SWODY1
SPC AC 021951
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT WED SEP 02 2009
VALID 022000Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL PLAINS...
...CENTRAL PLAINS...
CENTRAL PLAINS HAVE BEEN SLOW TO DESTABILIZE THIS AFTERNOON...THOUGH
AN AXIS OF STRONG HEATING DOES EXTEND OFF THE HIGH PLAINS EWD ALONG
THE SD/NE BORDER. THIS IS CONTRIBUTING TO A SMALL POCKET OF 1000
J/KG MLCAPE ALONG THE SRN PERIPHERY OF UPPER LOW. LATEST VIS
IMAGERY SUPPORTS THIS WITH THE GREATEST/THICKER CU DEVELOPMENT NOW
OCCURRING WITHIN STEEPER LAPSE RATE ENVIRONMENT ACROSS SRN SD INTO
NCNTRL NE. THUNDERSTORMS SHOULD EVOLVE WITHIN THIS DEEPENING CU
FIELD OVER THE NEXT FEW HOURS...A FEW MAY OBTAIN SUPERCELL
CHARACTERISTICS...IN LINE WITH LATE MORNING FORECAST.
...SOUTHWESTERN DESERTS...
AN AXIS HIGH PWAT EXTENDS NWD ALONG THE LOWER CO RIVER VALLEY INTO
SERN CA/SWRN AZ WITH VALUES IN EXCESS OF 1.5 INCHES. ALTHOUGH
BOUNDARY LAYER CU HAVE YET TO DEVELOP ACROSS THIS REGION...AS
TEMPERATURES WARM IN EXCESS OF 100-105F SCATTERED THUNDERSTORMS
SHOULD DEVELOP WITHIN THIS MOISTURE/INSTABILITY AXIS. GIVEN THE
AMOUNT OF MOISTURE CONTENT...A FEW DOWNBURSTS MAY BE OBSERVED WITH
STRONGER ACTIVITY.
..DARROW/COOK.. 09/02/2009
.PREV DISCUSSION... /ISSUED 1126 AM CDT WED SEP 02 2009/
...CENTRAL PLAINS INTO THE CENTRAL/SRN HIGH PLAINS...
NOT MUCH CHANGE TO ONGOING OUTLOOK...WITH MODELS CONSISTENT IN SLOW
SSEWD MOTION TO MID/UPPER LOW NOW OVER SD. 12Z UPPER AIR ANALYSES
INDICATE SYSTEM CONTAINS SLIGHTLY WARMER MID LEVEL TEMPERATURES IN
ITS CORE. HOWEVER...SUFFICIENT LOW LEVEL MOISTURE/HEATING SHOULD
SUPPORT AXIS OF MARGINAL MLCAPE BY THE MID TO LATE AFTERNOON ALONG
AND JUST EAST OF ASSOCIATED LEE TROUGH/N-S SURFACE FRONT EXTENDING
ACROSS CENTRAL-WRN SD/NEB. IN ADDITION...ENHANCED BELT OF NWLY
MID/UPPER LEVEL WINDS ALONG SWRN PERIPHERY OF UPPER CIRCULATION WILL
MAINTAIN MODEST TO STRONG DEEP LAYER SHEAR WITH SFC-6 KM SHEAR
AROUND 40 KT. STORMS SHOULD INCREASE/DEVELOP SWWD INTO GREATER
INSTABILITY DURING THE AFTERNOON/EVENING AND LIKELY SUSTAIN AT LEAST
A LOW-END SLGT RISK OF HAIL/WIND GIVEN DEGREE OF SHEAR AND
POSSIBILITY OF A SUPERCELL OR TWO.
FARTHER SW...EXPECTED SEVERE THREAT GETS INCREASINGLY MARGINAL AS
DIURNAL STORMS DEVELOP NEAR LEE LOW/SURFACE TROUGH AND MOVE OFF
HIGHER TERRAIN INTO THE SRN/CENTRAL HIGH PLAINS. STEEP LAPSE RATES
AND MODERATE INSTABILITY SHOULD OVERCOME WEAK DEEP LAYER SHEAR TO
SUPPORT AT LEAST LOW PROBABILITY THREATS OF SEVERE HAIL/WIND.
...SRN AZ...
COMPLEX FORECAST ACROSS AZ TODAY WITH WV IMAGERY INDICATING SEPARATE
MID LEVEL MOISTURE PLUMES PERSISTING OVER SRN AND NRN AZ...WITH AREA
OF DRYING/SUBSIDENCE BETWEEN. HEATING SHOULD BE SUFFICIENT FOR
SCATTERED THUNDERSTORM DEVELOPMENT OVER THE HIGHER TERRAIN WITHIN
THESE AREAS OF GREATER MID LEVEL MOISTURE. STEEP LOW LEVEL LAPSE
RATES AND OVERALL INCREASE IN PW/S SHOULD PRODUCE A FEW STRONGER
CORES...ESPECIALLY OVER SRN AZ WHERE PW/S WILL BE APPROACHING 1.5
INCHES.
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