Alert archive / Wyoming / Special Weather Statements in 2011

Special Weather Statement, NWS Riverton, WY

August 9, 2011Natrona County, Wyoming

NWS Riverton, WY issued this special weather statement at Aug 9, 2011, 4:59 PM MDT for Natrona County, Wyoming. It was in force for 31 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Aug 9, 2011, 4:59 PM MDT (22:59 UTC)
Expired
Aug 9, 2011, 5:30 PM MDT
In force
31 min
Issued by
NWS Riverton, WY

County Natrona County, WY

The radar

The Riverton/Lander radar (KRIW), 175 km from the middle of the area, began a volume at 23:00 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Riverton, WY (KRIW), launched 12:00Z, 11.0 hours before the alert went out and 169 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Riverton, WY at 12:00Z on 2011-08-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 27 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Riverton, WY at 12:00Z on 2011-08-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 141 square meters per square second.1939587897117Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
27 J/kg
Mixed-layer CIN
-359 J/kg
Mixed-layer LCL
2045 m above ground
0-6 km bulk shear
57 kt
0-1 km storm-relative helicity
141 m²/s²
0-3 km storm-relative helicity
250 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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What forecasters said that day

The local office's own words before this special weather statement went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Riverton, WY wrote its last area forecast discussion before this special weather statement went out at Aug 9, 3:16 PM MDT, 1 hour 43 minutes earlier.

Area forecast discussion, Aug 9, 3:16 PM MDT, 1 hour 43 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
316 PM MDT TUE AUG 9 2011

.SHORT TERM...TONIGHT THROUGH FRIDAY

A SWATH OF MID AND UPPER LEVEL MOISTURE WITH PRECIPITABLE WATER
VALUES FROM 125 TO 150 PERCENT OF NORMAL FROM SATELLITE ESTIMATES
EXTENDS ACROSS THE NORTHERN HALF OF THE FORECAST AREA WITH DRY AIR
ACROSS THE SOUTH WITH VALUES OF 60 TO 75 PERCENT OF NORMAL. THE
NORTHERN MOISTURE IS ASSOCIATED WITH A SHORT WAVE TROUGH OVER
WESTERN MONTANA. WEAK UPPER LEVEL DIVERGENCE AND MODERATE
INSTABILITY SUPPORTING SHOWERS AND THUNDERSTORMS ACROSS THE NORTH.
A SERIES OF WEAK SHORT WAVE TROUGHS IN THE WESTERLY FLOW WILL
KEEP SOME SHOWERS AND ISOLATED THUNDERSTORMS GOING THROUGH THE
NIGHT AND INTO WEDNESDAY MORNING. THE MOISTURE IS EXPECTED TO
SHIFT NORTH LIMITING CONVECTION NORTH OF THE OWL CREEK MOUNTAINS
AND THE SOUTHERN BIGHORN MOUNTAINS. TEMPERATURES WILL WARM SLIGHTLY.
THE MOISTURE WILL SHIFT NORTH OF THE AREA WITH DRY AND MORE STABLE
AIR IN PLACE FOR THURSDAY AND FRIDAY. ISOLATED SHOWERS AND
THUNDERSTORMS WILL BRUSH THE NORTHERN MOUNTAINS ON THURSDAY.
BREEZY WEST WINDS WILL INCREASE ACROSS THE AREA THURSDAY AND
FRIDAY.

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY

RIDGE OF HIGH PRESSURE WILL REMAIN OVER THE CWA
THROUGH SATURDAY EVENING WITH GENERALLY DRY CONDITIONS AND LIGHT
WIND EXPECTED. THE AXIS OF THE RIDGE WILL SLIDE EAST SUNDAY
MORNING...ALLOWING SOME MONSOONAL MOISTURE TO BEGIN ITS RETURN TO
CENTRAL AND WESTERN WYOMING. THIS ADDITIONAL MOISTURE WILL BRING
ISOLATED SHOWERS AND THUNDERSTORMS ACROSS THE AREA FOR SUNDAY
AFTERNOON...ALONG WITH INCREASED SURFACE WINDS.

