Minor winter storm on Sunday, extended period of dry weather ahead

January 18, 2019 – Light showers over the Sierra this morning then light rain and mountain snow today and Saturday mainly north of interstate 80. A moderate storm passage through NorCal Sunday then drying Monday with dry conditions continuing through the end of the week. Valley fog possible night and morning hours.

Discussion

Scattered light showers continue this morning over the Sierra but significant additional snowfall amounts are not expected. Therefore, the winter storm warning will be allowed to expire. Remainder of CWA drying out this morning although some mid cloud cover continues to spill over the fairly flat ridge over the west coast. Warm frontal precipitation associated with the next upstream Pacific weather system is forecast to spread over the forecast area later today but most precipitation should remain north of interstate 80. Precipitation amounts should remain on the light side with snow levels climbing to between 5000 and 6000 feet. Therefore, impacts are expected to be minimal today.

Upper ridge amplifies and moves inland on Saturday keeping any precipitation from cold frontal portion of system north of interstate 80 and relatively light. The upper ridge axis is forecast to push eastward into the Great Basin Sunday allowing a stronger and moister Pacific cold front into NorCal during the day on Sunday.

Precipitation amounts in the valley are not likely large enough to cause much problem but snowfall amounts and snow levels below pass levels will likely make for travel impacts over the Sierra Sunday and Sunday evening. Pressure gradients indicate gusty south winds as well. Precipitation drops off quickly on Monday as the main upper low shifts east of the state and high pressure starts building over the west coast. At this time, this building ridge looks to be the main weather influence for much of the coming week.

Extended Discussion (Tuesday through Friday)

Models similar in showing dry weather through the extended as high amplitude upper ridging remains off the West Coast. Pattern will be conducive to the formation of areas of night and morning fog in the Central Valley and mountain valleys. Above normal daytime highs expected Tuesday through Friday with 60s in the Central Valley and 40s to low 60s for the mountains and foothills.