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2 products issued by NWS for: Yellowstone National Park WY
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Hydrologic Outlook

Hydrologic Outlook
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 and select the rivers & lakes tab for
graphical forecasts and additional information.


Hazardous Weather Outlook

Hazardous Weather Outlook
National Weather Service Riverton WY
210 AM MDT Mon May 21 2018

Yellowstone National Park-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-
Teton and Gros Ventre Mountains-Jackson Hole-
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-Star Valley-
Salt River and Wyoming Ranges-Upper Green River Basin Foothills-
Upper Green River Basin-South Lincoln County-
Rock Springs and Green River-Flaming Gorge-East Sweetwater County-
210 AM MDT Mon May 21 2018

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and Tonight

Isolated afternoon and evening thunderstorms mainly over the
northern and western portions.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Tuesday...Widespread showers and thunderstorms by late afternoon,
continuing overnight. Heavy rain with localized flooding with the
stronger storms, especially east of the Divide. Some stronger
storms will have hail and strong wind gusts.

Wednesday...A chance of afternoon and evening thunderstorms,
especially over western and northern portions. Locally heavy rain
possible over the northwest.

Thursday...A chance of afternoon and evening thunderstorms over
and near the mountains. Isolated thunderstorms elsewhere.

Sunday...A chance of thunderstorms in the west. Isolated
thunderstorms elsewhere.


Spotter activation will not be needed today or tonight.


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Silver Spring, MD 20910
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