Fire Weather Outlook Discussion
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FNUS21 KWNS 191641
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1140 AM CDT Sat Aug 19 2017

Valid 191700Z - 201200Z

No changes have been made to the existing elevated areas.

Across portions of eastern MT/western ND, elevated conditions are
already being observed at some locations and these conditions will
persist through the afternoon. Critical RH/wind criteria may be
reached concurrently for a brief period this afternoon, but the
potential for a sufficient duration of critical conditions at any
given location appears too limited for an upgrade.

Further west, elevated to locally critical conditions still appear
likely across portions of ID/southwest MT/WY, and also across
portions of northern CA/southwest OR. See the previous discussion
below for additional information.

..Dean.. 08/19/2017

.PREV DISCUSSION... /ISSUED 0144 AM CDT Sat Aug 19 2017/

...Synopsis...
An upper trough over AB/SK will progress eastward towards MB today.
30-40 kt of mid-level westerly winds attendant to this upper trough
will overspread eastern MT into ND by this afternoon. At the
surface, a low over southern SK will also develop eastward into MB
by this evening, with a trailing cold front advancing southeastward
across the northern Plains.

...Portions of the Northern Great Basin into the Northern/Central
Rockies and Northern Plains...
Strong/gusty low-level winds should develop both along and ahead of
the surface cold front this afternoon across eastern MT into western
ND and northwestern SD. Short-term guidance shows sustained
west-northwesterly winds of 15-20 mph occurring in conjunction with
RH values lowering into the 15-25% range with diurnal heating of a
relatively dry boundary layer, supporting an elevated fire weather
threat. RH values are forecast to increase behind the front,
although strong surface winds approaching 20 mph and veering to
northwesterly may allow for continued elevated fire weather concerns
into the evening hours. Locally critical conditions may be realized
briefly across a small part of the elevated delineation, but
confidence in widespread winds in excess of 20 mph remains too low
to include a critical area.

Elevated fire weather conditions should also develop this afternoon
across part of the northern Great Basin into portions of the
northern/central Rockies, as the southern fringe of enhanced
mid-level westerlies overlies this region. Localized enhancement to
the low-level winds appears likely across part of the Snake River
Valley and vicinity into western/southern WY, with sustained
west-southwesterly winds of 15-20 mph combining with RH values of
10-20% and dry fuels to support an elevated fire weather threat. The
lack of even stronger forecast low-level flow precludes a critical
designation across this region.

...Southwestern OR/Northern CA...
A strengthening surface pressure gradient to the west of the
Cascades will encourage increasing northeasterly to northwesterly
winds across southwestern OR/northern CA this afternoon and evening.
Sustained winds of 15-20 mph appear likely at lower elevations, with
stronger gusts possible at mid/high elevations. RH values will
easily lower into the 15-25% range by afternoon given the dry
airmass in place, and overnight RH recovery is expected to remain
poor, particularly at higher elevations. This expected combination
of strong/gusty winds with lowered RH values, very dry fuels, and
numerous ongoing large fires necessitates the introduction of an
elevated area across this region.

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

$$



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