November 11, 2017 – Dry weather for today into early Sunday. Next storm system arrives Sunday afternoon into Monday with another round of rain and high elevation snow. Another storm system moves through NorCal on Wednesday. Dense Fog Advisory until 11 AM this morning.
Morning update (8:09 AM PST)
Clear skies and surface moisture from recent rains has allowed fog to form this morning in the central and southern Sacramento valley and northern San Joaquin valleys. This fog has become locally dense. Motorists should exercise extra caution this morning while driving due to rapidly changing visibility across the valley areas. Fog is expected to dissipate later this morning as temperatures increase.
Discussion
Weak high pressure aloft over the west coast bringing dry conditions this morning. Clearing skies and lingering surface moisture has allow for fog in the southern Sacramento and Northern San Joaquin valleys. A low cloud deck over the northern Sacramento valley has kept fog out of this area.
High pressure will keep NorCal dry today with clearer skies this afternoon bringing a little warming most areas. High pressure over the west coast will be short lived with the next Pacific frontal system approaching the coast on Sunday.
Latest models have this system digging and slowing a bit over previous forecast runs. Have therefore slowed down timing of next precipitation onset and as a result, only the coast range and northern mountains will see a precipitation threat during the day Sunday. Light prefrontal precipitation spreads southeastward over night with rain or snow chances over most of the CWA by early Monday morning.
Latest timing has frontal passage through NorCal during the morning hours on Monday. Breezy south winds will occur along the the fronts passage with periods of moderate precipitation over the mountains and fairly light precipitation over the valley.
Snow levels will be fairly high with this system as with the previous system so mountain travel impacts will be minimal. Snow levels drop on Monday night down to below 5000 feet but precipitation amounts will be decreasing so only light amounts of snow are expected at that level.
Brief ridging slides across the north state again on Tuesday for a brief dry out period but cooler airmass will bring down daytime highs slightly.
Extended discussion (Wednesday through Saturday)
Unsettled weather and below normal temperatures are expected for the extended period. Highs will reach the 50’s and 60’s for the Valley and 40’s and 50’s for the higher elevations.
Improving confidence is improving with precipitation spreading across the area on Wednesday and snow levels will likely be between 5000 and 6500 feet, bringing travel impacts to the mountains. Precipitation is expected to linger at least into early Thursday, though additional rainfall and snow look relatively light.
A ridge builds in for Friday into early Saturday with dry and slightly warmer weather. If things clear out quick enough Thursday night we will likely see lows fall into the 30’s across the Valley. The break looks brief, though, with another wet system moving in during the day Saturday and continuing through Sunday.