THE SOUTHWEST FLOW ASSOCIATED WITH THIS PATTERN WILL REMAIN OVER THE
AREA THROUGH TUESDAY EVENING. THIS WILL KEEP THE RETURN OF MONSOONAL
MOISTURE AND CONTINUED AFTERNOON SHOWERS AND THUNDERSTORMS ACROSS
THE FORECAST AREA. EMBEDDED DISTURBANCES IN THE FLOW WILL ALSO AID
TO DEVELOPING SHOWERS AND THUNDERSTORMS.

TEMPERATURES CONTINUE TO WARM THROUGH SUNDAY UNDER THE RIDGE...WITH
A SLIGHT COOL DOWN ANTICIPATED MONDAY AND TUESDAY.

&&

.AVIATION...

SHOWERS AND THUNDERSTORMS WILL CONTINUE TO IMPACT AIRPORTS IN THE
NORTHERN THIRD OF THE FORECAST AREA THROUGH THE OVERNIGHT HOURS
IMPACTING KCOD...KWRL...KGEY AND KBYG. SHOWER COVERAGE WILL BEGIN TO
DECEASE AFTER 06Z. ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE
OT IMPACT THE ABSAROKA MOUNTAINS...BIGHORN MOUNTAINS AND JOHNSON
COUNTIES THROUGH 18Z. A WEAK DISTURBANCE WILL COMBINE WITH SOME
RESIDUAL MOISTURE TO CONTINUE WITH SHOWERS AND THUNDERSTORMS ACROSS
THE NORTHERN THIRD OF THE FORECAST AREA THROUGH WEDNESDAY AFTERNOON
AND INTO THE EVENING. ANY SHOWER ACTIVITY WILL BRING THE POTENTIAL
FOR MVFR CONDITIONS...WITH IFR CONDITIONS POSSIBLE IN HEAVY RAIN.
ANY STORM ACTIVITY WILL CONTAIN POTENTIAL THREATS OF GUSTY WIND TO
40 KTS...SMALL HAIL...DANGEROUS LIGHTNING AND PERIODS OF HEAVY
RAINFALL. LIGHT WIND GENERALLY EXPECTED OUTSIDE OF STORM
ENVIRONMENTS...WITH WIND INCREASING ACROSS SOUTHERN AND WESTERN
WYOMING AFTER 18Z WEDNESDAY. THESE INCREASED WINDS WILL IMPACT
AIRPORTS WEST AND SOUTH OF A LINE FROM KCPR-KLND-KCOD.

&&

.FIRE WEATHER...

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL REMAIN OVER THE
NORTHERN PART OF THE FORECAST AREA THROUGH THE EVENING HOURS
TONIGHT. SHOWER ACTIVITY MAY CONTAIN GUSTY AND ERRATIC WIND TO 45
MPH...SMALL HAIL AND DANGEROUS LIGHTNING. SHOWER ACTIVITY IS
EXPECTED TO DECREASE AFTER MIDNIGHT...WITH GENERALLY DRY
CONDITIONS EXPECTED BY WEDNESDAY MORNING. TO THE SOUTH...DRY AND
BREEZY CONDITIONS WILL EXIST.  WARMING TEMPERATURES EXPECTED OVER
THE AREA FOR WEDNESDAY. A WEAK DISTURBANCE WILL MOVE ACROSS
NORTHERN WYOMING AGAIN ON WEDNESDAY AFTERNOON WHICH MAY GENERATE A
COUPLE SHOWERS AND THUNDERSTORMS ACROSS THE NORTH...WITH DRY
CONDITIONS IN CENTRAL AND SOUTHERN AREAS. THIS PATTERN WILL
CONTINUE THROUGH THURSDAY ACROSS THE DISPATCH AREA.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM...C.BAKER
LONG TERM...BRANHAM
AVIATION...BRANHAM
FIRE WEATHER...C.BAKER
Hazardous weather outlook, Aug 9, 4:00 AM MDT, 12 hours 59 minutes before
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
400 AM MDT TUE AUG 9 2011

