MESOSCALE PRECIPITATION DISCUSSION 0071
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1121 PM EDT SUN MAY 26 2013
 
AREAS AFFECTED...CENTRAL AND EASTERN NEB...EXTREME SOUTHEAST
SD...WESTERN AND CENTRAL IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 270320Z - 270830Z
 
SUMMARY...DEVELOPING CONVECTIVE COMPLEX OVER NORTHERN NEB WILL
GRADUALLY EXPAND EASTWARD AND INCREASE IN SIZE THE NEXT FEW HOURS.
EXPECTING SLOW PROPAGATION AND INTENSE RAINFALL RATES...WHICH WILL
SUPPORT AN ELEVATED FLASH FLOOD THREAT.

DISCUSSION...LATEST IR SAT IMAGERY SHOWS VERY COLD CONVECTIVE TOPS
RAPIDLY EXPANDING IN SIZE AND ORGANIZATION ATTM OVER NRN NEB IN
ASSOC WITH A SHORTWAVE IMPULSE TRAVERSING THE N CNTRL PLAINS AND
INTERACTING WITH A MOIST AND VERY UNSTABLE AIRMASS WHICH IS SEEN
OVERRUNNING A WELL-DEFINED STATIONARY FRONT. THE LATEST RAP
ANALYSIS SHOWS A 40 KT SRLY LOW LEVEL JET ALREADY ADVANCING UP
THROUGH THE CNTRL PLAINS...AND THE LATEST GLOBAL GUIDANCE SUPPORTS
THIS LOW LEVEL JET INCREASING NOCTURNALLY TO OVER 50 KTS AFTER
06Z...WITH THE NOSE OF IT AIMING INTO CNTRL/ERN NEB. MUCAPE VALUES
NEAR 4000 J/KG ATTM OVER S CNTRL NEB WILL SIGNIFICANTLY ENHANCE
THE CONVECTIVE EXPANSION OF THIS COMPLEX OVER THE NEXT 2 TO 3
HOURS...WITH THE COMPLEX BECOMING WELL ORGANIZED AND MOVING
GENERALLY EAST. THERE IS ALREADY A SMALLER SCALE MCS IMPACTING
NWRN IA ATTM WHERE FFG VALUES ARE ALREADY LOW DUE TO WET
ANTECEDENT CONDITIONS. IN TIME...EXPECT THE NEB CONVECTION TO
EXPAND EAST INTO NWRN IA. EXPECTING RAINFALL RATES OF 2 TO 2.5
INCHES/HR GIVEN PWATS OF AROUND 1.5 INCHES. CANNOT RULE OUT STORM
TOTAL AMTS OF OVER 5 INCHES OF RAINFALL IN ASSOC WITH THIS
EVENT...AND THEREFORE AN ELEVATED FLASH FLOOD RISK EXISTS.

ORRISON


ATTN...WFO...DVN...ARX...MPX...DMX...FSD...OAX...GID...LBF...

LAT...LON   41269844 41239694 41149611 40959443 41229277 41909162
            42979195 43459329 43589559 43489699 43069897 42160042
            41400050 41079977 41269844