Special Weather Statement, NWS Cheyenne, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1159 AM MDT THU JUL 5 2012

.AVIATION...18Z TAFS. THROUGH 00Z...SURFACE TROUGH WILL DEVELOP
AND STRENGTHEN FROM CASPER TO CHEYENNE TO DENVER WITH SCATTERED TO
NUMEROUS SHOWERS AND THUNDERSTORMS DEVELOPING FROM RAWLINS AND
LARAMIE TO DOUGLAS AND THEN EAST TO CHADRON...AND ISOLATED
THUNDERSTORMS ELSEWHERE. THUNDERSTORMS WILL PRODUCE LOCALIZED MVFR
ALONG WITH LOCALIZED SEVERE TURBULENCE. EXPECT STRENGTHENING
SOUTH AND SOUTHEAST WINDS WITH GUSTS UP TO 40 KNOTS. VFR OUTSIDE
OF THUNDERSTORMS.

FROM 00Z TO 06Z...SURFACE TROUGH OF LOW PRESSURE STRETCHES
FROM RAPID CITY SOUTHWARD THROUGH WESTERN NEBRASKA INTO NORTHEAST
COLORADO. SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL
OCCUR ALONG AND NEAR THE SURFACE TROUGH AXIS EAST OF A DOUGLAS
TO CHEYENNE LINE. THUNDERSTORMS WILL PRODUCE LOCALIZED MVFR ALONG
WITH TURBULENCE...SOME SEVERE...ESPECIALLY ACROSS WESTERN
NEBRASKA INCLUDING TAF SITES CHADRON...ALLIANCE...SCOTTSBLUFF
AND SIDNEY. LESSER COVERAGE OF THUNDERSTORMS WEST OF A DOUGLAS
TO LARAMIE LINE WITH THUNDERSTORMS ENDING IN THE EVENING. VFR
OUTSIDE OF THUNDERSTORMS.

AFTER 06Z...VFR. THUNDERSTORMS DECREASING IN COVERAGE BY 12Z TO
ISOLATED ACROSS FAR SOUTHEAST WYOMING AND WESTERN NEBRASKA EAST OF
A LUSK TO CHEYENNE LINE. SURFACE LOW MOVING INTO CENTRAL SOUTH
DAKOTA WITH WEST TO NORTHWEST WINDS DEVELOPING ACROSS TAF SITES.
LOCALIZED MVFR AND TURBULENCE NEAR THUNDERSTORMS...OTHERWISE VFR.

-RUBIN-

&&

.PREV DISCUSSION... /ISSUED 1115 AM MDT THU JUL 5 2012/

DISCUSSION...

A STRONG MID-LEVEL SHORTWAVE DISTURBANCE...COMBINED WITH INCREASING
SUBTROPICAL MOISTURE HAS GIVEN WAY TO ISOLATED TO WIDELY SCATTERED
SHOWERS AND TSTMS OVER THE LARAMIE RANGE FOOTHILLS AND ADJACENT HIGH
PLAINS THROUGH MUCH OF THE MORNING. WATER VAPOR SATELLITE IMAGERY IS
CLEARLY INDICATIVE OF A LARGE PLUME OF MID LEVEL MOISTURE ALONG THE
WESTERN FRINGE OF UPPER LEVEL RIDGING OVER THE CENTRAL AND EASTERN
US. CONDITIONS STILL LOOK PRIME FOR NUMEROUS SHOWERS AND TSTMS LATER
THIS AFTERNOON AS INCREASING MOISTURE COMBINES WITH LOW-LEVEL
UPSLOPE FLOW AND FORCED ASCENT ASSOCIATED WITH ADDITIONAL SHORTWAVE
DISTURBANCES. PWAT VALUES WELL IN EXCESS OF ONE INCH AND STRONG
LOW-LEVEL MOISTURE TRANSPORT...ALONG WITH TALL AND SKINNY CAPE
PROFILES ALL POINT TO A THREAT FOR VERY HEAVY RAINFALL FROM THESE
THUNDERSTORMS. SOUTHERLY STEERING FLOW AROUND 15 TO 25 KTS MAY KEEP
STORMS MOVING ENOUGH SUCH THAT A THREAT FOR FLASH FLOODING MAY BE
LIMITED. HOWEVER...WE WILL NEED TO BE CONCERNED ABOUT BURN SCARS AS
WELL AS TRAINING ECHOS ALONG THE FOOTHILLS. THE HIGHEST RISK FOR ANY
SEVERE CONVECTION SHOULD BE ACROSS OUR NORTHERN ZONES WHERE STRONGER
MID LEVEL FLOW AND BACKED/SOUTHEAST SURFACE WINDS CONTRIBUTE TO
STRONGER LOW-LEVEL AND DEEP LAYER SHEAR. -HAMMER-

