Severe Thunderstorm Warning 30, NWS Cheyenne, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
122 PM MDT MON MAY 24 2010

.SHORT TERM...TONIGHT THROUGH WEDNESDAY
TONIGHT...PRIMARY CHALLENGES WILL BE FREEZING TEMPERATURES AND
TIMING OF DECREASING WINDS. STRONG NEGATIVELY TILTED UPPER TROUGH
MOVES INTO WESTERN SOUTH DAKOTA THIS EVENING THEN TO WESTERN NORTH
DAKOTA BY MORNING. APPEARS THE SURFACE THROUGH 700 MB PRESSURE
GRADIENT WILL WEAKEN ENOUGH THIS EVENING TO ALLOW THE HIGH WIND
WARNING TO EXPIRE EARLY TO MID EVENING. WILL LEAVE THE HIGH WIND
WARNING IN PLACE AND PASS ON TO THE EVENING SHIFT THEY MAY NEED TO
EXTEND THE HIGH WIND WARNING A FEW HOURS AS GRADIENTS MAY TAKE
LONGER TO WEAKEN.

STRONG COLD AIR ADVECTION OVERNIGHT AND WITH EXPECTED DECREASE IN
MIXING LATE TONIGHT...LOW TEMPERATURES IN THE MID 20S TO UPPER 30S
ANTICIPATED WITH CLEARING SKIES. HAVE ALREADY ISSUED A SPECIAL
WEATHER STATEMENT ABOUT THE COLD TEMPERATURES EXPECTED TONIGHT. THE
EVENING SHIFT MAY NEED TO ISSUE A FROST OR FREEZE HIGHLIGHT FOR
TONIGHT BUT WILL HOLD OFF FOR NOW WITH OUR HIGH WIND WARNING IN
EFFECT.

TUESDAY...SOUTHWEST FLOW ALOFT PREVAILS. WILL NEED TO WATCH FOR
ISOLATED THUNDERSTORMS TO DEVELOP IN THE AFTERNOON ALONG THE
INVERTED SURFACE TROUGH FROM CENTRAL COLORADO NORTHWARD ACROSS
THE INTERSTATE 25 CORRIDOR.

TUESDAY NIGHT...SHORTWAVE TROUGH MOVES NORTHEAST ACROSS EASTERN
COLORADO THUS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS
OUR FAR SOUTHEAST WYOMING AND SOUTHWEST NEBRASKA COUNTIES AFTER
MIDNIGHT...DRY ELSEWHERE.

WEDNESDAY...SOUTHWEST FLOW ALOFT CONTINUES. LOW LEVEL WINDS WILL BE
SOUTHEAST ADVECTING IN ABUNDANT LOW LEVEL MOISTURE ALONG AND EAST OF
THE LARAMIE RANGE. EXPECT TO SEE ISOLATED TO SCATTERED AFTERNOON
THUNDERSTORMS ALONG AND EAST OF THE LARAMIE RANGE IN LOW LEVEL
MECHANICAL UPSLOPE LIFT AND DIFFERENTIAL HEATING.

&&

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
THE 12Z NUMERICAL GUIDANCE IS IN GENERAL AGREEMENT WITH SYNOPTIC
PATTERN DURING THIS FORECAST PERIOD. MAINTAINED THE ECMWF SOLUTION
FOR THE STRENGTH AND TIMING OF THE NEXT UPPER TROUGH MOVING INTO
THE WRN STATES. SWLY FLOW ALOFT WILL CONTINUE WEDNESDAY THROUGH
SATURDAY BETWEEN THE HIGH AMPLITUDE RIDGE OVER THE PLAINS AND
TROUGH TO THE WEST. ABOVE NORMAL TEMPERATURES WILL LEAD TO A
CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS EAST AND NORTH OF
THE LARAMIE RANGE AS THE AIR MASS BECOMES UNSTABLE. MID LEVEL
MOISTURE WILL ALSO BE PRESENT DURING THIS TIME. FOR THURSDAY...
SIMILAR CONDITIONS WILL OCCUR...HOWEVER LATE DAY THUNDERSTORMS
WILL BE LIMITED TO THE NRN CWA. WARMEST TEMPERATURES OF THE SEASON
THUS FAR WILL THURSDAY AND FRIDAY AS A STRONG THERMAL RIDGE BECOMES
ESTABLISHED OVER THE ROCKIES AND GREAT PLAINS. A GRADUAL INCREASE
IN THUNDERSTORM COVERAGE WILL OCCUR FRIDAY AS THE WEST COAST UPPER
TROUGH MOVES INLAND WITH S TO SW DIVERGENT FLOW ALOFT OVER THE
CWA. A PACIFIC COLD FRONT WILL MOVE ACROSS THE FORECAST AREA
SATURDAY AS THE UPPER TROUGH AXIS MOVES INTO WRN WY. THIS WILL
TRIGGER SHOWERS AND LATE DAY THUNDERSTORMS OVER MUCH OF THE AREA.
COOLER TEMPERATURES WILL ALSO OCCUR ACROSS THE CWA. WLY FLOW WILL
OCCUR ALOFT SUN AS THE UPPER TROUGH MOVES ACROSS THE FORECAST AREA
AND WEAKENS. TEMPERATURES WILL BEGIN TO MODERATE SUNDAY.

