Tornado Warning 15, NWS Hastings, NE

SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
250 PM CDT SUN MAY 20 2001

COLD FRONT AND ITS IMPLICATIONS THE FOCUS OF THIS FORECAST.

FRONT WAS SLICING ITS WAY ACROSS NW CWFA AT 19Z.  BROKEN LINE OF
SHOWERS/STORMS FORMING ALONG FRONT.  THIS LINE SHOULD FILL IN AS
DAYTIME HEATING CONTINUES TO DESTABILIZE THE ATMOSPHERE AND AS
BETTER MOISTURE IS ENCOUNTERED.  THIS LINE WILL ADD TO FAIRLY HEAVY
RAIN AMOUNTS SCATTERED ACROSS SE CWFA.  WILL BASE ZONE GROUPS ON
TIMING OF THIS PCPN THIS EVENING.  COULD NOT RULE OUT A SEVERE STORM
PRODUCING HAIL BUT WILL NOT MENTION IN TEXT OF ZONES TONIGHT.
NORTHWEST WINDS BEHIND THE FRONT WILL GUST TO AROUND 40 MPH THIS
EVENING BUT DOUBT IF WIND ADVISORY CRITERION WILL BE REACHED.

AS UPPER TROUGH AXIS PASSES OVERNIGHT...QUESTION AS TO WHETHER
ADDITIONAL PCPN...NOW IN NW NEBR/SW SDAK/ERN WY AREA...WILL AFFECT
CWFA.  WHILE LOW LEVEL MOISTURE GETS SCOURED OUT...UPPER LEVEL
DYNAMICS SHOULD BE EFFICIENT AT SQUEEZING OUT WHAT IS LEFT OVER.
BEST OVERALL SETUP LOOKS TO BE OVER SOUTHWEST CWFA.  WORDING WILL BE
TRICKY FOR TIMING OF PCPN HOWEVER.

HAVE REINTRODUCED SLGT CHC OF AFTERNOON SHOWERS MONDAY AS COLD POOL
ALOFT PASSES BY.  ETA FORECAST SOUNDINGS SHOW A LAYER OF LOW LEVEL
MOISTURE AND STEEP LAPSE RATES.  EVEN CAPES OF 100-200 J/KG ARE
EVIDENT BY LATE IN THE DAY.  SHOWERS/SQUALLS WILL HAVE POTENTIAL
FOR WIND GUSTS TO 40 MPH.

REST OF FORECAST PERIOD WILL REMAIN WITH DRY WORDING.  MODELS
HANDLING OF UPPER LOW INTO ERN US HAS COME INTO BETTER AGREEMENT...
HOWEVER TIMING OF ANY IMPULSES ROTATING AROUND THE CENTER IS IN
QUESTION AND MOISTURE AVAILABILITY APPEARS SUSPECT.

TEMPWISE...ETA LOW LEVEL PROGS ARE WARMER AND APPEAR MORE REASONABLE
THAN THE AVN/NGM. THIS FITS IN WITH RECENT RELEASE CONCERNING AVN
LOW LEVEL COOL TEMP BIAS MENTIONED BY LBF IN COORDINATION CALL.
THEREFORE MAV/FAN GUIDANCE THROWN OUT.  EVEN THOUGH BASED ON THE
NGM...WARMER FWC NUMBERS ACTUALLY MATCH ETA PROGS PRETTY WELL AND
ARE PREFERRED.  MORE SPECIFICALLY FOR TONIGHT...WINDS SHOULD KEEP
AIR MIXED ENOUGH TO KEEP TEMPS FROM FALLING TOO FAR.

.GID...NONE.

DROZD

KSZ005>007-017>019-NEZ039>041-046>049-060>064-072>077-082>087-202100-

SEVERE WEATHER OUTLOOK - SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS
NATIONAL WEATHER SERVICE HASTINGS NE
1108 AM CDT SUN MAY 20 2001

...SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EARLY EVENING
ACROSS PORTIONS OF SOUTH CENTRAL NEBRASKA AND NORTH CENTRAL KANSAS...

A COLD FRONT WILL DROP SOUTHWARD THROUGH CENTRAL NEBRASKA THIS
AFTERNOON...AND THEN MAKE ITS WAY INTO NORTH CENTRAL KANSAS BY EARLY
THIS EVENING. THIS FRONT WILL ROUGHLY BE POSITIONED FROM FULLERTON...
TO GRAND ISLAND...TO HOLDREGE AT MID AFTERNOON...WITH SCATTERED
THUNDERSTORMS EXPECTED TO REDEVELOP ALONG AND SOUTH OF THIS FRONT.
MARGINAL INSTABILITY ACROSS SOUTH CENTRAL NEBRASKA AND NORTH CENTRAL
KANSAS COULD ALLOW A FEW OF THESE STORMS TO APPROACH SEVERE LIMITS.

THE MAIN SEVERE THREAT WITH THESE STORMS WOULD BE HAIL UP TO ONE INCH
IN DIAMETER...ALTHOUGH SOME DAMAGING WINDS CANNOT BE RULED OUT. WITH
THE COLD FRONT EXPECTED TO PUSH THROUGH THE AREA BY EARLY THIS
EVENING...THE MAIN TIMING FOR ANY SEVERE WEATHER WOULD BE BETWEEN
2 PM AND 7 PM.

EMERGENCY MANAGEMENT OFFICIALS AND SPOTTER GROUPS ACROSS SOUTH
CENTRAqL NEBRASKA AND NORTH CENTRAL KANSAS SHOULD KEEP APPRISED OF THE
WEATHER SITUATION TODAY...AND BE PREPARED FOR THE POSSIBILITY OF
ACTIVATION THIS AFTERNOON AND EARLY EVENING.

GUYER