MESOSCALE PRECIPITATION DISCUSSION 0456
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
140 AM EDT WED AUG 19 2015
 
AREAS AFFECTED...NORTHERN OKLAHOMA...NORTHWEST
ARKANSAS...SOUTHWESTERN MISSOURI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 190540Z - 191140Z
 
SUMMARY...VERY STRONG MOISTURE CONVERGENCE ALONG FRONTAL ZONE WITH
NEARLY PARALLEL FLOW SETTING UP TRAINING ENVIRONMENT FOR POSSIBLE
FLASH FLOODING.

DISCUSSION...UNSEASONABLY STRONG CYCLONE LIFTING OUT FO THE UPPER
MIDWEST DRAPES STRONG COLD FRONT ACROSS THE DISCUSSION AREA.
UPSTREAM SHORTWAVE KICKER EXITING THE HIGH PLAINS IS INCREASING
BOUNDARY LAYER FLOW ON EITHER SIDE OF THE FRONTAL ZONE FOR NEARLY
60 KTS OF NEARLY 180 DEGREE CONVERGENCE.  THIS IS ALLOWING FOR
STRONG FRONTOGENESIS BUT ALSO GREAT ASCENT WITHIN A MODERATELY
MOIST PROFILE ENVIRONMENT WITH TOTAL PWATS IN THE 1.5-2" RANGE
(WEST TO EAST).  STRONG JET STREAK IN THE DRY SLOT WILL LEAVE THE
RIGHT ENTRANCE REGION DYNAMICS TO TRACE ALONG THE FRONT.  GIVEN
THE STRENGTH OF THE JET 90+ KTS...THE BROAD SCALE UVVS FROM THE
DIVERGENCE SHOULD BE STRONG TO SUPPORT UPDRAFT CORE
EVACUATION...INCREASING CELL EFFICIENCY.  EXPECTATION OF RATES IN
THE 2"/HR RANGE ARE LIKELY WITH SOME INCREASED RATES WHERE SOME
CELLS MERGE ALONG THE BOUNDARY.  

ALSO WITH HEIGHT FALLS WEST WITH THE SHORTWAVE...ALLOWS FOR THE
SURFACE FRONT TO REMAIN GENERALLY ORIENTED WEST TO EAST AHEAD OF
THE TROF AXIS...WITH LITTLE MOVEMENT WITH DEEP UNIDIRECTIONAL FLOW
IN THE CLOUD BARING LAYER (ABOVE 800MB) TO ALLOW FOR A TRAINING
ENVIRONMENT ACROSS N OK INTO NW AR/SW MO BEFORE SHIFTING MORE
NORTH-NORTHEAST.  STRONG FLOW SHOULD LIMIT EXTREME TOTALS AS THE
BACK EDGE OF THE LINE SHOULD PROGRESS QUICKLY FROM THE TEXAS
PANHANDLE THROUGH CENTRAL AND EASTERN OKLAHOMA OVER THE NEXT 6
HOURS WITH TOTALS IN THE 2-4" EXPECTED.  IT WOULD NOT BE SHOCKING
FOR SOME ISOLATED HIGHER TOTALS IN THE 5-6" RANGE IF HANG
UPS/MERGERS OCCUR...BUT THIS APPEARS TOO RANDOM FOR ANY CONFIDENCE
TO PINPOINT THIS SCENARIO.   CONFIDENCE IS RELATIVELY HIGH GIVEN
THE HIGH CLUSTERING OF HI-RESOLUTION CONVECTION ALLOWING MODELS TO
SUPPORT THIS EVOLUTION...SUCH AS THE ARW/NMMB/THEIR PARALLEL
RUNS/ESRL HRRR/06Z NAM-CONEST. 

GALLINA

ATTN...WFO...ICT...LZK...OUN...SGF...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...

LAT...LON   37819262 37099170 36329279 35379463 35159596 
            34999828 34959946 35309991 36109992 36599944 
            36879651 37089449 
A