February 1, 2020 – Dry with above normal temperatures through Saturday. Pacific storm brings much cooler conditions with light precipitation Sunday into Sunday night, mainly over the foothills and mountains. Breezy northerly wind develops Sunday and persists into early Tuesday. Dry conditions expected throughout much of next week.
Discussion
Satellite imagery this morning depicts a mix of high and fog. Sacramento Airport (SMF) and other local airports have been reporting visibility around a quarter of a mile or less. Expect these conditions to generally expand south and eastwards, perhaps even banking against the Sierra foothills. Some northward, perhaps up to the Chico and Oroville area, expansion is possible as well with Colusa lighting up on satellite. The HREF and HRRR guidance depicts these scenarios thus a Dense Fog Advisory is in effect through 10AM this morning. Travelers this morning should be mindful of this and consider allowing extra time before heading to their destination. Once the fog dissipates, we can expect to see one more day of mild temperatures. Highs will be a bit cooler than what we saw on Friday and that is due to the increasing clouds ahead of the offshore system.
On Sunday, a rather cold upper trough descends on the region but will be somewhat moisture starved. Additionally, the northwest to southeast movement of this system is typically not the most conducive to widespread Valley precipitation. Cannot rule out a few hundredths of an inch of rain making it into the Valley, but it will be of low impact.
Across the foothills and mountains, light to locally moderate precipitation is expected as forcing from the trough swings through. Initial snow levels around 4,000 to 5,000 feet quickly drop to the 2,000 to 3,000 foot range by Sunday afternoon. The latest model guidance tends to keep the area fairly dry, with most of the snow accumulation occurring before hand.
Up toward pass level, 2 to 4 inches of snow is likely, perhaps a tad higher toward the summits. Minor travel impacts are possible with the activity gradually winding down by the late evening.
While precipitation will not be a major issue, the gusty northerly winds may be the bigger hazard here. Sharpening north/south gradients on Sunday and Monday should lead to an uptick in wind speeds across the region. On Sunday afternoon, 925-mb winds reach the 40 to 45 knot range which could mix down given a favorable time of day. At this juncture, expecting Valley wind gusts to maximize in the 30 to 45 mph range while reaching the 40 to 55 mph levels over the mountains. While the gusty winds will not be constant, some downed tree branches and hazardous driving conditions are possible on Sunday and Monday. After that, winds will decrease 5 to 10 mph during the overnight hours; however, they’re expected to remain breezy through Tuesday.
Overall temperatures will remain on the cool side in response to the upper trough passage. Relative to the warm period to conclude the work week, high temperatures are forecast to drop by around 15 degrees as Valley locations remain in the low to mid 50s on Sunday into Monday. A warming trend returns by midweek as a ridge returns to the forecast.
Extended Discussion (Wednesday through Saturday)
By mid-week, the focus shifts toward another upper ridge set to maintain its presence into the first half of next weekend. This will allow temperatures to warm back up to above average and maintain dry weather. Global ensembles do keep indicating the approach of a trough late next weekend, but model inconsistencies and poor run-to-run agreement preclude much mention of sensible weather details at this time.