Alert archive / Wyoming / Special Weather Statements in 2021

Special Weather Statement, NWS Riverton, WY

September 2, 2021

NWS Riverton, WY issued this special weather statement at Sep 2, 2021, 3:21 PM MDT. It was in force for 24 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
Sep 2, 2021, 3:21 PM MDT (21:21 UTC)
Expired
Sep 2, 2021, 3:45 PM MDT
In force
24 min
Issued by
NWS Riverton, WY
Hail
0.25 in
Wind
30

The radar

The Riverton/Lander radar (KRIW), 57 km from the middle of the area, began a volume at 21:20 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, 9.4 hours before the alert went out and 55 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 2021-09-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 31 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 2021-09-02The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 19 square meters per square second.19395878Sfc1 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
31 J/kg
Mixed-layer CIN
-197 J/kg
Mixed-layer LCL
1437 m above ground
0-6 km bulk shear
40 kt
0-1 km storm-relative helicity
19 m²/s²
0-3 km storm-relative helicity
24 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

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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 Sep 2, 2:27 PM MDT, 54 minutes earlier.

Area forecast discussion, Sep 2, 2:27 PM MDT, 54 minutes before
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Hazardous weather outlook, Sep 2, 3:04 PM MDT, 17 minutes before
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In the hours before

Special weather statement, Sep 2, 1:27 PM MDT, 1 hour 54 minutes before
Special Weather Statement
National Weather Service Riverton WY
127 PM MDT Thu Sep 2 2021

WYZ015>018-022200-
Wind River Mountains East-Upper Wind River Basin-Wind River Basin-
Lander Foothills-
Including the cities of Dubois, Riverton, Shoshoni, and Lander
127 PM MDT Thu Sep 2 2021

...Showers and Thunderstorms Will Create Gusty Outflows...

This is a special weather statement from the National Weather
Service Office in Riverton.

* WHAT...Showers and thunderstorms could create strong to gusty
  outflows through early afternoon.

* WHERE...Wind River Basin.

* WHEN...Through 4 PM this afternoon.

* ADDITIONAL DETAILS...An area of showers and thunderstorms is
  moving into the Wind River Basin. These storms are generating
  frequent cloud-to-ground lightning. Gusty wind of 30 to 40 mph
  along with small hail and brief heavy rain is also possible.

Vorst
Special weather statement, Sep 2, 1:34 PM MDT, 1 hour 47 minutes before
Special Weather Statement
National Weather Service Riverton WY
134 PM MDT Thu Sep 2 2021

WYZ016-017-022000-
Wind River Basin-Upper Wind River Basin-
134 PM MDT Thu Sep 2 2021

...A strong thunderstorm will impact portions of central Fremont
County through 200 PM MDT...

At 133 PM MDT, Doppler radar was tracking a strong thunderstorm near
Diversion Dam Rest Area, or 12 miles north of Fort Washakie, moving
east at 45 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This strong thunderstorm will be near...
  Morton and Pilot Butte Reservoir around 145 PM MDT.
  Pavillion and Kinnear around 150 PM MDT.

Other locations in the path of this storm include Ocean Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Brief torrential rainfall is also occurring with this storm.

If on or near Ocean Lake, get out of the water and move indoors or
inside a vehicle. Remember, lightning can strike out to 10 miles
from the parent thunderstorm. If you can hear thunder, you are close
enough to be struck by lightning. Move to safe shelter now! Do not
be caught on the water in a thunderstorm.

&&

LAT...LON 4310 10913 4328 10908 4327 10846 4295 10857
TIME...MOT...LOC 1933Z 281DEG 40KT 4318 10896

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

Vorst
Special weather statement, Sep 2, 2:21 PM MDT, 1 hour before
Special Weather Statement
National Weather Service Riverton WY
221 PM MDT Thu Sep 2 2021

WYZ007-009-017>020-022045-
Owl Creek and Bridger Mountains-Wind River Basin-Bighorn Mountains
Southeast-Green Mountains and Rattlesnake Range-Natrona County Lower
Elevations-Lander Foothills-
221 PM MDT Thu Sep 2 2021

...Strong thunderstorms will impact portions of northwestern Natrona
and southeastern Fremont Counties through 245 PM MDT...

At 220 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 9 miles northwest of Lysite to 8 miles
southeast of Red Canyon. Movement was southeast at 40 mph.

HAZARD...Wind gusts of 50 to 55 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Strong thunderstorms will be near...
  Lysite around 235 PM MDT.
  Lost Cabin around 240 PM MDT.

Other locations in the path of these storms include Sweetwater
Station.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

If on or near Boysen Reservoir, get out of the water and move
indoors or inside a vehicle. Remember, lightning can strike out to
10 miles from the parent thunderstorm. If you can hear thunder, you
are close enough to be struck by lightning. Move to safe shelter
now! Do not be caught on the water in a thunderstorm.

&&

LAT...LON 4332 10716 4229 10795 4272 10863 4340 10807
TIME...MOT...LOC 2020Z 293DEG 36KT 4335 10786 4258 10851

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...55 MPH

Vorst
Special weather statement, Sep 2, 2:33 PM MDT, 48 minutes before
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Special weather statement, Sep 2, 3:01 PM MDT, 20 minutes before
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Special weather statement, Sep 2, 3:21 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
Sep 2, 10:28 AM MDTSpecial Weather StatementRIW47 min
Sep 2, 11:19 AM MDTSpecial Weather StatementRIWSublette41 min
Sep 2, 1:34 PM MDTSpecial Weather StatementRIWFremont26 min
Sep 2, 1:50 PM MDTSevere Thunderstorm WarningRIWFremont40 min
Sep 2, 2:21 PM MDTSpecial Weather StatementRIW24 min
Sep 2, 2:33 PM MDTSpecial Weather StatementRIWLincoln27 min
Sep 2, 3:01 PM MDTSpecial Weather StatementRIWLincoln29 min
Sep 2, 3:30 PM MDTSpecial Weather StatementRIWSublette30 min
Sep 2, 4:02 PM MDTSpecial Weather StatementRIW28 min

Nearby

Special Weather Statements in Wyoming, 2021Every special weather statement in 2021

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.