the next update, the instability parameters will be more clearly understood.

[janetjanet998]

Once again the tornado threat appears to be migrating to the I-44 corridor of SW MO. In fact the risk axis is almost directly aligned with I-44. The old weather joke in NW AR about this tendency is that "tornadoes are like everybody else, they like to take the interstate."

This might be one of those setups that escalates quickly if the instability can be realized. Probably be the time of the next update, the instability parameters will be more clearly understood.

an interesting feature if that all models hang the front up over the ozarks....dewpoints return more north over SW amd SE MO then they do over S central MO...

[David Reimer]

Taking a look at all the data coming in this morning (12Z NAM, 13Z RUC) I can't help but feel like the severe weather threat will be higher then SPC is indicating towards the I-40 corridor. Everything I'm looking at this morning has everything coming together right over that area. Now there may be a slight bias here as I'm not willing to go into MO to chase today, but I feel like US-69/I-40 is a good initial target spot, with a westward jog possible.

[JoMo]

an interesting feature if that all models hang the front up over the ozarks....dewpoints return more north over SW amd SE MO then they do over S central MO...

This is somewhat normal in these situations. Due to the Ozark Mountains, moisture typically has to take the long way around once it has been scoured out.

[tornadotony]

I'm going to pretty much just echo what's already been said. Today looks like a rough day along the I-44 corridor from Stroud to Lebanon and points S and E...high shear, high low-level instability, and decent enough lapse rates should paint a pretty ugly picture by late afternoon. My biggest fear with this is that favorable conditions for tornadoes, a few strong, are probably going to last WELL into the night, so this could be a prolonged event with much of it happening after dark.

[janetjanet998]

new outlook no change really

well now says MLCAPE 1000-1500 keeps creeping up

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1015 AM CST WED NOV 24 2010

VALID 241630Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EARLY

TONIGHT PORTIONS OF LOWER MO VALLEY INCLUDING OK...

..ERN OK TO LOWER MO VALLEY

RICH GULF MOISTURE CONTINUES TO FLOW NWD THRU THE SRN PLAINS AHEAD

OF THE INTENSE COLD UPPER LOW AND TROUGH NOW CROSSING THE ROCKIES.

WHILE THE STRONG COLD FRONT NOW SURGING SEWD ACROSS CENTRAL NEB TO

CO WILL NOT INTERCEPT THE MOIST WARM SECTOR UNTIL AFTER DARK...IT

NOW APPEARS THAT SURFACE HEATING WILL BE SUFFICIENT TO INITIATE

SEVERE THUNDERSTORMS BY MID/LATE AFTERNOON IN VICINITY OF THE

RETURNING WARM FRONT.

WITH SURFACE TEMPS RISING THRU THE 70S F AND DEWPOINTS AT LEAST MID

60S...MLCAPES OF 1000-1500 J/KG WITH LITTLE CINH WILL BE IN PLACE

ERN OK BY MID AFTERNOON. SURFACE BASED STORMS SHOULD DEVELOP

INITIALLY FROM SERN CORNER KS/SWRN MO INTO NERN OK WHERE SURFACE

CONVERGENCE ALONG WARM FRONT WILL BE GREATEST.

FORECAST SOUNDINGS SUGGEST LOW LEVEL AND DEEP LAYER VERTICAL SHEAR

PROFILES WILL BE VERY FAVORABLE FOR SUPERCELLS AS 100KT MID LEVEL

JET TRANSLATES EWD ACROSS LOWER MO VALLEY THIS AFTERNOON AND

EVENING. INCREASING LARGE SCALE FORCING FOR ASCENT OVER THE WARM

SECTOR SHOULD LEAD TO A FEW DISCRETE SUPERCELLS AHEAD OF THE COLD

FRONT OVER NERN OK/SWRN MO AND ADJACENT PORTIONS OF KS AND AR.

THESE WOULD POSE THE RISK OF A FEW TORNADOES FROM LATER THIS

AFTERNOON THRU THE EVENING HOURS. OTHERWISE...DAMAGING WINDS AND

HAIL APPEAR POSSIBLE AS STORMS BECOME MORE NUMEROUS ALONG THE COLD

FRONT BY THIS EVENING AND DEVELOP SOUTHWARD ACROSS THE SLIGHT RISK

AREA .