ZCZC SPCFWDDY2 ALL
FNUS22 KWNS 170711
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0211 AM CDT Tue Jul 17 2018
Valid 181200Z - 191200Z
An upper-level ridge will become established across the western
CONUS during the Day 2/Wednesday period. A belt of stronger
mid-level flow will traverse the ridge during the late afternoon
hours across the northeastern Great Basin, towards the Front Range.
A surface high will also develop over the higher terrain of the
Rocky Mountains, promoting the development of modest pressure
gradients and associated downslope flow across the Great Basin into
southeast portions of the Pacific Northwest.
...Central Oregon/Washington into Idaho and northern Nevada...
Downslope flow east of the Cascades and 35-45 knot mid-level flow
partially mixing to the surface via a deep boundary layer will
likely promote sustained 15-25 mph surface winds and 15-25% surface
RH across much of the region. Locally critical conditions (driven by
periods of 15% RH and 25 mph sustained surface winds) are possible
along the lees of the Cascades and White Knob Mountains for brief
periods during the late afternoon hours. An elevated area was
maintained for areas east of the Cascades to the Snake River Plain
given the availability of receptive fuels in this area.
A well-mixed boundary layer will allow for more efficient transport
of stronger winds aloft to the surface compared to areas farther
southwest. 15-25 mph surface winds and 10-15% RH will be common
across grassland regions of northern Montana, east of the northern
Rockies. Locally critical winds may potentially overlap critical RH,
with fuels recently becoming receptive to fire spread. An elevated
area was thus continued for northern Montana.
Downslope flow is expected to prevail across the lower terrain of
southwestern Wyoming, with 15-20 mph sustained surface winds and
10-20% surface RH expected during the mid to late afternoon hours in
the Green River Valley and to the lee of the Wind River Range. Fuels
are expected to be at least marginally receptive to fire spread in
this area, so the elevated delineation was maintained.
Recent CAM guidance suggests that isolated thunderstorms may develop
off of the higher terrain of the northern Rockies across southwest
Montana, amidst modest mid-level flow, marginal buoyancy, and
0.5-0.75 inch precipitable water values. Isolated dry lightning may
occur in this region, but spread among model guidance precludes an
isolated dry thunderstorm delineation at this time.
...Please see www.spc.noaa.gov/fire for graphic product...
CLICK FOR DAY 2 FIREWX AREAL OUTLINE PRODUCT (KWNSPFWFD2)