DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 092003
SWODY1
SPC AC 092000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT THU MAY 09 2013

VALID 092000Z - 101200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLNS ENE INTO THE
ARKLATEX...

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

...SOUTHERN PLAINS/ARKLATEX TO LOWER MS VALLEY...
FOR ADDITIONAL SHORT-TERM DETAILS REGARDING AN ONGOING MCS ACROSS
CENTRAL TX...SEE MESOSCALE DISCUSSION 610. DAMAGING WINDS AND SEVERE
HAIL IS EXPECTED TO REMAIN A CONCERN AS IT PERSISTS SOUTHEASTWARD
ACROSS SOUTHEAST TX INTO THIS EVENING.

FARTHER WEST...ADDITIONAL STORM DEVELOPMENT IS EXPECTED THROUGH LATE
AFTERNOON/EARLY EVENING FROM PORTIONS OF OK SOUTHWESTWARD INTO
WEST/SOUTHWEST TX IN VICINITY OF FRONT/DRYLINE. LITTLE OUTLOOK
ADJUSTMENTS NEEDED FOR THIS SCENARIO...ALTHOUGH ADDITIONAL PARTS OF
THE TX RIO GRANDE VICINITY WERE ADDED TO THE SLIGHT RISK. SEE PRIOR
OUTLOOK DISCUSSION BELOW AND SUBSEQUENT MESOSCALE DISCUSSIONS.

...MIDDLE MS VALLEY/OH VALLEY...
SOME SOUTHWARD SPATIAL ADJUSTMENTS WERE MADE TO SLIGHT RISK TO
ACCOUNT FOR PRIMARY /ALBEIT MODEST/ DESTABILIZATION FOCUSED ACROSS
DOWNSTATE IL/INDIANA...IMMEDIATELY AHEAD OF EAST-NORTHEASTWARD
MOVING VORT ACROSS FAR EASTERN MO/SOUTHWEST IL THIS AFTERNOON. BOUTS
OF DAMAGING WINDS/HAIL WILL BE POSSIBLE...AT LEAST ON AN ISOLATED
BASIS INTO THIS EVENING.

..GUYER.. 05/09/2013

.PREV DISCUSSION... /ISSUED 1130 AM CDT THU MAY 09 2013/

...SYNOPSIS...
WEAK SPLIT FLOW PATTERN WILL PREVAIL OVER THE LWR 48 THIS PERIOD AS
FOUR CORNERS/CNTRL RCKYS UPR LOW CONTINUES TO DEVOLVE INTO AN
ELONGATED POSITIVE-TILT TROUGH...AND NE U.S. LOW ACCELERATES ENE TO
BECOME REABSORBED IN THE WLYS. MODERATE WSW FLOW WILL PREVAIL FROM
THE SRN PLNS/OZARKS INTO THE OH/TN VLYS ON SRN FRINGE OF ELONGATING
TROUGH.

NRN STREAM COLD FRONT WILL CONTINUE TO ADVANCE S/SE ACROSS THE
CNTRL/SRN PLNS...DELIMITING THE NRN AND WRN EXTENT OF A RATHER LARGE
AREA EXTENDING FROM PARTS OF TX AND OK NEWD INTO THE OH VLY/MIDWEST
THAT WILL HAVE AT LEAST A CONDITIONAL RISK FOR SVR TSTMS THROUGH
TNGT. THE FRONT...AND CONFLUENCE AXES/OUTFLOW BOUNDARIES TO ITS S
AND E...SHOULD BE THE MAIN LOW-LVL FOCUS FOR STORM DEVELOPMENT
THROUGH THE PERIOD.

...SRN PLNS/ARKLATEX TODAY/TNGT...
SATELLITE SHOWS AN UPR DISTURBANCE NOW OVER THE TX BIG BEND THAT
SHOULD CONTINUE ENE ACROSS THE REMAINDER OF TX TODAY AND INTO AR/W
TN TNGT/EARLY FRI. ASCENT WITH THIS FEATURE...AND MODEST SFC HEATING
OF RATHER MOIST AND CONDITIONALLY UNSTABLE ENVIRONMENT ON ITS
PERIPHERY...SHOULD SUPPORT INTENSIFICATION AND AREAL EXTENSION OF
EXISTING TSTMS CLUSTER NOW OVER CNTRL TX.

