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U.S. Day 1 Fire Weather Outlook
ZCZC SPCFWDDY1 ALL
FNUS21 KWNS 131634
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1134 AM CDT Thu Jun 13 2024
Valid 131700Z - 141200Z
The main change to the updated Day 1 Fire Weather Outlook was to add
isolated dry thunderstorm highlights to portions of central and
northern AZ. Fuels across this region are becoming critically
receptive to wildfire spread, with ERCs exceeding the 90th
percentile over several locations. Thunderstorms are expected to be
brief and sparse through much of the afternoon, with a slight
increase in coverage possible tonight. While thunderstorm coverage
may not reach 10 percent over any short interval of time, the
longer-term summation of strikes (wet or dry) over fuels primed for
ignitions suggests that isolated dry thunderstorm highlights are
warranted. Otherwise, the previous forecast remains on track, with
occasionally Elevated dry and breezy conditions still expected over
portions of the Lower Colorado River Basin.
..Squitieri.. 06/13/2024
.PREV DISCUSSION... /ISSUED 0159 AM CDT Thu Jun 13 2024/
...Synopsis...
A midlevel trough will advance eastward across southern CA, while a
related belt of moderate/strong southerly flow aloft overspreads
western AZ into southern NV and UT. This will promote a tightening
surface pressure gradient and 15-20 mph sustained southerly surface
winds across these areas. These winds, coupled with a deep/dry
boundary layer (single-digit RH) and receptive fuels, will favor
elevated to locally critical fire-weather conditions.
Additionally, isolated thunderstorms are possible during the late
afternoon into the overnight hours across portions of AZ into UT --
aided by ascent preceding the aforementioned midlevel trough. If
afternoon thunderstorms can develop, these storms would be
high-based in an environment characterized by a deep inverted-V
thermodynamic profile -- and isolated lightning-induced ignitions
would be possible. However, confidence in afternoon storm
development is low owing to very marginal instability, precluding
Dry Thunderstorm highlights at this time. Confidence in thunderstorm
development is higher during the overnight period, when a mix of
wet/dry storms are expected. However, increasing boundary-layer RH
and midlevel moisture may temper the overall threat of ignitions.
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U.S. Day 2 Fire Weather Outlook
ZCZC SPCFWDDY2 ALL
FNUS22 KWNS 130700
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0200 AM CDT Thu Jun 13 2024
Valid 141200Z - 151200Z
...Synopsis...
A southern-stream midlevel trough, accompanied by moderate
south-southwesterly flow aloft, will advance east-northeastward
across the Southwest during the day. At the same time, a weak
surface low south of south-central NM will promote modestly breezy
westerly surface winds across southeastern AZ and southwestern NM.
Given a deep/dry boundary layer across the area (single-digit RH),
elevated to locally critical fire-weather conditions are expected.
The primary limiting factor for the addition of a Critical area is
marginal surface winds (15-20 mph), though if surface winds trend
upward, a Critical area could be warranted in future outlooks.
Farther north, strong deep-layer westerly flow in the base of a
midlevel trough will overspread the Northwest. The associated
downslope flow across the Cascades and Sierra will favor locally
dry/breezy conditions across portions of northwestern NV and eastern
WA/northeastern OR. As a result, elevated conditions are expected
for both areas, with locally critical conditions possible in
northwestern NV -- where 20-25 mph sustained westerly surface winds
are expected.
On the backside of the southern-stream midlevel trough, low/midlevel
offshore flow will gradually strengthen across southern CA. As a
result, locally breezy/gusty northerly surface winds will likely
overlap low RH across portions of southern CA during the overnight
hours, with locally elevated fire-weather conditions possible where
fuels are receptive to fire spread. An Elevated area was considered
for portions of the area, though the threat appears too localized
for such highlights at this time.
..Weinman.. 06/13/2024
U.S. Day 3-8 Fire Weather Outlook
ZCZC SPCFWDD38 ALL
FNUS28 KWNS 122219
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0519 PM CDT Wed Jun 12 2024
Valid 141200Z - 201200Z
...Summary...
Elevated to critical meteorological fire spread conditions, in
conjunction with increasingly receptive fuels, will slowly become
more widespread late this week through early next week across
portions of the Pacific Northwest, southward through the Great Basin
and Southwest.
...Synopsis...
A small area of 70 percent Critical probabilities remains in the
forecast for D3/Friday near the NM/AZ border. However, trends over
the past couple of days are starting to suggest slightly weaker flow
in the mid-levels within the base of a shortwave trough, and
subsequently weaker westerly surface winds ahead of an approaching
cold front. Confidence remains just high enough to keep higher
probabilities in the forecast for now, but these could be reduced if
similar trends are present in near future forecasts. Further north
across far western NV and east of the Cascade Mountains, breezy, dry
westerlies will accompany a mid to upper large-scale trough entering
the Pacific Northwest, and a mid-level shortwave trough in its base
near the southern Great Basin.
While surface wind speeds will weaken a bit across much of the Great
Basin D4/Saturday, persistent, and even stronger, westerly downslope
winds will continue across the Cascades. Fuels east of the range by
this time are expected to become even more receptive to fire spread
and ignition. Therefore, 40 percent Critical probabilities have been
included there. These probabilities could increase depending on
later fuel assessments.
The upper trough is expected to dig southeastward late this weekend
through D6/Monday into the Intermountain West and Great Basin.
Widespread increasing mid to upper flow within the base of this
trough, and tightening surface pressure gradients, will yield an
increasing threat of at least 40 percent critical probabilities
spreading across more of the Southwest by D6/Monday behind a
dryline. This pattern may continue into D7/Tuesday-D8/Wednesday, and
additional low probabilities may eventually be introduced across the
Southwest if forecast confidence increases.
..Barnes.. 06/12/2024
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