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| Mesoscale Discussion 787 |
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MESOSCALE DISCUSSION 0787
NWS STORM PREDICTION CENTER NORMAN OK
1202 AM CDT SUN MAY 10 2009
AREAS AFFECTED...PARTS OF NRN TX/SRN OK INTO THE ARKLATEX
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 100502Z - 100700Z
POTENTIAL FOR HEAVY RAINFALL MAY INCREASE OVERNIGHT. THE RISK FOR
SEVERE STORMS SEEMS RELATIVELY LOW/MARGINAL...BUT TRENDS WILL BE
MONITORED.
AS THE NEXT BROAD...LOW AMPLITUDE IMPULSE DIGS ACROSS THE GREAT
BASIN AND CENTRAL ROCKIES...AN INCREASE IN CONVECTIVE DEVELOPMENT
APPEARS TO BE UNDERWAY ACROSS THE REGION. THIS IS OCCURRING
GENERALLY WITHIN A ZONE OF STEEPER ISENTROPIC ASCENT NORTH OF A
STALLED SURFACE FRONT...WHERE LAPSE RATES REMAIN RELATIVELY
STEEP...AND MOISTURE CONTENT IS CHARACTERIZED BY PRECIPITABLE WATER
OF 1.5 TO 1.75+ INCHES. MIXED LAYER CAPE ON THE ORDER OF 1000-2000
J/KG IS SUPPORTIVE OF VIGOROUS UPDRAFTS...BUT A CAPPING ELEVATED
MIXED LAYER HAS SLOWED STORM DEVELOPMENT WEST OF THE ARKLATEX.
SUSTAINED LIFT MAY CONTINUE TO WEAKEN INHIBITION NEAR THE RED RIVER
VALLEY DURING THE NEXT FEW HOURS...ALLOWING FOR A GRADUAL
INTENSIFICATION OF CONVECTION. GIVEN WEAK BUT VEERING WIND PROFILES
WITHIN THE INFLOW LAYER...BENEATH MODEST WESTERLY 500 MB FLOW ON THE
ORDER OF 30 KTS...MID-LEVEL UPDRAFT ROTATION MAY CONTRIBUTE TO THE
RISK FOR AT LEAST MARGINALLY SEVERE HAIL IN STRONGEST CELLS.
IT IS POSSIBLE THAT A MID-LEVEL SPEED MAXIMUM COULD ENHANCE
MID/UPPER FORCING FOR UPWARD VERTICAL MOTION ACROSS THE REGION...ON
THE SOUTHERN FRINGE OF THE STRONGER WESTERLIES TOWARD THE 07-09Z
TIME FRAME. IF THIS OCCURS...AN EVOLVING STORM CLUSTER WITH
TRAINING CELLS MAY EVENTUALLY CONTRIBUTE TO THE RISK FOR EXCESSIVE
RAIN TOTALS IN THE PRESENCE OF THE HIGH MOISTURE CONTENT.
..KERR.. 05/10/2009
ATTN...WFO...LZK...SHV...TSA...FWD...OUN...
LAT...LON 33919724 34309635 34169394 33749301 33359257 32809328
32649394 32759473 32949594 32899685 32849719 33489768
33919724
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