708
FNUS28 KWNS 302036
FWDD38

Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0334 PM CDT Mon Sep 30 2024

Valid 021200Z - 081200Z

Fire weather concerns will persist intermittently through the
extended period across the western half of the CONUS. Long-range
ensemble guidance continues to show a general ridging pattern over
the southern half of the country, which will continue to favor
stronger mid/upper-level flow along the U.S./Canadian border. This
regime will favor seasonal to above-normal temperatures for the
Plains into the West and mostly dry conditions. Consequently, dry
fuels will likely be maintained and gradually expand in coverage for
many locations. Fire weather concerns will emerge as shortwave
troughs embedded within the mean zonal flow (and their attendant
surface lows/fronts) propagate across the northern CONUS.

...D3/Wednesday - Southern Wyoming...
Strong zonal flow is expected to persist across the northern CONUS
through late D3/Wednesday. This will maintain a downslope flow
regime into the WY Basin with afternoon RH values forecast to reach
into the teens to low 20s. Deterministic and ensemble guidance show
a signal for 15-25 mph winds, and with ERCs generally near the 90th
percentile, elevated to critical fire weather conditions appear
likely.

...D3/Wednesday - Coastal Southern CA...
Upper ridging over the Great Basin combined with a weak coastal low
will promote a modest offshore flow regime across southern CA.
Unseasonably hot temperatures will continue to dry fuels and
maintain very dry conditions. Localized elevated fire weather
conditions are possible - mainly within the higher coastal terrain -
late Wednesday into early Thursday morning.

...D5/Friday - northern Great Basin...
Latest water-vapor imagery reveals a broad upper trough over the
central Pacific, which is forecast to reach the West Coast by
D5/Friday. Stronger flow overspreading the Pacific Northwest will
promote downslope winds and surface pressure falls in the lee of the
Cascades/northern Sierra Nevada. While run-to-run trends continue to
show some variability regarding the strength of the winds, recent
European solutions, which typically under-forecast winds, align with
latest GEFS wind probabilities and suggests fire weather concerns
may emerge during D5/Friday afternoon.

...D6/Saturday - northern Rockies/High Plains...
The upper trough that is forecast to reach the Pacific Northwest on
D5/Friday is expected to migrate into the northern Plains through
D6/Saturday. As this occurs, lee cyclogenesis is probable and should
support strengthening low-level pressure gradient winds both ahead
of and behind the primary surface trough/cold front. While some
uncertainty remains regarding the degree of RH reductions across the
region, very dry fuels already in place (ERCs well above the 90th
percentile) combined with a strong wind signal hint that a fire
concern is possible. Further adjustments/expansions into the Plains
are possible as guidance continues to come into better alignment.

..Moore.. 09/30/2024

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

$$