Spring 2018 Flood and Water Resources Outlook
by National Weather Service - Riverton Wyoming
February 19, 2018
This Spring and early Summer 2018 flood outlook includes the Wind, Big Horn, Green, Powder, Sweetwater, Shoshone, and Upper Yellowstone River Basins. A small portion of the Snake and the Lower North Platte Basins is also used to make this runoff forecast. The outlook is from today through the end of June.
Many basins east of the continental divide receive up to 55 percent of their water year total for precipitation during the months of March through May. Accordingly, mountain snowpack can drastically change from late winter to late spring for basins east of the continental divide.
Wyoming generally does not see any significant mountain snowmelt runoff until early to middle May, with mountain snowmelt runoff peaking around early June. Therefore, at this time, it is way too early to make any long range prediction on & the magnitude of flooding due to mountain snowmelt runoff.
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), amount of biological factors (beetle kill, blight), low elevation snow depths, and likely temperature and precipitation trends into late spring/early summer.
Current water precipitation is averaging 90 to 100 percent of normal across Wyoming.
Mountain snowpack across Wyoming is 100 to 115 percent of average.
Wyoming carryover reservoir storages are 115 to 125 percent of average for February.
Above normal snowmelt streamflow volumes are expected across major drainages from central through northwestern Wyoming.
Other hydrological information for Wyoming can be found at the NOAA website: www.weather.gov/riw/local_hydrology
For the current Wyoming spring flood potential graphic, please refer to: www.weather.gov/images/riw/hydro/floodoutlook.png
For the current Wyoming water supply graphic, please refer to:
For the latest Wyoming average monthly precipitation by basin graphics, please refer to:
For the latest monthly Wyoming hydrologic summary and graphics, please refer to: www.weather.gov/media/riw/hydro/hydro_report.pdf
For current and forecast Wyoming streamflows and/or river stages, please refer to: www.water.weather.gov/aphps2/index.php?wfo=riw
For Wyoming drought information, please refer to: