MESOSCALE PRECIPITATION DISCUSSION 0116
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
620 PM EDT TUE MAY 01 2018

AREAS AFFECTED...SOUTHEAST NEB....SOUTHWEST TO NORTHEAST
IA...SOUTHEAST MN...SOUTHWEST AND WEST-CENTRAL WI

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 012220Z - 020420Z

SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS WILL TEND TO EXPAND
FURTHER IN COVERAGE OVER THE NEXT FEW HOURS. SOME LOCALIZED FLASH
FLOODING WILL BE POSSIBLE.

DISCUSSION...RADAR IMAGERY SHOWS SEVERAL CLUSTERS OF STRONG
THUNDERSTORMS DEVELOPING ALONG AND AHEAD OF A DRYLINE ACROSS
NORTH-CENTRAL KS AND ALSO UP ALONG AND AHEAD OF A QUASI-STATIONARY
FRONT FROM SOUTHEAST NEB UP ACROSS NORTH-CENTRAL IA. THE
CONVECTION IS BEING FOSTERED BY A COMBINATION OF STRONG DIURNAL
HEATING...MOISTURE TRANSPORT AS AIDED BY A 40 TO 50 KT S/SW LOW
LEVEL JET AND PROXIMITY OF A LOW-AMPLITUDE SHORTWAVE LIFTING
NORTHEAST ACROSS THE NORTH-CENTRAL PLAINS REGION WHICH WITH THE
AFTERNOON HEATING HAS GREATLY ERODED THE AFTERNOON CINH.

CONVECTIVE CLOUD TOPS CONTINUE TO COOL WITH CONVECTION ALIGNING
ITSELF ALONG THE NORTHWEST GRADIENT OF AN AXIS OF 2000 TO 3000
J/KG OF MLCAPE. STRONG INSTABILITY FOCUSED ALONG AND JUST AHEAD OF
THE FRONT IN CONCERT WITH THE AFOREMENTIONED LOW LEVEL JET SHOULD
SUSTAIN NUMEROUS CLUSTERS OF CONVECTION WELL THROUGH THE EVENING
HOURS...WITH A GRADUAL TENDENCY TO FOCUS MORE ORGANIZED CONVECTION
FARTHER TO THE NORTHEAST WITH TIME UP ACROSS AREAS OF
NORTH-CENTRAL IA...SOUTHEAST MN AND OVER INTO
SOUTHWEST/WEST-CENTRAL WI. THE LATEST HRRR FORECASTS FAVORS SOME
MODEST UPPER JET COUPLING IN VICINITY OF THE FRONT RELATED TO THE
AFOREMENTIONED SHORTWAVE WHICH WILL FURTHER SUSTAIN THE CONVECTIVE
THREAT GIVEN ROBUST MOISTURE/INSTABILITY TRANSPORT.

IN FACT...THE MOISTURE TRANSPORT PER RECENT RAP/HRRR FORECASTS ARE
FORECAST TO BECOME QUITE STRONG ACROSS CENTRAL/NORTHERN
IA...SOUTHEAST MN AND SOUTHWEST WI BY 03Z AND THIS WILL PROMOTE
GREATER EFFICIENCY WITH RAINFALL RATES THAT MAY REACH UPWARDS OF
1.5 INCHES/HR. STORM TOTAL AMOUNTS THROUGH LATE EVENING WILL BE ON
THE ORDER OF AS MUCH AS 2 TO 4 INCHES WITH ISOLATED HEAVIER
AMOUNTS. THE CONVECTION WILL TEND TO BE ALIGNED SOMEWHAT WITH THE
MEAN LAYER FLOW OUT OF THE SOUTHWEST AND ALSO WITH NEARLY PARALLEL
ORIENTATION TO THE FRONT...AND SO THE THREAT FOR SOME REPEATING OF
CELLS WILL EXIST. THEREFORE...EXPECT AT LEAST SOME LOCALIZED FLASH
FLOODING CONCERNS.

AREAS FARTHER BACK TO THE SOUTHWEST ACROSS SOUTHEAST NEB AND
NORTH-CENTRAL KS MAY ALSO NEED TO BE MONITORED AGAIN CLOSER TO THE
06Z TIME FRAME FOR CONVECTIVE REDEVELOPMENT AS THE LOW LEVEL JET
INTENSIFIES FURTHER HERE AND INTERACTS WITH THE FRONT AND ANY
POSSIBLE LOW LEVEL COLD-POOLS LAID DOWN FROM THE CURRENT AXIS OF
CONVECTION.

ORRISON

ATTN...WFO...ARX...DMX...DVN...EAX...FSD...GID...GRB...MKX...
MPX...OAX...

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

LAT...LON   45229126 45139031 44678949 43448972 42629098
            41619301 40829492 40229686 40179808 40819844
            41569734 42399611 43489450 44249337 44999194