CLOUDS WILL LIMIT SFC HEATING...BUT GIVEN QUALITY OF MOISTURE INFLOW
/PW VARYING FROM AROUND 1.00 INCH IN THE EDWARDS PLATEAU TO ABOVE
1.50 IN E CNTRL AND SE TX/...DEEP EML...AND PERSISTENT
ASCENT...POTENTIAL WILL EXIST FOR STRONG UPDRAFTS WITH LARGE HAIL
AND LOCALLY DMGG WIND.

THE CURRENT AREA OF STORMS APPEARS TO BE ASSOCIATED WITH A SFC-850
MB CONFLUENCE ZONE AHEAD OF SRN PLNS COLD FRONT. THIS CONFLUENCE
ZONE SHOULD SHIFT ENE ACROSS CNTRL TX THROUGH THE DAY...WITH THE
GREATEST POTENTIAL FOR SVR STORMS POSSIBLY OCCURRING AS THE
CONFLUENCE ZONE REACHES AND MOVES E BEYOND THE I-35 CORRIDOR LATER
TODAY INTO TNGT. 40-45 KT WSWLY DEEP SHEAR...COUPLED WITH MOISTURE
AVAILABILITY...MAY SUPPORT FORWARD-PROPAGATING/BOWING SEGMENTS WITH
HIGH WIND EWD ACROSS THE MID/UPR TX CSTL PLN...THE SABINE RVR
VLY...AND PARTS OF AR/LA BY EARLY FRI.

N AND W OF THE ABOVE ACTIVITY...TSTMS ALSO MAY FORM ALONG COLD FRONT
LATE THIS AFTN FROM CNTRL OK SWWD INTO W TX. A FEW STORMS ALSO COULD
FROM NEAR INTERSECTION OF THE FRONT WITH LEE TROUGH/DRY LINE IN W
TX. POCKETS OF AMPLE SHEAR/INSTABILITY SHOULD EXIST IN THESE AREAS
TO SUPPORT A CONDITIONAL RISK FOR SUSTAINED UPDRAFTS/SUPERCELLS WITH
SVR HAIL/WIND. ABSENCE OF STRONG FORCING FOR ASCENT AND MODEST LLJ
SUGGEST THAT THESE STORMS SHOULD WEAKEN BY MID TO LATE EVE.

...MID MS/LWR OH VLYS THIS AFTN/EVE...
A BELT OF ENHANCED /30+ KTS AT 500 MB/ WSWLY LOW TO MID-LVL FLOW
WILL PERSIST OVER THE MID MS/LWR OH VLYS TODAY...ASSOCIATED WITH NRN
STREAM TROUGH NOW OVER IA...AND CONVECTIVELY-INDUCED CIRCULATIONS
LEFT FROM OVERNIGHT MCSS. COUPLED WITH SFC HEATING...THIS MAY
SUPPORT ONE OR TWO CORRIDORS OF STRONGER STORM DEVELOPMENT THIS AFTN
FROM PARTS OF ERN MO ENE INTO CNTRL/SRN IL...IND...AND PERHAPS
NRN/WRN KY. WHILE THE LWR LVLS ARE NOT PARTICULARLY MOIST...AREA 850
MB/VWP DATA SUGGEST THAT SUFFICIENT MOISTURE ADVECTION WILL OCCUR TO
SUPPORT SUSTAINED STORMS S AND E OF THE ERN EXTENSION OF PLNS COLD
FRONT. RELATIVELY MODEST MID-LVL LAPSE RATES SHOULD MITIGATE OVERALL
SVR RISK...BUT A CONDITIONAL RISK FOR SVR WIND GUSTS AND HAIL WILL
NEVERTHELESS EXIST...ESPECIALLY IN IL.

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