Severe Weather Thread (April 2, 2012 - April 4, 2012)

[MnWeatherman]

Thanks for sharing! Heard of Accuweather Pro before, but never looked into it. I'm impressed with the large amount of graphics.

[andyhb]

Day 1, large SLGT, 5% tor, 30% sig-hatched hail:

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0100 AM CDT MON APR 02 2012

VALID 021200Z - 031200Z

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

CENTRAL PLAINS EWD INTO E TX/SRN AR AND MUCH OF LA...

...SYNOPSIS....

MODELS ARE IN FAIRLY GOOD AGREEMENT SHOWING THE SRN EXTENT OF THE

WRN U.S. TROUGH BECOMING CUT-OFF FROM THE NRN STREAM BY THE START OF

DAY 1. THE CLOSED LOW WILL MOVE SLOWLY EWD TODAY ACROSS NM...GIVEN

THE PRESENCE OF A RATHER STRONG DOWNSTREAM RIDGE EXTENDING NWD FROM

THE LOWER MS VALLEY/CENTRAL GULF COAST STATES TO THE WRN GREAT

LAKES. MEANWHILE...HEIGHTS WILL RISE ACROSS THE SERN STATES AS A

TROUGH LOCATED ALONG THE MIDDLE/NRN ATLANTIC COAST MOVES EWD. A

WEAK MIDLEVEL CIRCULATION...CURRENTLY MOVING SLOWLY NWD INLAND FROM

THE MID-UPPER TX COAST...SHOULD TRACK NEWD TODAY THROUGH E

TX/ARKLATEX AND LOWER MS VALLEY REACHING THE OZARKS AND NRN MS BY

12Z TUESDAY.

THE NRN EXTENT OF THE WRN TROUGH...CURRENTLY MOVING EWD THROUGH THE

NRN INTERMOUNTAIN WEST PER WATER VAPOR IMAGERY...IS EXPECTED TO

TRACK ENEWD THROUGH THE NRN HIGH PLAINS THIS AFTERNOON AS IT PHASES

WITH A SEPARATE TROUGH MOVING THROUGH CENTRAL CANADA. MODELS DIFFER

WITH THE EFFECT THE SRN PORTION OF THESE PHASED TROUGHS HAS ACROSS

NRN MN...BUT THE 12Z ECMWF/00Z GFS AGREE THAT 40-60 METER HEIGHT

FALLS SHOULD OCCUR ACROSS THAT REGION MONDAY NIGHT.

AT THE SURFACE...A COLD FRONT WILL ADVANCE E/SEWD INTO THE UPPER MS

VALLEY THIS FORECAST PERIOD...AND SWD WHERE IT WILL MERGE WITH A

NE-SW ORIENTED DRY LINE ACROSS CENTRAL KS THIS AFTERNOON. THE DRY

LINE WILL THEN EXTEND SWD FROM A TRIPLE POINT OVER SWRN-SOUTH

CENTRAL KS THROUGH WRN OK TO CENTRAL TX THIS AFTERNOON. THE WRN

EXTENT OF A WARM FRONT...INITIALLY LOCATED OVER NRN MO...IS EXPECTED

TO SPREAD NWD AND REACH ERN IA/NWRN IL BY THIS EVENING.

MEANWHILE...A COLD FRONT WILL MOVE SWD THROUGH THE CAROLINAS

REACHING ERN GA BY 12Z TUESDAY.

...CENTRAL TX/WRN AND CENTRAL OK/CENTRAL AND ERN KS...

A SHORTWAVE TROUGH...CURRENTLY MOVING INTO THE BASE OF THE WRN

TROUGH OVER SWRN AZ PER WATER VAPOR IMAGERY...IS EXPECTED TO MIGRATE

THROUGH THE SERN-ERN PERIPHERY OF THE PARENT CLOSED LOW TODAY ACROSS

SW-W TX INTO WRN OK AND POSSIBLY SWRN KS BY 03/00Z. WEAK HEIGHT

FALLS ACROSS THE SRN PLAINS...DPVA ATTENDANT TO THE MIGRATORY

SHORTWAVE TROUGH...AND DIFFLUENT MID-UPPER LEVEL FLOW ALL EXPECTED

ACROSS THE DRY LINE DURING THE MID-LATE AFTERNOON SUGGEST TSTM

DEVELOPMENT WILL BE LIKELY FROM CENTRAL/SOUTH CENTRAL TX NWD THROUGH

WRN OK TO SOUTH CENTRAL KS. THE STRONGEST LOW LEVEL CONVERGENCE

SHOULD EXTEND FROM NWRN OK/ADJACENT KS NEAR THE TRIPLE POINT NEWD

ALONG THE COLD FRONT/DRY LINE MERGER INTO CENTRAL KS...WITH MUCH OF

THE KS TSTM ACTIVITY EXPECTED TO BE MORE ANAFRONTAL-TYPE

DEVELOPMENT.

