Fire Weather Outlook Discussion

Days 3 - 8 Storm Prediction Center Norman, Oklahoma

802 
FNUS28 KWNS 132049
FWDD38

Day 3-8 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0347 PM CDT Sun Oct 13 2019

Valid 151200Z - 211200Z

A mid/upper-level ridge is forecast to move across much of the
western United States and out over the Rockies Day 3/Tuesday. The
relatively weak low/mid-level winds underneath the ridge should
temper large-scale fire weather concerns Day 3/Tuesday. The ridge is
forecast to breakdown Day 4/Wednesday as a mid-level shortwave
trough moves onshore across the Pacific Northwest. This shortwave
trough is then forecast to progress eastward toward the
northern/central High Plains through Day 5/Thursday. A large area of
enhanced mid-level zonal flow over the western United States is
forecast in the wake of the shortwave Day 6/Friday, before another
mid-level shortwave trough comes onshore across the Pacific
northwest Day 7/Saturday. 

...Day 4/Wednesday: Far northeast California, northwest Nevada,
southeast Oregon, southwest Idaho...

Enhanced mid-level flow -- associated with the initial mid-level
shortwave trough -- is forecast to overspread a near-critically dry
low-level air mass over portions of the central/northern Great Basin
during peak heating. An area of 40% probability for critical fire
weather conditions was introduced where the greatest likelihood of
elevated to near critical fire weather conditions currently
conditions exists and where fuels should be at least marginally
receptive to large-scale fire spread.

...Day 4/Wednesday - Day 5/Thursday: Wyoming and northwest
Colorado...
Enhanced mid-level flow is forecast to redevelop over portions of
Wyoming by Day 4/Wednesday as mid-level ridging is suppressed to the
south. Elevated to near critical fire weather conditions are
expected by afternoon along/west of the Laramie range as vertical
mixing leads to breezy downslope westerly winds amidst a relatively
dry low-level air mass. An area of 40% probabilities for critical
fire weather conditions was introduced Day 4/Wednesday. 

Elevated to critical fire weather conditions are expected to
continue Day 5/Thursday as the area of enhanced mid-level flow near
the initial shortwave trough impinges on the area. The area of 40%
probabilities was maintained (with some areal adjustment) as
persistently large timing uncertainties from ensemble guidance
regarding where the stronger flow will be during peak heating
precluded increasing probabilities.

...Day 5/Thursday: Southern High Plains...
Low-level flow is forecast to strengthen Day 5/Thursday as the area
of enhanced mid-level flow near the base of the initial shortwave
trough sags southward over the area. While there remains some
uncertainty regarding the magnitude of low-level dryness (especially
with southward extent), enough potential for elevated to locally
critical fire weather conditions remains to retain (with some areal
adjustment) the inherited area of 40% probabilities of critical fire
weather conditions. 

...Day 7/Saturday - Day 8/Sunday: Southwest into southern High
Plains... 
Fire weather concerns may increase as early as Day 7/Saturday over
the Southwest and into the southern High Plains Day 8/Sunday as the
secondary (and perhaps more vigorous) mid-level trough crosses the
area. While critical fire weather conditions are possible,
uncertainties are currently too large to introduce 40% probabilities
for critical fire weather conditions.  

...Day 8/Sunday: Southern California...
Offshore flow may increase over Southern California as early as Day
8/Sunday as a surface high strengthens while building into the Great
Basin. While there remains too much uncertainty to highlight
probabilities for critical fire weather conditions, the pattern
could favor a possible offshore wind event across Southern
California. This potential will continue to be monitored in future
outlooks.

..Elliott.. 10/13/2019

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

$$