Severe Thunderstorm Warning 381, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
325 PM CDT THU JUL 19 2001

MAIN FORECAST CHALLENGE IS TSTM/HEAVY RAIN THREAT TNGT THEN AGAIN
FRI NIGHT.  MODELS ARE EACH A LITTLE DIFFERENT WITH QPF PLACEMENT
AND HAVEN'T BEEN HANDLING THINGS EXACTLY THE BEST...BUT HAVE LEANED
TWD 12Z MESOETA WHICH IS CLOSEST TO PERSISTENCE WHICH HAS GENERALLY
BEEN DOING THE BEST RECENTLY.

SHORT TERM...SUBTROPICAL MOISTURE REMAINED IN PLACE WITH
PRECIPITABLE WATER AT OMA OVER 2 INCHES ON 12Z SOUNDING.  AFTN SFC
ANLYS SHOWD SVRL BOUNDARIES THAT COULD AFFECT AREA.  MAIN WARM FRONT
APPEARED TO BE A BIT FTHR S THAN YDA ATTM...MAYBE A TIER OF COUNTIES
S OF KS BORDER.  OTHER OUTFLOW BOUNDARY HAS BEEN WORKING SWWD AND
WAS GENERATING HIGH BASED SHOWERS/TSTMS ALONG NEBR SRN TIER
COUNTIES.  FINALLY ANOTHER BOUNDARY...FM LEFT OVER NRN PLAINS
CONVECTION... PUSHED INTO EXTREME NERN NEBR LATE THIS MORNING.  THIS
BOUNDARY WAS MORE ILL-DEFINED...BUT SFC HEATING...AND THUS CAPE AND
INSTABILITY WAS HIGHEST NEAR IT'S REMNANTS.  ALTHOUGH BOUNDARIES
GIVE ENTIRE CWA A TSTM THREAT TNGT...FOCUS OF STGEST STORMS AND
HEAVIEST RAIN APPEARS TO BE OVER FAR SERN NEBR AGAIN TNGT.
CONVECTION SIMILAR TO YDA COULD DVLP NEAR NRN EDGE OF HEAT JUST S OF
CWA WITH ACTIVITY DVLPG/MOVING ENE INTO SERN NEBR AS LOW LVL JET
FIRST BACKS AND STRENGTHENS EARLY THIS EVENING BFR VEERING LATER
TNGT.  AFTER COORDINATION WITH EAX...TOP AND GID WILL ISSUE FLASH
FLOOD WATCH FOR TNGT FAR SERN ZONES.  WILL USE PERSISTENCE FOR LOWS.

ON FRI...RESIDUAL CLOUDS COULD HOLD TEMPS DOWN AGAIN IN FAR
SERN/ECNTRL NEBR AND WILL KEEP HIGHS ARND 90...OTRW 90 TO 95 LOOKS
OK.  MESOETA BRINGS SHORTWV OVR MEAN UPR RIDGE SO WL KEEP POPS MOST
AREAS WITH HIGH MOISTURE REMAINING IN PLACE.

12Z MESOETA DVLPD QPF MAX NCNTRL NEBR FRI AFTN AND BROUGHT IT SE
ACRS CWA FRI NGT AS THETA E ADVCTN INCREASED NEAR UPR SHRT WV TROF.
PREV FCST HAD RELATIVELY HIGH POPS GOING NRN ZONES SO WL KEEP THEM
IN FCST ALTHOUGH MODELS DON'T REALLY BRING A FRONT INTO THE AREA AS
YDAS RUNS DID.

WILL COUNT ON UPR RIDGE BUILDING WITH DRIER CONDS AND MORE SUNSHINE
ON SAT SO WL GO A LTL WARMER MOST AREAS.  WL KEEP MORNING CONVECTION
IN SERN ZONES BUT OTRW DRY.  WITH PATTERN CHANGING LTL WL KEEP SMALL
DIURNAL POPS IN FOR SAT NGT.

.OMA...FLASH FLOOD WATCH TNGT NEZ088>093
CHERMOK

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-192300-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
612 PM CDT THU JUL 19 2001

STORM SPOTTERS MAY BE NEEDED THIS EVENING OR TONIGHT IN EASTERN
NEBRASKA AND SOUTHWEST IOWA.  THE BEST CHANCE OF SEVERE STORMS WILL
BE BETWEEN 700 PM AND MIDNIGHT.

AN VERY UNSTABLE AIR MASS CONTINUES TO EXIST OVER THE AREA.
THUNDERSTORMS HAVE ALREADY BEEN OCCURRING IN SOUTHEAST NEBRASKA AND
NEW DEVELOPMENT HAS STARTED ALONG AN EAST TO WEST BOUNDARY OVER
NORTHERN KANSAS.  THIS IS LIKELY THE AREA WHERE STORMS WILL INITIATE
AND GRADUALLY MOVE INTO SOUTHERN NEBRASKA.  ANOTHER AREA OF
DEVELOPMENT MAY BE FROM JUST SOUTH OF NORFOLK TO NEAR MISSOURI
VALLEY.  THIS IS WHERE ANOTHER BOUNDARY EXISTS.

SOME FAVORABLE WIND SHEAR EXISTS IN THE LOWEST LEVELS OVER SOUTHERN
NEBRASKA FOR SEVERE THUNDERSTORMS.  THE MAIN SEVERE THREAT IS
EXPECTED TO BE DAMAGING WIND.

SMITH