Severe Thunderstorm Warning 246, NWS Omaha, NE

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
135 PM CDT WED SEP 13 2000

MAIN SHORT TERM FCST CHALLENGE IS WHETHER TSRA WL DVLP EARLY TNGT
ALG THE ADVANCING CDFNT.  BEYOND THIS...TEMPS/WINDS BECOME THE
PRIMARY CONCERN.

LATEST STLT IMAGERY SHOWING A STG AUTUMN LIKE SHRTWV DROPPING INTO
NRN AND ERN ND FM SRN CANADA.  ON THE BACK SIDE OF THE SHRTWV...A
100KT JET CORE WAS ENTERING WRN ND.  THE MDLS ARE IN GOOD AGREEMENT
IN DROPPING THE SHRTWV INTO MN TNGT AND NRN IA BY 12Z THU AND THE OH
VLY LATER THU.  AN UPPER TROF DEEPENS OVER THE UPPER MDWST AND MID
MS VLY RGN TNGT AS THE SHRTWV MOVES SE.  AT 18Z..SFC LOW PRES WAS
ALG THE NEB/SD BDR WITH THE CDFNT TRAILING NW INTO ERN MT. A TROF
EXTENDED FM THE LOW INTO SW NEB.  SFC WNDS HAVE BROUGHT SHALLOW
LAYER OF LOWER-MID 60S SFC DWPTS N INTO THE CWA.  CAPE HAS RISEN TO
800-1400 J/KG BUT CIN REMAINS RATHER HIGH WITH 200-300 J/KG EVIDENT
OVER THE CWA.  THE FRONT SHD MOVE THROUGH NRN AREAS OF THE CWA EARLY
TNGT...THEN THE SE CORNER AROUND 3 AM.  ALTHOUGH MID LVL TEMPS ARE
PROGGED TO RISE TO +11C BY 00Z...STILL FEEL GIVEN STRENGTHEN OF THE
SHRTWV AND CDFNT THAT ISOLD TSRA MAY DEVELOP AS IT BEGINS TO SURGE
SE AND MEETS WITH INCREASINGLY MOIST AIR AND WILL LEAVE IN THE SE
ZONES PER GOING FCST.  85-70H Q-VECTOR DIVERGENCE FIELDS SUGGEST
GUSTY NW WNDS ACROSS THE CWA THURS...ESP FROM AROUND 9AM AFTER THEY
COUPLE TO THE GROUND...THROUGH MID AFTERNOON BEFORE DIMINISHING.

THU NITE AND FRI...THE UPPER TROF SHIFTS EAST OF THE AREA THURS
NIGHT AS SFC HIGH PRES RIDGE BLDS SE FM CANADA INTO THE UPPER MDWST
AND CNTRL PLNS.  EXPECT CLEAR SKIES THURS NIGHT.  MDLS RH FIELDS DO
INDICATE SOME INCREASE IN HIGH LVL RH FIELDS DURG THE DAY FRI AS
SOME WAA HIGH CLDS MOVE OVER THE AREA...THUS WL GO WITH PTLY TO
MSTLY SUNNY SKIES.

GIVEN EXTREMELY DRY GROUND AND ABUNDANT SUNSHINE...FAN GUID TEMPS
APPEARS TOO COOL THURS AND FRI AND WILL GO MORE TWD THE FWC/MAV
SOLNS.

IN THE EXTENDED...PROGRESSIVE FLOW PATTERN IS MAINTAINED OVER THE
CNTRL PLNS AS NW FLOW IS MAINTAINED.  LITTLE MSTR WILL MOV N INTO
THE AREA...SO MAINLY DRY CONDITIONS SHD PREVAIL.  SAT APPEARS WARM
AND DRY.  THE NEXT IN A SERIES OF SHRTWVS DROPPING SE IN THE FLOW
MOVES INTO THE UPPER MDWST/GREAT LAKES RGN SUN.  A WEAK CDFNT MAY
BACKDOOR ERN NEB FOR SUN...BUT MAIN COOLING WITH THIS SYSTEM APPEARS
TO BE FOCUSED TO THE E AND NE OF OUR CWA.  A SLIGHT CHC OF PRECIP
FOR MON AS ANOTHER STG SHRTWV DROPS SE INTO THE AREA...BUT MSTR WL
BE LIMITED.

**AIRMASS IS DESTABLIZING RAPIDLY AS MSTR RETURN CONTINUES.  CIN IS
ALSO DECREASING OVER THE SE CWA AND IS DOWN TO 20J/KG.  18Z RUC AND
MESOETA BOTH DEVELOP A WAVE OF LOW PRESSURE OVER S CNTRL NE WHICH
WHICH MOVES NE INTO E CNTRL NE BY 06Z.  THIS WILL LIKELY DELAY THE
FRONTAL TIMING SOMEWHAT AND ALLOW DEEPER MSTR TO WORK NWD.  NEW
MESOETA PROGS 400-425 HELICITY INTO SE CORNER BY 06Z.  ALL IN
ALL...CONDITIONS APPEARING MORE FAVORABLE FOR TSRA THAT PREVIOUSLY
THOUGH AND I HAVE EXPANDED POPS AS FAR N AS OLU/OFK GROUPING.

.OMA...NONE.

SKERRITT
I