SURFACE HEATING WITHIN THE WARM SECTOR COMBINED WITH VERY STEEP

MIDLEVEL LAPSE RATES /EXCEEDING 8 C PER KM/...AND SURFACE DEWPOINTS

IN THE 60S WILL RESULT IN MODERATE TO VERY STRONG INSTABILITY WITHIN

THE TX/OK/KS PORTION OF THE SLIGHT RISK AREA. EFFECTIVE BULK SHEAR

WILL BE STRONGEST ACROSS S TO N CENTRAL TX WITH SHEAR VECTORS

ORIENTED PERPENDICULAR TO THE DRY LINE. THIS WILL PROVE FAVORABLE

FOR DISCRETE SUPERCELLS PRODUCING HAIL...SOME VERY LARGE /EXCEEDING

2 INCH DIAMETER/...AND A COUPLE OF TORNADOES. ALTHOUGH DEEP LAYER

SHEAR WILL DECREASE WITH NWD EXTENT...WITH A GREATER POTENTIAL FOR

PULSE-TYPE STORMS INTO KS...THE PRESENCE OF STRONG INSTABILITY WILL

SUPPORT VERY LARGE HAIL WITH THIS ACTIVITY AS WELL. THE THREAT FOR

AN ISOLATED TORNADO WILL ALSO EXTEND NWD THROUGH WRN OK TO THE

TRIPLE POINT IN SWRN-S CENTRAL KS.

...E TX/MUCH OF LA/SRN AR...

THE AIR MASS IS EXPECTED TO BECOME MODERATELY UNSTABLE ACROSS MUCH

OF THIS REGION INTO THE AFTERNOON. FORCING FOR ASCENT ATTENDANT TO

THE NEWD MOVING MIDLEVEL CIRCULATION WILL SUPPORT WIDESPREAD TSTM

DEVELOPMENT. EFFECTIVE BULK SHEAR AROUND 30 KT SUGGESTS MULTICELLS

WILL BE THE PRIMARY STORM MODE WITH AN ATTENDANT THREAT FOR HAIL AND

STRONG WIND GUSTS.

...UPPER MS VALLEY/WRN GREAT LAKES TO NRN IL/IND...

A FEW STRONG TO ISOLATED SEVERE ELEVATED STORMS ARE POSSIBLE AT THE

START OF DAY 1 FROM ERN SD INTO NRN MN WITHIN A STRONG LOW LEVEL WAA

REGIME. WEAK-MODERATE ELEVATED INSTABILITY AND 25-30 KT OF

EFFECTIVE BULK SHEAR SUPPORT THIS MARGINAL SEVERE HAIL THREAT.

ELEVATED CONVECTION/EMBEDDED TSTMS ARE POSSIBLE FROM NERN SD INTO

NRN MN THROUGH THE DAY...BUT WEAKER INSTABILITY WILL PRECLUDE A

SEVERE WEATHER THREAT. A GREATER COVERAGE OF TSTMS...AGAIN MAINLY

ELEVATED...IS EXPECTED TO DEVELOP BY EARLY EVENING ACROSS PARTS OF

SRN MN/POTENTIALLY NRN IA...NEAR AND N OF A SURFACE LOW MOVING INTO

NWRN IA FROM NEB TODAY.

IF SURFACE BASED STORMS CAN DEVELOP NEAR THE LOW IN IA...THEN THE

SLIGHT RISK AREA MAY NEED TO BE EXTENDED NWD...AS MODERATE TO STRONG

INSTABILITY WOULD SUPPORT A GREATER SEVERE WEATHER THREAT.

OTHERWISE...A STRENGTHENING/VEERING LLJ FROM THE UPPER MS VALLEY

INTO THE WRN GREAT LAKES IS EXPECTED TO SUPPORT ELEVATED TSTMS

DEVELOPING AND SPREADING ESEWD ACROSS THESE AREAS. ALTHOUGH

EFFECTIVE BULK SHEAR IS FORECAST TO WEAKEN OVER THE WRN GREAT LAKES

TO NRN IL/IND MONDAY NIGHT...STEEP MIDLEVEL LAPSE RATES AND MODERATE

ELEVATED INSTABILITY WILL SUPPORT PRIMARILY ISOLATED HAIL WITH THE

STRONGER STORMS.

...SRN APPALACHIANS/SC/ERN GA...

THE AIR MASS IS EXPECTED TO BECOME MODERATELY UNSTABLE BY AFTERNOON

WITH TSTMS DEVELOPING ALONG AND S OF THE COLD FRONT MOVING THROUGH

THIS REGION. WEAK DEEP LAYER SHEAR WILL RESULT IN GENERALLY

PULSE-TYPE STORMS WITH AN ATTENDANT THREAT FOR ISOLATED STRONG WIND

GUSTS AND/OR SOME HAIL.

..PETERS/ROGERS.. 04/02/2012

There is just a ton of instability associated with this thing.

[brettjrob]

I'll be very interested to see the structure and mode of warm sector convection tomorrow, in light of the wildly-unconventional profiles I mentioned in my last post... *if* we get it before sundown, that is. Model guidance seems very iffy on that prospect to my eyes, but SPC sounds a bit more confident. The only area with a strong signal for convection prior to 00z is right along the CF in KS, and that activity will likely tend to get undercut fairly quickly.

[andyhb]

I can only imagine what we'd be looking at right now had this ridge not screwed up the phasing of this system...

[brettjrob]

I can only imagine what we'd be looking at right now had this ridge not screwed up the phasing of this system...

This is at least the third time this year that sentence has been appropriate, and soon to be a fourth this coming Friday...

[andyhb]

Late week looks more like a problem with getting the trough to dig far enough south (for you, Brett at least, down in OK and TX), at least on the GGEM/GFS, although there are a few areas that look decent if a few variables (stronger SLP, better moisture return depending on the evolution of this cutoff) change here and there (parts of KS, MO, NE, perhaps IA). Despite this, the ridge will still likely have some say in this, and if its anything like its recent influences, it will likely be a negative one.

