SPC AC 120539
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1239 AM CDT SAT JUN 12 2010
VALID 121200Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN HIGH PLAINS TO THE
OH VALLEY...
...CENTRAL/SRN PLAINS...
BOTH THE NAM AND GFS ARE IN REASONABLE AGREEMENT REGARDING THE SHORT
TERM EVOLUTION OF WRN U.S. TROUGH. IT APPEARS A SUBSTANTIAL MID
LEVEL SPEED MAX WILL ROTATE ACROSS NM EARLY IN THE PERIOD BEFORE
EJECTING INTO ERN CO DURING THE AFTERNOON HOURS. SRN LOBE OF THIS
STRONGER FLOW SHOULD SPREAD ACROSS THE TX PANHANDLE WITH UPWARDS OF
40KT AT 500MB NEAR THE FRONTAL ZONE BY PEAK HEATING. THERE IS SOME
CONCERN THAT THE MODELS MAY BE UNDERESTIMATING THE SWD EXTENT OF
EXPECTED FRONTAL SURGE THROUGH THE HIGH PLAINS. EARLY MORNING
FRONTAL POSITION CURRENTLY EXTENDS FROM NEAR GLD...SWWD TO LHX AND
JUST NORTH OF TAD. ALTHOUGH THIS BOUNDARY WILL LIKELY SAG A BIT
FARTHER SOUTH THAN 00Z MODELS SUGGEST...STRONG BOUNDARY LAYER
HEATING OVER ERN NM AND THE TX SOUTH PLAINS ALONG WITH MERIDIONAL
FLOW ALOFT SUGGEST SFC FRONT WILL SLOW AND LIKELY STALL OVER THE TX
PANHANDLE. SUSTAINED SELY BOUNDARY LAYER FLOW INTO THIS FRONTAL
ZONE WILL MAINTAIN MID 60S TO NEAR 70F SFC DEW POINTS ENHANCING THE
PROSPECT FOR A VERY UNSTABLE AIRMASS BY PEAK HEATING...SBCAPE VALUES
SHOULD EXCEED 3500 J/KG. FORECAST SOUNDINGS FAVOR SUPERCELL
DEVELOPMENT BY 19-20Z NEAR THE WIND SHIFT...POSSIBLY DELAYING TO
NEAR 00Z ALONG THE DRYLINE OVER WEST TX. VERY LARGE HAIL...LIKELY
EXCEEDING 2 INCHES...COULD ACCOMPANY THIS ACTIVITY AND SHEAR
PROFILES ALSO FAVOR A FEW TORNADOES WHERE UPDRAFTS ARE NOT UNDERCUT
BY COLD FRONT.
WITH THE LLJ EXPECTED TO INCREASE ACROSS THE SRN PLAINS INTO SCNTRL
NEB THERE WILL LIKELY BE A SUBSTANTIAL INCREASE IN STRONG/SEVERE
THUNDERSTORM ACTIVITY NEWD ALONG THE FRONTAL ZONE WELL INTO THE
OVERNIGHT HOURS.
...OH VALLEY...
WELL AHEAD OF THE WRN U.S. TROUGH...A FAIRLY ACTIVE BUT NARROW BAND
OF MODEST MID-HIGH LEVEL FLOW WILL EXTEND FROM NERN MEXICO...NEWD
ACROSS THE MID MS VALLEY INTO THE OH VALLEY...ALONG THE PERIPHERY OF
UPPER ANTICYCLONE NEAR THE FRINGE OF STRONGER WLY FLOW. WITHIN THIS
FLOW THERE ARE SEVERAL EMBEDDED DISTURBANCES THAT SHOULD ENCOURAGE
ENHANCED DIURNAL CONVECTIVE DEVELOPMENT...ESPECIALLY NEAR THE
FRONTAL ZONE AS IT SAGS INTO OH/IND/IL. DEEP LAYER SHEAR IS NOT
PARTICULARLY STRONG AND LAPSE RATES ARE ONLY MODESTLY STEEP...THUS
ANY SEVERE THUNDERSTORMS THAT MANAGE TO DEVELOP ACROSS THE OH VALLEY
WILL LIKELY REMAIN MULTI-CELLULAR IN NATURE AND LIKELY POSE
PRIMARILY A WIND OR HAIL THREAT. SFC HEATING WILL CONTRIBUTE
GREATLY TO UPDRAFT STRENGTH AND NOCTURNAL COOLING WILL RESULT IN
RAPID WEAKENING OF THUNDERSTORM ACTIVITY.
ADDITIONALLY...REMNANTS OF EARLY MORNING PLAINS MCS SHOULD PROPAGATE
INTO IA/NRN MO EARLY IN THE PERIOD. RENEWED CONVECTIVE DEVELOPMENT
IS LIKELY BY EARLY AFTERNOON NEAR THE EFFECTIVE OUTFLOW/FRONTAL
POSITION AS BOUNDARY LAYER WARMS. AGAIN...SHEAR PROFILES ARE NOT
EXPECTED TO BE PARTICULARLY STRONG AND CONVECTIVE MODE SHOULD REMAIN
MULTI-CELLULAR IN NATURE.
..DARROW/GARNER.. 06/12/2010
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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