Severe Thunderstorm Warning 257, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
222 PM CDT WED AUG 1 2001

FORECAST CHALLENGE WILL BE POPS TONIGHT...

POSITION AND TIMING OF PRECIPITATION MAIN CONCERN TONIGHT AS MAIN
FRONTAL BOUNDARY MOVES SOUTHEAST SLOWLY. BEST FORCING WILL BE NORTH
OF BOUNDARY THROUGH 7 PM WITH H5 WAVES TRANSVERSING NORTHEAST...
BOTH EVIDENT ON MESOETA AND RUC...ACROSS THE PANHANDLE AND
NORTHEAST. SURFACE ANALYSIS AT 18Z SHOWED SURFACE HIGH RIDGING
SOUTHWEST ACROSS THE PANHANDLE WITH COLD FRONT EAST OF YKN...
BURWELL AND IML LINE. SECOND BOUNDARY EVIDENT FURTHER EAST WHICH
EXTENDS SOUTHWEST THROUGH WESTERN KANSAS THEN NORTHWEST ACROSS
CENTRAL COLORADO TO LOW CENTER OVER NORTH CENTRAL WYOMING.
WRAPAROUND MOISTURE AROUND LOW NORTH OF EAR HAS KEPT DEWPOINTS INTO
THE LOW 70S. SATELLITE CURRENTLY SHOWS NARROW BAND OF CLOUDS
EXTENDING NORTHEAST ACROSS THE NORTHERN FORECAST AREA WITH WEAK
RETURNS ON RADAR ACROSS THE PANHANDLE AND EXTREME NORTHEAST FORECAST
AREA.

TIMING ISSUES EXIST IN WAVES AS H5 HIGH CENTER BUILDS WEST...WITH
BLEND OF MODELS USED. GUIDANCE CLOSE WITH NGM MOS WARMEST BUT WILL
TREND CLOSER TO COOLER NUMBERS AS SOUTHEAST FLOW SETS UP THURSDAY AS
FRONT RETURNS NORTH.

BY ZONE ISSUANCE WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL
CONTINUE TO DEVELOP ACROSS CENTRAL SECTIONS AS SERIES OF H5 WAVES
LIFT NORTHEAST. BEST HEATING AND MOISTURE WILL BE FOUND FURTHER
SOUTHEAST WITH POTENTIAL FOR THUNDERSTORM DEVELOPMENT WITH LOW POPS
RETAINED AS SURFACE MOISTURE CONVERGENCE TO INCREASE ALONG
BOUNDARY EXTENDING EAST FROM NEAR GLD TO HLC THEN NORTHEAST WITH
STRONGER WAVE TO LIFT NORTHEAST AFTER 06Z WITH FRONT INDICATED TO
RETURN NORTHWARD INTO SOUTHERN NEBRASKA NEAR THE STATELINE BY
MORNING. BOUNDARY LAYER MOISTURE NOT AS PLENTIFUL IN WESTWARD
RETURN AS SURFACE HIGH BUILDS EAST AND WINDS RETURNS SOUTHEAST
OVER THE NORTHWEST LATE WITH PARTLY CLOUDY SKIES.

THURSDAY SOUTHWEST FLOW ALOFT CONTINUES WITH H5 HIGH CENTERED OVER
NORTHWEST KANSAS. WINDS TURN ON TO THE SOUTHEAST THROUGHOUT AS SEMI
STATIONARY FRONT BACKS TO NEAR THE FOOTHILLS. SERIES OF WAVES
MOVE NORTHEAST ACROSS THE PANHANDLE FOR POSSIBLY ISOLATED SHOWERS
OTHERWISE DRY DAY EAST OF THE PANHANDLE. TEMPERATURES INTO MID 80S
TO NEAR 90.

THEN LITTLE CHANGE OCCURS THURSDAY NIGHT INTO FRIDAY BEYOND LEESIDE
TROUGH EXTENDING SOUTH ALONG THE HIGH PLAINS. WEAK ENERGY EJECTS
NORTHEAST WHICH MAY BRING ISOLATED TO SCATTERED CONVECTION INTO
THE PANHANDLE AND WEST EARLY FRIDAY. THEN AS UPPER HIGH CENTER BUILDS
FURTHER WEST CAP STRENGTHENING AND INHIBITING CONVECTION. SOUTHEAST
WIND FLOW CONTINUES WITH READINGS AROUND 90 ON FRIDAY WITH BETTER
HEATING AND LESS CLOUDS.

LONG RANGE MODELS CLOSER WITH MRF 01/12Z RUN MORE IN LINE WITH THE
EUROPEAN MODEL. THE H5 RIDGE SOUTHWEST AXIS WILL REORIENTATE
SATURDAY LIFTING NORTH AS MAIN HIGH CENTER BUILDS WESTWARD AND
INTO SOUTHERN WYOMING BY MONDAY EVENING. A WEAKNESS IS REFLECTED
SATURDAY NIGHT INTO SUNDAY AS LEESIDE TROUGH MOVES OFF THE HIGH
PLAINS. TRACE AMOUNTS OF QPF GENERATED WITH ANY CONVECTION TO REMAIN
ISOLATED AND SLOW MOVING OFF THE MOUNTAINS IN WEAK STEERING
ENVIRONMENT. THE SURFACE TROUGH WILL EXTEND SOUTHWEST ACROSS CENTRAL
SOUTH DAKOTA MONDAY WITH ZONAL FLOW OVER THE NORTHERN PLAINS MINIMIZE
SOUTHERN PUSH UNTIL TUESDAY AS H5 RIDGE STRENGTHENS. TUESDAY THE
NORTHWEST FLOW BECOMES ESTABLISHED ALOFT WITH THE FRONT TO DRIVE
SOUTHEAST WITH CHANCE OF THUNDERSTORMS MAINLY ACROSS THE NORTH AND
NORTH CENTRAL AS WAVES TRANSIT SOUTHEAST INTO WEDNESDAY. GUIDANCE
NUMBERS HAVE COOLED EXCEPT FOR THE NORTHWEST WHICH IS SUSPECT WITH NO
CHANGES TO TEMPERATURES MADE IN THE LONG TERM.

.LBF...NONE.

KECK

NEZ004>010-022>029-035>038-056>059-069>071-020500-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1104 PM CDT WED AUG 1 2001

...SEVERE THUNDERSTORM WATCH FOR SOUTHWESTERN NEBRASKA HAS BEEN
ALLOWED TO EXPIRE...

SEVERE THUNDERSTORM WATCH NUMBER 649...PREVIOUSLY VALID FOR
SOUTHWESTERN NEBRASKA...HAS BEEN ALLOWED TO EXPIRE. OVERNIGHT...
THUNDERSTORMS WILL CONTINUE TO MOVE INTO PORTIONS OF WESTERN AND
SOUTHWESTERN NEBRASKA AND SHOULD REMAIN BELOW SEVERE LEVELS. GUSTY
WINDS...SMALL HAIL AND HEAVY RAIN WILL BE THE MAIN THREAT FROM THESE
THUNDERSTORMS INTO THE EARLY MORNING HOURS.

CLB