Severe Thunderstorm Warning 91, NWS Cheyenne, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
132 PM MDT TUE SEP 14 2004

.SHORT TERM...IMPRESSIVE S/WV (SHORTWAVE) TROF MOVING EWRD ACROSS WY
TODAY. NORTH-SOUTH ORIENTED LOW LEVEL CONVERGENCE BOUNDARY SETS UP
ACROSS FAR ERN WY OR NEAR THE WY-NEB STATE LINE BY LATE AFTERNOON.
WITH MORE THAN ADEQUATE WIND SHEAR (BOTH SPEED/DIRECTIONAL) AND
BUOYANT ENERGY (CAPE)...EXPECT SCT-NUMEROUS TSTMS TO DEVELOP
ALONG/EAST OF THE BOUNDARY THRU EVENING WITH SOME STORMS
SEVERE...AIDED BY UVM (UPWARD VERTICAL MOTION) FROM S/WV TROF. TSTM
COVERAGE LESSER WEST OF THE BOUNDARY DUE TO MORE LIMITED
MOISTURE...BUT DYNAMICAL LIFT WILL OVERCOME LACK OF MOISTURE. TSTM
COVERAGE WILL DECREASE QUICKLY AFTER 06Z IN SUBSIDENCE BEHIND S/WV
TROF AND WITH STRONG DOWNSLOPE LOW/MID LEVEL WINDS. MORE TRANQUIL
WEATHER EXPECTED ON WED AS DRY WLY ZONAL FLOW PREVAILS. NO TSTMS ON
WED DUE TO LACK OF LOW/MID LEVEL MOISTURE. GUIDANCE TEMPS
ACCEPTED.   /RUBIN/

.LONG TERM...A DRIER AND MORE WESTERLY WIND FLOW ALOFT WILL BE OVER
THE CWA THURSDAY AND FRIDAY.  ON THOSE DAYS THE TEMPERATURES WILL
BE BACK TO JUST ABOVE NORMAL VALUES AND THERE WILL BE BREEZY TO
EVEN DAYTIME WINDY PERIODS.  THE FLOW ALOFT TURNS MORE TO THE
SOUTHWEST AHEAD OF THE UPSTREAM UPPER LEVEL TROUGH OVER THE
WEEKEND...WITH CONDITIONS OVER THE CWA STILL MILD...BREEZY AND DRY.
MODELS STILL ALL SHOW THE LARGE AMPLITUDE UPPER LEVEL TROUGH MOVING
THROUGH THE CWA LATE SUNDAY NIGHT THROUGH MONDAY EVENING.  THAT
FEATURE WILL BRING THE NEXT THREAT OF PRECIPITATION TO THE REGION AS
WELL AS COOLER TEMPERATURES.  MODELS STILL DIFFER ON TIMING OF THE
FEATURE WITH THE NOGAPS SLOWER AND SEEMING TO TREND SLOWER AND OTHER
MODELS TRENDING FASTER.  WILL FOLLOW THE FASTER TREND OF MOST OF THE
MODELS FOR THIS FORECAST.  THE ASSOCIATED COLD FRONT MOVES THROUGH
THE CWA SUNDAY NIGHT...WITH THE COLD AIR ADVECTION AND DEVELOPING
TIGHT SURFACE PRESSURE GRADIENT CAUSING STRONG WINDS THROUGH
MONDAY.  AS THE UPPER LEVEL TROUGH AXIS PASSES AND THE SURFACE LOW
MOVES FURTHER AWAY...THE PRECIPITATION SHOULD DIMINISH MONDAY
NIGHT.  700MB TEMPERATURES APPROACH 0C AND 1000 TO 500 MB THICKNESS
VALUES LOWER TO WELL BELOW THE VALUES FOR SNOW MONDAY NIGHT.
DEPENDING ON HOW FAST SKIES CLEAR MONDAY NIGHT AS THE SURFACE HIGH
BUILDS IN...MANY LOCATIONS COULD BE IN THE 30S LATE MONDAY NIGHT AND
TUESDAY MORNING.

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.

