NWS Riverton Issues Spring 2017 Snowmelt Flood Potential Outlook

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WYOMING — Mountain snowpack and associated snow water equivalents (SWEs) across central through western Wyoming continued to be much above average by the middle of March; while SWEs across basins in southeastern Wyoming were generally above average.

SWEs at the peak snowmelt runoff elevations (8,500’ – 10.000’) were the highest across the Wind and the Upper Green Basins at 170-to-180 percent of median.

The Tongue and Powder River Drainages had SWEs at 85-to-near 100 percent of median at the peak snowmelt runoff elevations.

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This outlook is based on various diverse hydrological factors such as: snow water equivalents (SWEs) in the mountain snowpack, basin morphology (i.e. how basins respond to snowmelt runoff), antecedent soil moisture, amount of forest canopy damage, recent burn scars, low elevation snow depths, and likely temperature and precipitation trends during late spring/early summer.

Highlights

Moderate to high potential for flooding associated with snowmelt is expected over several basins across the Little and Big Wind Watersheds.

Moderate to high potential for flooding associated with snowmelt is expected over several headwater basins of the Upper GreenBasin.

Moderate to high potential for snowmelt flooding is expected over headwater basins of the Snake River Basin (to include theSalt River Drainage).

Moderate to high potential for snowmelt flooding is expected over portions of the North and South Forks of the Shoshone RiverBasin.

Moderate potential for flooding associated with snowmelt is also expected across the upper to middle portions the of the Little and Big Wind Watersheds, the middle to upper portions of the Upper Green Drainage, the lower and/or upper portions of the North/South Forks of the Shoshone Basin, the upper and lower sections of the Upper Bear Watershed, and several basins across the Snake River Watershed.

All other headwater basins across Wyoming can expect a generally Low potential for flooding due to springtime snowmelt.

The next outlook will be issued by the 20th of April.