MESOSCALE PRECIPITATION DISCUSSION 0088...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
751 PM EDT TUE MAR 15 2016
 
CORRECTED FOR GRAPHIC

AREAS AFFECTED...EASTERN IA...FAR SOUTHEAST MN...NORTHWEST
IL...SOUTHWEST WI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 152345Z - 160545Z
 
SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS THIS EVENING WILL EXPAND
IN COVERAGE AND DRIVE AT LEAST SOME RISK OF FLASH FLOODING OVER
THE NEXT SEVERAL HOURS.

DISCUSSION...IR SATELLITE IMAGERY SHOW COOLING CONVECTIVE TOPS
WHICH ARE EXPANDING IN COVERAGE OVER EASTERN IA AND WESTERN IL IN
RESPONSE TO THE ARRIVAL OF A STRONG SHORTWAVE IMPULSE CROSSING THE
MID MS VALLEY AND INTERACTING WITH AN AXIS OF WEAK TO MODERATE
INSTABILITY OUT AHEAD OF A DEEPENING AREA OF LOW PRESSURE MOVING
ACROSS THE MS RIVER INTO WESTERN IL.

THE LATEST RAP ANALYSIS SHOWS A NOSE OF MLCAPE VALUES OF 1000 TO
2000 J/KG NOSING UP THROUGH WESTERN IL CURRENTLY...WITH SOME OF
THIS ELEVATED IN NATURE GIVEN CURRENT PROXIMITY OF A WARM FRONT.
IN FACT...MUCH OF THE ONGOING CONVECTION IS ROOTED JUST ABOVE THE
BOUNDARY LAYER AHEAD OF A FRONTAL OCCLUSION AND WITHIN THE NOSE OF
THE INSTABILITY AXIS.

BLENDED TPW IMAGERY/GPS DATA ONLY SHOWS PWATS OF 1 TO 1.1
INCHES...WHICH IS NOT PARTICULARLY HIGH...BUT THE CONVECTION OVER
THE NEXT FEW HOURS SHOULD TEND TO BECOME A BIT BETTER ORGANIZED AS
STRONGER SHORTWAVE DYNAMICS CONTINUES TO INTERACT WITH THE
NORTHWARD TRANSPORT OF INSTABILITY WHICH WILL BE AIDED BY A
SOUTH/SOUTHEAST LOW LEVEL JET OF 30 TO 40 KTS.

THE MAIN CONCERN OVER THE NEXT FEW HOURS WILL BE FOR A FEW
CELL-MERGERS AND A RESULTING CONSOLIDATION OF CONVECTION A BIT
FARTHER TO THE NORTHEAST OVER FAR EASTERN IA...NORTHWEST IL AND
SOUTHWEST WI...WHERE HEAVIER RAINFALL RATES WILL BE EXPECTED AS A
RESULT. ALREADY A FEW OVERSHOOTING TOPS HAVE BEEN NOTED TOO AS PER
THE GOES-OTD ALGORITHM...AND THIS WILL FOSTER SOME EVEN HEAVIER
RAIN RATES WHICH COUPLED WITH CELL MERGERS MAY APPROACH 1.5
INCHES/HR.

HIRES GUIDANCE SUGGESTS SHORT-TERM RAINFALL AMOUNTS OF 2 TO 4
INCHES THROUGH 06Z WITH ISOLATED HEAVIER AMOUNTS...AND THIS MAY
RESULT IN SOME LOCALIZED FLASH FLOODING CONCERNS.

ORRISON

ATTN...WFO...ARX...DVN...GRB...ILX...LOT...MKX...

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

LAT...LON   44499095 44358965 43598877 42048847 41008864 
            40428920 40168994 40449083 41059127 42179159 
            43359190 44089162