Severe Thunderstorm Warning 198, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
255 PM CDT TUE AUG 10 1999

WEAK SHORTWAVE AND DIFFLUENT UPPER LEVEL FLOW PRODUCED CLOUDS AND
SHOWERS FROM NORTHEAST CO INTO SOUTHERN PANHANDLE THIS MORNING AND AREA HAS
INTENSIFIED INTO SCATTERED TSRA INTO FAR SW CWFA EARLY THIS AFTERNOON.
STRONGER SHORTWAVE EVIDENT ON WV IMAGERY AND LIGHTNING DATA FURTHER
UPSTREAM MOVING OUT OF NEW MEXICO INTO COLORADO. THIS FEATURE SHOULD
COMBINE WITH INCREASING LOW LEVEL JET TO PRODUCE WIDESPREAD
THUNDERSTORMS ACROSS SOUTHWEST AND WEST CENTRAL NEBRASKA TONIGHT.

AVN AND NGM HAVE BETTER HANDLE ON THESE SHORTWAVES COMPARED TO ETA
LOOKING AT SATELLITE DATA AT 18Z. ALL MODELS CONTINUE TO HAVE
SHORTWAVES IN SW FLOW ALOFT EJECTING N-NE INTO MOISTURE PLUME THAT
EXTENDS NWD FROM OLD MEXICO INTO NORTHERN CO. MAIN H5 TROUGH OVER CA
GRADUALLY WEAKENS AND MOVES NE THROUGH NEB ON THURSDAY. ETA IS
FASTEST WITH PROGRESSION OF THIS FEATURE...BUT ALSO WEAKEST. AT
SURFACE...ETA ALSO IS FASTER WITH ASSOCIATED LOW ACROSS S DAKOTA
INTO MN BY THURSDAY AM...WHILE NGM/ETA HOLD IT BACK IN EASTERN SOUTH
DAKOTA. WILL GENERALLY FOLLOW BLEND OF AVN/NGM...LEANING TOWARD
HIGHER FAN POPS FOR THUNDERSTORM CHANCES TONIGHT THROUGH WEDNESDAY
NIGHT.

WILL HAVE TO HAVE SCATTERED WORDING FOR ONGOING CONVECTION AT
ISSUANCE IN SW AND FAR W ZONES...OTHERWISE...PLANNED ON LIKELY POPS
FOR S HALF TONIGHT WHEN BEST MID LEVEL Q-VECTOR CONVERGENCE AND 850
MB MOISTURE FLUX CONVERGENCE MOVES OVER REGION. MOS LOW TEMPERATURES
LOOK ACCEPTABLE. ON WEDNESDAY...BEST INSTABILITY SHIFTS MAINLY EAST
AND S OF FORECAST AREA...BUT FORCING AHEAD OF MAIN SHORTWAVE WILL BE
ENOUGH TO WARRANT ISOLATED TO LOW SCATTERED POPS. TEMPERATURES WILL
BE SIMILAR TO TODAY AND WILL STAY CLOSE TO GUIDANCE. WILL INCLUDE
LOW POPS IN NORTH FOR EARLY THURSDAY AS SHORTWAVE MOVES THROUGH
SD...BUT KEEP DRY FORECAST FURTHER SOUTH. SHOULD BE SLIGHTLY COOLER
TEMPS WITH WEAK CAA BEHIND SURFACE TROUGH AND GUIDANCE VALUES ABOUT
5 DEG BELOW WEDNESDAY ACCEPTABLE.

IN EXTENDED...FLAT UPPER LEVEL RIDGE REBOUNDS FOR FRIDAY AND
SATURDAY. FLOW BECOMES FASTER AND MORE ZONAL BY SUNDAY WITH LEE
TROUGHING POSSIBLY PRODUCING SOME PCPN...BUT BULK OF UPPER LEVEL
ENERGY SHOULD STAY TO NORTH AND WILL LEAVE OUT MENTION OF PCPN FOR
NOW.

.LBF...NONE

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