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498
FNUS28 KWNS 162120
FWDD38

Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0420 PM CDT Mon Oct 16 2017

Valid 181200Z - 241200Z

A progressive upper pattern is forecast to continue across the CONUS
from Day 3/Wednesday through the upcoming weekend. A large-scale
upper trough should amplify while moving quickly from the eastern
Pacific to the Plains from Day 4/Thursday to Day 7/Sunday. An upper
ridge is then forecast to develop over much of the western CONUS
from Day 7/Sunday into Day 8/Monday. Subsidence beneath this upper
ridge should promote a broad area of surface high pressure across
the Great Basin.

...Day 4/Thursday - Day 5/Friday: Portions of the Northern/Central
High Plains...
Enhanced southwesterly mid-level winds associated with the
previously mentioned upper trough will overspread parts of the
northern and central High Plains beginning on Day 4/Thursday and
continuing into Day 5/Friday. Some of these winds may reach the
surface through diurnal mixing of the boundary layer and overlap
with pockets of reduced RH values. However, the degree of low-level
warming/drying remains too uncertain to include probabilities for
critical fire weather conditions for any part of the
northern/central Plains at this time.

...Day 6/Saturday - Day 8/Monday: Portions of Southern CA...
A prolonged moderate to perhaps locally strong offshore wind event
may begin around Day 6/Saturday and continue through the end of the
forecast period across parts of southern CA. Latest medium-range
guidance remains in general agreement that the surface pressure
gradient will strengthen to near-critical thresholds by Saturday
night, and the potential for critical fire weather conditions
through next Monday remains apparent.

Given the forecast prolonged nature of this offshore flow event,
have opted to maintain 40%/marginal probabilities for Day 6/Saturday
and Day 7/Sunday with no changes, while also introducing a
40%/marginal area for Day 8/Monday. A 40%/marginal area has also
been included for part of the lower CO River Valley on Day
6/Saturday. If model guidance begins to suggest an even stronger
pressure gradient across southern CA during some portion of this
time frame, then 70%/critical probabilities may be needed.

..Gleason.. 10/16/2017

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

$$