WYZ001>020-022>030-101200-
ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS SOUTHEAST-
BIGHORN MOUNTAINS WEST-CASPER MOUNTAIN-CODY FOOTHILLS-
EAST SWEETWATER COUNTY-FLAMING GORGE-
GREEN MOUNTAINS AND RATTLESNAKE RANGE-JACKSON HOLE-LANDER FOOTHILLS-
NATRONA COUNTY LOWER ELEVATIONS-NORTH BIG HORN BASIN-
NORTHEAST JOHNSON COUNTY-OWL CREEK AND BRIDGER MOUNTAINS-
ROCK SPRINGS AND GREEN RIVER-SALT RIVER AND WYOMING RANGES-
SOUTH LINCOLN COUNTY-SOUTHEAST BIG HORN BASIN-
SOUTHEAST JOHNSON COUNTY-SOUTHWEST BIG HORN BASIN-STAR VALLEY-
TETON AND GROS VENTRE MOUNTAINS-UPPER GREEN RIVER BASIN-
UPPER GREEN RIVER BASIN FOOTHILLS-UPPER WIND RIVER BASIN-
WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST-
YELLOWSTONE NATIONAL PARK-
400 AM MDT TUE AUG 9 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING.

.DAY ONE...TODAY AND TONIGHT

ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED ACROSS NORTHERN AND
CENTRAL WYOMING AND THE FAR WEST. HEAVY RAIN...LIGHTNING AND GUSTY
WINDS ARE LIKELY HAZARDS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

ISOLATED THUNDERSTORMS REMAIN POSSIBLE MAINLY OVER THE NORTH
WEDNESDAY AND THURSDAY.

AFTER A DRY PERIOD FRIDAY AND SATURDAY...ISOLATED THUNDERSTORMS WILL
RETURN TO THE WEST SUNDAY AFTERNOON AND ACROSS THE NORTH SUNDAY
NIGHT. THEN WIDELY SCATTERED THUNDERSTORMS WILL OCCUR MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ASKED TO REPORT HAIL SIZE AND STRONG WIND GUSTS AS WELL
AS ANY DAMAGE. THANK YOU.

TEAM RIVERTON

In the hours before

Special weather statement, Aug 9, 3:25 PM MDT, 1 hour 34 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
325 PM MDT TUE AUG 9 2011

WYZ017>020-022-100000-
CASPER MOUNTAIN-GREEN MOUNTAINS AND RATTLESNAKE RANGE-
LANDER FOOTHILLS-NATRONA COUNTY LOWER ELEVATIONS-WIND RIVER BASIN-
325 PM MDT TUE AUG 9 2011

...SCATTERED SHOWERS AND THUNDERSTORM ACROSS CENTRAL WYOMING...

THUNDERSTORMS WILL CONTINUE TO DEVELOP ACROSS CENTRAL WYOMING THIS
AFTERNOON AND EVENING...ESPECIALLY AROUND THE BORDER BETWEEN FREMONT
AND NATRONA COUNTIES. STORMS WILL MOVE EAST AT 25 TO 30 MPH. THE
PRIMARY THREATS WITH THESE STORMS WILL BE WINDS GUSTING TO 50 MPH...
BRIEF HEAVY RAIN...SMALL HAIL...AND DANGEROUS LIGHTNING. PEOPLE
PLANNING OUTDOOR ACTIVITIES SHOULD BE PREPARED TO MOVE TO A SAFE
LOCATION WHEN STORMS APPROACH.

WOLCOTT
Special weather statement, Aug 9, 3:55 PM MDT, 1 hour 4 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
355 PM MDT TUE AUG 9 2011

WYZ009-011-092230-
BIGHORN MOUNTAINS SOUTHEAST WY-SOUTHEAST JOHNSON COUNTY WY-
355 PM MDT TUE AUG 9 2011

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN JOHNSON COUNTY UNTIL
430 PM MDT...

AT 354 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 13 MILES WEST OF MAYOWORTH...OR 21 MILES WEST OF
KAYCEE...MOVING EAST AT 25 MPH.

HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN AND FREQUENT
DANGEROUS LIGHTNING.

THIS STORM WILL BE NEAR...
STATE HWY 191 MILE MARKER 10 AND MAYOWORTH AROUND 425 PM MDT.
STATE HWY 190 MILE MARKER 100 AROUND 430 PM MDT.

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

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

REPORT HAZARDOUS WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN
RIVERTON AT 1-800-211-1448.

