Atmospheric River Will Run Through The Holidays

A series of warm atmospheric rivers will bring periods of moderate to heavy rain to the San Joaquin Valley, the foothills, and the mountains during the week of Christmas.

The prolonged period of rain and excessive rainfall will bring the risk of flooding to each of these locations.

The National Weather Service has issued a Flood Watch for the Mother Lode, the western slope of the northern Sierra Nevada, the Sierra Nevada of Mariposa County, Yosemite National Park and the northern San Joaquin Valley From this afternoon through next Friday afternoon. Additionally, a Flood Watch will also be in effect for the Mariposa County foothills and the central San Joaquin Valley from Tuesday afternoon through Friday afternoon.

Heavy runoff will result in rises and possible flooding along area rivers. Small streams and creeks may rise out of their banks. Flooding may occur in low-lying, poor drainage, and urban areas. Mudslides and rockslides may occur in mountain and foothill areas. Low-water crossings may be flooded.

Debris flows are not expected over recent burn scars, but you should anticipate enhanced runoff in or below the scars.

Monitor later forecasts and be alert for possible Flood Warnings. Those living in areas prone to flooding should be prepared to take action should flooding develop.

As far as snow, a Winter Storm Warning is in effect for Yosemite National Park (above the Valley floor), from 4 PM this afternoon until 4 PM Friday. Additionally, a Winter Storm Watch has been issued for the western slope of the northern Sierra Nevada from Tuesday evening until Friday morning.

Heavy snow is forecast.

Snow accumulations will remain near or above pass levels through Tuesday, then drop to around 5,500 feet during the day Wednesday.

Snow accumulation amounts may range from around one foot at 5,500 feet, up to eight feet at the highest elevations.

The winds may gust as high as forty-five to fifty mph. Such gusty winds could bring down tree branches.

Expect dangerous travel conditions with chain controls and road closures possible. There may be low visibility due to combination of wind and heavy snow. Travel could be very difficult to impossible. If you must travel, keep an extra flashlight, food, and water in your vehicle in case of an emergency.