possible severe outbreak in TX/OK on thursday?

[cheezyWXguy]

spc day 3 has all most of texas and oklahoma in a slight risk area, with mention of a possible moderate risk being issued if current trends continue. Anyone have any thoughts on this?

[Ed Mahmoud]

spc day 3 has all most of texas and oklahoma in a slight risk area, with mention of a possible moderate risk being issued if current trends continue. Anyone have any thoughts on this?

Did you see the 12Z WRF, which has rain from about I-20 North in the Dallas area, with 2000 J/Kg CAPE, and like 500 J/Kg helicity.




Interesting to see 0Z WRF


12Z GFS was a little less spooky looking, with less CAPE in the bottom 2 km of the atmosphere, but still looks spooky.

[Tampa Bay Hurricane]

That helicity value looks strong for some convective vorticity.

April is climatologically favored for severe weather in tornado alley, and
if there is a lot of shear, moisture feed, and warmth there could be
some intense action.

You might get some action there.

[cheezyWXguy]

Our AFD talks about the potential for rapidly developing severe thunderstorms along the dryline on thursday and from the looks of the models, a day similar or worse than monday does not appear to be out of the question.

[Ed Mahmoud]

New 0Z WRF trickling in...

[Ed Mahmoud]

New 0Z WRF trickling in...

You don't see an EHI over six very often...

[RL3AO]

Looks like an interesting multi day event shaping up.

[CrazyC83]

I think the SPC long range maps greatly underestimate the risk from the Ohio Valley northward on Friday and Saturday...this could be a historic outbreak brewing I think (especially considering it could be a 3-day or 4-day outbreak from a single system - which is quite uncommon)

[RL3AO]

The SPC mentioning that they almost went moderate on day 3 is somewhat eye opening. But it is that time of year where the big ones happen in the South central plains.

[CrazyC83]

I sense that Friday (and maybe even Saturday) will be bigger than Thursday, since that region has high bust potential as it is more conditional on the dryline.

[cheezyWXguy]

I sense that Friday (and maybe even Saturday) will be bigger than Thursday, since that region has high bust potential as it is more conditional on the dryline.

I dunno...with such high shear and instability, coupled with a front intersecting the dryline, supercells and strong MCS's seem like a good bet. From what I can see, the southern plains could be looking at a pretty decent tornado threat out of this.

[CrazyC83]

SPC AC 020559

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT WED APR 02 2008

VALID 031200Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF N TX...OK AND WRN
AR...

...THERE IS A SLGT RISK OF SVR TSTMS FROM SOUTH CNTRL TX THROUGH THE
REMAINDER OF AR INTO THE LWR OH/TN VLYS...

...SYNOPSIS...
UPR LOW NOW OFF THE CA CST WILL MOVE E INTO SRN CA BY EARLY
THURSDAY. THE SYSTEM SHOULD ACCELERATE E ACROSS AZ/NM AS A
DEAMPLYFING WAVE LATER THURSDAY/EARLY FRIDAY AS IT BECOMES ABSORBED
WITHIN STRENGTHENING LARGER SCALE TROUGH OVER THE RCKYS.

AT LWR LEVELS...A SERIES OF WAVES WILL TRACK ENE FROM NW TX AND
WRN/SRN OK THROUGH AR INTO THE LWR OH VLY...ALONG FRONTAL ZONE THAT
WILL EVOLVE OVER THE SRN PLNS/OZARKS DURING THE NEXT 36 HRS. AS THE
AZ/NM TROUGH CONTINUES EWD...WRN PART OF FRONT SHOULD ACCELERATE S
ACROSS WRN PARTS OF SRN PLNS THURSDAY EVENING. S AND E OF THE
FRONT...INCREASINGLY RICH MOISTURE WILL SPREAD NWD...WITH THE 60 DEG
F SFC ISODROSOTHERM LIKELY REACHING SE MO/WRN KY BY 00Z FRIDAY.

...SRN PLNS INTO LWR TN/OH VLYS...
...SIGNIFICANT SVR TSTMS POSSIBLE OVER PARTS OF N TX/OK AND WRN AR
THURSDAY AFTN THROUGH EARLY FRIDAY...

COMBINATION OF STRENGTHENING DEEP WIND FIELD...INCREASING
MOISTURE/LARGE SCALE ASCENT...AND DAYTIME HEATING EXPECTED TO YIELD
AN ENVIRONMENT FAVORABLE FOR SUSTAINED SUPERCELLS WITH VERY LARGE
HAIL...HIGH WIND AND TORNADOES INVOF SFC WAVE AND ASSOCIATED DRY
LINE AND WARM/STATIONARY FRONT OVER NW TX AND WRN/SRN OK THURSDAY
AFTN.

