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FNUS28 KWNS 232031
FWDD38

Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0330 PM CDT Sun Jul 23 2017

Valid 251200Z - 311200Z

A mid/upper ridge initially centered over the central/southern
Plains will flatten some and shift westward through the upcoming
week, as a series of impulses within the northern stream advance
eastward near/along the Canadian border. Additionally, a shearing
impulse initially over northern California will gradually become
absorbed within this northern-stream flow over the northern Rockies
around mid-week. Global guidance suggests the ridge will amplify
across the western US late this week into next weekend, bringing
warmer/drier conditions to some parts of the region.

...Pacific Northwest and Northern Rockies...
Several days of thunderstorm activity will have already occurred
over the region, in response to the aforementioned impulse over
northern California (along with convectively induced perturbations)
and increasing monsoon-related moisture. This added moisture will
assist in the transition of storms from dry to wet modes across the
northern Great Basin and vicinity early this week. However, along
the northern/western fringe of this moisture pool, thermodynamic
profiles may be favorable for mixed wet/dry modes from northern
California to southwest Montana. Farther north, the background
pattern appears relatively unfavorable for thunderstorm activity. As
such, the D3/Tue 10% area is shifted southward to capture the
corridor of overlap between favorably dry thermodynamic profiles and
greater thunderstorm coverage.

After D3/Tue, some dry-thunderstorm potential may persist on the
northwestern fringe of the monsoonal moisture, but the narrow nature
of such a favorable corridor lends considerable forecast
uncertainty, precluding any dry-thunderstorm areas D4/Wed and
onward.

The predictability of critically low RH/gusty winds appears too low
across the western US for any highlights at this time. Passing
mid/upper disturbances and related surface frontal passages may
bring breezy conditions (and perhaps elevated fire-weather concerns)
to parts of the northern Rockies and interior Pacific Northwest
during the second half of the week. However, the subtle nature of
these systems suggests high uncertainty with their timing at this
forecast range.

..Picca.. 07/23/2017

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

$$


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