MESOSCALE PRECIPITATION DISCUSSION 0638
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
959 PM EDT SUN AUG 06 2017

AREAS AFFECTED...NEAR THE TX/OK BORDER AND SOUTHERN AR

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 070158Z - 070758Z

SUMMARY...SHOWERS AND THUNDERSTORMS ARE FORMING NEAR AND NORTH OF
THE RED RIVER AND ACROSS SOUTHERN AR.  HOURLY RAIN RATES TO 2.5"
WITH LOCAL AMOUNTS TO 5" ARE POSSIBLE.

DISCUSSION...NON-OPERATIONAL GOES-16 VISIBLE IMAGERY REVEALS THAT
AN OUTFLOW BOUNDARY FROM EVENING CONVECTION HAS INITIATED
CONVECTION ACROSS SOUTHWEST OK.  THERE ARE ALSO SIGNS OF ELEVATED
CONVECTION NEAR AN 850 HPA BOUNDARY FORMING EASTWARD ACROSS
SOUTHERN OK INTO SOUTHERN AR.  PRECIPITABLE WATER VALUES ARE ~2"
PER GPS VALUES.  INFLOW AT 850 HPA IS 20-25 KTS PER VAD WIND
PROFILES, WITH EFFECTIVE BULK SHEAR OF 20-30 KTS PER SPC
MESOANALYSES.  MU CAPE VALUES OF 1000-2000 J/KG EXIST ACROSS THE
REGION.

THE 23Z HRRR EXPERIMENTAL, 18Z CANADIAN REGIONAL, AND 18Z NAM
CONEST HAVE SOME CONCEPT OF WHAT'S BEGINNING TO MATERIALIZE. 
INFLOW AT 850 HPA IS EXPECTED TO INCREASE WHILE VEERING WHICH
COULD FOSTER SOME BACKBUILDING BUT EVENTUALLY SHOULD SHIFT
ACTIVITY FROM WEST TO EAST ACROSS THE AREA OF CONCERN.  HOURLY
RAIN RATES UP TO 2.5" HAVE BEEN OBSERVED RECENTLY ACROSS SOUTHWEST
AND SOUTH-CENTRAL OK, AND ARE EXPECTED IN AREAS TO THE EAST WITH
TIME.  THE GENERAL SIGNAL AMONGST THE MESOSCALE GUIDANCE IS FOR
LOCAL AMOUNTS OF 3-5".  THE CONVECTION EVOLUTION IS MORE UNCERTAIN
THAN USUAL GIVEN THE SOLUTIONS SEEN IN MOST OF THE MESOSCALE
GUIDANCE.  NEIGHBORHOOD PROBABILITIES SUGGEST THAT THE BEST CHANCE
OF HEAVY RAINFALL IS THROUGH 05Z BEFORE THE SIGNAL SLOWLY
DEGRADES. SOILS HAVE BEEN PARTIALLY SATURATED BY RECENT RAINS, SO
FLASH FLOODING IS A CONCERN.

ROTH

ATTN...WFO...FWD...JAN...LZK...OUN...SHV...TSA...

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

LAT...LON   34769740 34389390 33439188 32399345 33539684
            34019843 34429976