Look for a brief break in the winter weather later today and Friday before a strong atmospheric river brings what the National Weather Service’s Reno office is calling, ‘copious amounts of rain and snow’ to the region from Saturday through Monday. According to NWS forecasters, some flooding is looking likely for mainstem rivers, creeks and streams, including the Susan River, this weekend into early next week.
Thursday and Friday
Expect snow showers off and on throughout the day today until late tonight when we should finally see a break in the precipitation with clearing skies and very cold temperatures.
Chris Smallcomb, NWS Reno’s Warning Coordination Meteorologist said, “This is the time to prepare for the next atmospheric river event over the weekend and make sure all drains are clear of snow and other debris.”
According to the NWS, atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics. These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow.
Saturday through Monday
- Moderate to Strong Atmospheric River likely Saturday-Monday.
- Flood Impacts Likely Sunday-Monday. Prepare now!
- Freezing rain possible in valleys below 5,500 feet Saturday morning.
- Poor conditions for travel and outdoor activities this weekend.
Precipitation will likely start Friday night or early Saturday morning in the form of snow all areas with some freezing rain possible in valleys below 5,500 feet. Widespread travel impacts are possible due to snow and ice covered roads.
Snow levels should rise rather quickly Saturday afternoon and evening as deeper moisture and warmer air arrives. Snow levels are forecast to peak by early Sunday morning, then remain steady through Sunday night during the period of most intense precipitation.
“North of I-80 we`re looking at snow levels near 8,000 feet,” explained Smallcomb, “near 9,000 feet for Reno-Carson-Tahoe.”
A Flood Watch Has Been Issued for Lassen, eastern Plumas and eastern Sierra counties
A Flood Watch will be in effect from Saturday evening through late Sunday night.
NWS forecasters expect that liquid amounts could approach an astounding 12 inches along the entire length of the Sierra Crest, with 6-12 inches between the Sierra Crest and foothills west of US-395. Along US-395 rain totals this weekend could approach 3 inches, with less than 2 inches along and east of a line from Gerlach, Pyramid Lake, Lyon County, Mono Lake.
Snow levels should lower to 6,000 feet during the day Monday which could bring some snow accumulations to the Sierra passes as the system nears an end.
The Susan River and the Honey Lake Valley
“Now is the time to prepare for flooding!” warns Smallcomb. “Do not wait until Sunday.”
Beginning late Saturday night, through Monday morning, hourly rainfall rates should exceed 0.50 inches per hour in the Sierra and Carson Ranges. Snow levels will lower on Monday near the end of the event which will end the flood threat in the mountains, though high flows on the main stem rivers may continue into Tuesday.
“Soils are saturated and based on the response of rivers, creeks, streams and drainage ditches from today, it won`t take much rainfall to generate flood impacts across the Sierra and western Nevada,” explains Smallcomb.
Creeks, streams, urban areas and farmland are all at risk for flooding late this weekend.
Main rivers with fewer flood control measures, like the Susan River, may have a slightly higher risk of flooding.
Peak flows are forecast to hit late Sunday afternoon and evening on the Susan River. Currently forecasters are expecting the river to top out at 11.3 feet, which is slightly above the ‘action stage’ and historically has resulted in local minor lowland flooding below Susanville in Johnstonville, Leavitt Lake, Standish and Litchfield rural areas.
Smallcomb said that the recent 3 to 6 feet of snow in the higher elevations of the Sierra may also play a role by initially absorbing quite a bit of rain, and/or melting off and adding to the runoff.
There will be a break in the moist onshore flow Monday, but models show potential for additional systems for January 10th through the 14th.
Live hydrology readings from the Susan River… always current and updated
For more information you can always find current conditions at LassenWeatherNetwork.com.
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