WEILAND

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHEYENNE WY
933 AM MDT TUE SEP 14 2004

NEZ001>003-019>021-054-055-WYZ059>070-151130-
BANNER NE-BOX BUTTE NE-CHEYENNE NE-CHEYENNE FOOTHILLS WY-CONVERSE WY-
DAWES NE-GOSHEN WY-KIMBALL NE-LARAMIE RANGE WY-LARAMIE VALLEY WY-
MORRILL NE-NIOBRARA WY-NORTH CARBON WY-NORTH LARAMIE RANGE WY-
PINE BLUFFS WY-PLATTE WY-SCOTTS BLUFF NE-SIOUX NE-SNOWY RANGE WY-
SOUTHWEST CARBON WY-
INCLUDING THE CITIES OF...ALLIANCE...CHADRON...CHEYENNE...DOUGLAS...
KIMBALL...LARAMIE...LUSK...RAWLINS...SCOTTSBLUFF...SIDNEY...
TORRINGTON AND WHEATLAND
933 AM MDT TUE SEP 14 2004

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

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING ACROSS FAR SOUTHEAST WYOMING AND THE SOUTHERN HALF OF THE
WESTERN NEBRASKA PANHANDLE. LARAMIE...PLATTE AND GOSHEN COUNTIES ARE
INCLUDED IN THE SLIGHT RISK AREA.

A LOW LEVEL CONVERGENCE BOUNDARY WILL DEVELOP THIS AFTERNOON ACROSS
FAR EASTERN WYOMING...NEAR THE WYOMING AND NEBRASKA STATE LINE.
SCATTERED THUNDERSTORMS WILL DEVELOP ALONG THIS BOUNDARY THIS
AFTERNOON AND CONTINUE INTO THE EVENING HOURS. SOME OF THESE
THUNDERSTORMS THIS AFTERNOON AND EVENING MAY BECOME SEVERE...WITH
THE PRIMARY THREATS BEING DIME SIZE HAIL OR LARGER...AND WIND GUSTS
IN EXCESS OF 60 MPH. STORM MOVEMENT WILL BE EAST AT 25 MPH.

OTHER SCATTERED THUNDERSTORMS WILL DEVELOP FURTHER WEST ACROSS
WYOMING THIS AFTERNOON AND EVENING IN CONJUNCTION WITH AN APPROACHING
WEATHER DISTURBANCE...BUT THE VAST MAJORITY OF THESE STORMS WILL BE
NON-SEVERE...PRODUCING BRIEF HEAVY RAIN...WIND GUSTS TO 50 MPH AND
SMALL HAIL.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER ACTIVATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND EVENING ACROSS
FAR SOUTHEAST WYOMING AND PORTIONS OF THE WESTERN NEBRASKA PANHANDLE.

RUBIN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
235 PM MDT TUE SEP 14 2004

..TIME...   ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE...   ....MAG....     ..COUNTY LOCATION...ST.. ...SOURCE....
            ..REMARKS..

0223 PM     HAIL             9 S MCGREW              41.62N 103.42W
09/14/2004  0.75 INCH        BANNER             NE   CO-OP OBSERVER

&&

RUBIN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
259 PM MDT TUE SEP 14 2004

..TIME...   ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE...   ....MAG....     ..COUNTY LOCATION...ST.. ...SOURCE....
            ..REMARKS..

0245 PM     HAIL             16 WNW HARRISBURG       41.64N 104.03W
09/14/2004  0.75 INCH        BANNER             NE   PUBLIC

&&

RUBIN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
305 PM MDT TUE SEP 14 2004

..TIME...   ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE...   ....MAG....     ..COUNTY LOCATION...ST.. ...SOURCE....
            ..REMARKS..

0300 PM     HAIL             BRIDGEPORT              41.67N 103.10W
09/14/2004  1.00 INCH        MORRILL            NE   CO-OP OBSERVER

&&

RUBIN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
326 PM MDT TUE SEP 14 2004

..TIME...   ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE...   ....MAG....     ..COUNTY LOCATION...ST.. ...SOURCE....
            ..REMARKS..

0315 PM     HAIL             5 SE BRIDGEPORT         41.62N 103.03W
09/14/2004  1.00 INCH        MORRILL            NE   CO-OP OBSERVER

&&

RUBIN