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FNUS28 KWNS 212049

Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0349 PM CDT Fri Jul 21 2017

Valid 231200Z - 291200Z

A mid/upper ridge will remain anchored over parts of the Great Basin
late this weekend, before gradually shifting east/southeast towards
the southern/central Plains. This will occur in conjunction with
multiple northern-stream impulses advancing eastward near the
Canadian border, as well as a weak upper low approaching the
northern California coast. As this low approaches and the
aforementioned high shifts east, monsoon-related moisture will
stream north across the Great Basin, eventually reaching the
northern Rockies during the first half of next week. Thereafter,
generally cyclonic flow should envelop the Northwest, with
thunderstorm chances persisting to the east/southeast across parts
of the Great Basin and northern Rockies.

Thunderstorm chances will increase late this weekend across the
western/northern Great Basin and parts of the Pacific Northwest, as
mid-level moisture advances north and interacts with the approaching
low. Favorably dry fuels and deep/dry boundary-layer conditions will
support the risk of dry lightning strikes on D3/Sun. While there may
be some pockets of more focused coverage (potentially necessitating
a scattered/critical dry-thunder area in upcoming outlooks), modest
storm motions and uncertainty in the location of more focused areas
preclude an upgrade at this time. As moisture continues to stream
northward, storms will gradually transition to wetter modes through
the first half of next week, shunting the highest probability of dry
lightning strikes northward. This transition is reflected in the
inclusion of 10%/marginal areas on D4/Mon and D5/Tue.

With the influence of the larger-scale trough (and more subtle
passing impulses) across the interior Pacific Northwest through the
week, there may be occasional periods of breezy/dry conditions
across the Columbia Basin and northern Rockies. However, the
potential for widespread critical wind speeds appears too low for
probabilities at this time.

..Picca.. 07/21/2017

...Please see for graphic product...

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