Severe Thunderstorm Warning 233, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA NE
300 AM CDT TUE JUN 5 2001

FORECAST CHALLENGES -- HEAVY RAINFALL POTENTIAL SERN ZONES THIS
MORNING

SYNOPSIS -- LATEST REGIONAL 88D Z MOSAIC SHOWED MCS CONTINUING TO
EVOLVE ACROSS N-CNTRL KS IN A ZONE OF LOW-LEVEL WARM ADVECTION/
ISENTROPIC ASCENT.  07Z MANUAL AND MSAS ANALYSIS DEPICTED A SURFACE
LOW JUST W OF EMP WITH AN ATTENDANT WARM FRONT EXTENDING EWD INTO
CNTRL MO AND AN INVERTED TROUGH STRETCHED NWD INTO ERN NEB.  ALOFT,
EARLY MORNING MOISTURE CHANNEL IMAGERY SHOWED A CLOSED MID LEVEL
CIRCULATION CENTERED OVER S-CNTRL MT AND A POTENT SHORTWAVE
DOWNSTREAM FROM THIS FEATURE, EJECTING NEWD ACROSS NWRN NEB AND WRN
SD.

FORECAST -- WE WILL FOLLOW A BLEND OF THE ETA AND AVN THIS FORECAST
PER PMDHMD AND 6-HR QPF VERIFICATION.  IN THE SHORT TERM, THE HEAVY
RAINFALL THREAT ACROSS FAR SERN ZONES IS THE MAIN CONCERN.  LATEST
KUEX 88D IMAGERY SUGGESTS THAT THE SEVERE WEATHER POTENTIAL AND
HEAVIEST RAINFALL WILL REMAIN CONFINED TO NERN KS.  HOWEVER, OTHER
CONVECTION CONTINUES TO DEVELOP TO THE N OF THE HIGHEST REFLECTIVITY
VALUES OVER S-CNTRL NEB.  SINCE FLASH FLOOD GUIDANCE VALUES ARE VERY
LOW AND RIVERS ARE RUNNING HIGH ACROSS THE FAR SRN ZONES, WE WILL
EXTEND THE CURRENT FLASH FLOOD WATCH UNTIL NOON.

THE SURFACE LOW CURRENTLY NEAR EMP IS FORECAST PROPAGATE NEWD TO
AROUND FNB BY NOON, COINCIDENT WITH A WEAK FRONTAL BOUNDARY.  THIS
BOUNDARY IS EXPECTED TO MOVE SLOWLY S DURING THE AFTERNOON AND WILL
BE THE FOCUS FOR CONVECTIVE REDEVELOPMENT, POSSIBLY AFFECTING THE
SERN ZONES.  THUS, WE WILL MAINTAIN THE HIGHEST POPS IN THESE
AREAS.  ELSEWHERE, WE WILL CARRY POPS OR AREAL COVERAGE DESCRIPTORS
THIS MORNING AND GO WITH A DRY FORECAST IN THE PM.

A WEAK SURFACE RIDGE IS FORECAST TO QUICKLY MOVE THROUGH THE AREA
TONIGHT INTO WEDNESDAY, AS INCREASING MID LEVEL, ZONAL FLOW OVER THE
ROCKIES INDUCES CYCLOGENESIS TO OUR W.  THE ETA IS QUITE BULLISH ON
LOW-LEVEL MOISTURE RETURN INTO THE WRN HALF OF NEB TONIGHT INTO
WEDNESDAY.  THIS MAY BE A BIT PREMATURE AND WE HAVE FOLLOWED A BLEND
OF THE ETA AND AVN ON THE HANDLING OF THIS RETURN MOISTURE.

THE NEXT CHANCE FOR PRECIPITATION WILL BE WEDNESDAY NIGHT AS A
SHORTWAVE AND ASSOCIATED SURFACE SYSTEM TRANSLATE ACROSS SD.  THE
ETA INDICATES THE POSSIBLE DEVELOPMENT OF AN MCS MOVING SEWD ALONG
THE MO RIVER.  MOISTURE, STEEPER LAPSE RATES AND LARGE-SCALE ASCENT
WILL INCREASE ACROSS OUR NRN ZONES AT THAT TIME, SO THIS IS A
POSSIBLE SCENARIO.  WE WILL INCLUDE SLIGHT CHANCE/CHANCE POPS ALL
LOCATIONS, THE HIGHEST BEING ACROSS THE ERN ZONES.

FOR TEMPERATURES, WE FOLLOWED A BLEND OF FWC AND MAV NUMBERS THIS
FORECAST.

IN THE EXTENDED, THE NEW RUN OF THE AVN DEPICTS A SHORTWAVE AND
ASSOCIATED SURFACE FRONTAL SYSTEM PUSHING SEWD THROUGH THE AREA LATE
FRIDAY.  THUS, WE WILL GO AHEAD AND INSERT A CHANCE OF THUNDERSTORMS
TO ACCOUNT FOR THIS.  OTHERWISE, NO CHANGES ARE PLANNED AT THIS
TIME.

.OMA...FLASH FLOOD WATCH UNTIL NOON NEZ088>093

COORDINATED WITH DSM, TOP AND MCI

MEAD