Special Weather Statement, NWS Cheyenne, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
447 PM MDT SAT AUG 3 2013

.UPDATE...
ISSUED AT 344 PM MDT SAT AUG 3 2013

LONG TRACKED SEVERE THUNDERSTORM CONTINUES TO HOLD TOGETHER AND
MOVE NORTH INTO NORTHERN LARAMIE COUNTY. WENT AHEAD AND ADDED
PLATTE AND GOSHEN COUNTIES TO THE TORNADO WATCH AS THIS STORM
COULD PRODUCE SEVERE THUNDERSTORMS THERE. PLUS THE ENVIRONMENT IS
PROBABLY BETTER UP THERE FOR MORE WIDESPREAD THUNDERSTORM
DEVELOPMENT. UPDATES HAVE BEEN SENT.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 300 PM MDT SAT AUG 3 2013

FORECAST CHALLENGES DEAL WITH THUNDERSTORM TIMING AND LOCATION OF
SEVERE THUNDERSTORMS THIS AFTERNOON THROUGH EVENING HOURS.

CURRENTLY...BOUNDARY LAYING ALONG THE LARAMIE RANGE EARLY THIS
AFTERNOON...SEPARATING FAIRLY DRY AIR TO THE WEST FROM REALLY
MOIST AIR TO THE EAST. DEWPOINTS IN LARAMIE IN THE MID 30S...HERE
AT CHEYENNE WE ARE SEEING UPPER 50S AND OUT BY SIDNEY...MID 60
DEWPOINTS. STRATUS HAS BEEN SLOW TO BREAK UP LATE THIS
MORNING/EARLY THIS AFTERNOON. STILL GETTING REPORTS OF STRATUS IN
THE PANHANDLE AND AS FAR WEST AS TORRINGTON. CHEYENNE HAS REMAINED
UNDER MOSTLY SUNNY SKIES AND CUMULUS HAS BEGUN TO BUILD OVER THE
SOUTHERN LARAMIE RANGE...EXTENDING SOUTH INTO THE MOUNTAINS OF
COLORADO. GETTING OBSERVED LIGHTNING STRIKES OVER CENTRAL
COLORADO...BUT SO FAR...THE CHEYENNE CWFA HAS REMAINED PRETTY MUCH
ECHO FREE. MONSOONAL MOISTURE CONTINUES TO MOVE INTO SOUTH CENTRAL
WYOMING ON WATER VAPOR IMAGERY...MAINLY OVER SOUTHERN CARBON AND
ALBANY COUNTIES THROUGH THE MORNING HOURS.

DO BELIEVE ITS ONLY A MATTER OF TIME FOR CONVECTION TO INITIATE
THIS AFTERNOON. LATEST SPC MESOANALIST PAGE SHOWING SURFACE BASED CAPE
VALUES INCREASING TO AROUND 3500 J/KG JUST SOUTH OF THE CWFA IN
COLORADO WITH AROUND 2500 TO 3000 J/KG JUST NUDGING INTO THE SOUTH
LARAMIE RANGE. STILL SEEING SOME CONVECTIVE INHIBITION EAST OF
CHEYENNE...SPREADING NORTH AND EAST. SPC MESOANALYST PAGE SHOWING
STILL AROUND 100-150 J/KG CONVECTIVE INHIBITION FOR THESE AREAS.
CURRENTLY THINKING AND THIS IS BACKED UP BY LATEST HRRR FORECASTS
IS THAT CONVECTION WILL INITIATE JUST WEST OF CHEYENNE...THEN
SLOWLY SPREAD EAST AND NORTH AS THE CAP ERODES.

MAIN THREATS WITH THUNDERSTORMS TODAY LOOKS TO BE LARGE HAIL AND
DAMAGING WINDS. BULK SHEAR ON THE ORDER OF 40 TO 45KTS. BUT LATER
THIS AFTERNOON...NAM SOUNDINGS ARE SHOWING HELICITY VALUES
INCREASING ABOVE 200 M2/S2 FOR CHEYENNE AND THE SOUTHERN
PANHANDLE...SO CAN NOT RULE OUT SOME TORNADIC SUPERCELLS LATE THIS
AFTERNOON AND EARLY EVENING. LCLS PRETTY LOW...WITH NAM FORECASTING
ANYWHERE FROM 2K TO 3K AGL. FINALLY...HEAVY RAIN IS A CONCERN WITH
PWATS CLIMBING TO OVER 1 INCH HERE AT CHEYENNE AND 1.4 INCHES OUT
BY SIDNEY. STORM MOTIONS ARE FAIRLY SLOW...GENERALLY OUT OF THE
WEST AT LESS THAN 10KTS...SO WE COULD BE LOOKING AT A FLASH FLOOD
THREAT AS WELL IN AREAS THAT SEE TRAINING STORMS. STORMS SHOULD
CONTINUE INTO THE MID TO LATE EVENING HOURS...SPREADING INTO THE
PANHANDLE BY 6 PM OR SO TONIGHT.

