May 22, 2018 – Afternoon and evening thunderstorms possible mainly over higher terrain this week. These may extend through the Valley late in the week. Slightly cooler than normal temperatures continue across most of the region this week warming to above normal early next week.
A low pressure area centered over Nevada will drift northward during the day. We will still have predominately easterly flow aloft so activity that starts in the mountains during the day will be trying to push towards the valley once again with the best chances in the valley during the evening hours over the central and northern Sacramento valley. The Delta breeze is expected to remain moderate to locally strong through the day and tonight. This will help to keep inland temperatures fairly cool today for this time of year. The only exception will be over the north end of the valley which will warm well into the 80s. Some stratus will possibly advect into the valley the next couple of mornings.
A low pressure area centered to our northwest will not only help to keep an enhanced Delta breeze but may help to keep some showers overnight on Tuesday in the mountains.
On Wednesday we will still have a decent Delta breeze in place and temperatures are expected to be slightly cooler across the region. Unstable air over the mountains will continue with possible afternoon and evening thunderstorm activity.
The low pressure area to our Northwest will continue to move closer to the region Thursday and Friday moving through Friday night. This low will have cooler air associated with it so expect temperatures to remain below normal for the latter part of the week and unstable conditions each day. Snow levels may drop to around pass levels during the day and below Friday night. At this time though precipitation amounts look light but 2 to 4 inches of snow across the peaks looks possible. There should be an increase in shower activity as that low moves closer and through the region Friday and Friday night.
Extended discussion (Saturday through Tuesday)
A low pressure area will be passing through during the morning hours and into Nevada in the afternoon on Saturday. Colder air associated with the low may bring some snow down around pass levels but at this time the amount of precipitation is minimal so not expecting much at or below pass levels. The precipitation should be winding down Saturday night as the low moves further to the east. Behind the system northerly winds will develop and temperatures will be warming up to between 85 and 95 for most valley locations with 90s possible both Monday and Tuesday of next week.