Tornadoes and Hail in Nebraska, April 20, 2001

SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
155 PM CDT FRI APR 20 2001

...IMMEDIATE THUNDERSTORMS CHCS AND THEN PRECIP FOR SUNDAY CONCERN
THIS TIME AROUND...

DONT PLAN ON MAKING THIS OVERLY LONG IN CASE TSTMS POP UP IN NEAR
FUTURE. WEST/EAST SFC BOUNDARY IN OUR KANSAS CWA HAS MOVED ONLY A
LITTLE NORTH THE PAST SIX HOURS. BEST SFC MOISTURE STILL OFF TO THE
EAST AND SE BUT TRYING ITS BEST TO ADVECT WESTWARD. 850 MOISTURE
WAS ALSO WELL EAST AT 12Z BUT FBY AND RWD PROFILERS HAVE BEEN RUNNING
EAST ALL MORNING SO MODELS LOOK ON TRACK TO BRING SOME OF THAT
MOISTURE IN AS WELL. POTENT SHORTWAVE SEEN ON UPPER AIR ANALYSIS AND
SATELLITE IMAGERY APPROACHING FROM EASTERN COLORADO.  ALSO HAS 70 KT
JET AT 500 MB AT 12Z OVER AZ/WRN NM WHICH WAS MOVING INTO THE
WESTERN PART OF THE PROFILER NETWORK.  OTHER NOTES...TEMPS IN THE
80S...WITH 60S FOR DEWPTS...SOUTH OF BNDRY WHILE COOLER 70S NORTH.
FCST SOUNDINGS OVER GRI FOR 0Z FROM MESOETA HAD PROJECTED CAPES OF
NEAR 3000 J/KG WITH SRH OF OVER 300 M2/S2...AND LCL OF 1800 FT. WILL
HAVE TO KEEP CLOSE WATCH ON SFC WINDS AND BOUNDARY ONCE CONVECTION
STARTS.

FAST MOVING SYSTEM SHOULD CLR MOST OF CWA BY MIDNIGHT. ATTENTION
THEN TURNS TO SUNDAY. MODELS DIFFER ON SPEED OF UPPER LOW BUT ALL
AGREE ON PRECIP GENERATION. ETA IS QUICKER AND MORE ROBUST WITH
QPF. BIGGEST DILEMMA IS PRECIP TYPE. ETA BRINGS 850 TEMPS DOWN TO
ZERO BY SAT EVENG AND KEEPS THEM -2 TO -4C ON SUN IN OUR NWESTERN
CWA. AVN RUNNING ABOUT 10 DEGREES WARMER THAN THAT. THINK ETA IS
TOO AGGRESSIVE WITH SYSTEM AND COLD AIR WHILE AVN LACKING. WILL
DECIDE ABOUT SNOW MENTION IN WEST AFTER COORD WITH LBF.  TEMPS WILL
ALSO HAVE TO BE ADJUSTED FOR SUNDAY.

WILL TAKE QUICK LOOK AT EXTENDED BUT MAIN CHANGE WILL PROBABLY BE TO
REMOVE RAIN CHCS FOR TUES AS LATEST AVN KEEPS UPPER LOW PROGRESSIVE.

.GID...NONE

EWALD

KSZ005>007-017>019-NEZ039>041-046>049-060>064-072>077-082>087-210200-

SEVERE WEATHER OUTLOOK - SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS
NATIONAL WEATHER SERVICE HASTINGS NE
429 PM CDT FRI APR 20 2001

...SPOTTER ACTIVATION WILL LIKELY BE NECESSARY THIS EVENING...

A STRONG LOW PRESSURE AREA WILL CONTINUE TO ADVANCE THROUGH EASTERN
COLORADO AND WESTERN KANSAS THIS EVENING...ALL WHILE A WARM FRONT
LIFTS NORTHWARD FROM INTERSTATE 80 IN SOUTH CENTRAL NEBRASKA.
AS THIS SYSTEM APPROACHES...THUNDERSTORMS WILL CONTINUE TO DEVELOP
ACROSS THE WESTERN SECTIONS OF NEBRASKA AND KANSAS EARLY THIS
EVENING. THESE STORMS ARE EXPECTED TO INITIALLY SPREAD INTO AREAS TO
THE WEST OF HIGHWAY 183 BETWEEN 6 PM AND 8 PM...AND THEN CONTINUE
HEADING EASTWARD THROUGH THE REST OF SOUTH CENTRAL NEBRASKA AND NORTH
CENTRAL KANSAS DURING THE EVENING. DAYTIME HEATING AND AMPLE LOW
LEVEL MOISTURE HAS SET UP A MODERATELY UNSTABLE AIRMASS ACROSS SOUTH
CENTRAL NEBRASKA AND NORTH CENTRAL KANSAS...SETTING THE STAGE FOR
THUNDERSTORMS TO BECOME SEVERE ACROSS THE AREA.

THE BULK OF THIS ACTIVITY IS EXPECTED TO OCCUR IN SOUTH CENTRAL
NEBRASKA AND NORTH CENTRAL KANSAS BETWEEN 7 PM AND 2 AM. THE MAIN
THREAT WITH THESE STORMS WILL BE LARGE HAIL AND DAMAGING WINDS...
ALTHOUGH AN ISOLATED TORNADO CANNOT BE RULED OUT.

AREA EMERGENCY MANAGEMENT OFFICIALS AND SPOTTER GROUPS SHOULD PAY
CLOSE ATTENTION TO THIS DEVELOPING SITUATION...WITH SPOTTER
ACTIVATION A GOOD POSSIBILITY THIS EVENING.

GUYER