Severe Thunderstorm Warning 153, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
245 PM CDT FRI JUL 2 1999

...FORECAST CHALLENGES ARE THUNDERSTORM CHANCES TONIGHT THEN
TEMPERATURES...

SURFACE WARM FRONT HAS LIFTED NORTH THROUGH MOST OF CWFA PUSHING
DEWPOINTS INTO LOWER TO MID 70S SE OF AXIS FROM VTN TO IML. WARM
FRONT EXTENDED SW TO LOW IN FAR SE WY. CI FROM CONVECTION OVER MTNS
HAS KEPT TEMPERATURES A BIT COOLER THAN EXPECTED SO FAR. VERY
UNSTABLE BUT CAPPED ATMOSPHERE IS OVER AREA FROM MCK TO VTN.
FORECAST PROBLEM IS WHERE CONVECTION WILL DEVELOP TONIGHT. NEAREST
UPSTREAM TSRA ACTIVITY AT 19Z WAS FROM CENTRAL CO TO SW KS
ASSOCIATED WITH WEAK SHORTWAVE MOVING OUT OF NEW MEXICO. WITHOUT
STRONG DYNAMICS...WILL LEAVE IN 20 PERCENT POPS FOR OVERNIGHT
THUNDERSTORMS ACROSS FORECAST AREA...EXCEPT IN THE NE. IN ONL TO ANW
GROUP THE PROXIMITY TO THE WARM FRONT AND UPSTREAM SURFACE DEWPOINTS
IN MID 70S WILL WARRANT KEEPING POPS A BIT HIGHER AT 30 PERCENT.
THIS AREA WILL ALSO NEED TO BE WATCHED FOR POTENTIAL HEAVY RAINFALL
AS FLASH FLOOD GUIDANCE VALUES THERE ARE LOW DUE TO RECENT RAINFALL.

ETA HAD BEST RUN TO RUN MODEL CONSISTENCY AND WAS BETTER THAN NGM
WITH SURFACE DEWPOINTS. IT ALSO HAD GOOD HANDLE ON VORT MAX AT 18Z
MOVING OUT OF SW AND THUS MODEL OF CHOICE. NOT A LOT OF DIFFERENCE
BETWEEN MODELS IN HANDLING OF MAJOR FEATURES.

WENT CLOSER TO WARMER FAN TEMPERATURES FOR HIGHS SAT AND SUNDAY WITH
OVERNIGHT LOWS CLOSE TO GUIDANCE. EXPECT CAP TO REMAIN STRONG ENOUGH
TO LEAVE OUT MENTION OF TSRA SATURDAY AND WILL KEEP FORECAST DRY AND
HOT WITH BREEZY CONDITIONS MENTIONED IN MOST ZONES. HOT AND DRY
TREND WILL PERSIST SUNDAY WITH SURFACE TROUGH HANGING TOUGH OVER
WESTERN NE. IN EXTENDED...93P GUIDANCE NOW HAS HIGHS ONLY IN LOWER 80S
FOR MONDAY WITH MRF SHOWING DRY COLD FRONT TO PUSH INTO FORECAST
AREA AND WILL CUT HIGHS BACK SOME FOR MONDAY AND ADD CHANCE OF
THUNDERSTORMS FOR WEDNESDAY WITH SHORTWAVE MOVING OVER RIDGE THROUGH
AREA.

.LBF...NONE.
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