Periods of moderate to heavy rain are forecast during this week of Christmas.
The National Weather Service has issued a Flood Watch for the Mother Lode, the northern San Joaquin Valley the Sierra Nevada, and Yosemite National Park until Friday afternoon. Additionally, a Flood Watch for the Mariposa County foothills and the central San Joaquin Valley will run from 4 PM this afternoon until Friday afternoon.
This is a severe event that is possible to develop flooding, caused by excessive rainfall.
Excessive runoff will result in rises along area rivers, creeks, streams. 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 the mountain and foothill areas. Debris flows are not expected over recent burn scars in northern California, but do anticipate enhanced runoff in and below the scars.
You should 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.
Additionally, a High Wind Warning has been issued for the Mother Lode and the northern San Joaquin Valley, from 4 PM this afternoon until 4 PM Thursday. A Wind Advisory will also be in effect for Mariposa County, the Yosemite National Park Valley floor and the central San Joaquin Valley, from 4 PM this afternoon until 4 PM Thursday.
Two periods of strong wind gusts are expected tonight into Wednesday morning and then again from Wednesday night into Thursday, with a lull during the day on Wednesday.
South winds of fifteen to thirty-five mph are forecast, with gusts ranging from forty to sixty mph.
Strong winds and saturated soils could blow down trees and power lines resulting in widespread power outages. Gusty winds will cause impacts to loose and unsecured items, including temporary structures and holiday decorations. Watch for falling debris and tree limbs.
Winds this strong can make driving difficult, especially for high profile vehicles. Use caution if you must drive. Take time now to prepare for potential power outages.
Finally, the Winter Storm Warning issued for Yosemite National Park, above the Valley floor, remains in effect until 10 PM Friday. The Winter Storm Warning for the western slope of the northern Sierra Nevada will start at 10 PM tonight and continue until 10 PM Friday.
Heavy snow is likely. Snowfall rates of one to two inches per hour are possible at times.
Snow levels are around 7,000 to 8,000 feet today and will lower to around 4,500 to 6,000 feet during the day Wednesday through Friday.
Total snow accumulations of up to a foot are likely between 4,500 to 5,500 feet. Four to eight feet of snow is likely above 5,500 feet. The higher you go, the more the snow.
Upper elevation Winds could gust as high as fifty-five to sixty mph, which could cause tree damage.
Travel may be very difficult to dangerous to impossible with chain controls, road closures, localized tree damage, power outages, and low visibility due to the combination of heavy wet snow and strong winds. If you must travel, keep an extra flashlight, food, and water in your vehicle in case of an emergency.
