Apr 5, 2013 - By Eric Blom, Staff WriterSnowpack in the Wind and Sweetwater river basins remains below average, but Riverton has seen more precipitation this year compared with last year, and officials expect more moisture this month.
"April is our wettest month and into May," National Weather Service specialist Rich Miller said. "So I would say this is the most critical part of the year."
The most recent precipitation to hit Riverton fell March 29 and March 30, but only trace amounts were recorded. The city saw a total of .11 inch of precipitation in March, which is about 20 percent of that month's average monthly total of .55 inch. March 2012 brought even less moisture, however. The city received .03 inches of precipitation that month.
March 2013 in Riverton also was warmer than usual. The month saw a mean temperature of 36.5 degrees, 3 percent above the normal of 35.4 degrees.
Average precipitation for April in Riverton is 1.3 inches, Miller said, and the forecast shows a typical amount of moisture for the month. If that prediction proves true, this April will be wetter than the same month in 2012, when .51 inch of precipitation fell.
A total of .76 inch of precipitation has been measured this year since Jan. 1 -- 29 percent less than the 1.06-inch average. But last year was drier yet: Riverton only saw .50 inches of precipitation between Jan. 1, 2012, and the end of March 2012 -- 34 percent less moisture than this year.
Since July 1, Riverton has seen 19.9 inches of snow, 25 percent less than the 26.4 inches the city received in the same period during the previous snow year.
Across the Wind River Basin, the snow water equivalent, or the amount of liquid water snowpack would melt into, stood at 79 percent of the 30-year average at the end of March for that time of year. The National Resource Conservation Service released a weekly report on snowpack April 1.
This week's number is a slight improvement over the 78 percent seen two weeks ago.
Three weeks ago, snowpack in the basin stood at 83 percent of normal. Last year at this time, the snow water equivalent measured at 96 percent of normal.
The Sweetwater River Basin, which crosses the southern third of Fremont County, has followed a similar trend. Its most recent measurement at 72 percent of normal is 1 percent lower than last week and down 6 percent from two weeks ago.
Accumulated snow in the mountains feeds streams and rivers in Fremont County as it melts through the spring and summer.
Current snowpack in the southern Fremont County river valley stands lower than the 82 percent seen at this time last year.
"We've had fairly significant melting at the lower elevations," National Weather Service meteorologist Chuck Baker said. "That's kind of typical for this time of year."
The average of snow water equivalent measurements across Wyoming at the start of the month was 82 percent, an improvement over the 76 percent seen at that time last year.
The National Oceanic and Atmospheric Administration released a map last weak showing a three-month drought forecast. Fremont County straddles the line between areas where conditions are expected to improve and where the drought should persist or intensify.
The line runs from the northwest along the Wind River and continues southeast after the river bends north. South of the line, NOAA expects the drought to continue or worsen, and north of it the federal agency predicts the dry conditions to slacken.
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