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FNUS28 KWNS 182156
FWDD38

Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0455 PM CDT Fri Aug 18 2017

Valid 201200Z - 261200Z

Quasi-zonal flow is forecast to remain across the Pacific Northwest
into the northern High Plains late in the weekend and into early
next week as closed cyclone meanders near the southern CA coast.
Mid/upper-level heights begin to rise across much of the northwest
CONUS midweek with ridging building into the area. Breakdown of the
ridge is then forecast to occur late next week as troughing
approaches the Pacific Northwest.

...Day 3/Sunday: Northern Great Basin...
Similar setup as Day 2/Saturday is expected Sunday with westerly
flow promoting terrain-induced channeling of surface winds across
southern ID -- particularly through the Snake River Valley -- in a
region of low RH values and dry fuels. Have introduced 40%
probabilities to account for the potential for at least
locally-critical fire weather conditions.

...Day 5/Tuesday through Day 6/Wednesday: Northern CA into Southern
OR Tuesday expanding into parts of the Northern Rockies Wednesday...

Aforementioned closed cyclone over southern CA will promote a steady
northward advection of moisture through early next week with
increasing chances/coverage of thunderstorms. Introduced 10% dry
thunder probabilities for Day 5/Tuesday across northern CA into
southern OR as potential for CG lightning flashes are forecast to
work far enough northward to overlap areas of receptive fuels and
low RH values. Dry thunder potential is forecast to expand farther
northeastward Day 6/Wednesday as deep-layer moisture continues to
stream northward. A larger 10% area was introduced for Wednesday
across the Northwest to account for the increasing/expanding dry
thunder threat.

While threat for dry thunder may continue late in the week as trough
continues to approach the area, predictability is too low to
delineate an area with this outlook. Furthermore, wind/RH fire
weather threats are also expected to develop late next week as
trough crosses portions of the Northwest. Though, predictability is
currently too low to include 40% probabilities for wind/RH.

..Elliott/Picca.. 08/18/2017

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

$$



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