MESOSCALE DISCUSSION 0482
NWS STORM PREDICTION CENTER NORMAN OK
0156 PM CDT THU APR 16 2009
AREAS AFFECTED...PORTIONS TX SOUTH-PLAINS REGION...TX PANHANDLE...OK
PANHANDLE.
CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
VALID 161856Z - 162000Z
--- RE-TRANSMITTED ---
SFC-BASED CONVECTION IS DEVELOPING BETWEEN LBB-EVW...WITH ADDITIONAL
CONVECTION POSSIBLE NWD THROUGH CENTRAL PANHANDLE AND SWWD TOWARD
TX/NM BORDER AREA E HOB. DAMAGING GUSTS AND LARGE HAIL WILL BE
POSSIBLE FROM ACTIVITY OVER THIS AREA THROUGH REMAINDER OF AFTERNOON
INTO EVENING.
SFC MESOANALYSIS INDICATES DRYLINE BULGE OVER THIS REGION...WITH
DRYLINE ARCHING THROUGH ERN DALLAM...ERN CASTRO...HALE...WRN LUBBOCK
COUNTIES...THEN SWD TO NEAR MAF. MESOANALYSIS...RADAR REFLECTIVITIES
AND VIS IMAGERY INDICATES BOUNDARY LAYER CONVERGENCE LINE COLLOCATED
WITH DRYLINE N OF LBB COUNTY...THEN EXTENDING SWWD THROUGH NWRN
GAINES COUNTY. DRYLINE SHOULD KEEP MIXING EWD ACROSS MOST OF SOUTH
PLAINS REGION...BUT BECOME MORE NW-SE ALIGNED FARTHER N AS
BACKED/INTENSIFYING LOW LEVEL FLOW PERSISTS ACROSS CENTRAL/NRN
PANHANDLE AND OK PANHANDLE. DRYLINE ACTUALLY MAY RETREAT WWD
SOMEWHAT OVER NRN TX AND OK PANHANDLES AMIDST STRENGTHENING
ISALLOBARIC FORCING...EXTENDING SOME SVR POTENTIAL INTO WHAT NOW IS
DRY AIR MASS. MODIFIED RUC/OBSERVED SOUNDINGS INDICATE VERY STEEP
MIDLEVEL LAPSE RATES ACCOMPANYING ERN EDGE OF COOLING ALOFT
OVERSPREADING REGION. FURTHER DESTABILIZATION ALOFT IS EVIDENT JUST
UPSTREAM OVER SERN NM -- WHERE CONSIDERABLE MIDLEVEL CONVECTION HAS
DEVELOPED OVER VERY DRY NEAR-SFC LAYER. THIS...COMBINED WITH SFC
DEW POINTS 50S F E OF DRYLINE...YIELDS MLCAPE 1500-2000 J/KG
IMMEDIATELY E OF DRYLINE...IN NARROW ZONE OF FAVORABLY STG
INSOLATION W OF CLOUD SHIELD FROM ACTIVITY DISCUSSED IN MESOSCALE
DISCUSSION 481.
FAVORABLE STORM-RELATIVE FLOW IS EXPECTED...GIVEN RELATIVELY BACKED
SFC WINDS EVIDENT IN TX MESONET DATA AND FCST TO CONTINUE BETWEEN
THIS AREA AND CAPROCK. MODIFIED RUC SOUNDINGS SUGGEST SE FLOW WILL
CONTRIBUTE TO FAVORABLE DEEP-LAYER SHEAR...E.G. EFFECTIVE SHEAR
MAGNITUDES 45-50 KT FOR SFC-ROOTED PARCELS. WEAK WINDS JUST ABOVE
SFC...IN 1-2 KM AGL LAYER -- WILL KEEP LOW LEVEL HODOGRAPHS
RELATIVELY SMALL OVER INITIATION AREA. HOWEVER...HODOGRAPHS WILL
EXPAND EWD WITH PROXIMITY TO 40-50 KT LLJ...AND WITH TIME THIS
EVENING.
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