June 5, 2020 – A cooldown is expected through the weekend, with chances for showers, thunderstorms, and light mountain snow. Dry weather is expected to return Monday, with a warming trend bringing above normal temperatures by mid-week.
Thursday afternoon high temperatures were within a degree of tying records at downtown Sacramento, Sacramento Executive Airport, Stockton, and Modesto. Onshore flow has increased as upper level ridging shifts eastward. Overnight temperatures are cooler than last night, especially in Delta breeze influenced areas. At 3 am Sacramento International Airport was 10 degrees cooler than the same time last night. Winds in the Delta have gusted to 25 to 33 mph. This is expected to increase further this afternoon and evening.
Highs across the area this afternoon will be 10-20 degrees as an trough approaches the coast. Dry weather is expected this afternoon except for a few showers and thunderstorms along the Sierra crest south of Highway 50.
A slight chance for precipitation will be in the higher elevations from eastern Shasta County through the Sierra crest tonight into Saturday morning. A higher potential for convective activity is expected Saturday afternoon and evening for the northern Sacramento Valley and surrounding foothills. CAPE levels around 200-500 j/kg will be enough to see some thunderstorms. CAMS models suggest the best potential will be over the eastern side of the northern Sacramento Valley. Low level shear looks fairly low, though mid level shear is moderate. Inverted V sounding suggests gusty winds would be the main threat with any storms, along with some small hail. Locally heavy rain is possible, but Precipitable Water levels are much less impressive than last weekend, so there is less moisture for storms to work with.
Precipitation shifts back over higher elevations overnight into Sunday. Overall, the southern Sacramento and northern San Joaquin valleys looks to remain dry with some breezy winds.
Some light snow is possible late Saturday night through Sunday as snow levels rapidly fall during the day Saturday, reaching to around 5 kft by early Sunday morning, with a light coating possible around Blue Canyon. The higher peaks may see some snow accumulation of 1 to 3 inches. Snow falling at pass levels which may create slick roads over the mountains. Weekend drivers should be prepared for slowdowns. Anyone planning high elevation hiking and camping should expect wintry conditions.
Mountain showers and snow showers continue Sunday into the evening, with thunderstorms once again possible in the afternoon in the northern Sacramento Valley and the mountains. Conditions begin to clear Sunday night.
Weekend high temperatures will be seasonably cool, remaining in the 70s for the Valley and Delta. Monday looks dry and a little warmer but still below average.
Extended Discussion (Tuesday through Friday)
Upper level ridging will be in place for the start of the extended forecast. This will bring warm temperatures to the region with highs making it back into the 90s. Wednesday looks to be the warmest day of the week with highs about 5 to 10 above average. We will start to see height falls on Thursday as an upper level trough approaches CA. This will be the start of a cooling trend. The trough will be just off the coast of CA on Friday with slight shower chances entering the forecast for higher elevations in northern areas.