AVIATION...12Z TAF ISSUANCE...
SCTD SHRAS AND A FEW TSHRAS BETWEEN KLAR AND KRWL AS WELL AS VCTY
KSNY SHOULD END BY MID MORNING.  MORE WIDESPREAD ACTIVITY EXPECTED
THIS AFTERNOON INTO THIS EVENING AS MONSOONAL MOISTURE INCREASES
OVER THE REGION ON SW FLOW ALOFT.  PERIODS OF MAINLY MVFR VSBYS AND
GUSTY WINDS IN AND CLOSE TO STRONGER STORMS.  SHOWERS SHOULD
DECREASE DURING THE EVENING WITH WEAK SFC FRONT MOVING EAST ACROSS
THE TERMINALS TONIGHT.

PREV DISCUSSION... /ISSUED 529 AM MDT THU JUL 5 2012/

SHORT TERM...TODAY THROUGH SATURDAY...CURRENT KCYS RADAR LOOP
SHOWS RAIN SHOWERS AND EMBEDDED THUNDERSTORMS MAINLY WEST OF THE
LARAMIE RANGE AND ALSO JUST SOUTH OF THE COLORADO BORDER EARLY
THIS MORNING. THIS ACTIVITY IS IN RESPONSE TO A SURFACE FRONT
WHICH IS DRIFTING NORTHWARD AS A WARM FRONT. THERE SEEMS TO BE
SOME ENHANCEMENT OF SHOWER ACTIVITY ACROSS NE COLORADO...SO KEPT
ISOLATED THUNDER SHOWERS IN THE FORECAST THIS MORNING.

TODAY WILL LIKELY BE THE FIRST OF SEVERAL DAYS WITH THE POTENTIAL
FOR WIDESPREAD RAINFALL...WHICH WILL FALL HEAVY AT TIMES. CURRENT
WATER VAPOR LOOP SHOWS A DISTURBANCE ALOFT ACROSS EASTERN ARIZONA.
MODELS SHOW THIS DISTURBANCE LIFTING NORTH AND THEN NORTHEAST
ACROSS WYOMING THIS AFTERNOON THROUGH TONIGHT. WITH PW/S OVER 1.25
INCHES TO AROUND 1.50...COMBINED WITH PLENTY OF LOW TO MIDLEVEL
INSTABILITY AND UPSLOPE FLOW...BELIEVE RAIN SHOWERS AND TSTORMS
WILL BECOME WIDESPREAD ESPECIALLY ACROSS SOUTHEAST WYOMING THROUGH
TONIGHT. AFTER A BRIEF LULL IN THE ACTIVITY AROUND DAWN...SHOWER
ACTIVITY WILL DEVELOP QUICKLY LATER TODAY WITH HEAVY RAINFALL
POSSIBLE. EXPECT TRAINING OVER THE SAME AREAS AS THE TSTORMS TRACK
SOUTH TO NORTH. ANY SOUTHWARD TRACK LLVL OUTFLOW BOUNDARY WILL
ONLY ENHANCE TRAINING OF SHOWERS AND THUNDERSTORMS WITH LOCALIZED
FLASH FLOODING POSSIBLE. NOT CONFIDENT ENOUGH WITH A FLASH FLOOD
WATCH TODAY...BUT WILL HAVE TO MONITOR ENVIRONMENTAL CONDITIONS
OVER THE NEXT FEW DAYS. ANOTHER DISTURBANCE WILL PUSH INTO THE
AREA...THIS TIME A BIT FURTHER EAST...ON FRIDAY. WESTERN NEBRASKA
WILL THEN HAVE A POTENTIAL FOR FLASH FLOODING AS THESE TSTORMS
WILL MOVE VERY SLOW THROUGH FRIDAY NIGHT. MODELS SHOW A HIGHER
POTENTIAL FOR FLASH FLOODING ALONG THE FRONT RANGE...AS THE UPPER
LEVEL DISTURBANCE HARDLY MOVES FOR A FULL 24 HOURS INTO SATURDAY
AFTERNOON. NEED TO MONITOR THE DEVELOPMENT OF THIS DISTURBANCE
OVER THE NEXT FEW DAYS SINCE A FLASH FLOOD WATCH MAY BE NEEDED.
MODEL SOUNDINGS SHOW A NEAR SATURATED SOUNDING FROM THE SURFACE
ALL THE WAY UP TO THE TROPOPAUSE...SIMILAR TO AN UPPER AIR PROFILE
SHOWN OVER FLORIDA WITH PW/S BETWEEN 1.3 TO 1.6 INCHES. SOME OF
THESE THUNDERSTORMS TODAY AND FRIDAY MAY BECOME
SEVERE...ESPECIALLY WELL NORTH OF I80 FROM CONVERSE COUNTY
EASTWARD INTO DAWES COUNTY ACROSS WESTERN NEBRASKA AS MODEL
SOUNDINGS SHOW CONSIDERABLE LLVL WIND SHEAR AS THE FRONT PUSHES
NORTHWARD. INCREASED POP TODAY THROUGH SATURDAY UP TO 60 PERCENT
IN THE HIGH PLAINS AND VALLEYS...AND BETWEEN 60 TO 80 PERCENT IN
THE MOUNTAINS. THE GOOD NEWS IS TEMPERATURES WILL BE CONSIDERABLY
COOLER INTO SATURDAY...WITH HIGHS IN THE 70S AND 80S.

LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...
LITTLE CHANGE SEEN IN THE OVERALL PATTERN SUNDAY AND MONDAY WITH
AT LEAST SCATTERED SHOWERS AND TSTMS PERSISTING AS MONSOONAL
MOISTURE PREVAILS OVER THE AREA. SOME DIFFICULTY WITH TIMING OF
BETTER COVERAGE AND LOCATIONS BUT AFTERNOON AND EVENING SHOULD SEE
THE MOST. AT THE SAME TIME HOWEVER UPPER HIGH OVER THE SRN PART OF
THE COUNTRY WILL RETROGRADE WESTWARD SLOWLY OVER THE WEEKEND AND
THIS WILL ACT TO GRADUALLY CUT OFF THE MOISTURE FLOW...MOST LIKELY
BEGINNING LATE SUNDAY AND CONTINUING THROUGH MONDAY. AS A RESULT
MONDAY THROUGH WEDNESDAY LOOKING CONSIDERABLY DRIER WITH UPPER
FLOW BECOMING MORE NWLY AS UPPER HIGH MOVES OVER THE DESERT SW.
MILD TO WARM TEMPERATURES SUNDAY AND MONDAY WITH AMPLE CLOUDINESS
AND SCATTERED PCPN THEN WARMING TUESDAY AND WEDS WITH DRIER REGIME
TAKING OVER.

FIRE WEATHER...FIRE WEATHER CONCERNS WILL BE LOW THROUGH THE
WEEKEND AND INTO NEXT WEEK AS SUBTROPICAL MOISTURE MOVES NORTHWARD
ALONG THE ROCKIES AND HIGH PLAINS. THIS WILL RESULT IN A HIGH
PROBABILITY OF RAINFALL AND THUNDERSTORMS NEARLY EVERY DAY THROUGH
MONDAY OF NEXT WEEK...WITH A LIKELIHOOD OF WIDESPREAD WETTING RAINS.
LIGHT WINDS AND HIGH HUMIDITIES ARE ALSO EXPECTED THROUGH NEXT WEEK.

HYDROLOGY...SUBTROPICAL MOISTURE COMBINED WITH UPSLOPE WINDS WILL
BRING INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS STARTING
TODAY AND CONTINUING EACH AFTERNOON AND EVENING THROUGH THE
WEEKEND. DUE TO THE SLOW STORM MOTION AND ABUNDANT MOISTURE...THE
POTENTIAL EXISTS FOR LOCALLY HEAVY RAINFALL AND POSSIBLE FLASH
FLOODING. FLASH FLOODING POTENTIAL ALSO EXISTS FOR THE HIGHER
TERRAIN IN AND AROUND THE BURNED AREAS FROM THE RECENT WILDFIRES
IN SOUTHEAST WYOMING.

