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051
FNUS21 KWNS 261653
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1153 AM CDT Mon Jun 26 2017

Valid 261700Z - 271200Z

...CRITICAL FIRE WEATHER AREA FOR SCATTERED DRY THUNDERSTORMS ACROSS
PORTIONS OF EASTERN OR AND SOUTHWEST ID...
...CRITICAL FIRE WEATHER AREA FOR STRONG WINDS/LOW RH ACROSS
PORTIONS OF THE SOUTHERN CA MOUNTAINS AND ADJACENT FOOTHILLS...
...CRITICAL FIRE WEATHER AREA FOR STRONG WINDS/LOW RH ACROSS
PORTIONS OF NORTHWEST NV...
...CRITICAL FIRE WEATHER AREA FOR STRONG WINDS/LOW RH ACROSS
PORTIONS OF SOUTHERN/EASTERN NV...WESTERN UT...NORTHWEST AZ...

The primary changes to the forecast involve categorical upgrades
across parts of southern/eastern CA.

A Critical area for strong winds/low RH has been added across
portions of the southern CA mountains and adjacent foothills --
especially those foothills toward the general direction of the
desert (eastward). The VAD wind profiles at Sulphur Mountain (VTX)
and Santa Ana Mountains (SOX) are indicating relatively enhanced
(20-40 mph) westerly winds around 3.5-6.5 kft above ground. This is
highlighting the strong flow aloft that will be manifested at the
surface by vertical mixing across the added Critical area. Across
this area, westerly surface winds of 20-30 mph with higher gusts are
expected to combine with RH of 3-10 percent as hot surface
temperatures materialize and fuels remain dry. Poor RH recovery and
continued strong winds are expected to support critical conditions
into tonight.

Elevated areas over portions of the Great Basin / AZ and southern CA
have been connected -- adding areas along and east of the crest of
the southern Sierra mountains to Elevated designation. This is where
enhanced downslope winds are expected to combine with reduced RH.

Also, the southern CA Elevated area has been expanded westward
toward the coast, especially in Santa Barbara, Ventura, and Los
Angeles Counties. Diurnally enhanced vertical mixing into the dry
air aloft (e.g., PW around one-half inch per Vandenberg Air Force
Base 12Z sounding) will support minimum RH around 8-15 percent
inland and removed from the marine layer, amid modestly enhanced
winds.

The remainder of the forecast is unchanged.

..Cohen.. 06/26/2017

.PREV DISCUSSION... /ISSUED 0245 AM CDT Mon Jun 26 2017/

...Synopsis...
Shortwave trough currently off the northern CA coast will continue
progressing east-northeastward, reaching central OR by the early
afternoon and southern ID by the evening. Continued eastward
progress of this shortwave trough will take it through much of the
northern Rockies by 12Z Tuesday. Overall progression of this system
will result in the breakdown of the upper ridge which has remained
in place across much of the Intermountain West for the past week.
Additionally, the passage of the this shortwave trough will result
in both wind-driven and lightning-caused fire weather threats today
from the Pacific Northwest south into AZ today. Farther east, upper
troughing covering much of the central/eastern CONUS at the
beginning of the period will shift eastward as several shortwave
troughs track quickly through its base.

...Great Basin...AZ...
Strengthening mid-level flow coupled with deep boundary-layer mixing
and a tightening surface pressure gradient will support gusty winds
from southern OR across much of the Great Basin and into central AZ.
The strongest winds (i.e. sustained 20-25 mph) are anticipated
across northeast NV, where the mid-level flow is the strongest, and
across southern/eastern NV and adjacent southwest UT and northwest
AZ where the surface pressure gradient is the tightest.
Above-average temperatures are anticipated areawide with minimum RH
values ranging from the mid-teen to upper single-digits. As a
result, critical fire weather conditions are expected in those areas
where the winds are strongest.

...Pacific Northwest...Northern Rockies...
Mid-level moisture associated with the approaching shortwave trough
will advect into the Pacific Northwest/northern Rockies atop a very
dry antecedent airmass. Forecast soundings across much of the region
reveal deeply mixed inverted-v profiles by the early afternoon.
During the afternoon, PW values will likely range from around 1"
across central OR to closer to 0.60" across south-central ID. This
gradient in moisture combined with a deeply mixed boundary layer and
at least moderately fast storm motions (around 30 kt) will result in
an environment supportive of dry thunderstorm. The highest coverage
of dry storms is expected across east-central OR and southwest ID. A
more hybrid storm mode is anticipated across the remainder of Oregon
and into WA. Less storm coverage is anticipated across the remainder
of ID, with most of this storms expected to be on the drier side.

...Mountains and Western/desert Foothills of Southern CA...
Strong onshore flow is expected across much of the interior portions
of southern CA today. Best overlap of the windy and dry conditions
with receptive fuels will be across the higher elevations and
western/desert foothills during the afternoon and evening. Elevated
to locally critical fire weather conditions are anticipated across
these areas.

..Central/Eastern MT...
A strong surface pressure gradient will exist over the region
between the lower pressures to west (associated with the
aforementioned shortwave trough) and remnant high pressure across
the northern Plains/upper MS valley. This gradient will support
breezy southeast surface winds (i.e. 15-20 mph) from the early
afternoon through the evening. Above-average temperatures (i.e.
highs in the 90s) amidst a dry airmass will support afternoon RH
values from 15 to 20 percent. Guidance still suggests some
dissociation between the strongest winds (over north-central MT) and
the lowest RH (over southeast MT). Resulting conditions support an
elevated fire weather threat but the dissociation between the
strongest winds and lowest RH values currently precludes a critical
delineation.

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

$$