FNUS28 KWNS 222052

Day 3-8 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0350 PM CDT Thu Oct 22 2020

Valid 241200Z - 301200Z

A strong western upper-level trough and surface high pressure in the
northern Rockies/Great Basin will be the primary features of
interest during the extended period. Downslope and offshore flow in
California will be the primary concern from this weekend into early
next week. Fire weather concerns near and east of the Divide will
likely be low on account of cool/cold temperatures and

...Northern California...
After a brief respite from northerly/northeasterly flow, an inside
slider trough is expected to impact portions of the West Coast
beginning late D3/Saturday into D5/Monday. Model agreement in the
placement of the upper-level trough has improved significantly.
Strong mid-level winds will be well-aligned with the Sacramento
Valley. A strong surface high from the northern Rockies into the
Pacific Northwest will promote strong northerly to northeasterly
surface winds. The most significant fire weather conditions are
expected to begin during Sunday evening and persist into Monday
morning and perhaps early afternoon. As the mid-level jet progresses
south, the expectation is for dry, downslope flow push southward and
eventually impact the Bay Area. The favorable combination of the
surface gradient and mid-level winds should allow winds to reach 30
mph in some locations with higher gusts. Strong subsidence on the
back side of the trough will help to dry out the airmass where very
low RH can be expected. Given the ongoing drought and near-record to
record dry fuels, rapid spread of fires is probable. Conditions
should finally improve by sometime Monday afternoon as the mid-level
winds decrease from west to east and the surface gradient

...Southern California...
As the upper-level trough shifts to the southeast, surface high
pressure will continue southward into the Great Basin. This pattern
will favor offshore flow across parts of southern California. Unlike
earlier offshore wind events, mid-level flow will be stronger. The
main caveats for this event are the chance for light precipitation
to impact fuels prior to the offshore flow as well as somewhat
cooler temperatures than previous events. Even so, fuels within the
higher terrain remain quite dry with similarly record dry fuels in
some locations. Precipitation is not likely to impact the heavier
fuels enough to eliminate fire weather concerns. With the mid-level
wind support and strength of the surface gradient in model guidance,
confidence has increased in critical fire weather for D5/Monday with
lingering potential into D6/Tuesday.

...Lower Colorado River Valley...
High pressure in the Great Basin with drive potentially strong
northerly winds into the lower Colorado River Valley. This flow may
also be augmented by the mid-level jet, though the position of this
feature is somewhat uncertain. Given the low RH and winds that may
exceed 20-25 mph, highlights have been added for D5/Monday.

...Southern High Plains...
Westerly flow will increase across the Divide as the strong western
trough evolves and digs southeastward on D3/Saturday. This will help
to deepen another southeastern Colorado surface low during the
afternoon. With mid-level flow increasing during the day, strong
downslope flow is likely in the lee of the Sangre de Cristo
Mountains. With a cold front having just moved into the region on
Thursday, enough airmass modification to support high enough
temperatures (and low enough RH) away from the lee of the terrain is
not probable.

..Wendt.. 10/22/2020

...Please see www.spc.noaa.gov/fire for graphic product...