Governor Mead and the National Weather Service have proclaimed May 7 through 11 as Wyoming Flood Awareness Week. The awareness week is intended to promote flood safety and preparedness, understanding of the different flood hazards that can impact Wyoming, and improved monitoring of hydrologic conditions.
The transition to warmer temperatures in May often signals the majority of mountain snowmelt. Even during years of average or below normal snowpack, a quick warm-up can rapidly melt snow and lead to flooding of mountain streams and tributaries. Flooding from snowmelt is becoming more accurately forecast, providing officials more lead time to prepare for rises along these waterways.
|Lincoln County - June 2011||Crowheart River Gauge - July 2011||The Wind River Floods a Home Along HWY 26|
The record snow pack, late season storms, and a cooler than normal April and May led to increased flooding concerns again in 2011. However, with the flooding of 2010 fresh in a lot of minds around the state, officials were ready. Sandbagging efforts and reservoir releases began early, but we are always at the mercy of mother nature. The snowpack stayed in place very late into the season; it had to come down eventually, and it did so all at once as the state finally hit a warm spell in early July. The rapid snowmelt overwhelmed area rivers which resulted in flooding in Riverton and Kinnear. Flooding also occurred in the Bighorn Basin, flooding portions of Basin and Medicine Lodge State Archaeological Site, to name a few.
Snowmap from The University of Wyoming Illustrating Snowpack as a percentage of normal in 2011
Snow pack in area mountain ranges are below normal this year which decreases the chance for snowmelt flooding this season. However, there is still over 2 feet of water held within the snowpack over higher elevations that has yet to melt. NWS officials are urging residents of cities and towns near rivers to monitor www.weather.gov/riverton for details on the potential for flooding this year.
Flash flooding, typically the result of intense thunderstorms, is a different matter. There have already been several days with thunderstorm activity this year. Even during drought years, an intense thunderstorm can quickly inundate a drainage basin of a small stream or river, causing flash flooding in a matter of an hour, if not minutes. Historical flash flooding of Cheyenne on August 1, 1985, and of Kaycee on August 27, 2002, are two examples of heavy rain falling within small drainage basins resulting in rapid water rises. NWS officials are also urging residents of cities and towns to be prepared for the quick water rises in urban areas that can occur after intense rainfall, even if the rain only lasts 20 or 30 minutes.
“The flooding in Fremont County in 2010 was a good example of how several seemingly innocuous conditions can come together to create devastating floods,” said Kelly Allen, Meteorologist at the Riverton NWS office. “During this week we want to stress the importance of why the public should stay informed about changing conditions. Residents near rivers and streams should monitor the NWS web site or All Hazards NOAA Weather Radio for the most current information and they are strongly urged to develop a flood action plan.”
This week, NWS and emergency officials are reminding people to never swim, play, or walk through flooded areas and to avoid camping near streams or dry washes if there is a threat of flooding. Officials say that even if rain did not fall at your location, headwaters in the mountains may have received heavy rain which could cause rapid water rises downstream. Campers and hikers should consider taking along an All Hazards NOAA Weather Radio receiver, which provides easy access to current forecasts and alert information for weather and man-made disasters.
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