2011 Flood Summary and Info on Record Flows Expected in Yellowstone

As expected, a record snow pack led to record flows and lake levels around the state.

The snow pack on Togwotee Pass held nearly 50 inches of water this winter! Some late season storms dropped a couple of FEET of snow at once! All of this water drains into the Wind and Snake Rivers... The blue line shows the snow water equivalent on Togwotee Pass this winter - compare this to the purple line below (SWE average 1971-2000). The red line shows accumulated precip this water year, compare that to the orange line (precip average 1971-2000).


The record snow pack, late season storms, and a cooler than normal April and May led to increasing flooding concerns this year. 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. At first, the water came off slowly as we started off with a series of 6 warm spells in June, each lasting less than 3 days and each separated by a cool day or two. We also narrowly escaped a major rain storm that looked like it was heading straight for Wyoming on Father's Day; as the storm approached, a disturbance to the north and the base of a trough to the south split the energy and spared our ripe snow pack from receiving as much rain as was originally feared. Rain on top of a ripe snow pack was the primary cause of the flooding in 2010.

The Visible Satellite image above shows how much snow was still left in the mountains as of July 1st. The Visible Satellite image above shows how much snow was left in the mountains as of July 9th.

The water had to come down sometime and it came down very late. Many rivers had not only record high crests, they had record late crests. We finally hit a warm spell that was long enough and hot enough to bring the snow pack down in large volumes. As of July 1st: Grand Targhee at 9260 feet still had over 40 inches of water available (SWE) and ready to drain into the Snake River basin. Togwotee Pass still had over 20 inches of snow water equivalent ready to drain into the Wind and Snake River basins. Fisher Creek and Two Ocean Plateau SnoTEL sites were reporting around 25 inches - each - ready to come down. As of July 9th, Grand Targhee has 31 inches of SWE, Togwotee Pass has 17 inches, and Fisher Creek and Two Ocean Plateau have lost over 10 inches of SWE in the past week or so; they are both below 15 inches of SWE. Many lower sites have lost all of their snow pack (as seen in the two satellite images) but much of the snow pack still remains along the highest peaks.

For the latest SnoTEL summary, click here


Record Flooding on the Wind River at Crowheart - July 2, 2011 Record Flooding of the Wind River near Riverton - July 2, 2011

The following graph summarizes some 2011 crests of note with the new records highlighted in yellow. Flood stages and crests are reported in feet. The rivers that have may not have reached their potential crest for the season are highlighted in blue.

River Location Flood Stage 2011 Crest and Date Record Crest and Date
Big Horn Basin 11.0 10.80 on 6/11 10.49 on 6/7/1991
Blacks Fork Little America 10.0 10.40 on 5/31 11.18 on 3/13/1997
Clear Creek Buffalo 6.0 5.36 on 6/30 7.10 on 6/8/1997
Green River Green River 7.0 6.28 on 7/4 8.53 on 9/7/1965
Green River Labarge 9.5 9.35 on 7/3 10.50 on 6/9/1986
Little Wind Riverton 8.0 8.93 on 7/2 11.91 on 6/9/2010

Middle Fork Popo Agie

Sinks Canyon 6.5 5.91 on 7/1 7.69 on 6/16/1963
New Fork Big Piney 8.5 7.52 on 7/2 8.28 on 6/7/1986
North Fork Shoshone Wapiti 8.0 8.06 on 6/30 12.00 on 6/9/1981
North Platte Casper 8.0 7.90 on 6/20 8.34 on 6/9/1984
Salt River Etna 6.0 6.00 on 5/25 5.96 on 5/30/1983
Snake River Jackson 10.0 8.50 on 7/1 11.66 on 6/11/1997
Wind River Dubois 5.0 5.59 on 7/1 5.66 on 6/2/1956
Wind River Kinnear 9.0 9.69 on 7/2 8.97 on 6/10/1997
Wind River Riverton 9.0 11.80 on 7/2 10.86 on 6/10/1997
Yellowstone River Fishing Bridge 9.0 8.71 on 7/8 8.97 on 6/10/1997


The next record of note will occur in Yellowstone as we approach record lake levels at Yellowstone lake and record flows on the Yellowstone River near the Fishing Bridge. For details, check out our latest Flood Outlook. And keep an eye on the gage at the Fishing Bridge for the latest river forecast, and on our homepage for the latest flood products. Also, if you are visiting the park in the coming week, please review this refresher on what our different flood products mean and what to do if one is issued for your area.

The blue line represents the latest observations from the gage. The value in blue above the line is the latest crest. The green line represents the river forecast. Click on the image for more information on impacts and record crests.

This story was last updated on July 6, 2011

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