February 10, 2018 – Gusty north winds and slightly cooler on Saturday. A chance of light showers over the mountains Monday. Another round of Gusty north winds early next week.
Wind Advisory for Placer, Yuba, Plumas, El Dorado and Nevada counties
The National Weather Service in Sacramento has issued a Wind Advisory, which is in effect from 1 PM this afternoon to 4 AM PST Sunday.
* Winds: Winds 25 to 40 mph with gusts up to 65 mph. Strongest winds expected late Saturday afternoon into Saturday night.
* Impacts: Blowing debris and more difficult driving for higher profile vehicles.
Precautionary/Preparedness Actions
A Wind Advisory means that sustained winds of 25 mph or higher or gusts to 40 mph or higher are expected. Winds this strong can make driving difficult, especially for high profile vehicles. Use extra caution.
Discussion
Main forecast concern for the short term forecast is the expected gusty winds for the Valley and the Sierra Saturday afternoon and evening.
Upper level ridge continued to be in place overnight with a shortwave disturbance sliding across the Pacific northwest. High level clouds were beginning to slide across the forecast area with temperatures in the mid to upper 40s for the valley and the upper 20s for the Sierra. Patchy fog was developing for the lower San Joaquin Valley.
Latest model upper level progs show the shortwave to the north will continue moving to the south/southeast, which will clip the Sierra. Water vapor imagery shows a lack of moisture in front of the main system, so not expecting any precipitation today or tonight for the mountains. As the trough aloft passes, a surface high pressure system will move southward to the east of the Sierra into the Great Basin. This 1026 mb high, in combination with low pressure in the valley around 1010 mb, will create a wind driving pressure gradient across the valley during the afternoon. Expecting winds between 25 and 35 mph with gusts up to 50 for the west side of the Sacramento Valley in the I-5 corridor through this evening.
Latest model trends for the mountains show winds picking up late this afternoon and tonight, especially for higher Sierra elevations. As the high pressure moves southeast tonight just east of the Sierra, the pressure gradient will shift to the east along the crest and create strong winds through tonight. Omega values along the Sierra indicate sinking air overnight in a similar region to the lower and mid level jet of approximately 40 to 45 kts, which may indicate some upper level support for stronger winds tonight. Expecting winds between 25 and 40 mph with gusts as high as 65 mph. This will impact a portion of I-80 and Highway 50.
Winds will subside Sunday morning before another upper level disturbance moves southward across northern California in the afternoon. The track indicates a bit higher of moisture content, which could lead to some light rain and snow for the Sierra Sunday night through Monday night. Little to no snow accumulation expected north of highway 50, but about an inch south of Highway 50 for the mountains can be expected.
The cooler air masses will bring a break from record-setting warmth. Afternoon high temperatures this weekend through early next week will be near to slightly above normal.
Extended discussion (Wednesday through Saturday)
Dry pattern returns during the second half of next week as quasi- Rex block remains in place with strong ridging over the eastern Pacific and a cut-off low in the vicinity of SoCal. High temperatures will return to around 10 degrees above average.