Weather Alert - Green Mountains and Rattlesnake Range
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WWUS85 KRIW 221501

Special Weather Statement
National Weather Service Riverton WY
901 AM MDT Tue May 22 2018

Absaroka Mountains-Cody Foothills-North Big Horn Basin-
Southwest Big Horn Basin-Southeast Big Horn Basin-
Owl Creek and Bridger Mountains-Bighorn Mountains West-
Bighorn Mountains Southeast-Northeast Johnson County-
Southeast Johnson County-Wind River Mountains West-
Wind River Mountains East-Upper Wind River Basin-Wind River Basin-
Lander Foothills-Green Mountains and Rattlesnake Range-
Natrona County Lower Elevations-Casper Mountain-
Including the cities of Cody, Meeteetse, Thermopolis, Worland,
Buffalo, Kaycee, Dubois, Riverton, Shoshoni, Lander,
Jeffrey City, and Casper
901 AM MDT Tue May 22 2018

...Strong to Severe Thunderstorms Possible This Afternoon and
...Very Heavy Rain Also Possible with the Potential for Flash

An approaching weather disturbance will help organize showers and
thunderstorms later this afternoon through the nighttime hours.
The disturbance will approach Fremont and Natrona Counties late
this afternoon and then lift northward through the night. Showers
and thunderstorms will be widespread as they lift northward across
the area. Some of the storms will be quite strong to possibly
severe with hail, strong wind and very heavy rain. The strongest
storms could produce one inch hail, very strong wind gusts and
intense rainfall of 1 to 2 inches. Flash flooding is also
possible where heavy rain persists, especially around the
foothills of the Absarokas, Bighorn Mountains and Owl Creeks. The
Upper Wind River Basin Foothills including Dubois could also see
some very heavy rain this evening.

Stay tuned for the latest update on this very active weather day
from your National Weather Service office in Riverton. If you
encounter any severe weather, please call us at 1 800 211 1448 or
your local law enforcement office.

FGUS75 KRIW 211513
Hydrologic Outlook
National Weather Service Riverton WY
913 AM MDT Mon May 21 2018

...Accelerated snowmelt at the 9,000 to 10,000 foot elevation
Friday through Sunday...

...Significant rises in creeks and streams during the
Memorial Day Weekend...

There is still 20 to 30 inches of snow water equivalents (SWEs)
at the 9,000 to 10,000 foot elevation. The snowpack has ripened
considerably in the last week to 10 days due to mild temperatures
and recent rainfall.

Afternoon mountain temperatures at the 9,000 foot elevation are
expected to warm to near 60 for Friday--and into the lower to
middle 60s Saturday and Sunday. Morning low temperatures are
forecasted to be at or above the frost temperature of 37 degrees
Friday through Sunday.

Increased snowmelt at the 9,000 to 10,000 foot elevation Friday
through Sunday will cause significant rises in creeks and streams
during the Memorial Day Weekend.

Any rainfall on Sunday and Memorial Day will greatly increase creek
and river levels due to a combination of rain and snowmelt runoff.

During active snowmelt runoff, mountain creeks and streams are
at their highest levels during the late afternoon/early evening
hours. Crossing creeks and streams during that time is highly

Graphical forecasts are available at:
Visit weather.gov/riverton and select the rivers & lakes tab for
graphical forecasts and additional information.


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