Severe Thunderstorm Warning 111, NWS Cheyenne, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
145 PM MDT WED AUG 6 2003

SHORT TERM...WILL CONTINUE THE FORECAST OF A SCATTERED COVERAGE OF
THUNDERSTORMS THIS EVENING TO THE EAST OF THE LARAMIE RANGE.  MAIN
THREAT WILL CONTINUE TO BE STRONG WIND GUSTS ALONG WITH HAIL AND
HEAVY RAIN IN THE WESTERN NEBRASKA PANHANDLE.  MODELS INDICATE TWO
SHORTWAVE TROUGHS AFFECTING MAINLY WESTERN AND NORTHERN WYOMING THE
REST OF TONIGHT ALONG WITH DIFFLUENT FLOW AT 250 MB.  WILL KEEP SOME
SHOWERS IN THE FORECAST MAINLY FROM KLSK TO KRWL FOR MOST OF
TONIGHT.  PATTERN SIMILAR ON THURSDAY AS THAT OF TODAY AS THE LARGE
UPPER HIGH STAYS CENTERED OVER THE CENTRAL AND SOUTHERN ROCKIES WITH
MID AND UPPER LEVEL MOISTURE ROTATING AROUND THE HIGH...AND OVER THE
CWA.  MAIN DIFFERENCE WILL BE THAT MODELS DEPICT THE SURFACE LOW
PRESSURE TROUGH WHICH HAS BEEN ALONG THE CONTINENTAL DIVIDE
TODAY...SHIFTING EAST TO NEAR THE NEBRASKA AND SOUTH DAKOTA
BORDERS.  DRIER BOUNDARY LAYER AIR WILL BE BEHIND THE FEATURE...WITH
THE MOIST AND UNSTABLE AIR TO THE EAST OF THE BOUNDARY...OVER THE
NEBRASKA PANHANDLE.  THERE SHOULD AGAIN BE A SCATTERED COVERAGE OF
THUNDERSTORMS WITH THE POTENTIAL FOR A FEW STORMS TO BECOME SEVERE
LATE THURSDAY AFTERNOON IN PARTS OF THE PANHANDLE. TEMPERATURES ON
THURSDAY WILL BE SIMILAR TO THOSE OF TODAY AS 700 MB TEMPERATURES
AND 1000MB TO 500 MB THICKNESS VALUES SIMILAR.

IN LATER PERIODS...SAME OLD SAME OLD INTO NEXT WEEK WITH A BROAD
UPPER LEVEL TROUGH IN THE EASTERN PACIFIC OCEAN AND AN EQUALLY BROAD
UPPER RIDGE DOMINATING THE CENTER OF THE COUNTRY. TUE AND WED
SOUTHWEST FLOW ALOFT WILL BEGIN TO TAKE HOLD AS THE UPPER TROUGH
BEGINS TO PUSH ONSHORE OVER THE PACIFIC NORTHWEST. BEST HOPE FOR
RAINFALL OVER THE CYS FORECAST AREA WILL BE MID AND UPPER LEVEL
MONSOONAL MOISTURE ADVECTING SLOWLY CLOCKWISE AROUND THE BACKSIDE OF
THE UPPER HIGH PARKED OVER THE SOUTHERN PLAINS. WITH DIURNALLY
TRENDED AIRMASS INSTABILITY OCCURRING DAILY...BUT WITH A LACK OF ANY
STRONG FORCING DYNAMICS...EVERY DAY COULD HAVE AN OUTSIDE CHANCE OF
AFTERNOON AND EVENING THUNDERSTORMS. TEMPERATURES WILL REMAIN ON THE
WARM SIDE BUT LOOK TO MODERATE SOMEWHAT BY TUE AS THE SOUTHWEST FLOW
ALOFT USHERS IN INCREASING MOISTURE.

.CYS...
WY...NONE.
NE...NONE.

NEZ001>003-019>021-054-055-WYZ059>070-071130-

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE CHEYENNE WY
954 AM MDT WED AUG 6 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEASTERN WYOMING AND THE
WESTERN NEBRASKA PANHANDLE.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THE ATMOSPHERE WILL BECOME UNSTABLE THIS AFTERNOON OVER AREAS TO
THE EAST OF THE LARAMIE RANGE.  IN ADDITION...HUMIDITIES WILL BE
INCREASING OVER THAT AREA THROUGH THE EVENING HOURS.  AS AN UPPER
LEVEL DISTURBANCE MOVES INTO SOUTHEAST WYOMING THIS AFTERNOON...A
SCATTERED COVERAGE OF STORMS WILL PRIMARILY FORM ALONG OR NEAR THE
LARAMIE RANGE AROUND 2 PM.  THE ACTIVITY WILL THEN MOVE TO THE EAST
AT 20 MPH...MOVING INTO THE WESTERN NEBRASKA PANHANDLE LATE THIS
AFTERNOON OR EARLY IN THE EVENING.

THE GREATEST CONCENTRATION OF STRONG THUNDERSTORMS THIS AFTERNOON AND
EVENING WILL BE IN EAST CENTRAL WYOMING AND INTO NORTHERN SIOUX
COUNTY.  FURTHER TO THE SOUTH...ONE OR TWO OF THE STORMS WILL BECOME
STRONG. THE MAIN THREAT FROM THE STRONG THUNDERSTORMS WILL BE HAIL
UP TO ONE INCH IN DIAMETER...LIGHTNING...A PERIOD OF HEAVY RAINFALL
AND WIND GUSTS TO 45 MPH.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

WIDELY SCATTERED LATE DAY THUNDERSTORMS ARE POSSIBLE EACH DAY
PRIMARILY OVER THE SOUTHERN HALF OF THE REGION AS THE WEATHER
PATTERN WILL CHANGE VERY LITTLE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING IN AREAS
TO THE EAST OF THE LARAMIE RANGE.

WEILAND