MESO: Mesoscale Discussion 0860

ACUS11 KWNS 221930
SWOMCD
SPC MCD 221930
LAZ000-MSZ000-TXZ000-222230-

MESOSCALE DISCUSSION 0860
NWS STORM PREDICTION CENTER NORMAN OK
0230 PM CDT TUE MAY 22 2007

AREAS AFFECTED...SCENTRAL...CENTRAL AND WRN LA

CONCERNING...HEAVY RAINFALL

VALID 221930Z - 222230Z

HEAVY RAINFALL WITH HRLY RATES OVER 2 IN/HR ARE ANTICIPATED TO
CONTINUE TO DEVELOP ALONG A N-S ORIENTED DEEP CONVERGENCE AXIS
EXTENDING FROM SCENTRAL LA INTO NCENTRAL LA THROUGH THE NEXT SEVERAL
HOURS. IN ADDITION TO THE HEAVY RAIN THREAT...AN ISOLATED MARGINAL
SVR HAIL/WIND THREAT WILL ALSO BE POSSIBLE ACROSS MUCH OF WRN LA. A
WW IS NOT EXPECTED FOR THIS ACTIVITY.

LATEST OBJECTIVE ANALYSIS SHOWS AN AREA OF DEEP MOIST CONVERGENCE
EXTENDING FROM SCENTRAL LA INTO NCENTRAL LA. REGIONAL VWP/S SUPPORT
THIS WITH BROAD SSWLY LOW LEVEL FLOW OVER SWRN/WCENTRAL LA /ON THE
SW SIDE OF AN MCV/ AND SELY LOW LEVEL FLOW OVER SERN LA AND SWRN MS.
A MODERATE VALUE OF PWAT /120 PERCENT OF NORMAL AT LCH AT 12Z/
EXISTS OVER THE AREA. GIVEN RELATIVELY WEAK STEERING CURRENT/STORM
MOTIONS AND MODEST INSTABILITY /MUCAPES FROM 1500-2000 J/KG/ ONGOING
TSTMS OVER SCENTRAL/CENTRAL LA ARE EXPECTED TO CONTINUE TO REDEVELOP
OVER THE SAME LOCATIONS IN THE NEXT FEW HOURS WHILE MOVING SLOWLY
NWD /PARALLEL TO THE DEEP LAYER FLOW/. TSTMS ARE ALSO EXPECTED TO
BACKBUILD SLIGHTLY WSWWD INTO THE MODEST LAPSE RATE FEED. BOTH OF
THESE FACTORS WILL CONTRIBUTE TO CELL TRAINING AND VERY HEAVY
RAINFALL RATES /UPWARDS OF 2 IN/HR/. FURTHER WEST...STEEP MID LEVEL
LAPSE RATES /AROUND 7 C/KM/ AND INCREASING VERTICAL SHEAR /25 TO 30
KTS/ ON THE EAST SIDE OF AN MCV /OVER ECENTRAL TX/ ALONG WITH RECENT
CLEARING /DESTABILIZATION TRENDS SUPPORT THE POSSIBILITY OF A
MARGINAL SVR HAIL/WIND THREAT DEVELOPING OVER WRN LA IN THE NEXT FEW
HOURS.

.CROSBIE.. 05/22/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...JAN...LIX...LCH...SHV...

29419160 30769139 31629163 32479226 32299330 31639376
30789348 30359265 29159211

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