[Srain]

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0756 AM CDT MON APR 02 2012

VALID 021300Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM A LARGE PART OF TX N AND

NE INTO PARTS OF THE CNTRL PLNS AND LWR MS VLY...

...SYNOPSIS...

A COMPLEX UPR PATTERN WILL PREVAIL THIS PERIOD...WITH SVR TSTM

POTENTIAL LARGELY TIED TO UPR SYSTEM NOW CLOSING OFF NEAR THE FOUR

CORNERS. THE LOW SHOULD ELONGATE W-E AS IT DRIFTS ESE ACROSS NM

LATER TODAY/TNGT. ONE OF THE RESULTING VORT LOBES ALREADY IS

BECOMING APPARENT IN SATELLITE IMAGERY ATTM OVER SRN NM. THIS

FEATURE SHOULD PIVOT NNE ACROSS W TX LATER TODAY...AND NWD ACROSS

THE TX PANHANDLE TNGT...AS UPSTREAM LOBE MOVES S ACROSS AZ.

SE OF THE FOUR CORNERS LOW...VWP AND SATELLITE DATA INDICATE THAT A

FAIRLY BROAD MCV HAS EVOLVED OVER S CNTRL/SE TX FROM CONVECTIVE

COMPLEX THAT CROSSED THE REGION OVERNIGHT. ALSO LINGERING IN THE

AREA IS REMNANT OF THE SMALL UPR LVL CIRCULATION THAT FORMED OVER

THE TX GULF CST YESTERDAY. THE COMBINED CIRCULATIONS SHOULD MOVE

GENERALLY NNE ACROSS THE REMAINDER OF E TX AND LA/AR LATER

TODAY/TNGT AS THEY BECOME ABSORBED WITHIN STRENGTHENING MID/UPR LVL

FLOW DOWNSTREAM FROM THE FOUR CORNERS LOW.

FARTHER N...NRN PART OF TROUGH THAT GAVE BIRTH TO THE FOUR CORNERS

SYSTEM WILL TRACK E ACROSS MT AND THE DAKOTAS AS A HIGH AMPLITUDE

RIDGE PERSISTS FROM THE ERN GULF CST TO THE UPR GRT LKS. EWD MOTION

OF THE MT/DAKOTAS IMPULSE WILL MAINTAIN STEADY EWD ADVANCE OF

ASSOCIATED COLD FRONT NOW OVER THE NRN/CNTRL PLNS...WITH THIS

BOUNDARY EXPECTED TO EXTEND FROM ERN WI TO CNTRL MO BY 12Z TUE. A

MORE COMPLEX SFC EVOLUTION LIKELY WILL EXIST OVER THE SRN PLNS.

APPROACH OF AFOREMENTIONED NM VORT LOBE SHOULD DRIVE PACIFIC COLD

FRONT/DRY LINE E/NE ACROSS W CNTRL TX AND THE TX PANHANDLE THIS

AFTN...WHILE ASSOCIATED SFC LOW REMAINS QSTNRY NEAR AMA. FARTHER

S...COLD POOL FROM OVERNIGHT S TX MCS LIKELY WILL HAVE SOME

LINGERING INFLUENCE ON LOW LVL CONVERGENCE/UPLIFT PATTERNS FROM S

CNTRL TX NEWD INTO LA.

...W TX NNE INTO WRN/CNTRL KS AND SE NEB THIS AFTN/EVE...

CONDITIONS SHOULD BECOME INCREASINGLY FAVORABLE FOR STRONG TO SVR

STORMS ALONG AN ARC FROM W CNTRL TX NWD THROUGH WRN OK...SW KS...N

CNTRL KS...AND SE NEB LATER TODAY AS SFC HEATING DESTABILIZES REGION

ALONG AND AHEAD OF MERGING DRY LINE AND PACIFIC COLD FRONT.

EVOLUTION OF STORMS AND THEIR ATTENDANT SVR THREATS WILL BE

COMPLICATED BY THE VARIABLE WIND FIELDS THAT WILL EXIST ACROSS THIS

REGION THROUGH SPACE AND TIME AS NM VORT LOBE PIVOTS NE ACROSS

REGION. ATTM IT APPEARS THAT THE MOST FAVORABLE JUXTAPOSITION OF

DEEPLY VEERING WIND PROFILES...STEEP LOW TO MID LVL LAPSE

RATES...AND LOW LVL MOISTURE WILL EXIST FROM WRN N TX N AND NNW

THROUGH WRN OK INTO SW KS LATE THIS AFTN. EARLY PASSAGE OF THE VORT

LOBE IN TX ADDS A FURTHER COMPLICATION TO THE SITUATION. BUT

OVERALL COMBINATION OF PERSISTENT LOW LVL CONVERGENCE ALONG DRY

LINE/COLD FRONT...STRONG INSTABILITY /SBCAPE 2500-3500 J PER

KG/...AND WIND PROFILES THAT WILL BE SUFFICIENT FOR SUSTAINED

STORMS/SUPERCELLS EXPECTED TO YIELD A SIGNIFICANT SVR THREAT

NONETHELESS.

