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    Day 2 FW Outlook >
Oct 17, 2017 Day 1 Fire Weather Outlook
Updated: Tue Oct 17 07:01:03 UTC 2017 (Print Version | 20171017 1200Z Day 1 FireWX shapefile | 20171017 1200Z Day 1 FireWX KML)
Day 1 Fire
 Population  Cities/Towns  CWAs  Interstates  Counties  FEMA Regions  Day 1 Surface Analysis

Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
Critical 28,476 256,117 Great Falls, MT...Cheyenne, WY...Havre, MT...Torrington, WY...Douglas, WY...
   FNUS21 KWNS 170659

   Day 1 Fire Weather Outlook  
   NWS Storm Prediction Center Norman OK
   0159 AM CDT Tue Oct 17 2017

   Valid 171200Z - 181200Z


   A mid/upper-level ridge that is centered over the Desert Southwest
   will become suppressed/flattened today as an area of enhanced zonal
   flow -- with embedded subtle impulses -- ejects from the Pacific
   Northwest into the Northern Rockies and northern High Plains. At the
   surface, a cold front will move onshore across the Pacific Northwest
   then progress eastward into the northern High Plains.  

   ...Eastern Wyoming and Western Nebraska...
   Lead subtle shortwave trough -- with an associated compact mid-level
   speed maximum -- is forecast to pass over WY later today. Despite
   cool surface temperatures, steep-low level lapse rates are expected
   to foster efficient deep-layer mixing, which will allow for
   sustained easterly downslope surface winds of 15-25 mph (with higher
   gusts). Additionally, modest warming of a dry low-level airmass will
   allow for minimum afternoon RH values near 15% atop receptive fuels.
   The ongoing Elevated/Critical fire weather areas were maintained
   with only minor adjustments. The Critical area over southeastern WY
   is where the greatest confidence in overlapping strong winds,
   reduced RH values, and receptive fuels exists.  

   ...Central/Eastern Montana...
   Strong west-southwesterly pre-frontal winds around 15-40 mph (with
   higher gusts) are expected over MT later today in response to
   deepening surface low over Alberta/Saskatchewan. Despite cool
   surface temperatures, downslope warming of an antecedently dry
   low-level airmass is expected to allow afternoon RH values to fall
   to around 15-25%. Additionally, the lack of recent precipitation
   coupled with long-term drought have rendered fuels -- especially
   fine fuels -- sufficiently receptive to large fire starts.
   Confidence regarding the overlap of sustained surface winds greater
   than 20 mph, RH values less 20%, and sufficiently receptive fuels
   has increased enough that a Critical fire weather area was
   introduced over north-central MT. While near critical conditions are
   possible in the surrounding Elevated fire weather area, confidence
   in stronger winds overlapping sufficiently lowered RH values and/or
   critical fuel receptiveness is less. RH values should increase by
   evening in the wake of the cold frontal passage, but a rapid change
   in wind direction to westerly/northwesterly is expected.  

   ...Central/Southern California...
   A mid-level impulse is expected to move onshore this afternoon in
   the vicinity of Santa Barbara/San Luis Obispo Counties. While recent
   lightning data indicate a modest amount of lightning associated with
   the impulse, the expectation is for the lightning activity to
   diminish later today as the impulse encounters an increasingly
   stable atmosphere near land. If lightning is able to develop, then
   the very dry low levels would tend to limit the amount of
   precipitation reaching the surface. While there is a chance for a
   few lightning strikes, it currently appears that coverage will
   remain below the 10% threshold for the introduction of dry thunder

   ..Elliott.. 10/17/2017

   ...Please see for graphic product...

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Page last modified: October 17, 2017
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