LAT...LON 4387 10665 4351 10666 4367 10711 4386 10711
TIME...MOT...LOC 2155Z 271DEG 22KT 4377 10704

WOLCOTT
Special weather statement, Aug 9, 4:02 PM MDT, 57 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
402 PM MDT TUE AUG 9 2011

WYZ005>007-092245-
OWL CREEK AND BRIDGER MOUNTAINS WY-SOUTHEAST BIG HORN BASIN
WY-SOUTHWEST BIG HORN BASIN WY-
402 PM MDT TUE AUG 9 2011

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN WASHAKIE AND CENTRAL HOT
SPRINGS COUNTIES UNTIL 445 PM MDT...

AT 358 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM NEAR HWY JCT 171 AND 120...OR 23 MILES NORTHWEST
OF THERMOPOLIS...MOVING EAST AT 30 MPH.

HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN AND FREQUENT
DANGEROUS LIGHTNING.

THIS STORM WILL BE NEAR...
SAND DRAW RD AND STATE HWY 120 MILE MARKER 20 AROUND 410 PM MDT.
LOWER COTTONWOOD CREEK RD AROUND 425 PM MDT.
WINCHESTER AND KIRBY AROUND 440 PM MDT.

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

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

REPORT HAZARDOUS WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN
RIVERTON AT 1-800-211-1448.

LAT...LON 4402 10807 4370 10806 4379 10864 4395 10864
TIME...MOT...LOC 2202Z 268DEG 25KT 4387 10853

MCDONALD
Special weather statement, Aug 9, 4:20 PM MDT, 39 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
420 PM MDT TUE AUG 9 2011

WYZ011-092300-
SOUTHEAST JOHNSON COUNTY WY-
420 PM MDT TUE AUG 9 2011

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN JOHNSON COUNTY UNTIL
500 PM MDT...

AT 419 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM NEAR KAYCEE...MOVING EAST AT 40 MPH.

HAIL UP TO THE SIZE OF NICKELS AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN AND FREQUENT
DANGEROUS LIGHTNING.

THIS STORM WILL BE NEAR...
STATE HWY 192 MILE MARKER 10 AROUND 425 PM MDT.
STATE HWY 192 MILE MARKER 20 AND SUSSEX AROUND 435 PM MDT.
LINCH AND STATE HWY 192 MILE MARKER 30 AROUND 445 PM MDT.

THIS INCLUDES INTERSTATE 25 IN WYOMING BETWEEN MILE MARKERS 239 AND
259.

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

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

REPORT HAZARDOUS WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN
RIVERTON AT 1-800-211-1448.

LAT...LON 4349 10602 4357 10667 4379 10666 4382 10601
TIME...MOT...LOC 2220Z 275DEG 42KT 4369 10656

MCDONALD
Special weather statement, Aug 9, 4:48 PM MDT, 11 minutes before
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Special weather statement, Aug 9, 4:59 PM MDT, 0 minutes before
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The office that day

Everything else NWS Riverton, WY issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 8, 6:47 PM MDTSpecial Weather StatementRIWNatrona43 min
Aug 9, 1:25 PM MDTSpecial Weather StatementRIWHot Springs50 min
Aug 9, 2:09 PM MDTSevere Thunderstorm WarningRIWHot Springs51 min
Aug 9, 2:38 PM MDTSevere Thunderstorm WarningRIWHot Springs22 min
Aug 9, 2:56 PM MDTSpecial Weather StatementRIWWashakie34 min
Aug 9, 3:22 PM MDTSpecial Weather StatementRIWHot Springs38 min
Aug 9, 3:55 PM MDTSpecial Weather StatementRIWJohnson35 min
Aug 9, 4:02 PM MDTSpecial Weather StatementRIWHot Springs43 min
Aug 9, 4:20 PM MDTSpecial Weather StatementRIWJohnson40 min
Aug 9, 4:29 PM MDTSevere Thunderstorm WarningRIWJohnson46 min
Aug 9, 4:48 PM MDTSpecial Weather StatementRIWHot Springs27 min

Nearby

Special Weather Statements in Wyoming, 2011Every special weather statement in 2011

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.