Another atmospheric river storm system this week is aimed at Carson City and surrounding counties, further bringing the chances for low elevation rain and high elevation snow to an already water-logged region, according to the National Weather Service.
Prior to the main storm system beginning, additional waves of moisture will keep rain and snow chances going Sunday and Monday, with a Flood Advisory continuing for Carson City, Douglas, Lyon, Mineral, Storey and Washoe counties. Urban and small stream flooding caused by rain and snowmelt is expected to continue through the early Sunday afternoon and subside slowly through this evening.
The stronger storm is likely to bring heavier precipitation with increased winter and hydrologic impacts Monday night through Tuesday, with unsettled and showery conditions through the week. A Winter Storm Warning is in effect until 5 p.m. Wednesday for the Lake Tahoe area, with additional snow accumulations of 2 to 4 feet above 7,000 feet and 4 to 12 inches at level through Monday and on Tuesday, 4 to 12 inches at lake level and Truckee with 1 to 3 feet above 7,000 feet.
The weather service warns snow loading on structures will increase due to the additional rain and snow being absorbed into the deep snowpack, along with higher risks for dangerous roof collapses. Travel could be very difficult to impossible at times.
Snow levels will vary between 6,000 to 6,500 feet through Monday, then rise between 7,500 to 8,000 feet Tuesday afternoon before falling below 6,000 feet Wednesday morning. The heaviest snowfall rates are expected on Tuesday.
Due to continued the nature of the storm, the weather service advises to avoid travel if possible. Those traveling should prepare for long delays and carry an emergency kit with extra food, water and clothing. Those staying at home should have a backup plan in case of power outages.
Minor to moderate flooding along creeks and streams as well as in low-lying, poor drainage and agricultural areas is expected. Most mainstem rivers have begun to recede with the exception of portions of the Carson River near Carson, the Walker River near Snyder Lane, and the Middle Fork Feather River near Portola. Even as rivers recede, high flows can still be expected, according to NWS forecasters.
The following is from the National Weather Service forecast discussion, which is updated twice daily. In Sunday morning’s briefing, forecasters discuss the upcoming storm and what to expect.
The storm will bring gusty winds, heavy-wet snow above 7,000 to 8,000, spillover rainfall to western Nevada and renewed flooding and snow load/avalanche issues. Compared to this past weekend’s AR, this one looks slightly cooler with lower snow levels, the weather service said.
WIND:
There will be gusty south-southwesterly winds Tuesday late morning through the afternoon ahead of the cold frontal passage Wednesday morning. Winds do not look as strong as this past Friday, which had several gusts over 50 mph across the Sierra, northeast California, and western Nevada. Wind gusts look to be on the order of 40-50 mph, with Sierra ridges feeling gusts of 100+ mph. Plan on impacts to travel, especially for aviation interests and high-profile vehicles.
SNOWFALL/SNOW LEVELS:
Surges of subtropical moisture associated with the next AR will move across northeast California, the Sierra Nevada, and into western Nevada Monday night into early Wednesday. Snow levels look to rise to 6,500 feet for northeast California, 7,000-7,500 feet for the Lake Tahoe Basin eastward across western Nevada along I-80 and US-50, and 8,000 feet for Mono County and western Nevada south of US-50 during the day Tuesday. As the cold front approaches the region late Tuesday, snow levels are anticipated to decrease 2,000 to 2,500 feet by early Wednesday morning.
However, precipitation will be lessening as this occurs. If the current forecast holds, heavy wet snowfall will be possible mainly above 7000′ across the Sierra Nevada. Some light snow, generally less than an inch, will be possible Wednesday morning in far western Nevada above 4,500 feet as the snow levels drop with the approach of the cold front.
The core of the AR looks to be directed mainly at the central, southern Sierra, which will bring heavy snowfall to parts of far western Mono County, which could receive 4+ feet of fresh heavy, wet snowfall. Farther north into the Lake Tahoe Basin, 2-3 feet are possible near the Sierra crest, with amounts quickly dropping off below 7,000 feet, with a few inches of wet snow likely during the onset and final stage of this storm.
We have seen several structural issues from snow loading in the Sierra Nevada from this past AR. Snow loading on structures will likely continue with this next AR due to heavy rainfall being absorbed by the already existing deep snowpack, especially for areas below 7000′ in the Lake Tahoe Basin and below 8000′ in the Eastern Sierra. There will also be a higher risk of roof collapses in these areas. Follow guidance from local officials and building inspectors for ways to monitor and mitigate the risk of increased snow loads on roofs.
LOWER ELEVATION RAINFALL:
Bands of rain look to extend across western Nevada beginning Tuesday morning, lasting through much of the day. The latest storm total precipitation forecast show 0.50-1.25 inches for far western Nevada communities of Reno, Virginia City, Carson City, and Minden, tapering off to 0.25-0.50″ into the Basin and Range of western Nevada. Depending on where the core of the AR centers over the Sierra Nevada, we could see higher rain totals south of US-50 in western Nevada, which have been hard hit from this past AR, with flooding and rockslides.
FLOODING RISKS:
Rises are currently forecast on all rivers and streams Tuesday into Wednesday. River forecast confidence remains varied since we are still 2-3 days out. However, wet soils, a receptive mid- elevation snowpack, and ongoing elevated streamflows could lead to more rapid runoff during this AR event. Use the next few days to prepare for possible flooding. Expect flood prone areas and streams below 7,000 feet to have problems again Tuesday through Wednesday. Do not let your guard down and stay tuned for updates on river forecasts at cnrfc.noaa.gov.
For the latest road conditions go to NVroads.com or call 511. Check back for updates.
