Tornadoes and Hail in Nebraska, July 24, 2002

SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
329 PM CDT WED JUL 24 2002

...MAIN FOCUS IS THUNDERSTORM CHANCES OVER NEXT SEVERAL DAYS AND
PROSPECTS FOR SEVERE WX TONIGHT...

12Z MORNING UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY SHOWING LOW
AMPLITUDE LARGE SCALE PATTERN OVER THE CONUS. UPPER RIDGE CENTERED
OVER THE FOUR CORNERS AREA YIELDING MODEST SUMMERTIME W/NW FLOW INTO
THE CENTRAL PLAINS. LOW TO MID LEVEL RIDGE CONTINUES TO SHIFT
EASTWARD...WITH 700MB/850MB MOIST AXIS FROM TX/OK THROUGH WESTERN
SECTIONS OF KS AND NEB.

LATEST AFTERNOON SUBJECTIVE SURFACE ANALYSIS FEATURING LOW PRESSURE
ADVANCING EASTWARD ACROSS CNTRL SD...WITH ASSOCIATED WARM FRONTAL
STRUCTURE EXTENDING E/SE THROUGH EASTERN SD INTO NW IA. TROUGH/WIND
SHIFT POSITIONED FROM THE SFC LOW SOUTHWARD INTO WESTERN NEB. AXIS OF
65F SFC DEWPOINTS LOCATED AHEAD OF THE TROUGH...AIDED BY MODEST 5-10F
SFC DEWPOINT RISES OVER THE PAST 24 HOURS.

SURFACE LOW TO CONTINUE TO TRACK FROM CENTRAL SD INTO NORTHEAST NEB
TONIGHT...WITH ACCOMPANYING LOW LEVEL TROUGH EXTENDING BACK TOWARD
WESTERN NEB. OPERATIONAL ETA CONFINES CONVECTIVE DEVELOPMENT TO
NORTHEAST NEB LATE THIS AFTERNOON/EVENING...WITH LATEST NCEP/FSL
RUC20 FOLLOWING SUIT. HOWEVER...12Z ETA KAIN-FRITSCH ALREADY DEVELOPS
CONVECTIVE ACTIVITY ALONG THE TROUGH BY 21Z IN NORTH CENTRAL NEB...
WITH MORE EXPANSIVE DEVELOPMENT SOUTHWARD INTO CENTRAL AND SCNTRL NEB
BY 00Z. WOULD EXPECT REALITY TO BE SOMEWHERE IN BETWEEN THESE
SOLUTIONS. OVERALL...ORIENTATION OF THICKNESSES AND ETA-BASED CORFIDI
VECTORS SUGGEST A GENERAL SSEWRD PROPOGATIONAL COMPONENT TO EVENING
THUNDERSTORM COMPLEX OVER NCNTRL/NE NEB.

ALTHOUGH BULK OF ACTIVITY SHOULD BE CONFINED TO THE N/NE SECTIONS OF
CWA...SOME ISOLATED PULSE-TYPE DEVELOPMENT POSSIBLE S/SW DOWN THE
TROUGH THROUGH THE WESTERN NEB CWA -- HOWEVER INCREASINGLY HIGHER
CINH/LFCS SHOULD GREATLY LIMIT S/SW EXTENT OF DEVELOPMENT.

SEVERE STORMS ARE A POSSIBILITY TONIGHT -- ESPECIALLY IN THE NE
PORTION OF THE CWA -- GIVEN LIKELY MCS PROPAGATION IN AMBIENT
ENVIRONMENT CHARACTERIZED BY AMPLE DEEP LAYER SHEAR / 40-50 KNOTS
0-6KM / FOR STORM ORGANIZATION AND MODERATE INSTABILITY. OBJECTIVELY
DERIVED SFC BASED CAPES RUNNING AROUND 3000 J/KG THIS AFTERNOON...
WITH 100MB MIXED LAYER CAPES AROUND 1500 J/KG. DAMAGING WINDS APPEAR
TO BE MAIN THREAT GIVEN DEEP LAYER SHEAR...30-50 KNOT MID LEVEL
FLOW...AND INVERTED-V CHARACTERISTICS. IN SPITE OF INSTABILITY AND
POTENTIAL FOR UPDRAFT ROTATION GIVEN DEEP LAYER SHEAR...RELATIVELY
HIGH FREEZING/WET-BULB ZERO LEVELS WILL TEND TO LIMIT LARGE HAIL
THREAT. HIGH LCLS/LFCS SUGGEST TORNADIC POTENTIAL AT A MINIMUM IN
CWA.

