Severe Thunderstorm Warning 168, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
319 PM CDT WED JUN 24 2009

.DISCUSSION...

SURFACE ANALYSYS AT 19Z SHOWED THE WARM FRONT AROSS CENTRAL SD
WITH A COLD FRONT EXTENDING BACK INTO SOUTHWEST SD. VISIBLE
SATELLITE IMAGERY SHOWS CU FORMING ALONG THESE BOUNDARIES. 18Z
SOUNDINGS FROM KLBF AND KUNR SHOW A CONVECTIVE TEMP OF 93/94
TODAY. WITH CONTINUED SOLAR HEATING OVER NEXT FEW HOURS AND GOOD
CONVERGENCE ACROSS THE NORTHWEST SECTIONS OF THE FORECAST AREA...SHOULD
BE ABLE TO GET THUNDERSTORM INITIATION BY 23Z. SBCIN CONTINUES TO
DIMINISH AS MUCAPE VALUES HAVE INCREASE TO AROUND 2000 J/KG.
EXPECT SOME SUPERCELLS TO DEVELOP AS SURFACE VORTICITY AND EHI
VALUES INCREASE. IF SUPERCELLS DEVELOP...STORM MOTION SHOULD BE TO
THE SOUTHEAST WHICH WOULD TAKE IT INTO BETTER MOISTURE. THE MAIN
WEATHER THREAT WITH THE STORMS IS STRONG WIND GUSTS...BUT AN
ISOLATED TORNADO IS NOT RULED OUT.

SOUTHEAST WINDS THURSDAY CONTINUE TO KEEP THE LOW LEVEL MOISTURE
OVER THE AREA. UPPER LEVEL RIDGE AXIS SHIFTS EASTWARD ALLOWING
SEVERAL SHORTWAVES TO PUSH INTO SOUTHWEST NEBRASKA THURSDAY
AFTERNOON. MLCAPE VALUES INCREASE TO >3000 J/KG OVER THE CENTRAL
SANDHILLS BY LATE AFTERNOON AND INCREASING IN COVERAGE THROUGH THE
EARLY EVENING. WILL LIKELY SEE ANOTHER ROUND OF SVR WX AS WARM AIR
ADVECTION INCREASES AND GFS/NAM ARE IN GOOD AGREEMENT BRINGING AN
AREA OF LOW PRESSURE AND SCATTERED SHOWERS AND THUNDERSTORMS OVER
THE AREA FRIDAY. THE GFS IS MUCH QUICKER MOVING THIS TROUGH
THROUGH AND BRINGING IN DRIER NORTHWEST FLOW THAN THE NAM. AS
WINDS SWITCH AROUND TO THE DRIER NORTH-NORTHWEST DOWNSLOPE
FLOW...THINK SHOWER ACTIVITY WILL DIMINISH QUICKLY.

UPPER LEVEL RIDGE AXIS AMPLIFIES OVER THE ROCKY MOUNTAINS WITH
NORTHWEST FLOW DOMINANT ACROSS THE NORTHERN PLAINS. GFS/ECMWF
DEVELOP A VERY INTENSE LOW PRESSURE OVER THE GREAT LAKES REGION
EARLY IN THE WEEK WITH THE LBF FORECAST AREA BETWEEN THE NORTHERN
AND SOUTHERN SYSTEMS. THEREFORE WILL KEEP THE FORECAST DRY UNTIL
TUE NIGHT AS GULF MOISTURE CREEPS BACK INTO THE HIGH PLAINS.

&&

.AVIATION...

STRONG TO SEVERE CONVECTION WILL BE POSSIBLE ACROSS PORTIONS OF
WESTERN AND NORTH CENTRAL NEBRASKA THIS EVENING. THE BEST CHANCES
LOOK TO BE EAST OF THE KVTN/KLBF TAF SITES WITH ISOLATED TO WIDELY
SCATTERED CHANCES KEEPING TSRA OUT OF THE PRIMARY CONDITIONS.
HOWEVER AIRCRAFT WILL NEED TO BE COGNIZANT OF ANY THUNDERSTORM IN
THE VCNTY OF TAF SITES AS HAIL AND VERY GUSTY WINDS WILL BE POSSIBLE
WITH THESE STORMS. HEAVY RAIN IS ALSO A THREAT WHICH WOULD MOST
LIKELY LOWER VSBY CRITERIA TO MVFR/IFR IN THE STRONGEST STORMS.
OUTSIDE OF CONVECTION VFR CONDITIONS LOOK TO PREVAIL.

&&

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

DDB/13

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
329 PM CDT WED JUN 24 2009

NEZ004>010-022>029-035>038-056>059-069>071-094-252030-
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-
329 PM CDT WED JUN 24 2009 /229 PM MDT WED JUN 24 2009/

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

.DAY ONE...TONIGHT.

NUMEROUS SURFACE BOUNDARIES LAYING ACROSS WESTERN AND NORTH
CENTRAL NEBRASKA COULD AGAIN BE THE FOCUS FOR STRONG TO SEVERE
STORMS THIS EVENING. HOWEVER THE AREA MOST LIKELY FOR SEVERE
THUNDERSTORM DEVELOPMENT LOOKS TO BE NORTH OF A FRONTAL BOUNDARY
EXTENDING ACROSS NORTH CENTRAL NEBRASKA TO A LOW IN SOUTHWEST
SOUTH DAKOTA. THIS WOULD PUT THE GREATEST RISK FOR LARGE HAIL AND
DAMAGING WINDS AND POSSIBLY AN ISOLATED TORNADO ALONG AND EAST OF
A VALENTINE THROUGH BROKEN BOW LINE WHERE SCATTERED THUNDERSTORMS
WILL BE POSSIBLE. OUTSIDE THIS AREA THUNDERSTORM DEVELOPMENT SHOULD BE
MORE ISOLATED IN NATURE.

HEAVY RAINFALL WILL BE A POSSIBILITY WITH ANY STORM THAT DEVELOPS
THIS EVENING AS WELL. AREAS THAT RECEIVED HEAVY RAINFALL ON
TUESDAY NIGHT MAY BE MORE SUSCEPTIBLE TO FLASH FLOODING...STAY
TUNED TO LOCAL STATEMENTS AND WARNINGS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

MOISTURE AND WEAK DISTURBANCES ROTATING AROUND AN UPPER LEVEL
HIGH PRESSURE RIDGE LOCATED OVER THE TEXAS PANHANDLE MAY BRING
THE CHANCE FOR THUNDERSTORMS AGAIN THURSDAY AFTERNOON AND THURSDAY
NIGHT.

A COLD FRONT IS FORECAST TO APPROACH THE OUTLOOK AREA
FRIDAY..THEN SWEEP ACROSS OVERNIGHT. THIS WILL BRING AN INCREASED
CHANCE FOR THUNDERSTORMS FRIDAY AFTERNOON AND FRIDAY NIGHT...SOME
WHICH MAY BECOME SEVERE. LITTLE OR NO THUNDERSTORM ACTIVITY IS
EXPECTED SATURDAY AND SUNDAY. THEN...AN ACTIVE WEATHER PATTERN IS
EXPECTED TO RETURN MONDAY AND TUESDAY AS THE UPPER RIDGE CENTER
MIGRATES WEST INTO THE DESERT SOUTHWEST...AND NORTHWEST FLOW
ACROSS THE CENTRAL PLAINS WILL ENHANCE THE CHANCES FOR AFTERNOON
AND NIGHTTIME THUNDERSTORMS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND TONIGHT
ACROSS WESTERN AND NORTH CENTRAL NEBRASKA.

&&

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

13