Severe Thunderstorm Warning 165, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
300 AM CDT WED JUL 11 2001

...THE TIMING OF THE SHORT WAVES COMING ACROSS THE RIDGE IS THE
FORECAST PROBLEM THIS MORNING WITH THEIR EFFECTS ON THE CONVECTION...

...05Z-07Z SYNOPSIS...
    MOISTURE AND INSTABILITY IS AVAILABLE FOR CONVECTION. SURFACE
DEWPOINTS AT OR ABOVE 65F COVER ALL OF NEBRASKA BUT THE NORTH CENTRAL
AND EXTREME SOUTHWEST PARTS AND THE WESTERN PANHANDLE. GOES DERIVED
TPW'S OF 35-40CM  AND LI'S ALSO DOMINATE CENTRAL AND WESTERN
NEBRASKA. SURFACE ANALYSIS INDICATED AN INSTABILITY LINE/TROUGH
THROUGH THE WESTERN NEBRASKA PANHANDLE AND ANOTHER COMING INTO
EXTREME SOUTHEAST NEBRASKA. THE SURFACE FRONT WAS STRUNG OUT ALONG
THE EASTERN FACE OF THE ROCKIES TO A LOW IN EXTREME SOUTHWEST KANSAS.
THE 6.7U SATELLITE IMAGERY LOOP SHOWED A PROMINENT VORTEX CENTERED
UNDER THE COLD CLOUD SHIELD IN SOUTHEAST WYOMING, NORTHEAST
COLORADO, OR THE SOUTHWEST NEBRASKA PANHANDLE. THE IR-IMAGERY
INDICATED THE COLDEST TOPS IN THE NEBRASKA PANHANDLE ON THE LINEAR
MCS. ON THE KLNX WSR-88D REFLECTIVITY...A STRONG CONVECTIVE LINE
EXTENDED FROM NEAR SCOTTSBLUFF TO JUST NORTHWEST OF GOODLAND.
...MODELS...
    THE ETA IS THE MODEL OF CHOICE FOR THE EARLY PERIODS. COMPARING
THE MSL SOLUTIONS...THE AVN IS FASTER WITH THE PROGRESS OF THE
SURFACE LOW...BUT IT HAS TRENDED TOWARD THE ETA WITH THE NEWEST RUN.
THERE IS VERY LITTLE DIFFERENCE BETWEEN THE TWO IN THE POSITION AND
STRENGTH OF THE UPPER HIGH OVER THE SOUTHERN PLAINS.

...FORECAST...
    THIS EVENING AT 00Z...850-700MB WARM ADVECTION IS PRESENT OVER
NEARLY ALL OF NEBRASKA UNTIL 06Z WHEN IT BECOMES QUITE STRONG AND
CONCENTRATES ALONG THE FRONT IN NORTHERN KANSAS. AT THAT TIME THE
MID-LEVEL (750-700MB) 2D-FRONTOGENESIS IS ALONG THE NEBRASKA-KANSAS
STATE LINE. ALSO...THE 850-700MB LAYER MEAN RH WILL BE 60 PERCENT
OR HIGHER FROM NORTHERN KANSAS NORTH INTO SOUTH DAKOTA. THE WEAKEST
CONVECTIVE INHIBITION IS ALSO ALONG AND NORTH OF THE KANSAS-NEBRASKA
BORDER...THOUGH THE HIGHEST POSITIVE ENERGY IS ACTUALLY SOUTH OF
THERE. LOW-LEVEL WIND PROGS SHOW THE JET TURNING TOWARD THE WEST
SOMEWHERE JUST SOUTH OF THE I70 CORRIDOR. THIS SITUATION THEN HOLDS
INTO THURSDAY NIGHT. THE STRONGEST COUPLING OF LOW-LEVEL CONVERGENCE
AND UPPER LEVEL DIVERGENCE WOULD SUPPORT THE DEVELOPMENT OF A MCS IN
NORTHEAST COLORADO TRACKING ALONG THE NEBRASKA-KANSAS BORDER AND
FINALLY INTO EASTERN KANSAS. THE TRACK THURSDAY NIGHT IS SIMILAR
INITIALLY...BUT IT THEN SHIFTS INTO EAST CENTRAL COLORADO AND
TRACKS THROUGH KANSAS. THAT MATCHES THE PRECIPITATION MAXIMA
INDICATED BY THE ETA QPF. IN OTHER AREAS...THERE SEEMS TO BE ENOUGH
OF A LOWER CONVERGENCE...UPPER DIVERGENCE COUPLET TO SUPPORT FAIRLY
HIGH PROBABILITIES IN WESTERN NEBRASKA TONIGHT AND AGAIN THURSDAY
NIGHT...THOUGH IT APPEARS THAT OTHER FORCING ELEMENTS ARE MISSING.
    DEPENDING ON THE AMOUNT OF RAINFAWLL THE SOUTHWEST GETS THIS
MORNING...A FFA MAY BE NEEDED LATER TODAY. FOR NOW...I WILL NOT GO
WITH IT.

.LBF...NONE.

SPRINGER