LARGE HAIL SHOULD BE THE DOMINANT SVR RISK...ALTHOUGH SOME POTENTIAL

ALSO WILL EXIST FOR TORNADOES...ESPECIALLY IN SW KS AND WRN OK WHERE

LOW LVL WINDS ARE APT TO REMAIN BACKED NE OF TX PANHANDLE SFC LOW.

FARTHER N...MORE SLOWLY-MOVING PORTION OF COLD FRONT IN NRN KS AND

SE NEB SHOULD BE THE FOCUS FOR HAIL AND LOCALLY DMGG WIND. THE

STORMS MAY EVOLVE INTO TWO OR THREE CLUSTERS THIS EVE...WITH A

GRADUALLY DIMINISHING RISK FOR SVR HAIL AND WIND.

...E TX INTO MUCH OF LA/AR LATER TODAY THROUGH THIS EVE...

SFC HEATING OF MOIST ENVIRONMENT DOWNSTREAM FROM S TX MCV WILL LEAD

TO MODERATE INSTABILITY ACROSS MUCH OF E TX...LA...AND AR LATER

TODAY...WITH SBCAPE LIKELY TO BE ON THE ORDER OF 2000 /KG. FORCING

FOR ASCENT ATTENDANT TO THE N TO NE-MOVING CIRCULATION SHOULD FOSTER

FAIRLY WIDESPREAD TSTM DEVELOPMENT. WHILE DEEP SHEAR WILL REMAIN

COMPARATIVELY MODEST /AROUND 30 KTS/...SETUP COULD YIELD SCTD STRONG

TO SVR WIND GUSTS AND HAIL. GIVEN THE PRESENCE OF FAVORABLE STORM

INTERACTIONS AND/OR SMALL SCALE CIRCULATIONS WITHIN EXPECTED STORM

CLUSTERS/BANDS...A CONDITIONAL RISK ALSO WILL EXIST FOR WEAK

TORNADOES.

...ERN KY/TN INTO WRN NC/SC/ERN GA THIS AFTN...

FRONT ASSOCIATED WITH UPR TROUGH THAT AMPLIFIED OVER THE NERN U.S.

LATE YESTERDAY SHOULD ADVANCE S ACROSS THE REMAINDER OF THE

CAROLINAS TODAY...WHILE WRN PORTION BECOMES STNRY OVER THE LWR OH

VLY. WEAK TO MODERATE DIURNAL INSTABILITY SHOULD DEVELOP ALONG AND

S OF THE BOUNDARY...WITH SCTD TSTMS EXPECTED FROM ERN KY SSE INTO

SC. MODERATE NWLY CLOUD LAYER SHEAR SHOULD YIELD MAINLY PULSE

STORMS...A FEW OF WHICH COULD PRODUCE MARGINALLY SVR HAIL/ISOLD DMGG

GUSTS.

...MN/IA INTO WI/IL/IND THROUGH PERIOD...

MOST OF THE UPR MS VLY/UPR MIDWEST WILL REMAIN BENEATH UPR RIDGE

THROUGH THE PERIOD. PERIODIC EPISODES OF ENHANCED WAA/MOISTURE

TRANSPORT MAY SUPPORT A FEW ROUNDS OF ELEVATED STORMS... ESPECIALLY

LATE TNGT/EARLY TUE AS NRN STREAM SHORTWAVE TROUGH APPROACHES

REGION. WHILE SOME OF THIS ACTIVITY MAY PRODUCE HAIL...MODEST

ELEVATED INSTABILITY AND SHEAR SHOULD MITIGATE ANY THREAT FOR

SUSTAINED SVR WEATHER.

..CORFIDI/COHEN.. 04/02/2012

[brettjrob]

Today's threat seems to be trending up at the last minute, which is always something worth noting. This image alone from the RUC should be enough to raise some eyebrows:

Short-term trends point toward a higher likelihood of dryline initiation than yesterday's runs suggested. If the RUC is fairly correct about the low-level wind fields, a mentionable tornado threat may develop over NW TX and SW OK by early evening. The backing above H5 is still an issue, but once you get S of I-40 it doesn't look like a dealbreaker for supercell structures.

[Thundersnow12]

Today's threat seems to be trending up at the last minute, which is always something worth noting. This image alone from the RUC should be enough to raise some eyebrows:

Short-term trends point toward a higher likelihood of dryline initiation than yesterday's runs suggested. If the RUC is fairly correct about the low-level wind fields, a mentionable tornado threat may develop over NW TX and SW OK by early evening. The backing above H5 is still an issue, but once you get S of I-40 it doesn't look like a dealbreaker for supercell structures.

I'd be in TX today most likely if I were chasing, the amount of backing at the sfc from 18-0z is pretty impressive adding WSW flow aloft raises some eyebrows. I'd start around Seymour, TX and go from there. And by 0z low level shear takes off with 0-1 SRH values between 150-200 m2/s2

[tornadotony]

You will probably have a sizable tornado threat still after dark in wrn OK tonight too, with the PBL slow to decouple, a cranking LLJ, strongly-backed sfc flow, and not terrible UL flow...

[Thundersnow12]

MESOSCALE DISCUSSION 0415

NWS STORM PREDICTION CENTER NORMAN OK

0300 PM CDT MON APR 02 2012

AREAS AFFECTED...NWRN TX...ERN OK/TX PANHANDLES...SWRN KS...WRN OK

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 022000Z - 022200Z

A TORNADO WATCH WILL LIKELY BE NEEDED FOR PORTIONS OF NWRN TX...THE

ERN OK/TX PANHANDLES...SWRN KS AND WRN OK THIS AFTERNOON AND

EVENING.

