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FNUS22 KWNS 221918

Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0217 PM CDT Tue Aug 22 2017

Valid 231200Z - 241200Z

...Portions of the Northern Great Basin/Rockies and Interior Pacific
Minor adjustments have been made to the ongoing isolated
dry-thunderstorm area, but the forecast rationale remains the same.
The latest guidance continues to suggest that the greatest
thunderstorm coverage will be over portions of central/eastern OR,
though with only subtle large-scale ascent impacting the area for
most of the period, some uncertainty remains regarding the evolution
of convection. Regardless, some threat for ignitions will exist over
a rather broad area, given isolated to widely scattered coverage of
thunderstorms and receptive fuels in place. See the previous
discussion below for more details.

..Dean.. 08/22/2017

.PREV DISCUSSION... /ISSUED 0145 AM CDT Tue Aug 22 2017/

As an upper trough/low moves over BC by Wednesday night, the
large-scale upper ridge over much of the western CONUS will begin to
shift eastward through the Day 2/Wednesday period. A weak upper low
off the coast of CA is forecast to advance eastward over southern CA
by the end of the period. Mid-level moisture emanating from the
Southwest monsoon will develop farther northward into portions of
the northern Great Basin/Rockies and interior Pacific Northwest,
supporting at least isolated convective potential across these
regions Wednesday afternoon and evening as a shortwave trough
approaches the Pacific Northwest from the eastern Pacific.

...Portions of the Northern Great Basin/Rockies and Interior Pacific
The glancing influence of large-scale ascent associated with the
previously mentioned shortwave trough from the eastern Pacific and
terrain-driven circulations will likely foster isolated to scattered
thunderstorms across portions of the northern Great Basin and the
interior Pacific Northwest into the northern Rockies. While
precipitable water values are forecast to increase along and east of
Cascade crest by Wednesday afternoon, they should still be
sufficiently marginal (0.8-1.0 inch) coupled with a dry/well-mixed
sub-cloud layer to support some dry thunderstorm potential.
Mid-level southwesterly flow is also forecast to modestly strengthen
to around 20 kt across central/eastern OR into southeastern WA and
parts of ID, which should promote some northeasterly storm motion
and limit wetting rainfall potential. A broad isolated dry
thunderstorm area has been included across these regions for Day
2/Wednesday to account for this convective fire weather threat, as
fuels remain very dry and receptive to large fire starts. If current
model trends continue, a scattered dry thunderstorm area may need to
be introduced in a later outlook across portions of central/eastern
OR and vicinity where the greatest thunderstorm coverage could

...Please see for graphic product...

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