MESOSCALE PRECIPITATION DISCUSSION 0471
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1015 PM EDT SAT JUL 16 2016
 
AREAS AFFECTED...FAR EASTERN SD...CENTRAL/SOUTHERN MN...NORTHERN
IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 170215Z - 170815Z
 
SUMMARY...THUNDERSTORMS WILL ORGANIZE AND EXPAND IN COVERAGE
OVERNIGHT...WITH MULTIPLE CELL-MERGERS EXPECTED ALONG WITH
CELL-TRAINING LATER IN THE NIGHT. FLASH FLOODING IS LIKELY.

DISCUSSION...THE LATEST IR SATELLITE IMAGERY SHOWS MULTIPLE
CONVECTIVE CLUSTERS ORGANIZING...WITH A BROKEN AXIS OF STRONG
THUNDERSTORMS ADVANCING EAST ACROSS WEST-CENTRAL SD IN ASSOCIATION
WITH A SHORTWAVE/JET MAX...AND THEN SEPARATE STRONG THUNDERSTORMS
EXPANDING OVER EASTERN SD AND SOUTHWEST MN IN RELATION TO A
STRENGTHENING LARGE SCALE WARM ADVECTION PATTERN.

THE UPPER LEVEL JET ENERGY STREAKING ACROSS SD WILL HELP DRIVE LOW
PRESSURE GRADUALLY EAST ALONG WITH A COLD FRONT OVERNIGHT...AND
THIS WILL ALLOW STRONG WARM ADVECTION TO SURGE EAST AND OVERRUN
MUCH OF EASTERN SD...CENTRAL/SOUTHERN MN AND NORTHERN IA. STRONG
WARM SECTOR INSTABILITY IS ALREADY NOSING UP THROUGH CENTRAL AND
EASTERN SD WITH MLCAPE VALUES OF 2500 TO 3000 J/KG. CONSECUTIVE
RAP RUNS INDICATE A S/SW LOW LEVEL JET INCREASING TO OVER 50 KTS
BY 06Z AIMED INTO FAR EASTERN SD...AND ESPECIALLY NORTHWEST IA AND
SOUTHWEST MN. STRONG WARM ADVECTION COUPLED WITH INCREASING LOW
LEVEL SPEED CONVERGENCE INTO THE WARM FRONT AND PROXIMITY OF A
STRONG INSTABILITY GRADIENT SHOULD HELP FOCUS AN INCREASINGLY
ORGANIZED AND STRONG CONVECTIVE COMPLEX WHICH SHOULD DRIVE
EAST-SOUTHEAST AND THEN SOUTHEAST ACROSS SOUTHERN MN AND INTO
NORTHERN IA BY LATER IN THE NIGHT. THE SET-UP TOWARD 06Z AND
BEYOND FAVORS CELL-MERGERS AND TRAINING AND ESPECIALLY AS THE LOW
LEVEL JET BEGINS TO GRADUALLY VEER. UPSTREAM CONVECTION
APPROACHING CENTRAL SD IS ALSO LIKELY TO MERGE WITH THE DOWNSTREAM
WARM ADVECTION/ELEVATED CONVECTION.

THE CELL-MERGER ACTIVITY AND EXPECTATION OF STRONG OVERSHOOTING
TOPS COUPLED WITH PWATS INCREASING TO NEAR 1.75 INCHES WILL FOSTER
VERY INTENSE RAINFALL RATES THAT WILL LIKELY APPROACH 3 INCHES/HR
IN SOME CASES. RECENT RUNS OF THE HRRR AND HRRRP SHOW SOME
DIFFERENCES WITH THE EXACT AXIS OF HEAVIEST RAINS...BUT DO SUGGEST
RAINFALL TOTALS APPROACHING 4 TO 6 INCHES WITH THE HEAVIEST TOTALS
OVER PORTIONS OF SOUTH-CENTRAL MN...AND BASED ON THE SET-UP...SOME
LOCALLY HEAVIER TOTALS WILL BE POSSIBLE. SOME FLASH FLOODING IS
LIKELY BASED ON THESE EXPECTED TOTALS. WILL CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...ABR...ARX...DMX...DVN...FGF...FSD...MPX...

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

LAT...LON   45829687 45689490 44889285 43749140 42909137 
            42599204 42559301 42799458 43209600 43869704 
            44809778 45409767