Critical fire weather for portions of NorCal

Day 1 Fire Weather Outlook  
   NWS Storm Prediction Center Norman OK
   0157 AM CDT Mon Sep 20 2021

   Valid 201200Z - 211200Z

   ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTHERN CALIFORNIA...

   ...Synopsis...
   In the wake of an upper-level trough moving across the northern
   Rockies this morning, strong northwesterly flow aloft will extend
   from the Pacific Northwest into the central Great Basin.  In
   response at the surface, high pressure will build into the northern
   Intermountain West increasing the pressure gradient across
   California.

   ...Northern California...
   Low-level northerly winds have increased across the region this
   morning per VAD wind profiles, indicating wind speeds over 40 mph
   around 1 kft above the ground.  While the low-level winds will
   weaken and become more easterly through the afternoon, the surface
   pressure gradient will continue to increase through the morning,
   resulting in sustained surface winds over 20 mph.  As heating and
   mixing commence at sunrise, RH values will fall below critical
   values by mid morning, resulting in a few hours of overlapping
   critical winds and RH values.

   ...Southern California...
   Locally elevated fire weather conditions are possible across Los
   Angeles, Ventura, and Santa Barbara counties as the surface pressure
   gradient supports offshore flow resulting in dry and breezy
   conditions in terrain-favored locations.