&&

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

&&

18Z TAFS AVIATION UPDATE...RUBIN
1115 AM DISCUSSION UPDATE...HAMMER
SHORT TERM/FIRE WEATHER/HYDROLOGY...TJT
LONG TERM/AVIATION...RE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHEYENNE WY
1043 AM MDT THU JUL 5 2012

WYZ101>119-061645-
CONVERSE COUNTY LOWER ELEVATIONS-NIOBRARA COUNTY-
NORTH LARAMIE RANGE-FERRIS/SEMINOE/SHIRLEY MOUNTAINS-
SHIRLEY BASIN-CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY-
EAST PLATTE COUNTY-GOSHEN COUNTY-CENTRAL CARBON COUNTY-
NORTH SNOWY RANGE FOOTHILLS-SOUTHWEST CARBON COUNTY-
SIERRA MADRE RANGE-UPPER NORTH PLATTE RIVER BASIN-SNOWY RANGE-
LARAMIE VALLEY-SOUTH LARAMIE RANGE-SOUTH LARAMIE RANGE FOOTHILLS-
CENTRAL LARAMIE COUNTY-EAST LARAMIE COUNTY-
1043 AM MDT THU JUL 5 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL WYOMING...
SOUTH CENTRAL WYOMING AND SOUTHEAST WYOMING.

.DAY ONE...TODAY AND TONIGHT

SUBTROPICAL MOISTURE COMBINED WITH UPSLOPE FLOW AND AN UPPER LEVEL
DISTURBANCE WILL BRING AN INCREASING CHANCE FOR SHOWERS AND
THUNDERSTORMS THIS AFTERNOON. THE PRIMARY HAZARD FROM THESE
THUNDERSTORMS WILL BE LOCALLY HEAVY RAINFALL. HOWEVER...A FEW
STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON AND
EVENING ACROSS AREAS NORTH OF INTERSTATE 80. LARGE HAIL AND
DAMAGING WINDS WILL BE POSSIBLE WITH THESE STORMS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

SUBTROPICAL MOISTURE WILL REMAIN OVER THE AREA THROUGH THE
WEEKEND...RESULTING IN ADDITIONAL HEAVY RAINFALL AND THE POTENTIAL
FOR FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS UNLIKELY...BUT MAY BE REQUIRED THIS
AFTERNOON.

&&

THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND
CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT...
HTTP://WEATHER.GOV/CHEYENNE

NEZ002-003-019>021-054-055-095-096-061645-
DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE-
NORTH SIOUX-SOUTH SIOUX-
1043 AM MDT THU JUL 5 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA
PANHANDLE.

.DAY ONE...TODAY AND TONIGHT

SUBTROPICAL MOISTURE COMBINED WITH UPSLOPE FLOW AND AN UPPER LEVEL
DISTURBANCE WILL BRING AN INCREASING CHANCE FOR SHOWERS AND
THUNDERSTORMS THIS AFTERNOON. THE PRIMARY HAZARD FROM THESE
THUNDERSTORMS WILL BE LOCALLY HEAVY RAINFALL. HOWEVER...A FEW
STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON AND
EVENING ACROSS AREAS NORTH OF INTERSTATE 80. LARGE HAIL AND
DAMAGING WINDS WILL BE POSSIBLE WITH THESE STORMS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

SUBTROPICAL MOISTURE WILL REMAIN OVER THE AREA THROUGH THE
WEEKEND...RESULTING IN ADDITIONAL HEAVY RAINFALL AND THE POTENTIAL
FOR FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS UNLIKELY...BUT MAY BE REQUIRED THIS
AFTERNOON.

&&

THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND
CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT...
HTTP://WEATHER.GOV/CHEYENNE

CLH

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHEYENNE WY
244 PM MDT THU JUL 5 2012

WYZ105-106-110-115-052115-
CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY WY-LARAMIE VALLEY
WY-NORTH SNOWY RANGE FOOTHILLS WY-SHIRLEY BASIN WY-
244 PM MDT THU JUL 5 2012

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL ALBANY AND EXTREME
EASTERN CARBON COUNTIES UNTIL 315 PM MDT...

AT 241 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 8 MILES SOUTH OF ROCK RIVER...OR 31 MILES
NORTHWEST OF LARAMIE...MOVING NORTHEAST AT 15 MPH.

HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
  ROCK RIVER...

&&

LAT...LON 4192 10602 4179 10566 4152 10592 4160 10617
TIME...MOT...LOC 2045Z 207DEG 15KT 4163 10601

MAZUR