MESOSCALE PRECIPITATION DISCUSSION 0145
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
903 PM EDT TUE APR 25 2017

AREAS AFFECTED...CENTRAL & NORTHEAST OK

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

VALID 260101Z - 260600Z

SUMMARY...BACKBUILDING AND TRAINING CONVECTION OVER AREAS
SATURATED SOILS FROM EARLIER THIS WEEK MAY POSE FLASH FLOODING
CONCERNS.

DISCUSSION... GOES-16 VIS/IR DENOTE RAPIDLY DEVELOPING CONVECTION
ALONG THE COLD FRONT ACROSS/JUST EAST OF  I-35 CORRIDOR.  00Z OUN
SOUNDING INDICATES STRONG INSTABILITY TO DRIVE THESE STORMS THE
PROFILE IS ALSO QUITE DRY AS THE ELEVATED MIX LAYER NOSED IN
ACROSS SW OK...SO INITIAL SETUP IS CLEARLY SEVERE MODE...PLEASE
SEE MCD 554 FROM SPC FOR ADDITIONAL DETAILS.

ALSO VWP DENOTES DEEP UNIDIRECTIONAL SHEAR THOUGH THE PROFILE
SUPPORTING STEERING LAYER FLOW TO BE QUITE STRONG TOWARD THE
NORTHEAST...YET IN THE SHORT-TERM BEFORE COLD POOL GENERATES AND
PROPAGATION OF THE LINE SHIFTS EAST...THERE IS A NARROW WINDOW
WHERE THESE CELL MOTIONS ARE PARALLEL TO THE FORCING BOUNDARY
WHICH COULD LEAD TO REPEAT TRACKS OF MODEST RAIN RATES
ACCOMPANYING HAIL...THIS IS OF PARTICULAR CONCERN OVER THE OKC
METRO GIVEN IMPERVIOUS GROUND FOR SOME URBANIZE FF CONCERNS. 

AT THE SFC...A WEAK SURFACE WAVE OVER OSAGE COUNTY IS NOTED IN 00Z
OBS WILL BE SUPPORTED TO DEVELOP AND TRACK NORTHEAST UNDER STRONG
DPVA FROM APPROACHING SHORTWAVE SEEN IN GOES-WV TO THE WEST.  AS
THIS WAVE LIFTS NORTHEAST...THIS ALONG WITH COLD POOL GENERATION
HAS THE POTENTIAL OF LAYING OUT A MORE E-W ORIENTED OUTFLOW ACROSS
NORTHEAST OR EAST CENTRAL OK...ALLOWING FOR STRENGTHENING SLY
BACKING TO SWLY LOW LEVEL FLOW/MST FLUX UP TO 45KT TOWARD EARLY
NIGHT-TIME HOURS SUPPORTING BACKBUILDING ALONG THE OUTFLOW WHILE
ALSO SUPPORTING A FAVORABLE TRAINING ENVIRONMENT.  WHILE TOTAL
AVAILABLE MOISTURE IS LIMITED TO THE BOUNDARY LAYER (+65F SFC TDS)
WITH TPW AOA 1.0-1.2"...THE TRAINING OF RATES UP TO 1.25-1.5" OVER
SATURATED SOILS FROM EARLIER THIS WEEK ACROSS NE OK TO SW MO/NW
AR...WITH 300%+ ABOVE NORMAL PRECIP POSES A SUFFICIENT THREAT FOR
FLASH FLOODING.  THIS IS SUPPORTED BY GLOBAL GUIDANCE AND LAST 4
RUNS OF THE HRRR...PROVIDING ENOUGH CONFIDENCE FOR WPC TO UPGRADE
TO A SLIGHT RISK OF EXCESSIVE RAINFALL. 

GALLINA

ATTN...WFO...OUN...TSA...

ATTN...RFC...ABRFC...

LAT...LON   36989528 36869470 36189467 35449525 35189725
            35459765 36329693 36839629