NWS Riverton WY - April 21 2004 - Five Year Anniversary of April Snowstorm

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Five Year Anniversary of April Snowstorm in Central Wyoming

The storm started on the evening of April 21, 1999 when rain quickly changed over to snow at Lander. The Riverton Airport soon followed with snow while downtown Riverton saw rain most of the evening, changing to snow early Thursday morning. A large upper level storm system moved out of the Pacific Northwest settled into southwest Idaho Thursday morning April 22, 1999. A moist easterly upslope flow developed aloft over central Wyoming Thursday as this storm sank south into Nevada by Thursday evening. At the surface low pressure formed in the Great Basin with high pressure over the northern United States. This brought a moist, lower level, east northeast flow into Central Wyoming Thursday into Thursday night. On Friday, April 23, 1999, a weather disturbance moved through the area and this brought another round of heavy snow to central Wyoming. The snow finally ended early Saturday morning in Riverton and Lander. Roads were closed over South Pass as well as to Muddy Gap during the height of the storm.

Record snowfall fell in Lander with a storm total of 52.7 inches. This was the biggest snowstorm on record for Lander. The 28.6 inches in one calendar day on April 22, 1999 was a record. Snow depths in Lander reached between 30 and 40 inches and there were power outages as well as damage to some roofs in town.

Lander also set an April monthly snowfall record with 70.4 inches.

Riverton airport received 22.2 inches from the storm while downtown Riverton had 17.5 inches. It took longer for the rain to change to snow in downtown Riverton, thus the storm total difference. Snow depth of 10 to 15 inches was observed across Riverton at the storm�s worst.

Rock Springs was deluged from this storm as well, with 18.5 inches recorded at the airport. In addition, wind speeds of 40 to 45 mph with gusts to 55 mph created blizzard conditions at times along Interstate 80 in Sweetwater County. In fact, at the storm�s worst, Interstate 80 was closed from the Utah state line to Rawlins.

*Snowfall Reports*
*April 21-23, 1999*
*Location*	Snowfall (inches)
Lander	52.7
Sinks Canyon	48
Red Canyon	42
South Pass City	31
Hudson	23
Riverton (Airport)	22.2
Gas Hills	20
Diversion Dam	18.3
Riverton (Downtown)	17.5
Burris	16
Dubois	15
Jeffrey City	12.5
Pavillion	10
Shoshoni	*ZERO*

NOAA National Weather Service Weather Forecast Office