FOR SUNDAY...MODELS INDICATING A REPEAT OF TODAYS WEATHER WITH
POSSIBLY CONVECTION FURTHER EAST INTO THE PANHANDLE INITIALLY.
SEVERE THUNDERSTORMS LOOK MORE OUT OVER THE PANHANDLE SUNDAY VS
INITIATING HERE IN SOUTHEAST WYOMING.

.LONG TERM...(TUESDAY THROUGH SATURDAY)

ISSUED AT 320 PM MDT SAT AUG 3 2013

MAIN FORECAST CONCERN THROUGH NEXT WEEK WILL BE A STRONG MID
SUMMER COLD FRONT PUSHING ACROSS THE GREAT PLAINS AND INTO THE
FORECAST AREA...AS THE DEEP 543DM UPPER LEVEL LOW SETTLES OVER
SOUTHERN CANADA NEAR THE GREAT LAKES REGION. THIS IS PRETTY
UNUSUAL FOR THIS TIME OF THE YEAR...ALTHOUGH THE ROCKY MOUNTAIN
REGION WILL NOT SEE THE MAJORITY OF THIS COOLER AIR. MODELS SHOW
THIS FRONT QUICKLY MOVING ACROSS THE AREA TUESDAY AND TUESDAY
EVENING WITH HIGH TEMPERATURES AROUND 10 TO 15 DEGREES COOLER ON
WEDNESDAY AND THURSDAY. WITH SUBTROPICAL MONSOON MOISTURE IN
PLACE...A DAILY CHANCE OF SHOWERS AND THUNDERSTORMS IS ANTICIPATED
ACROSS MOST OF THE FORECAST AREA. THE BEST CHANCE WILL REMAIN OVER
THE MOUNTAINS AND ALONG/EAST OF THE LARAMIE RANGE...PRIMARILY FROM
MID AFTERNOON THROUGH EARLY IN THE EVENING. SOME OF THESE SHOWERS
MAY CONTINUE INTO THE OVERNIGHT HOURS...ESPECIALLY WEDNESDAY AND
THURSDAY NIGHT.

&&

.AVIATION...(FOR THE 00Z TAF ISSUANCE)

SHOWERS AND TSTORMS WILL CONTINUE OVER SOUTHEAST WYOMING. LOW
CONFIDENCE IN TSTORMS ACROSS WESTERN NEBRASKA DUE TO ONGOING FOG AND
LOW CIGS...SO TOOK VCTS OUT OF MOST WESTERN NEBRASKA TERMINALS OR
STARTED VCTS LATER THIS EVENING. STORMS THAT OCCUR NEAR THE WY/NE
BORDER ARE CAPABLE OF PRODUCING LARGE HAIL AS WELL. TSTORMS WILL
DISSIPATE LATE TONIGHT...BUT WITH MOIST SOUTHERLY FLOW REMAINING
OVER THE AREA EXPECT PATCHY FOG AND LOW CIGS BELOW 1K FEET AGL TO
CONTINUE ACROSS THE HIGH PLAINS INTO WESTERN NEBRASKA THROUGH
TONIGHT.

&&

.FIRE WEATHER...
ISSUED AT 300 PM MDT SAT AUG 3 2013

LIGHT WINDS AND MONSOONAL MOISTURE SHOULD KEEP FIRE WEATHER ISSUES
AT BAY FOR TODAY AND SUNDAY. AREAS EAST OF THE LARAMIE RANGE
SHOULD SEE CONTINUED GOOD CHANCES AT WETTING RAINS...HIGH
HUMIDITIES AND EASTERLY UPSLOPING WINDS. AREAS WEST WILL SEE DRIER
CONDITIONS WITH AFTERNOON HUMIDITIES FALLING INTO MID TEENS.
FORTUNATELY...WINDS SHOULD STAY LIGHT OUT THAT WAY KEEPING FIRE
WEATHER CONCERNS MINIMAL. BY MONDAY...SURFACE HIGH PRESSURE MOVING
INTO NORTH CENTRAL COLORADO WILL RE-ESTABLISH WESTERLY WINDS WITH
DRIER AIR FILTERING IN TO AREAS EAST OF THE LARAMIE RANGE. WINDS
WILL REMAIN LIGHT THOUGH...WHICH WILL KEEP FIRE WEATHER MINIMIZED.

