DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 271629
SWODY1
SPC AC 271627

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1127 AM CDT FRI SEP 27 2013

VALID 271630Z - 281200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY
TONIGHT FROM CENTRAL NEB TO THE TX PANHANDLE...

...CENTRAL NEB TO TX PANHANDLE THIS AFTERNOON INTO EARLY TONIGHT...
A MIDLEVEL SHORTWAVE TROUGH OVER THE GREAT BASIN WILL EJECT ENEWD
OVER THE CENTRAL ROCKIES TODAY...REACHING THE CENTRAL/NRN PLAINS BY
EARLY SATURDAY. LEE CYCLOGENESIS IS EXPECTED ACROSS THE CENTRAL
HIGH PLAINS TODAY IN ADVANCE OF THE MIDLEVEL TROUGH...AND ONLY
SLOWLY EWD/SEWD MOTION OF A COLD FRONT IS EXPECTED THROUGH THIS
EVENING ACROSS NEB/WRN KS/TX AND OK PANHANDLES/ERN NM.
MEANWHILE...A MARITIME TROPICAL AIR MASS IS SPREADING NWD INTO
CENTRAL/NW TX AS OF MID MORNING...WITH LOW 60S DEWPOINTS EXPECTED TO
REACH WRN KS/S CENTRAL NEB BY MID-LATE THIS AFTERNOON. THE
MOISTENING WILL OCCUR BENEATH THE REMNANTS OF A RELATIVELY SHALLOW
EML PLUME /STEEPEST LAPSE RATES CONFINED TO 800-600 MB LAYER/...AND
COMBINED WITH DAYTIME HEATING...WILL RESULT IN A NARROW CORRIDOR OF
500-1250 J/KG MLCAPE.

THUNDERSTORM DEVELOPMENT IS EXPECTED BY MID AFTERNOON ALONG THE LEE
TROUGH/PACIFIC COLD FRONT...IN CONJUNCTION WITH THE BAND OF ASCENT
DENOTED BY THE WEAK MIDLEVEL CONVECTION NOW EXTENDING FROM THE TX/NM
BORDER TO WRN KS. THE INITIAL STORMS WILL FORM A LITTLE W/NW OF THE
RICHER BOUNDARY LAYER MOISTURE...WHERE VERTICAL MIXING WILL BE
GREATER AND TEMP-DEWPOINT SPREADS WILL LIKELY EXCEED 25 F. VERTICAL
SHEAR PROFILES WILL BE MORE FAVORABLE FOR SUPERCELLS WITH NWD EXTENT
FROM THE TX PANHANDLE INTO WRN KS...THOUGH LARGELY BOUNDARY-PARALLEL
DEEP-LAYER SHEAR VECTORS AND LINEAR FORCING FOR ASCENT SUGGEST A
FAIRLY QUICK TRANSITION TO A LINEAR CONVECTIVE MODE BY THIS EVENING.
THUS...DAMAGING GUSTS AND MARGINALLY SEVERE HAIL APPEAR TO BE THE
MAIN SEVERE WEATHER THREATS. THE TORNADO THREAT IS MORE UNCERTAIN
GIVEN THE EXPECTED LARGER TEMP-DEWPOINT SPREADS WITH THE INITIAL
STORMS...AS WELL AS THE TENDENCY FOR MORE LINEAR CONVECTION AND
GRADUAL STABILIZATION OF THE BOUNDARY LAYER PRIOR TO AN INCREASE IN
LOW-LEVEL SHEAR BY EARLY TONIGHT.

..THOMPSON/COHEN.. 09/27/2013

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