921
AWUS01 KWNH 300302
FFGMPD
MNZ000-IAZ000-NEZ000-SDZ000-300900-
MESOSCALE PRECIPITATION DISCUSSION 0550
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1102 PM EDT MON JUN 29 2026
AREAS AFFECTED...CENTRAL NEBRASKA THROUGH FAR SOUTHERN MINNESOTA
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 300301Z - 300900Z
SUMMARY...SHOWERS AND THUNDERSTORMS DEVELOPING AHEAD OF A COLD
FRONT WILL EXPAND AND TRAIN THROUGH THE OVERNIGHT HOURS. RAINFALL
RATES OF 1-2"/HR ARE LIKELY, LEADING TO 2-3" OF RAIN WITH LOCALLY
HIGHER AMOUNTS. THIS MAY CAUSE INSTANCES OF FLASH FLOODING.
DISCUSSION...THE REGIONAL RADAR MOSAIC THIS EVENING SHOWS RAPIDLY
DEVELOPING THUNDERSTORMS OVER PORTIONS OF CENTRAL NEBRASKA WITH
RECENT HOURLY MRMS RAINFALL UP TO 1.25 INCHES. THIS CONVECTION IS
BLOSSOMING IN RESPONSE TO INCREASING CONVERGENCE ALONG THE FRONT
BUT ALSO ON THE NOSE OF THE SW ORIENTED LLJ WHICH IS ANALYZED VIA
THE SPC RAP TO BE 30-40 KTS JUST TO THE SOUTHEAST. THERMODYNAMICS
ACROSS THE REGION ARE IMPRESSIVE AS REFLECTED BY PWS AS HIGH AS
1.9 INCHES OVERLAPPING MLCAPE OF AS MUCH AS 5000 J/KG WHICH WILL
MAINTAIN AMPLE FUEL FOR OVERNIGHT THUNDERSTORM DEVELOPMENT.
AS THE FRONT SAGS SOUTHEAST AND THE LLJ MAINTAINS THE IMPRESSIVE
DOWNSTREAM MOISTURE ADVECTION, THUNDERSTORMS WILL CONTINUE TO
DEVELOP ACROSS NEBRASKA. THIS IS WELL AGREED UPON BY THE AVAILABLE
HIGH-RES CAMS, ALTHOUGH WITH DIFFERING EVOLUTION AND INTENSITY. AS
STORMS BLOSSOM OVER NEBRASKA, THEY WILL LIKELY EXHIBIT
BACKBUILDING INTO THE HIGHER INSTABILITY, AND THEN TRAIN NORTHEAST
AS PROPAGATION VECTORS AND MEAN 0-6KM WINDS ALIGN FROM THE SW
PARALLEL TO THE FRONT. WITH RAINFALL RATES PROGGED BY BOTH THE
HREF AND REFS TO EXCEED 1"/HR (30-50% CHANCE) THIS BACKBUILDING
AND TRAINING WILL RESULT IN CORRIDORS OF 2-3" OF RAINFALL WITH
LOCALLY HIGHER AMOUNTS.
THERE CONTINUES TO BE SOME UNCERTAINTY AS TO HOW CONVECTION WILL
EVOLVE DUE TO PRONOUNCED SHEAR (40-50 KTS) LEADING TO ORGANIZATION
INTO CLUSTERS OR EVEN AN MCS. AS STORMS GROW UPSCALE, MORE RAPID
EASTWARD PROGRESSION OF CELLS MAY OCCUR THANKS TO OUTFLOWS WITHIN
1000-1500 J/KG OF DCAPE. THIS SUGGESTS THAT THE GREATEST FLASH
FLOOD RISK OVER THE AREA WILL BE IN THE NEXT FEW HOURS ACROSS NE,
RATHER THAN FARTHER DOWNSTREAM (BOTH TEMPORALLY AND SPATIALLY).
HOWEVER, 3-HR FFG ACROSS NEBRASKA IS HIGHER THAN INTO PARTS OF
IOWA AND MINNESOTA, POTENTIALLY OFFSETTING THE FLASH FLOOD RISK
OVERNIGHT. STILL, THE BACKBUILDING/TRAINING WHICH WILL LIKELY BE
EXHIBITED BY CONVECTION IN THE NEXT FEW HOURS STILL INDICATES AT
LEAST AN ISOLATED RISK FOR FLASH FLOOD INSTANCES THROUGH 08Z.
WEISS
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...ARX...DMX...FSD...GID...LBF...MPX...OAX...
ATTN...RFC...KRF...MSR...NWC...
LAT...LON 44089505 44029310 43529255 42429421 41739562
40979718 40529883 40429967 40570015 40970029
41530028 42159875 43059754 43059754 43619668
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