MESOSCALE PRECIPITATION DISCUSSION 0106
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1246 AM EDT WED MAY 20 2015
 
AREAS AFFECTED...SOUTHERN OK/NORTH TX... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 200445Z - 200800Z
 
SUMMARY...THE FLASH FLOOD THREAT REMAINS LIKELY INTO THE OVERNIGHT
HOURS AS CONVECTION FOCUSES ALONG THE RED RIVER. RECENT RADAR
IMAGERY SHOWS UPSTREAM REGENERATION IN THE VICINITY OF ALTUS...OK.
THIS HAS LED TO FLASH FLOOD CONDITIONS BASED ON RECENT LOCAL STORM
REPORTS.

DISCUSSION...THE 04Z RAP OBJECTIVE ANALYSIS SHOWED PLENTY OF
INSTABILITY LEFT IN THE ATMOSPHERE WITH 1000 TO 2000 J/KG OF
MIXED-LAYER CAPE ANCHORING THE MPD AREA. THERE IS A PRETTY SHARP
NORTH-SOUTH ORIENTED INSTABILITY GRADIENT AS STABLE AIR BEHIND THE
COLD FRONT SLOWLY NOSES SOUTHWARD. FARTHER EAST...THE BOUNDARY IS
EXPECTED TO REMAIN QUASI-STATIONARY WHICH WILL MAINTAIN MUCH OF
NORTH TX AND SOUTHERN/SOUTHEASTERN OK IN THE WARM/MOIST SECTOR.
DOPPLER RADAR IMAGERY SHOWS CELL MOTIONS GENERALLY TOWARD THE EAST
WITH CONTINUED REGENERATION TO THE WEST ALONG THE NOSE OF A
PRONOUNCED 925 TO 850-MB LLJ (40 TO 45 KTS BASED ON VWP DATA).
CURRENT HOURLY RAINFALL RATES ARE QUITE IMPRESSIVE BASED ON
MESONET DATA AND RADAR ESTIMATES. THE COMBINATION OF THE TWO
SUGGEST HOURLY RATES MAXIMIZING AROUND 2 TO 2.50 INCHES WITH SOME
OBSERVATIONS OF 3 TO 5 INCHES IN 3 HOURS. GIVEN THE AMOUNT OF CELL
MERGERS NOTED IN THE RADAR IMAGERY...EXPECT SUCH HEFTY RATES TO
CONTINUE INTO NIGHT.

THE 00Z HIGH-RESOLUTION MODELS HAVE DONE A MUCH BETTER JOB THAN
THE PREVIOUS CYCLE. IT APPEARS THE 00Z NAM-CONEST/NSSL-WRF...AND
HRW-ARW HAVE ADJUSTED FOR THE SOUTHWARD TREND. THESE SOLUTIONS IN
CONJUNCTION WITH THE 03Z HRRR SUPPORT VERY HEAVY RAINFALL TOTALS
DURING THE NEXT SEVERAL HOURS. THROUGH 09Z...SOME OF THE MODELS
SUPPORT 3 TO 6 INCHES OF RAINFALL WHICH SEEMS REASONABLE GIVEN THE
CURRENT TRENDS IN RADAR AND OBSERVATIONAL DATA. WILL REASSESS THE
SITUATION IN A FEW HOURS WITH AN ADDITIONAL MPD LIKELY BY 08Z.


RUBIN-OSTER

ATTN...WFO...FWD...LUB...LZK...OUN...SHV...SJT...TSA...

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

LAT...LON   35759505 35299424 34559436 33689472 33139513 
            32679598 32489720 32619852 32989955 34050058 
            34649937 35189841 35239752 35359670