Published: May 8,2015
Thoughts of Mother's Day typically include flowers and warmer temperatures. That will not be the vision for many in parts of the West and Plains this year.
A late-season snowstorm is setting up in the central and northern Rockies for Mother's Day weekend, that is likely to have significant travel road travel impact. Winter storm watches have already been posted in parts of Wyoming.
(INTERACTIVE MAP: Winter Alerts)
A closed upper-level area of low pressure has moved into the West Coast and will slide eastward this weekend, producing significant snow across the northern and central Rockies. The Sierra should also see at least some beneficial snowfall.
(MORE: Record Low Snowpack in the Sierra)
But this will not just be a mountain event. Sufficient cold air nosing southward down the High Plains and powerful lift in the upper atmosphere will allow precipitation to fall as snow even in lower elevations of the High Plains. That snow could be heavy, as well.
When, Where and How Much
Saturday Night's Forecast
Sunday's Forecast
Sunday Night's Forecast
Snowfall Forecast
Late week: Cooler conditions will move into parts of California Friday as an upper-level low digs southward into California from the Pacific Northwest. This is also known as an "inside slider". Snow began to fall in the higher elevations, especially over 7,000 feet, early Thursday and locally heavy snowfall continues to be possible. A few inches of snow, however, are possible down to 6,000 feet in the Sierra. This system will also bring showers and thunderstorms to the lower elevations.
If you are traveling through the Sierra expect slippery roads. Chains and a winter survival kit are recommended from the National Weather Service office in Hanford. There may even be a chain requirement on Interstate 80 and U.S. 50.
(FORECAST: Lake Tahoe, California | Sequoia National Park)
Saturday: The upper-level low will slide east this weekend, and the rain and snow will end in California. The chance for significant snow in parts of the Rockies will increase. The best chance for heavy snow will be in the higher elevations in central and eastern Wyoming, northern Colorado and the Black Hills of South Dakota. Snow levels are expected to lower Saturday night, with snow, possibly heavy, developing over lower elevations of the High Plains of these areas.
Travel may quickly become hazardous along parts of Interstates 80 and 25 in Wyoming, Interstate 90 in far western South Dakota and northeast Wyoming, and Interstate 70 in the Colorado high country.
(FORECAST: Aspen, Colorado | Yellowstone National Park | Casper, Wyoming)
Sunday: The snowstorm continues in the High Plains and mountains of eastern Wyoming, western South Dakota, the Nebraska panhandle and northern Colorado high country. Heavy snow may be accompanied by strong winds, producing whiteout conditions, at times.There are some differences in the computer forecast models, but it could be cold enough for snow in parts of the Denver metro (particularly the foothills).
Dangerous travel conditions are likely on Interstate 80 in southern Wyoming, Interstate 90 in far western South Dakota and northeast Wyoming and Interstate 25 in Wyoming. Parts of these interstates may have to shut down for a time. Travel may also remain difficult along Interstate 70 in the Colorado high country, as well.
(FORECAST: Denver | Cheyenne, Wyoming | Rapid City, South Dakota)
Rain and snow should slowly diminish Sunday night, and will likely clear the region by Monday morning. Snowy travel may linger into early Monday in these areas.
Snowfall up to a foot is possible in the Sierra's highest elevations.
The mountains in northern Colorado and Wyoming and the Black Hills of South Dakota should see total snowfall amounts of 1 to 2 feet, with locally higher amounts possible.
Some lower elevations of Wyoming, the Nebraska panhandle, and far western South Dakota may see 6 inches of wet snow or more.
(MAPS: Weekly Planner)
Plan ahead if you have plans to drive in any of these areas over the Mother's Day holiday weekend. Heed all National Weather Service winter storm watches and warnings. Staying informed ahead of the storm will keep you from being stranded in open country.
Are May Snow Storms Unusual?
(MORE: Winter Storm Zephyr Recap)
The average date for the last measurable snowfall (0.1 inches of snow or greater) in Cheyenne, Wyoming, is May 9, so this is not that unusual for the area. Casper, Wyoming, sees almost 3 inches of snow on average during the month of May.
In the Denver area, the average date for last measurable snowfall is April 27, so this is a little later than average. However, Denver has seen snow as late as June.
In Scottsbluff, Nebraska, an average of half an inch of snow falls in May. Rapid City, South Dakota averages 1.1 inches of snow in May and has received snow in June, with the latest date of measurable snowfall being June 13, 1969.
When digging into the record books, even one-foot snowfalls in a single May day are not as rare as you may think in this area.
Locations with at least 5 years of data that have reported their largest post-May 5 one-day snowfall of over a foot. Anchorage, Alaska-based meteorologist Brian Brettschneider found dozens of locations not just in the mountain West, but also in lower elevations from the High Plains of Montana and the Dakotas to even northwest Kansas and the Texas panhandle that have picked up over a foot of snow on any calendar day after May 5.
Brettschneider found a station near Lusk, Wyoming once measured 36 inches of snow in a single day on May 10, 1922. Three feet...on May 10!
So, while parts of the nation are dealing with severe thunderstorms, snowthrowers and snow plows will be busy in the Rockies and High Plains, on Mother's Day weekend.
Meteorologist Jonathan Erdman contributed to this report.
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