IT REMAINS TOO EARLY TO COMMENT SPECIFICALLY ON MESOSCALE
DETAILS...ESPECIALLY GIVEN LIKELIHOOD FOR ELEVATED WARM ADVECTION
STORMS IN OK EARLY IN THE DAY. BUT OVERALL SETUP SHOULD RESULT IN A
CORRIDOR OF UNCAPPED...VERY UNSTABLE AIR /SBCAPE AOA 2500 J PER KG/
NEAR AFOREMENTIONED SFC WAVE BY LATE THURSDAY AFTN. AS THE WAVE
DEVELOPS ESE TOWARD THE RED RVR...EXPECT AT LEAST A FEW DISCRETE
SUPERCELLS WILL EVOLVE IN THE INCREASINGLY SHEARED ENVIRONMENT.
THESE STORMS LIKELY WILL GROW UPSCALE THROUGH THURSDAY NIGHT/EARLY
FRIDAY...WITH SEVERE HAIL...HIGH WIND AND POSSIBLY ISOLATED
TORNADOES SPREADING EWD/SEWD ACROSS THE REMAINDER OF OK/CNTRL TX AND
INTO AR AND THE LWR TN/OH VLYS EARLY FRIDAY. ADDITIONAL
STORMS/CLUSTERS MAY ALSO FORM THURSDAY NIGHT THROUGH EARLY FRIDAY
ACROSS S CNTRL TX AS INCREASING UVV/LOW LEVEL CONVERGENCE STRENGTHEN
ALONG TRAILING DRY LINE.

..CORFIDI.. 04/02/2008

CLICK TO GET WUUS02 PTSDY2 PRODUCT

NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
CURRENT UTC TIME: 1153Z (7:53AM), RELOAD THIS PAGE TO UPDATE THE TIME

[RL3AO]

Pretty large 45H area.

[Ed Mahmoud]

New WRF shows little rain in North Texas or South Oklahoma at 18Z (1 pm CDT), six hours later, a fair amount has accumulated.

Already good instability at DFW at 18Z, low level wind fields decent, but nothing to write home about.



Instability down a tad, but helicity up at 0Z (7 pm CDT), but instability being down may be a result of rain in the area.



I wish the NIU Storm Machine skew-T forecast generator had 3 hour intervals (it does for the RUC model).

I have a feeling the forecast numbers for 4 pm tomorrow would be a little more impressive.

On the face of it, the forecast sounding is a liitle less supportive of tornadoes than yesterday, but I can't be certain some of it isn't due to rain before 0Z.

Looking really closely, it looks like the precip after 18Z may be associated with the returning warm front, and then the I-35 corridor may face a second round of storms on the cold front/dry line as it heads Southwest. They start off individually, and start to congeal near the I-35 corridor around midnight. The Southern end of that big line approaching Waco right after midnight. A little reduction in CAPE/added CINH due to cooling of the boundary layer after dark, but still a forecast sounding favorable for severe storms.

[Bunkertor]

SPC AC 021729

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT WED APR 02 2008

VALID 031200Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS OF CNTRL/SRN
OK...NRN TX INTO PARTS OF WRN AND NRN AR...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS INTO OH
VALLEY...

...SYNOPSIS...

PROGRESSIVE LARGE-SCALE PATTERN WILL CONTINUE THROUGH THE DAY TWO
PERIOD...FEATURING POSITIVELY-TILTED UPPER TROUGH WHICH WILL MOVE
FROM THE ROCKIES AND SWRN STATES EWD INTO THE PLAINS. MORE
SPECIFICALLY...LATEST MODEL GUIDANCE HAS TRENDED TOWARD A MORE
INTENSE LEAD SHORT WAVE TROUGH WHICH WILL TRANSLATE NEWD FROM THE
CNTRL HIGH PLAINS INTO OH VALLEY. MEANWHILE...STRONGER...LOWER
LATITUDE IMPULSE WILL SHIFT MORE EWD THROUGH THE SRN ROCKIES INTO
THE SRN PLAINS.

IN THE LOW LEVELS...PRIMARY SURFACE CYCLONE INITIALLY OVER SWRN KS
OR THE OK/TX PNHDLS WILL SLOWLY DEEPEN WHILE DEVELOPING SEWD INTO
NWRN TX BY 04/00Z...BEFORE WEAKENING ALONG SURGING COLD FRONT
THURSDAY NIGHT. GIVEN THE MORE INTENSE LEAD SHORT WAVE TROUGH...12Z
MODEL DATA NOW INDICATE A MORE INTENSE SURFACE WAVE WHICH IS
FORECAST TO DEVELOP MORE EWD ACROSS PARTS OF KS AND MO...AND
EVENTUALLY EWD ALONG THE OH RIVER. AN ASSOCIATED WARM FRONT WILL
LIFT NWD AHEAD OF THE SECONDARY SURFACE LOW THROUGH THE LOWER MS
VALLEY...MID SOUTH AND EVENTUALLY LOWER TO MIDDLE OH VALLEY.
BOUNDARY TRAILING SWWD FROM THIS LOW MAY EXHIBIT QUASI-STATIONARY OR
WARM FRONTAL PROPERTIES ACROSS OK THURSDAY AFTERNOON TO WHERE IT
LINKS WITH THE PRIMARY SURFACE LOW OVER NWRN TX. THIS BOUNDARY IS
EXPECTED TO MOVE SEWD AS A COLD FRONT THURSDAY NIGHT. FINALLY...A
DRYLINE WILL BECOME INCREASINGLY WELL DEFINED FROM THE PRIMARY
SURFACE LOW SWD THROUGH W-CNTRL TX SWD TOWARD THE TX BIG BEND.

