MESOSCALE PRECIPITATION DISCUSSION 0498
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
659 AM EDT THU JUL 28 2016
 
AREAS AFFECTED...LOWER MS VALLEY 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 281058Z - 281658Z
 
SUMMARY...SLOW OR BACKBUILDING HIGHLY EFFICIENT RAINFALL PRODUCING
CONVECTION MAY POSE FLASH FLOODING CONCERNS THIS MORNING.

DISCUSSION...WV LOOP/RADAR MOSAIC DEPICTS THE MAIN SHORTWAVE
ASSOCIATED WITH OLD TUTT NEAR KMEM MOVING EAST WITH AN ELONGATED
TROF EXTENDING SW ACROSS S AR JUST S OF KTKX INTO N TEXAS.  LOW
LEVEL CONFLUENCE JUST ABOVE THE BOUNDARY LAYER EXISTS TOWARD THE
WESTERN PORTION OF THE TROF AND IS BEGINNING TO MAXIMIZE SOME DEEP
MOISTURE CONVERGENCE ALONG IT.  RAP ANALYSIS INDICATES SOME
INSTABILITY AVAILABLE SOUTH AND EAST OF THE TROF FROM 1000 J/KG IN
W CENTRAL MS TO 2000 IN NE TEXAS WITHIN A VERY SATURATED PROFILE
WITH PWATS IN THE 2.0-2.3" RANGE.  EVEN IF THE VIGOR OF THE
UPDRAFTS IS LIMITED DUE TO THE SKINNY PROFILES...WARM CLOUD
PROCESSES SHOULD MAKE CELLS HIGHLY EFFICIENT WITH RATES AROUND
2-3"/HR POSSIBLE.

AS THE SHORTWAVE EXITS...CLOUD BEARING FLOW WILL BE QUITE WEAK
WITH CELL MOTIONS IN THE 5-10 KNOT RANGE AT BEST...AND WITH
STRONGER CONFLUENT INFLOW PROPAGATION VECTORS SUGGEST WESTWARD
DEVELOPMENT COUNTER TO THE CELL MOTION SUPPORTING RELATIVISTICALLY
STATIONARY CELLS ALLOWING FOR COMPOUNDING RAINFALL TOTALS. MAIN
LIMITING FACTOR APPEARS TO BE THE WEAK INSTABILITY ACROSS THE
AREA. HOWEVER A STRONG ENOUGH SOUTHWESTERLY INFLOW OUT OF THE
SLIGHTLY GREATER INSTABILITY POOL OVER EASTERN TEXAS MAY BE ENOUGH
TO SUPPORT CONTINUED CONVECTIVE DEVELOPMENT.
 
CONFIDENCE IS ONLY AVERAGE IN THE OVERALL EVOLUTION OF CONVECTION
ACROSS THIS AREA GIVEN THE MARGINAL INSTABILITY AND CURRENT
UNIMPRESSIVE STATE OF CONVECTION ACROSS THE REGION. HOWEVER GIVEN
THE SETUP MENTIONED ABOVE...AND A RATHER STRONG SIGNAL IN RECENT
HIGH RES GUIDANCE...THINK A FLASH FLOOD THREAT MAY END UP
DEVELOPING THROUGH THE MORNING. THE HIGH RES ARW/NMMB SHOW
ISOLATED TOTALS OVER 4"...WITH THE LAST SEVERAL RUNS OF THE HRRR
ALSO INDICATIVE OF THIS POTENTIAL. THE PARALLEL HRRR HAS ALSO
GENERALLY BEEN TRENDING TOWARD HIGHER QPF ACROSS THE AREA. 

GALLINA/CHENARD

ATTN...WFO...JAN...LZK...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...

LAT...LON   34009413 33819293 33189124 33098984 32608986 
            32209093 32149115 31649248 31539365 32079352 
            32409357 32839401 33129446 33639470