SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Fri Aug 09 2019
Valid 101200Z - 111200Z
Much of the previous forecast remains on track. Elevated to at least
locally critical wind/RH conditions are still expected across
eastern Nevada into eastern Idaho. The elevated delineation was
expanded southward into southern Nevada, as much of the latest
numerical guidance depicts sustained southerly surface winds
exceeding 15 mph during the late afternoon hours, amidst critically
low RH and fuels that are receptive to fire spread. Locally elevated
conditions may also occur along the lee of the northern Sierra
across parts of northwest Nevada, but the localized nature of the
threat precludes an elevated delineation at this time.
Elsewhere, the isolated dry thunderstorm area was expanded into
southwestern Idaho, as the most recent convection-allowing models
depict discrete convection developing in this area, where a deep,
relatively dry sub-cloud layer will be present. Given adequate
instability across this particular region, strong, erratic winds are
possible with the more intense storms. Across the remainder of the
isolated dry thunderstorm area, at least patchy areas of heavier
rainfall are expected on Day 1, which may locally temper the
wildfire spread threat on Day 2 to a degree. Nonetheless, given the
uncertainty associated with pinpointing more exact areas of
rainfall, no other changes have been made to the isolated dry
thunder area at this time.
..Squitieri.. 08/09/2019
.PREV DISCUSSION... /ISSUED 0126 AM CDT Fri Aug 09 2019/
...Synopsis...
The mid-level trough responsible for D1 fire weather concerns in the
West will take on a negative tilt while slowly migrating
northeastward over Oregon and vicinity. As this occurs, a belt of
enhanced mid-level flow will shift eastward toward eastern Nevada
and eastern Idaho. Meanwhile, areas of scattered to widespread
thunderstorm activity will once again migrate over inland portions
of the Pacific Northwest and northern California.
...Eastern Nevada, far western Utah, and eastern Idaho...
Vertical mixing processes beneath the mid-level jet core will
encourage development of a belt of relatively strong (15-25 mph)
south-southwesterly surface winds during peak heating periods across
the region. This region also resides on the western fringe of much
of the rainfall over the past month or so, with dry fuels supporting
ongoing fires across the region. One lingering uncertainty with
regard to the extent of the fire-weather threat in this area will be
potential for wetting rainfall over the region on D1/Fri, which may
temper fuels in a few areas. However, elevated to locally critical
fire weather will likely exist given near-critical RH values
expected during the afternoon. Some portions of this region may
need a critical upgrade in later outlook updates.
...Washington, Oregon, and northern California for thunderstorms...
The continued presence of mid-level moisture and a nearby trough
will again foster areas of northeastward-moving clusters of storms
across the region. However, the extent of dry thunder potential is
a bit less clear compared to prior days due to 1) expected areas of
wetting rainfall on D1/Fri, which should temper fuel states on at
least a localized basis and 2) the coverage of wetting rainfall
during the afternoon and evening, which should further temper fuel
states over a much broader area especially in Oregon. CAMS/high-res
guidance even depicts upscale growth into linear complex(es) during
peak heating hours. Nevertheless, areas that can remain dry will be
susceptible to isolated dry lightning strikes outside of heavier
thunderstorm cores, and gusty/erratic winds near downdrafts are
expected.
...Please see www.spc.noaa.gov/fire for graphic product...
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