Hail and Damaging Winds in Nebraska, July 20, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
400 AM CDT MON JUL 20 2009

.SYNOPSIS...
500 MB RIDGE CONTINUES OVER THE DESERT SOUTHWEST...HOWEVER TROF
MOVING ACROSS S CENTRAL CANADA HAS FLATTENED THE NORTHERN PART OF
THE RIDGE. AMPLIFIED TROF TO THE EAST...FROM THE GREAT LAKES
NEARLY TO THE GULF COAST. AT THE SURFACE...A LOW IS PUSHING ACROSS
CENTRAL CANADA WITH A TRAILING COLD FRONT ACROSS N DAKOTA AND JUST
PUSHING INTO NORTHERN WY. SEVERAL WEAK SLOWLY EASTWARD MOVING OR
STATIONARY BOUNDARIES ACROSS THE HIGH PLAINS.

&&

.DISCUSSION...
UPPER LEVEL SHORT WAVE PROVIDING THE NEEDED SUPPORT TO THE SURFACE
BOUNDARIES...SEEN IN H2O VAPOR IMAGERY...HELPING TO PRODUCE WIDELY
SCATTERED SHOWERS THIS MORNING ACROSS THE REGION. THESE SHOWERS
WILL CONTINUE IN A SOUTHEAST MOTION...HOWEVER ADDITIONAL DEVELOP
IN THE WAKE IS POSSIBLE. BETTER CHANCE WILL BE LATER THIS
AFTERNOON ALONG AND AHEAD OF COLD FRONT. CAPE VALUES REACHING NEAR
3K J/KG TO GO ALONG WITH STRONGLY SHEER ENVIRONMENT AS WINDS AHEAD
OF THE FRONT VEER FROM SOUTHEAST TO NORTHWEST. SUPERCELLS AND
LARGE HAIL TO BE A THREAT...AS OUTLOOKED IN SPC DY1 WITH HATCHED
AREA FOR HAIL. MAIN QUESTION WILL BE WHERE FRONT IS LOCATED WHEN
ACTIVITY BREAKS OUT...WHICH SHOULD BE EARLY AFTERNOON...IF NOT
SOON. MODELS DIFFER SLIGHTLY SO ONLY HAVE SVR WORDING IN MORE
CONFIDENT SOUTHEASTERN ZONES. WINDS BECOME NE BEHIND THE FRONT
AND PROVIDE A SLIGHT UPSLOPE TO CONTINUE THE THREAT FOR SHOWERS
BEHIND THE FRONT...HOWEVER NOT EXPECTING A SEVERE THREAT.

SURFACE HIGH BUILDS IN FOR TUESDAY AND WILL KEEP THINGS DRY AND
SEASONABLE COOL. HOWEVER BY TUESDAY NIGHT AS THE HIGH SLIDES TO
THE SE...UPSLOPING WILL AGAIN HAVE THE CHANCE TO FIRE SOME SHOWERS
OVER THE HIGHER TERRAIN TO THE WEST...THEN PUSH EAST ONTO THE
PLAINS...AS BEEN THE CASE MANY RECENT NIGHTS. WILL HAVE TO MONITOR
MID LEVEL SHORT WAVES IN NW FLOW...AS THIS WILL LIKELY BE NEEDED TO
PROVIDE ENOUGH CONVERGENCE.

ACTIVE PATTERN IS EXPECTED TO CONTINUE INTO THE WEEKEND...HOWEVER
LATEST RUN OF THE GFS REAMPLIFIES THE RIDGE TO THE WEST...WHICH
MAY DECREASE RAIN CHANCES AND BRING SOME WARMER TEMPS THAN GOING
FORECAST. NEW ECMWF DOES NOT HAVE THIS AMPLIFICATION. OTHERWISE
LIMITED CHANGES MADE BEYOND MIDWEEK.

&&

.AVIATION...
08Z-18Z THIS MORNING...ISOLATED THUNDERSTORMS WILL PRODUCE IFR
CONDITIONS ACROSS NCNTL NEB. STORM MOTION WILL BE EAST AND SOUTHEAST
AT 20 MPH.

18Z-03Z TODAY...A COLD FRONT WILL SETTLE ACROSS SWRN NEB THIS
AFTERNOON. THE FRONT IS EXPECTED TO ACT AS A FOCUS FOR ISOLATED TO
PERHAPS SCATTERED STRONG OR SEVERE THUNDERSTORMS. LARGE HAIL AND
WIND DAMAGE ARE THE MAIN CONCERN. THE FRONT IS EXPECTED TO STRETCH
NORTHEASTWARD ACROSS SWRN NEB THROUGH KBBW AND KONL WHERE
THUNDERSTORMS COULD ALSO FORM. THUS 21Z-03Z IS THE TIME FRAME
WHEREBY ISOLATED TO SCATTERED IFR CONDITIONS COULD DEVELOP ACROSS
THE AFOREMENTIONED AREA. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO
PREVAIL. STORM MOTION CONTINUES AT EAST AND SOUTHEAST AT 20 MPH.

03Z ONWARD...THE FRONT SHOULD BE LOCATED ACROSS NRN KS THROUGH ERN
NEB. VFR CONDITIONS ARE EXPECTED ACROSS WRN AND NCNTL NEB.

&&

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

&&

SHORT TERM/EXTENDED...MASEK
AVIATION...CDC

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1103 AM CDT MON JUL 20 2009

NEZ004>010-022>029-035>038-056>059-069>071-094-211000-
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-
1103 AM CDT MON JUL 20 2009 /1003 AM MDT MON JUL 20 2009/

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING FOR ALL BUT THE EXTREME NORTHWEST. A WEAK COLD FRONT WILL
CONTINUE TO PUSH INTO NORTHWEST NEBRASKA THIS AFTERNOON...WHILE AN
AREA OF LOW PRESSURE EXTENDS SOUTH THROUGH WESTERN NEBRASKA. AMPLE
MOISTURE IS IN PLACE TO FUEL THUNDERSTORM DEVELOPMENT AS SEVERAL
DISTURBANCES CONTINUE TO MOVE SOUTHEAST WITH THE GREATEST
INSTABILITY TO EXIST IN AREAS SOUTHEAST OF A LINE FROM VALENTINE
IN CHERRY COUNTY...TO BIG SPRINGS IN DEUEL COUNTY LATE THIS
AFTERNOON. THE PRIMARY THREATS WILL BE LARGE HAIL AND DAMAGING
WINDS AS CONVECTION CONTINUES TO DEVELOP AS THESE BOUNDARIES PUSH
SOUTHEAST.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

WEDNESDAY THROUGH FRIDAY...HEAT...MOISTURE AND INSTABILITY WILL
RETURN. A STATIONARY FRONT WILL BE LOCATED SOMEWHERE ACROSS THE
CENTRAL PLAINS. THE FRONT AND ANY DISTURBANCE WHICH CROSSES THE
CENTRAL PLAINS COULD BE SUFFICIENT FOR THUNDERSTORM DEVELOPMENT.
WINDS ALOFT WILL CONTINUE TO BE STRONG SUPPORTIVE OF ISOLATED
SEVERE THUNDERSTORMS CAPABLE OF LARGE HAIL OR WIND DAMAGE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND TONIGHT.

&&

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

KECK