Tornado and Hail in Nebraska, July 17, 2010

AREA FORECAST DISCUSSION...CORRECTED AVIATION AND EXTENDED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
345 PM CDT SAT JUL 17 2010

.SYNOPSIS...
    AT 19Z...LOW PRESSURE WAS CENTERED OVER NORTH CENTRAL SOUTH
DAKOTA WITH A DRY LINE EXTENDING THROUGH WESTERN SOUTH DAKOTA...
WESTERN NEBRASKA AND EASTERN COLORADO. THERE WAS ALSO A COOL FRONT
STRETCHING THROUGH SOUTHWEST SOUTH DAKOTA AND ACROSS NORTHERN
WYOMING. SURFACE DEWPOINTS IN THE 70S EXTENDED AS FAR WEST AND NORTH
AS ONEILL...BROKEN BOW AND NORTH PLATTE. IN THE NEBRASKA
PANHANDLE...UPPER 30S TO MID 40S WERE THE RULE. SATELLITE DERIVED
PRECIPITABLE WATER SHOWED A PLUME OF 20-25MM EXTENDING INTO NORTH
CENTRAL NEBRASKA AND EASTERN SOUTH DAKOTA. THE SURFACE LAPS DATA
SHOWED SURFACE BASED CONVECTIVE POTENTIAL ENERGY EXCEEDING 5000J/KG
EXTENDING TO ABOUT NORTH PLATTE AND GREATER THAN 3000J/KG EAST OF A
VTN-TIF-OGA-IML LINE. THE MOST FAVORABLE 0-6KM BULK SHEAR WAS IN THE
NORTHERN PART OF THE AREA WHERE IT WAS 40-45KT.
&&

.SHORT/MEDIUM RANGE...TONIGHT THROUGH TUESDAY NIGHT.
    THE RUC AND THE 12Z RUN OF THE NAM ARE VERY CLOSE WITH THE
TIMING OF THE FRONTAL PASSAGE THIS EVENING 00-06Z THROUGH ONEILL...
BROKEN BOW AND NORTH PLATTE. IN ADDITION...THE 12Z GEM SUPPORTS THE
NAM AND RUC. HOWEVER...AT THIS TIME...THE RUC SEEMS TO BE THE ONLY
ONE WITH A HANDLE ON THE SURFACE BASED MOISTURE...THOUGH THE
PRECIPITABLE WATER FIELD LENDS MORE SUPPORT TO THE NAM SOLUTION FOR
THE LOCATION OF THE HIGH CONVECTIVE POTENTIAL ENERGY. THE RUC
APPEARS TO BE BIASED BY THE HIGH SURFACE DEWPOINTS IN THE RELATIVELY
UNMIXED BOUNDARY LAYER. ANYWAY...THE BEST CHANCES FOR CONVECTION
APPEAR TO BE IN CENTRAL AND NORTH CENTRAL NEBRASKA...THOUGH THE
CONVECTIVE PARAMETERS INDICATE THAT CONVECTION MAY EXTEND WEST TO
VALENTINE AND NORTH PLATTE. SOME SEVERE POTENTIAL EXISTS...
ESPECIALLY IN THE HIGHER BULK SHEAR AREAS OVER CENTRAL AND NORTH
CENTRAL NEBRASKA...THE AREA EAST OF VALENTINE...THEDFORD AND NORTH
OF I-80. SINCE THE COVERAGE WILL BE LIMITED AND THE UNCERTAINTY IS
HIGH...WE WILL NOT MENTION SEVERE FOR NOW.
    AFTER THE FRONT PASSES TONIGHT...IT STALLS OVER KANSAS. IT THEN
WORKS ITS WAY NORTHWARD VERY SLOWLY...STALLING ONCE AGAIN NEAR THE
KANSAS-NEBRASKA BORDER. THIS SETS THINGS UP AGAIN FOR AFTERNOON AND
EVENING THUNDERSTORM DEVELOPMENT MONDAY AND TUESDAY. THOUGH IT IS
APPROPRIATE TO MENTION THUNDERSTORMS EACH OF THOSE DAYS...THE
UNCERTAINTY WOULD DICTATE KEEPING THE PROBABILITY FAIRLY
LOW.

