April 2013 Wyoming Spring Snowmelt Flood Potential Outlook
Upper Green River Basin flooding potential mostly Low
by Jim Fahey, Wyoming National Oceanic and Atmospheric Administration (NOAA) hydrologist
April 17, 2013
(SNOTEL data used to make this outlook and graphic as of April 16th)
Mountain snowpack and associated snow water equivalents (SWEs) across Wyoming have increased to 91 percent of average as of April 16th. SWEs at the peak snowmelt runoff elevations (8,000’ – 9.500’) were the highest across northern Wyoming at around 90 to 105 percent of normal; while across southern Wyoming, SWEs have increased to 75 to 95 percent of average at the peak snowmelt runoff elevations.
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), extent of burn scars from 2012 fires,amount of bark beetle kill, and likely temperature and precipitation trends during late spring/early summer.
Moderate potential for flooding associated with snowmelt is expected across various headwater streams along the Powder River Drainage as well as eastern portions of the Big Horn Basin (including the Middle Fork of the Powder, Nowood River, and Ten Sleep Creek).
All other of headwater basins across Wyoming can expect a generally low potential for flooding due to springtime snowmelt.
The next and last graphical outlook will be issued around the 10th of May.
NOAA hydrology website
Monthly Wyoming Hydrologic Summary and Graphics (updated monthly around the 15th of every month)
Wyoming Drought Information Page (updated at least once a month)
Wyoming Graphical Water Supply Outlook (updated by the 15th of every month—January-June)
Wyoming Average Precipitation by Basin (updated monthly)
Wyoming Spring Snowmelt Runoff Flood Potential Graphic (updated by the 25th of the month---January-May)
Current and Forecast Wyoming Streamflows and/or River Stages (Weather.gov)
Current and Forecast Wyoming Streamflows and/or River Stages (USGS water data)