...SRN PLAINS INTO THE OH/TN VALLEYS...

CLUSTERS OF ELEVATED TSTMS CAPABLE OF SEVERE HAIL ARE EXPECTED TO BE
ONGOING THURSDAY MORNING OVER PORTIONS OF KS/OK INTO THE OZARK
PLATEAU REGION. THIS ACTIVITY SHOULD DEVELOP QUICKLY EWD/NEWD
ACROSS THE OH VALLEY ALONG NOSE OF EXPANDING/STRENGTHENING LLJ WHERE
MOIST AND WARM THERMAL ADVECTIONS WILL SUPPORT RAPID AIR MASS
DESTABILIZATION /I.E. MUCAPES INCREASING TO AROUND 1000 J PER KG/.

DEWPOINTS INCREASING THROUGH THE 60S COUPLED WITH STEEP MIDLEVEL
LAPSE RATES ARE EXPECTED TO CONTRIBUTE TO A MODERATE TO STRONGLY
UNSTABLE AIR MASS IN THE WAKE OF THIS INITIAL ELEVATED TSTM
DEVELOPMENT WITH MLCAPES INCREASING TO 1500-3000 J/KG ACROSS
EXPANDING WARM SECTOR. INCREASING HEIGHT FALLS AHEAD OF UPPER
TROUGH COUPLED WITH BOUNDARY LAYER HEATING SHOULD ERODE CAP
SUFFICIENTLY TO SUPPORT MORE SIGNIFICANT SURFACE-BASED TSTM
DEVELOPMENT THURSDAY AFTERNOON INTO EVENING. THE MOST LIKELY AREAS
FOR THIS DEVELOPMENT ARE: 1) ALONG TRACK OF SECONDARY SURFACE LOW
AND RETREATING WARM FRONT OVER NRN AR /PERHAPS FAR SRN MO/...2)
WSWWD ALONG AND S OF QUASI-STATIONARY FRONT OVER CNTRL/SRN OK...AND
3) SWD ALONG DRYLINE OVER NWRN INTO W-CNTRL TX. 50-60 KT OF DEEP
LAYER SHEAR ACROSS ENTIRE WARM SECTOR WILL BE SUPPORTIVE OF
SUPERCELL DEVELOPMENT WITH A THREAT OF LARGE HAIL /SOME SIGNIFICANT/
AND DAMAGING WINDS.

LATEST MODEL GUIDANCE IS RELATIVELY CONSISTENT IN SUGGESTING THAT
THE STRONGER LOW-LEVEL SHEAR WILL RAPIDLY DEVELOP EWD THROUGH THE
OZARK PLATEAU REGION INTO MID SOUTH IN CONJUNCTION WITH THE
MIGRATORY LLJ AXIS. NEAR PARALLEL STORM MOTIONS TO RETREATING WARM
FRONT SUGGESTS THE POTENTIAL FOR TORNADIC SUPERCELLS AHEAD OF
SECONDARY SURFACE LOW GIVEN SUFFICIENT AIR MASS DESTABILIZATION AND
FAVORABLE STORM MODES. ANOTHER POTENTIALLY ENHANCED TORNADO THREAT
MAY DEVELOP NEAR TRIPLE POINT OF DRYLINE AND SW-NE ORIENTED BOUNDARY
OVER SWRN OK/NWRN TX WHERE LOW-LEVEL WINDS SHOULD REMAIN LOCALLY
BACKED WITHIN A STRONGLY UNSTABLE THERMODYNAMIC ENVIRONMENT.

THE POTENTIAL FOR TORNADOES...HAIL AND DAMAGING WINDS IS EXPECTED TO
SPREAD EWD/SEWD ACROSS SRN OK...NRN AND CNTRL TX OVERNIGHT ALONG AND
AHEAD OF COLD FRONT. ELSEWHERE...THE SEVERE THREAT SHOULD CONTINUE
INTO THE OVERNIGHT HOURS FROM AR NEWD ALONG THE OH RIVER.

..MEAD.. 04/02/2008

CLICK TO GET WUUS02 PTSDY2 PRODUCT

NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
CURRENT UTC TIME: 1739Z (7:39PM), RELOAD THIS PAGE TO UPDATE THE TIME

[RL3AO]

[CrazyC83]

The most recent models have definitely backed off some on this, making it more of a wait-and-see thing than a case of an imminent outbreak. It's been quite some time since there has been a tornado outbreak focused on North Texas (and southern Oklahoma)...

[CrazyC83]

The MDT was adjusted slightly north and east, and the 30% was expanded northeast quite a bit (squall line winds?)

[Ed Mahmoud]

NIU web site down, I was going to check GFS forecast soundings.

[Ed Mahmoud]

Sweet sassy molassy--if 18Z WRF is right, at or before 4 pm a single supercell pops somewhere near Abilene, and has over 50 knots of deep layer shear and between 2000 and 3000 J/Kg of CAPE to work with.