Mesoscale Discussion 795

MESOSCALE DISCUSSION 0795
NWS STORM PREDICTION CENTER NORMAN OK
0127 PM CDT TUE MAY 06 2008
AREAS AFFECTED...SWRN AND WRN TX THROUGH ERN NM
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 061827Z - 062100Z
STORMS ARE EXPECTED TO DEVELOP ACROSS PARTS OF SWRN TX...INITIALLY
OVER THE DAVIS MOUNTAINS BY MID AFTERNOON AND LATER FARTHER NWD
ACROSS ERN NM BY LATE AFTERNOON. INITIAL PRIMARY THREAT APPEARS TO
BE LARGE HAIL. HOWEVER...THREAT FOR ISOLATED TORNADOES MAY INCREASE
BY EARLY EVENING.
SELY BOUNDARY LAYER FLOW HAS ADVECTED LOW 60S DEWPOINTS INTO SWRN TX
AND SERN NM. HOWEVER...STRONG SURFACE HEATING AND MIXING HAS
RESULTED IN SURFACE DEWPOINTS FALLING TO THE UPPER 50S TO AROUND 60.
SWLY MID-UPPER FLOW DOWNSTREAM FROM UPPER TROUGH CENTERED OVER NW
MEXICO WILL MAINTAIN STEEP MID LEVEL LAPSE RATES ABOVE THE MOIST
AXIS. LATEST OBJECTIVE ANALYSIS DEPICTS MLCAPE FROM 2000-2500 J/KG
OVER SWRN TX INTO SERN NM. VISIBLE IMAGERY INDICATED CUMULUS HAS
BEEN INCREASING OVER THE DAVIS MOUNTAINS WHERE OROGRAPHIC FORCING IS
BEING AUGMENTED BY STRONG DIABATIC HEATING. THUNDERSTORMS INITIATION
MAY OCCUR IN THIS AREA BY 20Z AS THE CAP CONTINUES TO WEAKEN. SWLY
MID-UPPER FLOW WILL INCREASE OVER SWRN TX-SERN NM INTO THE EVENING
AS UPPER RIDGE AXIS SHIFTS EAST AND EXIT REGION OF UPPER JET
ROTATING THROUGH SHORTWAVE TROUGH APPROACHES THE AREA. SELY LOW
LEVEL FLOW VEERING TO SWLY AND INCREASING THROUGH 500 MB WILL RESULT
IN EFFECTIVE SHEAR SUPPORTIVE OF SUPERCELLS WITH INITIAL STORMS. THE
20+ DEGREES LOW LEVEL TEMPERATURE-DEWPOINTS SPREADS AND MODEST LOW
LEVEL HODOGRAPHS SUGGEST LARGE HAIL WILL PROBABLY BE THE MAIN
INITIAL THREATS. HOWEVER...THE LOW LEVEL JET IS FORECAST TO
STRENGTHEN BY EARLY EVENING ALONG WITH LOWERING LCL HEIGHTS...AND
THIS WILL PRESENT AN OPPORTUNITY FOR ISOLATED TORNADOES BEFORE THE
BOUNDARY LAYER DECOUPLES LATER IN THE EVENING.
..DIAL.. 05/06/2008