Severe Thunderstorm Warning 17, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
330 AM CDT SAT MAY 3 2003

FCST CHALLENGE TO BE PCPN CHANCES THROUGH WEEKEND.

H5 U/A ANALYSIS TONIGHT SHOWING ZONAL FLOW OVER PLAINS WITH
TEMPORARY S/W RIDGE OVER THE WESTERN HIGH PLAINS...WITH TROF OFF
WEST COAST BEGINNING TO MOVE ONSHORE WITH BEST HGHT FALLS OVER
CENTRAL CA/NV. THIS AND STRONG 130KT JET NOW ROUNDING TROF INTO AND
MOVING INTO DESERT SW. BEST MOISTURE STILL IN SOUTHERN PLAINS BUT
AREA PROFILER BEGINNING TO INCREASE AND SHOULD PULL MUCH OF THIS
INTO CENTRAL PLAINS FOR CONVECTION TOMORROW. SFC DOMINATED BY HIGH
OVER WESTERN GREAT LAKE...RIDGING INTO MO VALLEY. EALIER CONVECTION
DYING OUT AS IT PULLS AWAY FROM THETA E RIDGE OVER PANHANDLE.

UPPER FLOW WILL TRANSITION TO THE SW AS WESTERN TROF CONTINUES TO
MOVE INTO DESERT SW WITH RIDGE BEING FORCED INTO MIDWEST. THIS WILL
ALSO INCREASE WAA OVER REGION ESPECIALLY WITH MID LEVEL WINDS
INCREASING. SOUTHERLY LOW LVL FLOW WILL CONTINUE TO DRAW MOISTURE UP
INTO THE AREA...WITH LOW PRESSURE DEEPENING ACROSS FRONT RANGE AND
INCREASING GRADIENT WITH HIGH OVER GREAT LAKES...WITH THETA-E RIDGE
STRENGTHENING ACROSS WESTERN CWA. THIS IS WHERE BEST INSTABILITY IN
AFTERNOON IS WITH SB CAPES OVER 1000...0-6KM SHEAR 50+ KTS...AND
LIS -6 TO -8. BEST S/W ENERGY BACK IN 4 CORNERS AREA BUT WILL NOT
PULL POPS WITH DEGREE OF INSTABILITY. BOTH ETA/ETA-KF SHOW BEST
POTENTIAL IN THE WEST IN AFTERNOON...SO 40 WEST 30 EAST.

CHANCES FOR CONVECTION/PCPN INCREASE SAT NITE AS BETTER UPPER
SUPPORT ARRIVES WITH MAIN ENERGY EJECTING OUT OF ROCKIES AND MAIN
UPPER TROF MOVES INTO ROCKIES WITH FAVORABLE LF QUAD OF JET ALSO
APPROACHING. SFC LOW/TROF PUSHING OUT OF PANHANDLE...WILL DIRECT
THETAE RIDGE INTO CENTRAL CWA. CONVECTION LOOKS TO INCREASE IN THIS
AREA...AHEAD OF SFC BNDRY/DRY LINE THEN SHIFTS TO E/NE CWA LATE AS
SFC LOW MOVES INTO SC NE AND STRENGTHENING LOW LVL JET WILL ENHANCE
ELEVATED TSRA.

SUN BEST PCPN CHANCES STAY IN NORTHERN CWA ESPECIALLY NE CWA AS SFC
LOW LIFT ACROSS THIS REGION AHEAD OF MAIN H5 TROF AXIS AND ASSOC SW
WITH STRONG QVECT CONVERGENCE. ATMOS STILL RELATIVE UNSTABLE WITH
NEG LIS MOST AREAS WILL KEEP MENTION OF T IN FCST ESPECIALLY WITH
CORE OF UPPER LOW OVER CWA. SUBSIDENCE BEGINS TO SPREAD FROM S TO N
ACROSS CWA AS UPPER LOW ROTATES NORTHEAST. CURRENT FCST GOOD BLEND
WITH SURROUNDING OFFICES SO NO CHANGES PLANNED.

ONLY MINOR TWEAKS TO REAMINDER OF FCST.

.LBF...NONE.

DP

NEZ004>010-022>029-035>038-056>059-069>071-094-022045-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1142 AM CDT FRI MAY 2 2003

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

.DAY ONE...TODAY

A SLIGHT CHANCE OF SEVERE THUNDERSTORMS WILL EXIST TODAY INTO EARLY
THIS EVENING WEST OF A LINE EXTENDING FROM VALENTINE IN EASTERN
CHERRY COUNTY TO HAYES CENTER IN HAYES COUNTY. A WEAK WARM FRONT
ACROSS COLORADO WILL LIFT SLOWLY NORTHEAST INTO WESTERN NEBRASKA BY
THIS AFTERNOON.  MOISTURE WILL REMAIN LIMITED BUT WITH COLD AIR
ALOFT AND SUNSHINE EXPECTED THIS AFTERNOON THE ATMOSPHERE WILL
BECOME WEAKLY UNSTABLE.  THIS ALONG WITH A DISTURBANCE ALOFT MOVING
OUT OF THE ROCKY MOUNTAINS MAY PRODUCE ISOLATED THUNDERSTORMS.  A
FEW OF THESE STORMS MAY BRIEFLY BECOME SEVERE WITH THE PRIMARY
THREAT BEING LARGE HAIL.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE THREAT FOR SEVERE THUNDERSTORM DEVELOPMENT WILL INCREASE ON
SATURDAY. AN AREA OF LOW PRESSURE WILL EXTEND SOUTH ON THE HIGH
PLAINS EARLY WITH A SURFACE LOW PRESSURE CENTER TO FORM OVER
NORTHEAST COLORADO DURING THE AFTERNOON. THE ATMOSPHERE IS EXPECTED
TO BECOME INCREASINGLY UNSTABLE DURING THE AFTERNOON WITH A SLIGHT
RISK OF SEVERE THUNDERSTORMS SATURDAY AFTERNOON...AND NIGHT
THROUGHOUT THE OUTLOOK AREA. THE SURFACE LOW PRESSURE SYSTEM WILL
DEEPEN OVERNIGHT WITH MOVE NORTHEAST ACROSS NEBRASKA WITH A SLIGHT
RISK OF SEVERE THUNDERSTORM DEVELOPMENT ON SUNDAY AS A STRONG UPPER
LEVEL DISTURBANCE MOVES NORTHEAST. LATER UPDATES WILL REFINE THE
PATH AND POTENTIAL FOR SEVERE THUNDERSTORM DEVELOPMENT OVER THE
WEEKEND.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY WEST OF A LINE EXTENDING FROM
VALENTINE IN CHERRY COUNTY TO HAYES CENTER IN HAYES COUNTY.

AWJ