MESOSCALE PRECIPITATION DISCUSSION 0075
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
420 PM EDT SUN MAY 10 2015
 
AREAS AFFECTED...CENTRAL/NORTHEAST TX, SOUTHEAST OK, WESTERN AR 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 102019Z - 110219Z
 
SUMMARY...THUNDERSTORMS ARE EXPECTED TO TRAIN AND GROW UPSCALE
OVER THE NEXT FEW HOURS.  WITH HOURLY RAIN RATES UP TO 2"
ANTICIPATED OVER SATURATED SOILS, FLASH FLOODING IS CONSIDERED
LIKELY.

DISCUSSION...A WAVE ALONG A RELATIVELY STATIONARY OUTFLOW BOUNDARY
IN CENTRAL TX IS ACTING AS THE SOUTHWEST EDGE OF ACTIVE
CONVECTION, WITH THUNDERSTORMS OVERRIDING THE OUTFLOW BOUNDARY TO
ITS NORTHEAST.  THE 12Z SPCWRF APPEARS TO BE CAPTURING THE
CONVECTIVE PATTERN THE BEST, THOUGH IT IS TOO FAR WEST WITH
CONVECTION NEAR THE CENTRAL OK/TX BORDER.  BROAD 850 HPA INFLOW OF
30-50 KTS IS STREAMING INTO THE OUTFLOW BOUNDARY, EXCEEDING THE
850-400 HPA MEAN WINDS BY 15-20 KTS.  THE INFLOW IS TAPPING MIXED
LAYER CAPES OF 2000-3000 J/KG PER RECENT SPC MESOANALYSES. 
PRECIPITABLE WATER VALUES (PWS) ARE AROUND 1.6" PER RECENT GPS
INFORMATION.  THREE HOUR FLASH FLOOD GUIDANCE VALUES CONTINUE TO
PLUNGE DUE TO ONGOING RAINFALL.  THE STAGE IS SET FOR FLASH
FLOODING.

THE MESOSCALE GUIDANCE IS SHOWING SOME FORWARD PROPAGATION TO THE
ACTIVE CONVECTION, LIKELY DUE TO THE COMBINATION OF HIGH
INSTABILITY AND DIRECTIONAL WIND SHEAR, WITH MESOCYCLONES LEADING
TO A LEWP/QLCS PATTERN.  RECENT RAIN RATES HAVE DECLINED TO 1.5"
AN HOUR, THOUGH TRAINING BANDS WEST OF DALLAS/FORT WORTH HAVE LED
TO OCCASIONS OF 3-4" AN HOUR.  PWS ARE EXPECTED TO RISE TO 1.75"
PER RECENT RAP GUIDANCE, WHICH SHOULD SUPPORT 2" AN HOUR RAIN
RATES OUTSIDE OF CELL MERGERS/PROLONGED CELL TRAINING (WHERE
HOURLY RAIN RATES COULD BE SIGNIFICANTLY HIGHER).  THE PEAK OF THE
AFTERNOON/EVENING CONVECTIVE UPTICK SHOULD BE BETWEEN 20Z-01Z PER
THE 12Z SSEO NEIGHBORHOOD PROBABILITIES WITHIN THIS REGION. 
MESOSCALE GUIDANCE GENERALLY ADVERTISES LOCAL AMOUNTS OF 3-5" OF
RAIN DURING THIS TIME SPAN, WHICH COMBINED WITH SATURATED SOILS,
SHOULD LEAD TO FLASH FLOODING.

ROTH

ATTN...WFO...EWX...FWD...LZK...MEG...OUN...SGF...SHV...SJT...

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

LAT...LON   36609227 36269120 34479221 33089383 32169524 
            30759833 30819901 31799888 33129823 34229724 
            35949460 36339371