DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181945
SWODY1
SPC AC 181942

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0142 PM CST MON FEB 18 2013

VALID 182000Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE ARKLATEX...

...ARKLATEX...

MINOR CHANGES HAVE BEEN MADE TO THE 1630Z OUTLOOK TO ACCOUNT FOR THE
POTENTIAL FOR SEVERE TSTM DEVELOPMENT A BIT FARTHER WEST ACROSS NERN
TX...AND TO INCREASE SEVERE PROBS OVER NWRN AR WHERE ORGANIZED
CONVECTION HAS EVOLVED.

CONVECTION HAS RECENTLY INCREASED IN AREAL COVERAGE/INTENSITY ALONG
NERN PLUME OF STEEP LOW LEVEL LAPSE RATES OVER ERN OK. THIS
ACTIVITY IS STRONGLY SHEARED AND SHOULD REMAIN ORGANIZED AS IT
SPREADS INTO WRN AR OVER THE NEXT FEW HOURS. LATEST RADAR DATA
EXHIBITS MULTIPLE SUPERCELLULAR STRUCTURES AND HAIL MAY APPROACH
SEVERE LEVELS IN ADDITION TO THE THREAT FOR LOCALLY DAMAGING WINDS.
FOR THIS REASON HAVE INCREASED THE HAIL/WIND PROBS INTO NWRN AR TO
ACCOUNT FOR THIS THREAT.

STEEP LAPSE RATES...APPROACHING DRY ADIABATIC...ARE NUDGING INTO
NERN TX/SERN OK AND THIS APPEARS PARTLY RESPONSIBLE FOR RECENT
DEEPENING OF CU WITHIN VEERED WARM SECTOR BOUNDARY LAYER FLOW. WITH
TIME DISCRETE SUPERCELLS SHOULD EMERGE OVER THIS REGION WHERE SFC
DEW POINTS HAVE RISEN INTO THE UPPER 50S. WITH SFC TEMP/DEW POINT
SPREADS ON THE ORDER OF 15 DEG F THE STRONGEST SUPERCELLS MAY
ATTEMPT TO PRODUCE TORNADOES. FOR THIS REASON HAVE INCREASED THE
TORNADO THREAT TO 5 PERCENT ACROSS THIS REGION.

..DARROW.. 02/18/2013

.PREV DISCUSSION... /ISSUED 1024 AM CST MON FEB 18 2013/

...ARKLATEX...
MORNING WATER VAPOR LOOPS SHOW A DEEPENING SHORTWAVE TROUGH OVER
EASTERN CO/NM. THIS FEATURE IS EXPECTED TO ROTATE QUICKLY EASTWARD
ACROSS THE PLAINS AND INTO THE MS VALLEY OVERNIGHT. AHEAD OF THE
TROUGH...A COLD FRONT IS SURGING SOUTHEASTWARD ACROSS OK AND WILL
PROVIDE THE FOCUS FOR THUNDERSTORM DEVELOPMENT LATER TODAY AND
TONIGHT.

STRONG SOUTHERLY LOW LEVEL WINDS AHEAD OF THE FRONT ARE HELPING TO
TRANSPORT SURFACE DEWPOINTS IN THE 50S NORTHWARD INTO MUCH OF EAST
TX/WEST LA AND EVENTUALLY INTO MUCH OF AR. BROKEN CLOUDS IN THIS
REGION WILL YIELD A MARGINALLY UNSTABLE AIR MASS BY LATE AFTERNOON
WITH MLCAPE VALUES OF 500-700 J/KG AND LITTLE CONVECTIVE INHIBITION.
STORMS ARE LIKELY TO DEVELOP IN VICINITY OF THE COLD FRONT OVER
SOUTHEAST OK/WESTERN AR AND NORTHEAST TX BY 21-00Z...THEN SPREAD
SOUTHEASTWARD ACROSS THE SLIGHT RISK AREA THROUGH THE EVENING.
DESPITE RATHER LIMITED INSTABILITY...STRONG WIND FIELDS AND FORCING
ALONG THE FRONT MAY BE SUFFICIENT FOR AN ORGANIZED LINE OF
THUNDERSTORMS CAPABLE OF GUSTY/DAMAGING WINDS AND SOME HAIL.

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