Storm Prediction Center
Day 1 and Day 2 Fire Weather Outlooks

Day 1 Fire Weather Forecast graphic
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast

Click for Day 1 FireWX Areal Outline Product

   FNUS21 KWNS 171529

   Day 1 Fire Weather Outlook  
   NWS Storm Prediction Center Norman OK
   1029 AM CDT Tue Jul 17 2018

   Valid 171700Z - 181200Z

   Forecast looks on track and only minor changes were made. Please see
   the forecast discussion below for more details.

   ..Nauslar.. 07/17/2018

   .PREV DISCUSSION... /ISSUED 0209 AM CDT Tue Jul 17 2018/

   A weak 500 mb shortwave trough will pass over the northern Great
   Basin during the afternoon. Mid-level moisture will also move
   eastward in association with the shortwave trough. At the surface, a
   thermal trough will develop east of the Cascades down into far
   northern Nevada. 

   ...Central Washington/Oregon...
   A thermal low will become established along the lee of the Cascades
   during peak heating of the afternoon, as temperatures are expected
   to reach up to 100F in some locales. The thermal low induced
   pressure gradient will generate downslope sustained surface winds of
   at least 15-20 mph in tandem with 10-20% RH. Fuels are receptive in
   this area, with elevated RH/wind criteria being met for fire spread
   potential. Stronger surface winds (20-25 mph) may occur along the
   immediate eastward facing slopes of the Cascades along with
   critically low RH. The brevity of the critical conditions warrant
   only an elevated delineation at this time.  
   ...Southern Idaho...
   Strong surface heating during the mid-late afternoon may induce a
   weak pressure gradient in the Snake River Plain. Sustained surface
   winds of 15-20 mph are expected along with critical RH. An elevated
   delineation was added given the receptive nature of fuels in this

   ...Southwest Wyoming...
   A weak thermal low and associated pressure gradient may develop in
   the Green River Basin. 15-20 mph sustained surface winds are
   expected along with 15-20% RH. Though the RH is marginally low and
   recent rainfall from scattered storms has recently occurred, 10-hr
   fuels remain receptive to the spread of grass fires. An elevated
   delineation was added to account for the stronger surface winds
   overlapping rebounding finer fuels.  

   ...Idaho/Montana border into far western Wyoming...
   As the aforementioned mid-level shortwave trough progresses
   eastward, deep-layer ascent and at least marginal buoyancy will
   foster the development of isolated thunderstorms across the area.
   Precipitable water values of 0.5-0.75 inches and a relatively deep
   sub-cloud layer suggests that dry lightning will be possible. Modest
   mid-level flow will also allow faster storm motions (above 20
   knots), reducing accumulating rainfall atop fuels receptive for fire
   weather spreads.

   ...Please see for graphic product...

Day 2 Fire Weather Forecast graphic
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast

Click for Day 2 FireWX Areal Outline Product (KWNSPFWFD2)

   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. 

   ...Northern Montana...
   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.
   ...Southwest Wyoming...  
   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.

   ...Southern Montana...
   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.

   ..Squitieri.. 07/17/2018

   ...Please see for graphic product...


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