October 15, 2020 – Critical fire weather conditions are expected through Friday morning due to gusty winds and low humidities. Otherwise, dry and unseasonably warm weather continues.
Discussion
Strong offshore wind pattern continues across NorCal early this morning. MFR-SAC surface pressure gradient is up to 14.5 mbs while the RNO-SAC gradient is up to 8.5 mbs. Northerly wind gusts of 20-30 mph have been prevalent through the Sacramento Valley, especially the northern half and along the west side where low- level northerly barrier jet has set up (KDAX VWP indicating north winds of 45-55 kts from 1-2k ft above the surface). Local northeast gusts of 30-45 mph have been occurring over the foothills surrounding the valley, and across the west slopes of the northern Sierra Nevada.
Little change to the hot, dry, and windy pattern expected over the next 24 hours, and the red flag warning continues into midday Friday. The northerly surface pressure gradient may drop off a bit by tonight, but the east gradient is forecast to persist or even tighten a bit further into early Friday. So the gusty winds may slacken somewhat across the Sacramento Valley later today and tonight, but will likely persist in the foothills and west slopes of the northern Sierra.
Surface gradients forecast to relax considerably Friday and over the weekend resulting in less wind, but conditions will remain unseasonably warm and very dry.
Extended Discussion (Monday through Thursday)
Dry weather continues through the extended period. Newest deterministic model runs of the GFS/ECMWF have come into better agreement for the overall synoptic pattern next week. Weak troughing will bring back near to slightly above normal temperatures Monday through Wednesday.
A system begins to dig into the Central US Thursday which may bring back a period of breezy winds and elevated fire weather concerns late week.