MID-AFTERNOON MESOANALYSIS SHOWS A COLD FRONT WAS LOCATED FROM SWRN

KS INTO ERN NM...WHICH IS BEGINNING TO STALL IN RESPONSE TO PRESSURE

FALLS AHEAD OF A POTENT NEGATIVELY TILT MIDLEVEL SHORTWAVE TROUGH. A

DRYLINE ACCOMPANIED BY DEEPENING CUMULUS EXTENDED SWD FROM THE KS

PORTION OF THE COLD FRONT...WHILE A PACIFIC FRONT WAS BEGINNING TO

ENTER W TX. SURFACE TEMPERATURES ALONG THE DRYLINE HAVE WARMED INTO

THE MID 80S...AND DEWPOINTS E OF THE BOUNDARY RESIDE IN THE UPR 50S

TO MID 60S. THE WARM/MOIST AIRMASS LOCATED ACROSS THE WARM SECTOR

COMBINED WITH STEEP MIDLEVEL LAPSE RATES /IN EXCESS OF 8 C PER KM IN

THE 700-500 MB LAYER/ ARE CONTRIBUTING TO A VERY UNSTABLE

ENVIRONMENT...WITH MLCAPE VALUES NEAR 3000 J/KG.

AS THE UPPER DISTURBANCE LIFTS NWD ACROSS THE SRN HIGH PLAINS THIS

AFTERNOON AND EVENING...SHORT-TERM MODEL GUIDANCE INDICATES SURFACE

CYCLOGENESIS WILL RAPIDLY TAKE PLACE OVER NERN NM AND THE TX

PANHANDLE. STRONG LOW-LEVEL SWLY WINDS OVER W TX...POSSIBLY

ACCOMPANYING AN EWD SURGE OF THE PACIFIC FRONT...WILL QUICKLY SPREAD

EWD TOWARD THE DRYLINE...RESULTING IN STRENGTHENING LOW-LEVEL

CONVERGENCE. AS THIS TAKES PLACE...SCATTERED THUNDERSTORM ARE

FORECAST TO DEVELOP FROM THE KS TRIPLE POINT SWD ALONG THE DRYLINE

BY 22-00Z.

DURING THE EARLY STAGES OF THIS CONVECTIVE EPISODE

TEMPERATURE-DEWPOINT SPREADS WILL BE NEAR 20F OVER THE WARM

SECTOR...AND MIDLEVEL FLOW/DEEP LAYER SHEAR WILL BE MARGINAL FOR

SUPERCELLS...WHICH MAY NEGATIVELY INFLUENCE THE POTENTIAL FOR

TORNADOES DUE TO EXCESSIVE OUTFLOW. HOWEVER...IF STORMS CAN REMAIN

QUASI-DISCRETE INTO THE EVENING...THEN A COOLER/MORE HUMID BOUNDARY

LAYER COUPLED WITH BACKING/STRENGTHENING 0-1 KM FLOW MAY LEAD TO A

MORE SUBSTANTIAL THREAT OF TORNADOES. OTHERWISE...STORMS WILL POSE A

THREAT FOR VERY LARGE HAIL GIVEN THE PRESENCE OF LARGE BUOYANCY AND

VERY STEEP LAPSE RATES...IN ADDITION TO LOCALLY DAMAGING WIND GUSTS.

..GARNER.. 04/02/2012

[on_wx]

Severe thunderstorm watch instead of a tornado watch

[Srain]

We'll see if the CU field E of Aspermont, TX to just S of Clinton, OK will begin to fire off in the Severe Watch Area...

[icebreaker5221]

Looks like high LCLs may be a limiting factor.

That said, this is a great setup for storm chasing. LP supercells and any tornadoes that do form should be very visible.

[Thundersnow12]

based on WV and JTNT profiler, mid-level jet streak still a few hours away from the southern portion of the area (nw TX/sw OK) but already getting a few signs of forced ascent in western OK but nothing has gone up and sustained itself yet.

[Chinook]

It looks like things should be ripe for development with high CAPE in southern Kansas, and down along the dryline. Central Southern Texas has high CAPE, higher deep layer shear, but may have to wait a while. Still, though, there is moisture convergence down there.

Are you guys getting a few intermittent problems with SPC mesoanalysis web site? I am. I hope my computer isn't freaking out.

Looks like tomorrow could be somewhat active with severe weather.

7 mesoscale discussions today

79 reports (unfiltered) today

I don't think I've ever seen a bowing squall line bow out northeastward around Houston before. It looks like a quarter circle.

[OceanStWx]

It looks like things should be ripe for development with high CAPE in southern Kansas, and down along the dryline. Central Southern Texas has high CAPE, higher deep layer shear, but may have to wait a while. Still, though, there is moisture convergence down there.

Are you guys getting a few intermittent problems with SPC mesoanalysis web site? I am. I hope my computer isn't freaking out.

Looks like tomorrow could be somewhat active with severe weather.

The meso page is acting a little wonky for me too.

[andyhb]

Sfc winds backing in response to the 996 mb SLP in NW TX.

Looks like some initiation west of Abilene.

[andyhb]

Storm tops already over 20k feet on the cell near Winters.

