Tornado Warning 24, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
235 PM CDT MON MAY 3 1999

18Z SOUNDING SHOWS SOME INCREASED MOISTR ADVECTION AND SFC DEWPOINTS
UP TO 60 AT HSI LNK BIE FNB AND OFF.  ALL THREE MODELS WOULD INDICATE
IMPROVED UPPER SUPPORT LATER TONIGHT.  TOP AND OAX SOUNDINGS SHOWED ABOUT
57 AND 78 B- WITH LITTLE PROB WITH SECOND INVERSION ALOFT.  WITH JET
JUST ROTATING INTO SRN SIDE OF CIRC THIS EVE...AND THE PRONOUNCED S TO
N JET IN FRONT NOT PRESENT PRECIP MAY HOLD OFF UNTIL AFT MIDNIGHT.

ALL THREE MODELS WANT TO RAPIDLY EXPAND THE MOISTURE THROUGH THE STACK
TO 12Z...AND ALSO UNDERGO SOME SERIOUS DESTABLIZATION.  OVERNIGHT
ACTIVITY LIKELY TO LAST INTO TUE.  WITH RELATIVE HIGH RH BUT WARM
AIRMASS WILL FAVOR LOWER 70S OVER UPPER 60S TUE.  WITH VERY DISTINCT
COLD FRONT LIKELY TUE NIGHT COULD EXPECT FRONTAL WEATHER WITH SOMEWHAT
COOLER TEMPS TUE NIGHT AND LOWER TO MID 60S ON WED NOT UNWARRANTED.

.OMA...NONE
POERS

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-041200-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
530 PM CDT MON MAY 3 1999

...SEVERE WEATHER OUTLOOK FOR EASTERN NEBRASKA AND SOUTHWEST IOWA...

SPOTTER ACTION...
STORM SPOTTER ACTIVATION MAY BE REQUIRED TONIGHT IN EASTERN NEBRASKA
AND SOUTHWEST IOWA.

DISCUSSION...
AN UNSTABLE AND MOIST AIR MASS IS IN PLACE ACROSS EASTERN NEBRASKA AND
SOUTHWEST IOWA. STRONG SOUTH WINDS THROUGH THE NIGHT WILL LEAD TO AN
EVEN FURTHER INCREASE IN GULF MOISTURE INTO THE REGION. THIS AIR MASS
WILL INTERACT WITH DISTURBANCES IN THE UPPER ATMOSPHERE MOVING INTO THE
PLAINS AND SURFACE BOUNDARIES...TO BRING A CHANCE FOR THUNDERSTORMS TO
THE REGION TONIGHT.

DUE TO THE DEGREE OF INSTABILITY...SOME OF THESE STORMS COULD BECOME
SEVERE. LARGE HAIL AND DAMAGING WIND GUSTS APPEAR TO BE THE MAIN RISK.
HOWEVER ISOLATED TORNADOES ARE POSSIBLE BASED ON WIND SHEAR PROFILES IN
THE LOWER ATMOSPHERE.

GW