MESOSCALE PRECIPITATION DISCUSSION 0383
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
758 PM EDT SAT JUL 25 2015
 
AREAS AFFECTED...PORTIONS OF SD 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 252357Z - 260457Z
 
SUMMARY...A GROWING CONVECTIVE COMPLEX OVER SD IS DISPLAYING
HOURLY RAIN RATES NEAR 2.5" ON RADAR IMAGERY.  FLASH FLOODING IS
POSSIBLE.

DISCUSSION...AS A FOLLOW UP FROM SAB/NESDIS'S SPENES MESSAGE FROM
2209Z, CONVECTION HAS BEEN LENGTHENING ALONG A WEST-EAST AXIS
ACROSS A FEW COUNTIES IN SD TO THE NORTH OF A CAP, USING THE 12C
ISOTHERM AT 700 HPA AS A GUIDE.  INFLOW AT 850 HPA IS MODEST, ON
THE ORDER OF 20 KTS PER VAD WIND PROFILES.  PRECIPITABLE WATER
VALUES ARE BETWEEN 1.25-1.5" PER GPS INFORMATION.  THE SPC
MESOANALYSIS INDICATES THAT THE CLUSTER IS LOCATED IN THE MIDDLE
OF 1500-2000 J/KG MLCAPES, WITH 2000-4000 J/KG MLCAPES UPSTREAM
ACROSS CENTRAL NE.  CONVECTION APPEARS TO BE BACKBUILDING TOWARDS
A THERMAL RIDGE SHOWING UP IN THE 1000-500 HPA THICKNESS PATTERN
ACROSS THE CENTRAL DAKOTAS.  

THE EXPECTATION IS FOR THIS ACTIVITY TO EVENTUALLY MOVE
EAST-SOUTHEAST AT 25-30 KTS PER THE FORWARD PROPAGATING CONVECTIVE
VECTORS.  VISIBLE SATELLITE IMAGERY SHOWS AN ARC CLOUD MOVING OUT
OF THE COMPLEX WHICH SHOULD BEGIN TO IMPART SOME SOUTHWARD
TRAJECTORY IN THE NEAR FUTURE, PROBABLY WITHIN THE NEXT COUPLE
HOURS.  THE 12Z ARW, 12Z NMMB, 18Z NAM CONEST, 18Z CANADIAN
REGIONAL MODEL, AND RECENT RAP RUNS INDICATE LOCAL AMOUNTS IN THE
3-4" RANGE BY 05Z.  AS IT DOES NOT APPEAR THAT THE COMPLEX HAS
PEAKED IN STRENGTH BASED ON CONTINUED CLOUD TOP COOLING, SO
BELIEVE IT HAS AT LEAST ANOTHER FOUR HOURS TO SURVIVE BEFORE IT
BEGINS TO FADE.  THE 18Z SSEO NEIGHBORHOOD PROBABILITIES AGREE,
SHOWING THE 03Z-04Z PERIOD BEING THE POSSIBLE PEAK FOR THIS
COMPLEX'S LIFE CYCLE.  WITH HOURLY RAIN RATES UP TO 2.5" AN HOUR,
CELL TRAINING ALONG THE LENGTHENING BAND IS THE MAIN FLASH FLOOD
CONCERN.

ROTH

ATTN...WFO...ABR...FSD...MPX...

ATTN...RFC...MBRFC...NCRFC...

LAT...LON   45339798 44269562 42999612 43629865 44410046 
            45270038