.EXTENDED...WEDNESDAY THROUGH SATURDAY.
    PATTERN OVERALL WILL REMAIN UNCHANGED...AS UPPER LEVEL HIGH
PRESSURE REMAINS ANCHORED FROM THE SOUTHERN PLAINS INTO THE
SOUTHEAST CONUS. OUR AREA WILL REMAIN IN WESTERLY FLOW ALOFT TO THE
NORTH OF THE UPPER HIGH...AND WEAK SHORTWAVES WITHIN THE FLOW WILL
CONTINUE TO INTERACT WITH WITH A WARM...MOIST...AND UNSTABLE AIRMASS
TO BRING AT LEAST ISOLATED TSTMS DAILY TO THE REGION. TEMPERATURES
SHOULD REMAIN IN CHECK AS A FRONT OSCILLATES BACK AND FORTH...NO
REAL HOT WEATHER EXPECTED WITH THE FRONT IN THE AREA...BUT IT WILL
CONTINUE TO BE WARM AND HUMID.
&&

.AVIATION...
    WEAK COLD FRONT EXPECTED TO BE THE FOCUS FOR ISOLATED TSTMS
ACROSS NORTH CENTRAL AND WESTERN NEB LATE THIS AFTERNOON AND
EVENING. COVERAGE IS EXPECTED TO BE SUCH THAT TSTMS ARE NOT
CURRENTLY INCLUDED IN THE KVTN TAF...BUT THE THREAT IS NOT NON-ZERO.
SAME GOES FOR AREAS FURTHER SOUTH INCLUDING THE KLBF TAF SITE...AS
ISOLATED STORMS SHOULD SPREAD SOUTH AFTER 00Z AS THE WEAK FRONT
CONTINUES TO PUSH SOUTHEAST. WINDS WILL BE SOUTH AT 5 TO 15 KTS
AHEAD OF THE FRONT...WITH A SWITCH TO THE NORTHEAST AT 5 TO 15 KTS
BEHIND THE FRONT. OTHER THAN THE ISOLATED TSTMS...NO RESTRICTIONS TO
CEILINGS OR VISIBILITY EXPECTED.
&&

.LBF WATCHES/WARNINGS/ADVISORIES...NONE.
&&

SHORT/MEDIUM RANGE...SPRINGER
AVIATION/EXTENDED...TAYLOR

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
603 PM CDT SAT JUL 17 2010

NEZ004>010-022>029-035>038-056>059-069>071-094-182315-
SHERIDAN-EASTERN CHERRY-KEYA PAHA-BOYD-BROWN-ROCK-HOLT-GARDEN-
GRANT-HOOKER-THOMAS-BLAINE-LOUP-GARFIELD-WHEELER-ARTHUR-MCPHERSON-
LOGAN-CUSTER-DEUEL-KEITH-PERKINS-LINCOLN-CHASE-HAYES-FRONTIER-
WESTERN CHERRY-
603 PM CDT SAT JUL 17 2010 /503 PM MDT SAT JUL 17 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WESTERN AND
NORTH CENTRAL NEBRASKA.

.DAY ONE...TONIGHT.

SCATTERED TO ISOLATED THUNDERSTORMS WILL CONTINUE TONIGHT NEAR AND
ALONG A WEAK COLD FRONT. THIS WEAK FRONT IS EXPECTED TO EXIT THE
OUTLOOK AREA SOON AFTER MIDNIGHT. ISOLATED SEVERE STORM WILL BE
POSSIBLE...WITH DAMAGING WIND AND LARGE HAIL THE MAIN THREAT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

THE UPPER AIR PATTERN WILL KEEP WESTERN AND NORTH CENTRAL
NEBRASKA IN A FAST ZONAL FLOW...WITH THUNDERSTORMS POSSIBLE NEARLY
EVERY DAY THROUGH THE COMING WEEK. A WIDESPREAD OUTBREAK OF SEVERE
THUNDERSTORMS IS NOT EXPECTED...BUT ISOLATED SEVERE THUNDERSTORMS
ARE POSSIBLE NEARLY EVERY AFTERNOON AND EVENING OVER WESTERN AND
NORTH CENTRAL NEBRASKA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING.

&&

THIS PRODUCT IS NOW AVAILABLE...ALONG WITH OTHER WEATHER...
HYDROLOGICAL AND CLIMATOLOGICAL INFORMATION...AT
HTTP://WWW.WEATHER.GOV/NORTHPLATTE

KAR