&&

.AVIATION...18Z TAF ISSUANCE
CONVECTION WILL CONTINUE ALONG AND EAST OF THE LARAMIE RANGE...WITH
THE STRONGEST CELLS OVER THE NEB PANHANDLE PRODUCING MVFR AND
TURBULENCE AS WELL AS HAIL AND STRONG WINDS. WINDS OUTSIDE THE
CONVECTION WILL BE SHIFTING FROM EASTERLY TO WESTERLY AS A STRONG
COLD FRONT PUSHES EAST ACROSS THE AREA THIS AFTERNOON AND EARLY
EVENING. SUSTAINED WINDS OF 30 TO 50 MPH WILL DEVELOP BEHIND THE
FRONT WITH GUSTS AS HIGH AS 65 MPH. HIGHER TERRAIN OF SNOWY AND
SIERRA MADRE RANGES WILL BE OBSCURED IN SNOW SHOWERS THIS AFTERNOON.
WINDS WILL DIMINISH LATER TONIGHT WITH THE RELAXING PRESSURE GRADIENT.

&&

.FIRE WEATHER...FIRE WEATHER CONCERNS WILL INCREASE TODAY AS A
STRONG COLD FRONT MOVES EAST ACROSS THE DISTRICT WITH STRONG WEST
WINDS AND DECREASING RELATIVE HUMIDITIES THROUGH THIS EVENING.
FORTUNATELY...GROUND FUELS ARE MOIST FROM THE RECENT RAINS. MINIMAL
FIRE WEATHER CONCERNS TUESDAY AND WEDNESDAY DUE TO INCREASING RELATIVE
HUMIDITIES AND LIGHTER WINDS.

&&

.HYDROLOGY...WILL CONTINUE TO MONITOR THE UPPER NORTH PLATTE RIVER
AND THE ENCAMPMENT RIVER NEAR SARATOGA AND ENCAMPMENT WITH THE
ENCAMPMENT RIVER RISING INTO MONITORING STAGE LAST NIGHT. THE LITTLE
SNAKE RIVER IN SOUTHWEST CARBON COUNTY HAS FALLEN WELL BELOW
MONITORING STAGE TODAY AS COLDER AIR MOVES INTO THE AREA...LIMITING
SNOW MELT.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WARNING UNTIL 8 PM MONDAY FOR WYZ101-WYZ102-WYZ103-
     WYZ105-WYZ106-WYZ107-WYZ108-WYZ110-WYZ111-WYZ112-WYZ114-
     WYZ115-WYZ116-WYZ117-WYZ118-WYZ119.
     HIGH WIND WATCH UNTIL 6 PM MONDAY FOR WYZ104-WYZ109-WYZ113.
NE...HIGH WIND WARNING UNTIL 8 PM MONDAY FOR NEZ002-NEZ003-NEZ019-
     NEZ020-NEZ021-NEZ054-NEZ055-NEZ095-NEZ096.

&&

SHORT TERM/FIRE WEATHER/HYDROLOGY...RUBIN
LONG TERM/AVIATION...JAMSKI
SEVERE WEATHER OPERATIONS...TEAM CHEYENNE

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
133 PM MDT MON MAY 24 2010

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

0122 PM     HAIL             6 SW DALTON             41.35N 103.05W
05/24/2010  E1.00 INCH       CHEYENNE           NE   PUBLIC

0123 PM     NON-TSTM WND GST E CHEYENNE              41.15N 104.79W
05/24/2010  E70.00 MPH       LARAMIE            WY   PUBLIC

            INTERSTATE 25 MILE MARKER 11...WIND GUST ASSOCIATED WITH
            COLD FRONTAL PASSAGE.

0124 PM     HAIL             6 W CRAWFORD            42.69N 103.53W
05/24/2010  E2.75 INCH       SIOUX              NE   LAW ENFORCEMENT

            GOLFBALL TO BASEBALL SIZED HAIL ALONG HIGHWAY 20.

&&

HUTCHEON

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
202 PM MDT MON MAY 24 2010

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

0142 PM     HAIL             CRAWFORD                42.69N 103.41W
05/24/2010  E1.75 INCH       DAWES              NE   LAW ENFORCEMENT

            MARBLE TO GOLFBALL SIZED HAIL.

0142 PM     HEAVY RAIN       BRIDGEPORT              41.67N 103.10W
05/24/2010  E0.75 INCH       MORRILL            NE   TRAINED SPOTTER

            0.75 INCH RAIN IN 5 MINUTES...MARBLE SIZED HAIL AS WELL.

0145 PM     HAIL             CRAWFORD                42.69N 103.41W
05/24/2010  M2.00 INCH       DAWES              NE   TRAINED SPOTTER

            GOLFBALL TO HENS EGG SIZED HAIL FROM 145 TO 150 PM MDT.

0154 PM     NON-TSTM WND GST 11 SSE HORSE CREEK      41.26N 105.10W
05/24/2010  E70.00 MPH       LARAMIE            WY   TRAINED SPOTTER

            ASSOCIATED WITH COLD FRONT PASSAGE.

&&

HUTCHEON

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