MESOSCALE DISCUSSION 0421

NWS STORM PREDICTION CENTER NORMAN OK

0651 PM CDT MON APR 02 2012

AREAS AFFECTED...TX BIG COUNTRY

CONCERNING...SEVERE THUNDERSTORM WATCH 129...

VALID 022351Z - 030045Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 129

CONTINUES.

SEVERE THREAT WILL LIKELY EXTEND S OF THE ORIGINAL WW 129 AND LOCAL

EXTENSION HAS BEEN COORDINATED WITH WFO SJT/FWD. TSTMS WITHIN THIS

REGION SHOULD REMAIN MORE DISCRETE RELATIVE TO FARTHER N IN WW 129

ALONG THE TRAILING INFLUENCE OF THE SHORT WAVE IMPULSE ROTATING NWD

INTO THE TX PANHANDLE. STRONG MID-LEVEL W/SWLYS WILL SUPPORT

EFFECTIVE SHEAR OF 40-50 KT AND PROPAGATION INTO A MORE BUOYANT AIR

MASS FARTHER E WITH ACTIVITY CURRENTLY OCCURRING WITHIN LOWER 50S

SURFACE DEW POINTS. INTENSIFICATION INTO A FEW SUPERCELLS APPEARS

PROBABLE DURING THE EVENING WITH PRIMARY INITIAL RISK OF LARGE HAIL.

..GRAMS.. 04/02/2012

[Buckeye05]

Pretty confused as to what is going on now. Bunch of cells lined up and took off westward. Are we done for the night?

Edit: Maybe not, things are looking interesting in N Texas.

[Chinook]

Thinking back to the previous discussions, there was some talk of a "pesky" upper low in SE TX or LA that would inhibit the moisture in the plains. That was quite a few days ago, and of course the modeling has changed since then significantly. Then, it appears a "pesky" vortex set off a bowing squall line that went from Houston to much of Louisiana.

[Buckeye05]

Monster squall line coming together in north Texas now.

[Srain]

Thinking back to the previous discussions, there was some talk of a "pesky" upper low in SE TX or LA that would inhibit the moisture in the plains. That was quite a few days ago, and of course the modeling has changed since then significantly. Then, it appears a "pesky" vortex set off a bowing squall line that went from Houston to much of Louisiana.

Agreed. My hunch is tomorrow may well be the day to watch TX, LA, AR into S MO.

[Chinook]

Agreed. My hunch is tomorrow may well be the day to watch TX, LA, AR into S MO.

What I'm saying is-- I'm not even sure what happened to model depictions the smaller upper low that was supposed to be in east TX. That is, model depictions from a few days ago changed a lot. But a mesovortex popped in that area.

I also think tomorrow will be a pretty active severe weather day. I'm seeing pretty good parameters on the SREF (15z) for Dallas tomorrow afternoon. Maybe a few tornadoes in eastern Texas tomorrow.

[andyhb]

From 01z Outlook.

...CENTRAL TX...

THE AIR MASS ACROSS CENTRAL TX /FROM DRT AND TX HILL COUNTRY/ NWD

INTO N TX IS EXPECTED TO REMAIN MODERATELY-STRONGLY UNSTABLE

OVERNIGHT AND STRONGLY SHEARED. MODELS CONTINUE TO SUGGEST TSTMS

WILL DEVELOP ALONG THE DRY LINE AS THE PACIFIC FRONT OVERTAKES THIS

BOUNDARY. THIS LOW LEVEL CONVERGENCE COMBINED WITH DPVA ATTENDANT

TO A SECONDARY MIDLEVEL IMPULSE ROUNDING THE BASE OF THE NM LOW

REACHES CENTRAL TX TONIGHT. DEGREE OF INSTABILITY AND SHEAR VECTORS

PERPENDICULAR TO THE BOUNDARY WILL SUPPORT SUPERCELLS WITH ALL

FACETS OF SEVERE WEATHER POSSIBLE INCLUDING VERY LARGE HAIL.

Low level shear is increasing per mesoanalysis ahead of the boundary in Central TX.

Main mid level jet streak of 50-70 kts is just now approaching the area although LCL heights are still pretty high...

Storm east of Haskell, TX has a decent mid level meso.

[andyhb]

Sup north of Throckmorton looks to have some potential aproaching an area with 200+ m2/s2 effective SRH and lowering LCLs.

[Srain]

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0800 AM CDT TUE APR 03 2012

VALID 031300Z - 041200Z

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

PLNS...WRN OZARKS...AND LWR MS VLY...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE MID MS AND

LWR OH VLYS...

...SYNOPSIS...

NM UPR LOW EXPECTED TO MOVE ONLY SLOWLY E THIS PERIOD AS SYSTEM

REMAINS WELL REMOVED FROM MAIN BELT OF THE AMPLIFIED WLYS EXTENDING

ACROSS THE PACIFIC NW...CENTRAL CANADA...AND THE UPR GRT LKS-NERN

U.S. VORT LOBE ASSOCIATED WITH THE NM LOW...NOW EXTENDING SWD

THROUGH ERN NM...SHOULD PIVOT ENE ACROSS W TX LATER THIS MORNING AND

THEN TURN NE ACROSS WRN N TX AND WRN OK THIS AFTN.

FARTHER NE...SATELLITE AND VWP DATA SUGGEST THAT DISTURBANCE IN PART

RESPONSIBLE FOR LARGE MCS OVER E TX...AR...AND LA YESTERDAY NOW

EXTENDS IN AN ARC FROM SW MO THROUGH NE AR TO CSTL MS. THIS FEATURE

SHOULD CONTINUE ENE THROUGH THE DAY...REACHING A CNTRL IL...MIDDLE

TN...FL PANHANDLE LINE BY EVE.

