October 19, 2020 – Dry weather and breezy northerly flow will continue this week with periods of stronger winds resulting in elevated fire weather conditions. Cooler temperatures by the weekend with a slight chance of showers over the mountains.
Discussion
Broad ridge centered over the eastern Pacific extends into NorCal providing clear skies and persistent dry and warm weather. North and east surface pressure gradients have weakened slightly compared to 24 hours ago, but enough gradient remains for locally breezy northwest to northeast winds (15-25 mph) across the foothills surrounding the northern half of the Sacramento Valley.
Little change in temperatures expected across the region today and Tuesday with temperatures forecast to remain well above average (10-15 degrees). Northerly surface pressure gradient forecast to tighten tonight and Tuesday resulting in breezier north to east winds across the Sacramento Valley and surrounding terrain. Combined with the persistent low RH and dry fuels, elevated to locally critical, fire weather conditions are expected.
A series of short-wave troughs moving through the PacNW beginning Wednesday will weaken high pressure over NorCal during the second half of the week. Temperatures will begin to trend down slightly on Wednesday, with a bigger drop forecast on Thursday as highs return to only slightly above average. North and east pressure gradients forecast to take another jump upward on Wednesday night and Thursday resulting in a renewed period of elevated/critical fire weather conditions.
Extended Discussion (Friday through Monday)
Weak short wave trough digs through Friday, followed by a much deeper one moving through the PacNW into the Great Basin this weekend. This stronger system over the weekend could bring a threat of showers to Shasta County, Northern Sacramento Valley, and northeast foothills Saturday, and over the west slopes of the Northern Sierra Nevada Saturday and Sunday. Some breezy northerly wind looks possible Sunday into Monday. Near normal high temperatures Friday, cool to below normal Saturday through Monday.