THURSDAY SHOULD BE FAIRLY QUIET DURING THE DAY AS THUNDERSTORM
COMPLEX MOVES INTO IA...AND POSSIBLY NORTHERN MO DURING THE MORNING.
HOWEVER...REMNANT OUTFLOW BOUNDARIES FROM MCS MAY FIGURE INTO THE
MIX. AFTERNOON TEMPERATURES A FEW DEGREES WARMER ON THURSDAY AS UPPER
RIDGE SHIFTS EASTWARD AND BEGINS TO DAMPEN -- HIGH TEMPS LIKELY
APPROACHING 95 IN MUCH OF THE NEB CWA...WITH A FEW 100 DEGREE
READINGS POSSIBLE IN SOUTHERN CWA.

MCS THEN LOOKS TO DEVELOP IN WESTERN NEB THURSDAY NIGHT AS ETA
PROGGED 50KT LOW LEVEL JET GETS ACTIVE FROM WESTERN KS INTO SOUTHWEST
NEB. ACTIVITY WOULD SEEMINGLY PRESS EASTWARD ACROSS THE CWA OVERNIGHT
PER CORFIDI VECTORS. PLENTIFUL LOW TO MID LEVEL FRONTOGENESIS AND
IMPRESSIVE COUPLED UPPER JET STRUCTURE OVERSPREADING THE CENTRAL
PLAINS THURSDAY NIGHT WILL ADD INTO THE MIX AS WELL.

WITH SIMILAR SET-UP IN PLACE INTO FRI/SAT...WILL REINTRODUCE MAINLY
NIGHTTIME TSRA CHANCES.

IN THE OUTER PORTIONS OF THE FORECAST...LATEST EUROPEAN AND 00Z GFS
INDICATE LITTLE CHANGE IN BROAD SCALE PATTERN THROUGH THE WEEKEND...
HOWEVER THERE SOME HINTS OF WESTERN NORTH AMERICA TROUGH DEVELOPMENT
AND CORRESPONDING FLOW AMPLIFICATION BY THE EARLY TO MIDDLE PART OF
NEXT WEEK. OPERATIONAL GFS POSITIONING OF UPPER TROUGH OVER THE
NORTHERN ROCKIES BY LATE WEEKEND RATHER DEBATABLE GIVEN DEGREE OF
VARIABILITY AMONGST GFS ENSEMBLE MEMBERS. ALTHOUGH PRECIPITATION
POSSIBLE SOMETIME IN LATE WEEKEND/EARLY NEXT WEEK TIME FRAME...
GENERAL DRY FORECAST WILL BE MAINTAINED ATTM UNTIL DETAILS BETTER
AVAIL THEMSELVES. STATUS QUO FOR OUTER PERIOD TEMPS.

.GID...NONE

GUYER

KSZ005>007-017>019-NEZ039>041-046>049-060>064-072>077-082>087-251200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HASTINGS NE
515 PM CDT WED JUL 24 2002

...SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING ACROSS PARTS OF
SOUTH CENTRAL NEBRASKA...

AREAS GENERALLY NORTH AND EAST OF A LINE FROM ELWOOD TO SUPERIOR ARE
AT A RISK FOR SEVERE THUNDERSTORMS AFTER 600 PM. THE PRIMARY HAZARD
WILL BE DAMAGING WINDS TO 70 MPH...WITH ISOLATED LARGE HAIL UP TO AN
INCH IN DIAMETER POSSIBLE. IN ADDITION...AN ISOLATED TORNADO CANNOT
BE RULED OUT...PRIMARILY NORTH OF GRAND ISLAND.

SCATTERED THUNDERSTORMS FROM AROUND ONEILL SOUTHWEST TO BURWELL
WILL INCREASE IN COVERAGE AND INTENSITY AS THEY MOVE SOUTHEAST INTO
THE REGION. DURING THE EVENING...THUNDERSTORMS MAY DEVELOP INTO A
BOW ECHO...GIVING A GREATER THREAT FOR WIDESPREAD DAMAGING WINDS...
ESPECIALLY NORTH AND EAST OF HIGHWAY 281 AND I-80.

SPOTTER GROUPS...EMERGENCY MANAGEMENT AND OTHER INTERESTED PARTIES
SHOULD MONITOR NOAA WEATHER RADIO OR THEIR LOCAL MEDIA FOR LATER
UPDATED FORECASTS AND STATEMENTS.

GURNEY