Wyoming Water Outlook above average for headwater watersheds
by James Fahey, Hydrologist. NOAA/National Weather Service
March 30, 2011
Synopsis:
Snow water equivalents (SWEs) in early March continued above average (around 120 percent of normal) across Wyoming’s headwater watersheds.
Current SWE trends vs Historic SWEs & Peak Flow Probabilities for selected basins:
Snake River Basin:
• SWEs were 100 to 110 percent to normal in early March
• Current SWE trends are above the 30-year normal--but well below the record 1996 and 1997 SWE years.
• LOW to MODERATE potential for headwater spring snowmelt flooding
Snake River near Jackson
21 - 40% chance: >15,000 cfs
Flood flow = 20,000 to 22,000 cfs
Upper Green Basin:
• SWEs were 100 to 110 percent of average in early March.
• LOW TO MODERATE potential for headwater spring snowmelt flooding across much of the basin.
Green River near LaBarge
21 - 40% chance: >10,000 cfs
Other factors that lead to this outlook include: basin geometry/morphology, biological influences (i.e. beetle kill areas in southeast Wyoming), and advice from outside sources and experts.
Snowmelt flood potential in Wyoming is greatly influenced by the amount of mountain snowpack. The additional accumulation of snowpack during late April through early June is very crucial to the magnitude of runoff flooding that headwater basins across Wyoming will experience. Bottom line is that a lot can happen between now and the onset of the annual spring runoff when it comes to the potential for flooding.
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