AT LWR LVLS...QSTNRY SFC LOW THAT HAD BEEN PRESENT OVER THE TX

PANHANDLE HAS PARTLY FILLED AS A RESULT OF /1/ SWD MOVEMENT OF POLAR

AIR FROM KS-NEB...AND /2/ WIDESPREAD OUTFLOW FROM CONVECTION OVER

THE SRN PLNS-LWR MS VLY. AN ELONGATED LOW LVL CIRCULATION

WILL...NEVERTHELESS...LIKELY PERSIST TODAY OVER NW TX...NEAR

INTERSECTION OF THE POLAR COLD FRONT WITH MERGED DRY LINE-PACIFIC

COLD FRONT. THIS CIRCULATION OR WEAK LOW SHOULD DRIFT NE TOWARD THE

OK-KS BORDER BY EVE...AHEAD OF AFOREMENTIONED NM VORT LOBE.

FARTHER NE...RESIDUAL TRIPLE POINT LOW NOW IN SE IA SHOULD EDGE ESE

INTO IL-IND LATER TODAY AS THE APPROACH OF A SHORTWAVE IMPULSE IN

THE NRN STREAM /OVER THE UPR GRT LKS/ ENHANCES WSWLY LOW LVL FLOW

OVER THE OH VLY. THIS WILL ALLOW EXISTING STNRY FRONT EXTENDING E

FROM THE LOW TO ADVANCE ENEWD AS WARM FRONT INTO PARTS OF

IND...OH...AND KY.

THE VORT LOBE AND ASSOCIATED FRONT/DRYLINE OVER THE SRN PLNS...AND

THE LOW/WARM FRONT OVER THE OH VLY...WILL BE THE MAIN FOCI FOR

STRONG TO SVR TSTMS TODAY INTO TNGT.

...SRN PLNS INTO LWR MS VLY TODAY THROUGH TNGT...

SCTD TO NUMEROUS TSTMS AND STORM CLUSTERS ARE EXPECTED THROUGH THE

PERIOD OVER ERN PORTIONS OF THE SRN PLNS AND ADJACENT PARTS OF THE

WRN OZARKS/LWR MS VLY AS VORT LOBE ROTATING NNE AROUND ERN SIDE OF

NM UPR LOW...AND SUBSEQUENT WEAKER DISTURBANCES...ENHANCE ASCENT

ACROSS REGION.

GIVEN THAT OVERNIGHT MCSS HAVE SOMEWHAT STABILIZED REGION N OF THE

RED RIVER...THE STRONGEST DIURNALLY DRIVEN DEVELOPMENT IS EXPECTED

OVER CNTRL AND N TX. COMBINATION OF INCREASING ASCENT IN

MODERATELY-SHEARED...RICHLY MOIST LOW LVL ENVIRONMENT BENEATH

DEEP/PERSISTENT EML SHOULD YIELD STORMS CAPABLE OF VERY LARGE HAIL

AND LOCALLY DMGG WIND. WIND PROFILES WILL REMAIN DIFFICULT TO

GENERALIZE OVER SPACE AND TIME...AND EXPECTED FAIRLY WIDESPREAD

COVERAGE LIMITS PREDICTABILITY OF PREDOMINANT CONVECTIVE MODE/STORM

TYPE. BUT SETUP APPEARS AT LEAST CONDITIONALLY SUPPORTIVE OF A FEW

SUPERCELLS ALSO CAPABLE OF TORNADOES GIVEN QUALITY OF MOISTURE

INFLOW/DEGREE OF BUOYANCY. THE STORMS LIKELY WILL MERGE INTO ONE OR

MORE MCSS THIS EVENING. ONE OF THESE COULD BECOME RATHER LARGE AND

MOVE/DEVELOP E/SE TOWARD THE HOUSTON/BEAUMONT AREA TOWARD WED

MORNING...WITH A CONTINUING RISK FOR SVR WEATHER. A MORE

LIMITED...THOUGH NON-ZERO...RISK FOR SVR STORMS WILL EXIST IN MUCH

OF OK THROUGH EARLY TNGT...WHERE LARGE SCALE FORCING FOR ASCENT WILL

BE GREATER...BUT SFC-BASED INSTABILITY MORE LIMITED THAN IN TX.

...MID MS/LWR OH VLYS...

STRONG SFC HEATING WILL OCCUR TODAY IN WEAKLY SHEARED ENVIRONMENT

ALONG AND S OF WARM/STNRY FRONT IN THE MID MS/LWR OH VLYS. AREA

SOUNDINGS SHOW PRESENCE OF A DEEP EML ATOP A RELATIVELY MODEST MOIST

SFC LAYER. COMBINATION OF HEATING WITH WEAK LOW LVL CONFLUENCE AND

ASCENT AHEAD OF MID/UPR LVL VORT LOBE SHOULD SUPPORT DEVELOPMENT OF

CLUSTERS/SHORT BANDS OF WEAKLY ORGANIZED AFTN/EVE STORMS. THESE MAY

YIELD SVR HAIL AND LOCALLY DMGG WIND AS THE WARM SECTOR EXPANDS

FARTHER E INTO IND AND WRN OH. THE STORMS LIKELY WILL MERGE INTO A

FAIRLY EXTENSIVE...S TO SE-MOVING MCS OVER PARTS OF IL/IND/KY LATER

TNGT. THIS SYSTEM MAY FEATURE BOTH FORWARD-PROPAGATING

SEGMENTS/SMALL BOWS...AND BACK-BUILDING/WWD-DEVELOPING

ACTIVITY...WITH A DIMINISHING THREAT FOR LOCALLY SVR WIND AND HAIL.

...WRN/CNTRL KS LATER TODAY INTO TNGT...

ELEVATED TSTMS WILL BE POSSIBLE LATER TODAY/TNGT IN WRN/CNTRL KS AS

LEADING EDGE OF DCVA/ASCENT IMMEDIATELY AHEAD OF NM UPR LOW/ VORT

LOBE APPROACHES REGION. STEEP MID LVL LAPSE RATES COULD YIELD

MARGINALLY SVR HAIL.

...SERN U.S. THIS AFTN...

A LOW PROBABILISTIC RISK FOR SVR HAIL/LOCALLY DMGG WIND WILL EXIST

OVER A LARGE PART OF THE SERN U.S...WHERE RELATIVELY STEEP MID LVL

LAPSE RATES WILL RESIDE ATOP A FAIRLY MOIST/WEAKLY CONFLUENT

BOUNDARY LAYER. THE GREATEST CONCENTRATION OF SUCH ACTIVITY MAY

OCCUR OVER N FL AND ADJACENT PORTIONS OF GA...WHERE ASCENT WILL BE

ENHANCED BY APPARENT MCV/WEAK VORT MAX ON SRN END OF AFOREMENTIONED

UPR IMPULSE. ALTHOUGH THIS REGION IS SOMEWHAT DRIER THAN AREA

AFFECTED BY SIMILAR WIND PROFILES/LARGE SCALE ASCENT YESTERDAY OVER

LA...AR...AND MS...STRONG SFC HEATING/STEEPENING LOW LVL LAPSE RATES

MAY COMPENSATE FOR ENHANCED ENTRAINMENT TO YIELD STRONG SFC WIND

GUSTS.

..CORFIDI/COHEN.. 04/03/2012

[Srain]

MESOSCALE DISCUSSION 0428

NWS STORM PREDICTION CENTER NORMAN OK

0836 AM CDT TUE APR 03 2012

AREAS AFFECTED...CENTRAL AND NRN TX/SRN OK

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 031336Z - 031500Z

STRENGTHENING CONVECTION/INCREASING SEVERE POTENTIAL SUGGEST THAT WW

ISSUANCE MAY BE REQUIRED IN THE NEXT HOUR.

LATEST RADAR LOOP SHOWS STORMS INCREASING IN COVERAGE AND INTENSITY

ACROSS PARTS OF CENTRAL AND N TX...WITHIN ZONE OF ASCENT PIVOTING

NEWD ACROSS CENTRAL AND N TX AROUND THE SERN FRINGE OF THE SRN

ROCKIES UPPER LOW. STORMS ARE DEVELOPING IN CLOSE PROXIMITY TO THE

SURFACE COLD FRONT -- WHICH HAS PUSHED EWD ACROSS THE WRN HALF OF TX

AND NOW LIES ROUGHLY N-S FROM JUST W OF ABI TO JUST E OF JCT. E OF

THE FRONT WITHIN THE WARM SECTOR...A SLIGHTLY STABLE BOUNDARY LAYER

IS INDICATED...WITH WIDESPREAD LOW CLOUDS PER LATEST VISIBLE IMAGERY

LIKELY TO HINDER THE INITIATION OF BOUNDARY LAYER

HEATING/DESTABILIZATION OVER THE NEXT COUPLE OF HOURS.

STILL...MORNING FWD /FORT WORTH TX/ RAOB REVEALS STEEP LAPSE

RATES/MODERATE CAPE ABOVE THE BOUNDARY LAYER ALONG WITH AMPLE

CLOUD-LAYER SHEAR. THUS...EXPECT THREAT FOR LARGE HAIL WITH THE

DEVELOPING CONVECTION ALONG WITH LIMITED WIND GUST POTENTIAL --

POTENTIAL WHICH COULD INCREASE LATER THIS MORNING PRESUMING LOW

CLOUD EROSION ALLOWING HEATING TO COMMENCE.

..GOSS.. 04/03/2012

ATTN...WFO...FWD...OUN...EWX...SJT...

[Ed Lizard]

Impressive cells nearing DFW when morning sounding, and SPC mesoanalysis, both suggest it hasn't warmed enough for surface storms. DFW only needs to warm another 2 or 3º, and has ~2 more hours before storms arrive. DFW and FTW also saw a shift from East winds to South winds with slight rise in dewpoint, maybe a subtle boundary will enhance the action.

I was starting to get worried with the radar fairly quiet around 6 am. Anyway, NWS FWD is saying Texas Tech and OU WRF models handling the storms much better than HRRR, which is too bad, I don't have those bookmarked. Maybe one of the highly paid pro-mets have access to that.

Sweet, DAL has broken into partial sunshine in last hour, surface temp is up to 74ºF, which should be really close for surface based storms.

[Srain]

The sun is breaking through the clouds in NW Harris County and temps are beginning to respond. Keeping an eye to our W along the dry line for storm initiation near the Edwards Plateau...