SWODY1
SPC AC 240039
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0739 PM CDT SUN AUG 23 2009
VALID 240100Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN HIGH
PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER CO
RIVER VALLEY...
...NRN HIGH PLAINS...
WATER VAPOR IMAGERY AND RUC ANALYSIS CURRENTLY SHOW AN UPPER-LEVEL
RIDGE OVER THE NRN PLAINS WITH HEIGHTS FALLING WEST OF THE RIDGE IN
ERN MT. A SHORTWAVE TROUGH APPEARS TO BE MOVING TOWARD THE REGION
FROM THE SOUTHWEST AND THIS WILL PROVIDE SUPPORT FOR AN INCREASE IN
CONVECTION LATE THIS EVENING. THE LATEST SHORT-TERM MODELS SUGGEST
SCATTERED THUNDERSTORM INITIATION WILL TAKE PLACE ALONG THE THERMAL
AXIS IN ERN MT OVER THE NEXT FEW HOURS. THE THUNDERSTORMS WILL BE
AIDED BY CONVERGENCE ALONG AN INVERTED TROUGH WITH THE CONVECTION
MOVING ENEWD INTO INCREASING MOISTURE LATE THIS EVENING. RUC
ANALYSIS SHOWS MODERATE INSTABILITY IN PLACE ACROSS ERN MT WITH THE
LATEST WSR-88D VWP FROM GLASGOW HAVING A 0-6 KM SHEAR VALUE AROUND
55 KT. NOT ALL OF THIS SHEAR WILL BE REALIZED DUE TO A WEAK CAPPING
INVERSION. HOWEVER...THE SHEAR...INSTABILITY AND STEEP MID-LEVEL
LAPSE RATES SHOULD BE SUPPORTIVE OF SUPERCELLS WITH LARGE HAIL. A
FEW DAMAGING WIND GUSTS MAY ALSO OCCUR ESPECIALLY IF A STORM CAN GET
ROOTED CLOSER TO THE SFC OR A BOWING LINE-SEGMENT CAN ORGANIZE.
ALTHOUGH STILL UNCERTAIN...THE SLIGHTLY CAPPED AIRMASS MAY KEEP
CONVECTIVE COVERAGE SCATTERED AS THE STORMS MOVE NEWD ACROSS WRN ND
DURING THE OVERNIGHT PERIOD.
FURTHER SOUTH ACROSS ERN WY...SEVERAL THUNDERSTORMS ARE ONGOING
ALONG THE WRN EDGE OF MODERATE INSTABILITY. THE WSR-88D VWPS FROM
RAPID CITY SD AND CHEYENNE WY HAVE ABOUT 20 KT OF VERTICAL SHEAR
SUGGESTING STORM ORGANIZATION WILL BE LIMITED. THE STRONGER
MULTICELLS SHOULD BE CAPABLE OF PRODUCING HAIL AND STRONG GUSTY
WINDS.
...LOWER CO RIVER VALLEY...
SCATTERED THUNDERSTORMS ARE CURRENTLY ONGOING IN THE LOWER CO RIVER
VALLEY ALONG A SFC TROUGH ORIENTED NWWD FROM A 1004 MB SFC LOW IN SW
AZ. WATER VAPOR IMAGERY SHOWS A DUAL SHORTWAVE TROUGH PATTERN FROM
THE BAJA CA INTO CNTRL CA. LIFT ASSOCIATED WITH THESE FEATURES
SHOULD HELP SUSTAIN CONVECTIVE COVERAGE ACROSS THE REGION THIS
EVENING. THE RUC SUGGESTS MODERATE INSTABILITY IS PRESENT ACROSS
MUCH OF SRN CA WITH THE STRONGEST INSTABILITY LOCATED IN THE MOJAVE
DESERT WHERE SFC DEWPOINTS ARE IN THE LOWER 50S F. IN ADDITION...THE
WSR-88D VWP FROM LAS VEGAS NV CURRENTLY HAS A 0-6 KM SHEAR VALUE
AROUND 30 KT SUPPORTIVE OF STRONG TO SEVERE MULTICELLS. SFC
TEMP-DEWPOINT SPREADS AROUND 40 DEGREES F AND SUBSTANTIAL DCAPE
COULD ENHANCE THE DOWNDRAFT EVAPORATIVE COOLING PROCESS RESULTING IN
ISOLATED DAMAGING WIND GUSTS. HAIL WILL ALSO BE POSSIBLE DUE TO
STEEP LAPSE RATES AND RELATIVELY COLD TEMPS ALOFT...500 MB TEMPS OF
-10 TO -11 C.
..BROYLES.. 08/24/2009
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