Severe Thunderstorm Warning 236, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
244 PM CDT SAT AUG 12 2000

...LOCATION OF LOW TSTM POPS NEXT TWO DAYS WILL BE THE CHALLENGE...

VERY PERSISTENT UPPER PATTERN WITH RIDGING EXTENDING FROM THE
SOUTHWESTERN U.S. INTO THE CENTRAL PLAINS...A CLOSED LOW ALONG THE
EAST COAST AND ZONAL FLOW ALONG THE CANADIAN BORDER. AT THE
SURFACE...A COLD FRONT EXTENDS FROM NORTHERN MN...ACROSS EASTERN
SD...FROM NEAR ONL TO NEAR MCK...AND INTO WESTERN KANSAS.

PREFER ETA SOLUTION IN DEVELOPING CONVECTION ALONG BOUNDARY TONIGHT
AND SUNDAY AFTERNOON AS IT STALLS IN VICINITY OF NE/KS BORDER.
ALREADY EVIDENCE OF THIS OCCURRING IN NORTHEASTERN COLORADO. DESPITE
UNIMPRESSIVE CAPES...THIS MOISTURE IS IN REGION OF BEST MID LEVEL
LAPSE RATES AND LOW LEVEL CONVERGENCE ALONG AND NORTH OF SURFACE
FRONT. OTHER MODELS PUSH FRONT FURTHER SOUTH AND EAST AND KEEP
CONVECTION OUT OF THE CWA.

PER ETA MODEL THE FRONT SHOULD STALL JUST SOUTH OF THE CWA TONIGHT
AS IT BECOMES WELL REMOVED FROM UPPER SUPPORT THAT WILL MOVE INTO
THE NORTHERN GREAT LAKES. WIDELY SCATTERED CONVECTION WILL DEVELOP
IN REGION OF LOW LEVEL CONVERGENCE AND HIGHEST CAPES/LAPSE RATES
ALONG AND NORTH OF FRONT OVER FAR SOUTHERN AND EASTERN PORTIONS
OF CWA. 25 TO 30 KNOT SOUTH/SOUTHWEST WINDS SOUTH OF THE SURFACE
BOUNDARY SUPPORTS THE POTENTIAL FOR STORMS THROUGH THE NIGHT.
SHOULD BE DRY FURTHER NORTH AND WEST OF FRONT.

FRONT WILL BEGIN TO GRADUALLY WASH OUT SUNDAY ALONG THE NE/KS BORDER.
HOWEVER...PER ETA/NGM MOISTURE SHOULD REMAIN POOLED IN THAT GENERAL
AREA. ETA HINTS AT HIGHER CAPES EVOLVING ALONG BOUNDARY AS LOW LEVEL
FLOW VEERS AROUND TO THE SOUTHEAST AND ADVECTS HIGHER DEWPOINTS INTO
THE AREA. STILL SOME EVIDENCE OF LOW LEVEL CONVERGENCE IN SAME
GENERAL AREA SO ANOTHER LOW POP IS WARRANTED OVER THE SOUTHERN PART
OF CWA. ONCE AGAIN...QUIET FURTHER NORTH AWAY FROM THE BOUNDARY.

WILL CONTINUE LOW POP OVER SOUTHERN PART OF CWA INTO SUNDAY NIGHT
FOR REASONS IN ABOVE PARAGRAPH. IN ADDITION THE ETA DEVELOPS A WAVE
AT 00Z MONDAY INTO SWRN NE/NERN CO/NWRN KS WITH AN EASTWARD DRIFT AS
UPPER FLOW FLATTENS AND WESTERLIES INCREASE. YET ANOTHER WAVE
FORECAST TO MOVE ACROSS THE DAKOTAS. THE TAIL END OF WHICH MAY
SUPPORT THE DEVELOPMENT OF CONVECTION ALONG SURFACE LOW EXPECTED TO
BE IN WESTERN SOUTH DAKOTA. ETA/NGM DEVELOP CONVECTION CLOSE ENOUGH
TO THE AREA FOR A LOW POP IN CHERRY/SHERIDAN COUNTIES. SINCE FEATURE
IS EXPECTED TO LIFT EAST/NORTHEAST ALONG WITH BEST INSTABILITY AND
LOW LEVEL SUPPORT...WILL NOT CARRY POPS ANY FURTHER EAST.
AFOREMENTIONED FEATURE WILL DRAG ANOTHER FRONT INTO WESTERN PORTION
OF CWA. LOW LEVELS LIKELY TO REMAIN WELL MIXED EAST OF FRONT AND
WILL GO ABOVE MOS TEMPS SUNDAY NIGHT.

NEXT FRONT EXPECTED TO STALL IN A SIMILAR LOCATION ALONG THE EASTERN
AND SOUTHERN FRINGE OF CWA BY 00Z TUESDAY. HOWEVER...NONE OF THE
MODELS HAVE RESOLVED MOISTURE OF ANY SIGNIFICANCE...SO GOING
FORECAST WILL BE DRY. MAXES SHOULD BE SIMILAR TO TODAY WITH WARMEST
READINGS ALONG AND AHEAD OF FRONT WHERE A WESTERLY COMPONENT TO WIND
IS MAINTAINED. AS A RESULT...HAVE OPTED TO GO ABOVE MOS MAXES FOR
MONDAY.

IN THE EXTENDED...PATTERN TO REMAIN UNCHANGED WITH THE NEXT UPPER
WAVE AND SURFACE FRONT TO MOVE THROUGH ON WEDNESDAY. SHOULD BE DRY
AND WARM BOTH TUESDAY AND THURSDAY IN BETWEEN WAVES WITH FLAT UPPER
RIDGE STILL IN CONTROL.

.LBF...NONE

DJB