&&

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

UPDATE...CLAYCOMB
SHORT TERM...CLAYCOMB
LONG TERM...TJT
AVIATION...TJT
FIRE WEATHER...CLAYCOMB

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHEYENNE WY
347 PM MDT SAT AUG 3 2013

WYZ101>119-042100-
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-
347 PM MDT SAT AUG 3 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST WYOMING.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER THE
MOUNTAINS OF SOUTHEAST WYOMING THIS AFTERNOON AND WILL MOVE EAST
ACROSS THE PLAINS THROUGH THE EVENING. A TORNADO WATCH IS IN EFFECT
UNTIL 10 PM LATE THIS EVENING FOR LARAMIE...PLATTE AND GOSHEN
COUNTIES. FREQUENT CLOUD TO GROUND LIGHTNING...LARGE HAIL...AND
STRONG WINDS UP TO 70 MPH ARE ALSO EXPECTED WITH THESE THUNDERSTORMS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

ISOLATED TO SCATTERED THUNDERSTORMS WILL DEVELOP EACH AFTERNOON
AND EVENING. LOCALLY HEAVY RAIN...SMALL HAIL AND GUSTY WINDS WILL
BE POSSIBLE OUT OF SOME THUNDERSTORMS EARLY NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ACTIVATION IS REQUIRED THIS AFTERNOON AND THIS EVENING
FOR SOUTHEAST WYOMING...MAINLY ALONG AND EAST OF THE LARAMIE RANGE.

&&

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

NEZ002-003-019>021-054-055-095-096-042100-
DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE-
NORTH SIOUX-SOUTH SIOUX-
347 PM MDT SAT AUG 3 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA
PANHANDLE.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER THE
MOUNTAINS OF SOUTHEAST WYOMING THIS AFTERNOON AND WILL MOVE EAST
ACROSS THE PLAINS AND INTO THE NEBRASKA PANHANDLE THROUGH THE
EVENING. SOME OF THESE STORMS COULD BECOME SEVERE...WITH HAIL
LARGER THAN QUARTERS...DAMAGING WINDS UP TO 60 MPH AND HEAVY RAIN
THE MAIN THREATS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

ISOLATED TO SCATTERED THUNDERSTORMS WILL DEVELOP EACH AFTERNOON
AND EVENING. LOCALLY HEAVY RAIN...SMALL HAIL AND GUSTY WINDS WILL
BE POSSIBLE OUT OF SOME THUNDERSTORMS EARLY NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE THIS AFTERNOON AND THIS EVENING.

&&

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

TT

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHEYENNE WY
438 PM MDT SAT AUG 3 2013

WYZ106-115>118-032345-
CENTRAL LARAMIE COUNTY WY-CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE
COUNTY WY-LARAMIE VALLEY WY-SOUTH LARAMIE RANGE WY-SOUTH LARAMIE
RANGE FOOTHILLS WY-
438 PM MDT SAT AUG 3 2013

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN PLATTE...
NORTHWESTERN LARAMIE AND EASTERN ALBANY COUNTIES UNTIL 545 PM MDT...

AT 437 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 5 MILES WEST OF IRON MOUNTAIN...OR 22 MILES
NORTHEAST OF LARAMIE...MOVING NORTHEAST AT 20 MPH.

HAIL UP TO THE SIZE OF NICKELS AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
  IRON MOUNTAIN...

THIS INCLUDES INTERSTATE 25 IN WYOMING BETWEEN MILE MARKERS 33 AND
38.

THIS STORM MAY INTENSIFY...SO BE CERTAIN TO MONITOR LOCAL RADIO AND
TV STATIONS...AS WELL AS LOCAL CABLE TV OUTLETS... FOR ADDITIONAL
INFORMATION AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE.

TORRENTIAL RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND
UNDERPASSES...IS ALSO LIKELY. DO NOT DRIVE YOUR VEHICLE ON A FLOODED
ROADWAY.

&&

LAT...LON 4196 10526 4146 10482 4134 10565 4152 10563
TIME...MOT...LOC 2238Z 215DEG 17KT 4155 10531

HAMMER/RUBIN

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHEYENNE WY
450 PM MDT SAT AUG 3 2013

WYZ101-103-105-107-032345-
CONVERSE COUNTY LOWER ELEVATIONS WY-EAST PLATTE COUNTY WY-NORTH
LARAMIE RANGE WY-SHIRLEY BASIN WY-
450 PM MDT SAT AUG 3 2013

...SIGNIFICANT WEATHER ADVISORY FOR EXTREME NORTHWESTERN PLATTE...
SOUTHWESTERN CONVERSE...NORTHERN ALBANY AND EXTREME NORTHEASTERN
CARBON COUNTIES UNTIL 545 PM MDT...

AT 446 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 8 MILES SOUTH OF
LAPRELE RESERVOIR TO LITTLE MEDICINE SCHOOL...AND MOVING EAST AT 10
MPH.

HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THESE STORMS...ALONG WITH HEAVY RAIN AND FREQUENT
DANGEROUS LIGHTNING.

THESE STORMS WILL BE NEAR...
LITTLE MEDICINE SCHOOL AROUND 455 PM MDT.
CAMPBELL CREEK CAMPGROUND AROUND 505 PM MDT.

IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A
STURDY BUILDING.

TORRENTIAL RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND
UNDERPASSES...IS ALSO LIKELY. DO NOT DRIVE YOUR VEHICLE ON A FLOODED
ROADWAY.

&&

LAT...LON 4257 10525 4231 10588 4242 10610 4261 10597
      4267 10568
TIME...MOT...LOC 2250Z 282DEG 11KT 4259 10558 4241 10604

RUBIN