Valley fog and stratus this morning. Another weak weather system will bring a chance of light precipitation this evening into early Friday. Dry and milder weather with night and morning Valley fog and stratus expected over Christmas weekend. An extended period of wet weather with higher snow levels returns next week.

Discussion

Fog and stratus continue this morning. Dense fog has not been widespread thus far with stratus limiting coverage to areas on the edges of the stratus deck. Expect the fog and status to gradually lift through the morning, as mid and upper level cloud cover spread into the area from the west with approaching weather system. Upper ridge pattern remains in place over NorCal. Weak short wave trough will ride over the top of the ridge tonight producing scattered light showers mainly over the mountains where 0.20-0.40 inches of precipitation is possible. Generally less than 0.10 inches over the Valley, except over Shasta county where up to 0.25 inches will be possible. High snow levels above 7000 feet with the system will limit snow amounts with only around an inch expected at pass level.

Upper ridge will reamplify Friday and Saturday with dry and warmer weather returning. Fog will be possible once again during the overnight and morning and this may lower high temperatures from reaching their peak levels. Current forecast would have high temperatures from the mid 50’s to low 60’s, but these values could be 10 degrees cooler if fog persists through the day.

Extended Discussion (Monday through Thursday)

Ensembles are in good agreement with a transition into an unsettled weather pattern for the extended period. Deep troughing will be digging out of the Gulf of Alaska and this will bring multiple rounds of precip. The first round will come later Monday with the highest precip chances on Tuesday as a cold front pushes south through the area. We will see plenty of moisture ahead of the front with the IVT showing 500+ kg/ms. This will bring a period of moderate to heavy rain. This will also be a warmer system with high snow levels above pass level.

Another round of higher precip chances look to come on Thursday with additional chances over the weekend. Early QPF estimates indicate up to 2.50 inches of rain possible over the Valley and up to 3 to 5 inches over the mountains and foothills into early Wednesday.

Significant flooding from snow melt is not expected to be an issue at this point since river and reservoir levels are low. However, urban and small stream flooding could be possible if the forecast holds. Keep an eye on updates as the forecast unfolds!