Severe Thunderstorm Warning 349, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
300 AM CDT WED SEP 18 2002

COMPLEX FORECAST WITH MAIN CHALLENGE BEING TSTM TIMING AND CHANCES
FIRST TWO PERIODS.

SYNOPSIS...DIGGING LONG WAVE TROF OVR WRN US HAS SENT FIRST
SHORTWAVE INTO WRN NEB AND CNTRL SD...WHILE MAIN ENERGY LIES FURTHER
BACK INTO NEVADA AREA. AT THE SFC...DOUBLE BARRELED LOW HAS TAKEN
SHAPE WITH THE UPPER LEVEL SUPPORT AIDING THE NRN LO OVR WRN SD.
SECOND LO IS OVR SWRN KS AND WL SEE BETTER SUPPORT ONCE PREVIOUS
MENTIONED SHORTWAVE OVR NEVADA KICKS OUT LATER TDY.  IN THE
MEANTIME...STRONG MOIST AND WARM AIR ADVECTION UNDERWAY ACROSS THE
REGION WITH A 50KT LLJ NOTED ON REGIONAL PROFILERS.  SFC DEWPOINTS
HAVE CLIMBED TO AROUND 60 OVR MUCH OF AREA.  SCATTERED THUNDESTORMS
ARE ONGOING OVR PORTIONS OF THE CWFA...LIKELY AIDED BY MOIST
ADVECTION AND NOSE OF LLJ.  HAIL NOT OUT OF THE QUESTION WITH LOW
WET BULB ZERO HEIGHT THIS AM.

FORECAST...SCATTERED CONVECTION POSSIBLE INTO MID DAY AIDED BY LLJ
AND WAA.  HAVE SLIGHTLY LOWERED HIGHS BASED ON FORECASTED CLOUD
COVER.  MOST ACTIVE TIME WL BE LATE AFTERNOON/EARLY EVENING WHEN THE
UPPER LEVEL SUPPORT FINALLY ROLLS IN AND ETA SUGGESTING UPPER
COUPLED JET STRUCTURE. REGION WL BE MODERATELY UNSTABLE WITH ETA-KF
GIVING AREA CAPE VALUES OF 2500-3000J/KG.  SHEAR IS SUFFICIENT...
FOR SUPERCELLS...ESPECIALLY OVR SERN NEB.  MODERATE RISK FOR SERN
COUNTIES AND SLIGHT RISK FOR REMAINDER OF AREA.  WL INCLUDE SVR
WORDING IN SERN ZONES.  SFC TROF WL MOVE THRU BY MIDNIGHT AND MAY
SEE LINGERING ACTIVITY INTO EARLY MORNING.  UPPER TROF AXIS FINALLY
MOVES THRU THU MORNING AND ETA AND AVN BOTH GENERATING PRECIP OVR
SERN NEB AND NERN KS.  WL MENTION 20 POPS FOR THIS TIME FRAME.

AREA IN COOL NWRLY FLOW AFTER THIS SYSTEM.  NEXT CHANCE OF PRECIP
WAS SAT AND HAVE LOWERED POPS SLIGHTLY AS MOISTURE LOOKS RATHER
LIMITED FOR NOW.  OTHERWISE...NO CHANGES MADE TO EXTENDED.

.OMA...NONE.

GRIFFIS