April 28, 2017 – Dry weather into next week with warming temperatures. Breezy to windy north winds today for the Valley and tonight for the mountains.
Discussion
Dry northwest flow over the area will become northerly during the day as the area is located between an upper low dropping southward over the Rocky Mountains into the 4 Corners area. The surface pressure gradient will tighten during the day, with winds increasing late morning into the afternoon. The strongest winds are expected over the northern San Joaquin Valley, with northwest winds 15 to 30 mph gusting to 40 to 45 mph in the afternoon. The surface pressure gradient will relax through the evening. A Wind Advisory is in effect from 11 am until 8 pm this evening. Breezy winds are expected into the southern Sacramento Valley, but are expected to remain below Advisory criteria, with gusts to around 30 to 35 mph.
Temperatures this afternoon are expected to be similar to a few degrees higher than yesterday. Temperatures trend higher Saturday and Sunday as the upper level ridging develops. Valley/Delta highs Saturday around 80 expected, with low 80s by Sunday. By Monday, mid 80s are forecast. While above normal, these temperatures are expected to remain well below record levels.
Extended discussion (Tuesday through Friday)
Temperatures continue to warm Tuesday and Wednesday as an upper level ridge slides across the west coast. Daytime highs Wednesday are forecast to reach from 10 to 15 degrees above normal. Surface and upper level gradients indicate breezy north winds through Tuesday night. Surface gradient and only moderate upper level support should keep winds from becoming significantly strong. Upper ridge axis shifts inland on Wednesday which should bring decreasing winds. Upper ridge continues to shift eastward on Thursday as a weak upper trough moves into the Pacific Northwest. Onshore flow will bring a little cooling although daytime highs will still be well above normal.
GFS and GEM painting some precipitation over the far north state Thursday afternoon. Although dynamics over Norcal are weak, can not rule out a slight threat of light showers over Shasta county in the afternoon and evening hours. Weak upper trough continues to dig in over the west coast Friday bringing just a slight drop in temperatures. Northeast California remains east of the trough axis so a slight threat of showers remains in the forecast for the higher elevations of Shasta, Plumas and Lassen counties. Elsewhere, skies will remain generally fair for the end of next week.