Storm Prediction Center Fire Weather Outlook

• Day 1 fire weather outlook and map
• Day 2 fire weather outlook and map

Day 1 Fire Weather Outlook

	    
   NWS Storm Prediction Center Norman OK
   1143 AM CDT Wed Jun 28 2017

   Valid 281700Z - 291200Z

   ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF UT...EASTERN
   NV...NORTHERN AZ...NORTHWESTERN NM...WESTERN CO...SOUTHWEST WY...

   No changes have been made to the ongoing forecast, with elevated and
   critical wind-driven fire-weather risk and isolated dry-thunderstorm
   potential affecting portions of a broad region from the southwest
   states to the central Great Basin and central Rockies. While
   critical fire-weather conditions will be likely across the entire
   Critical area, there is particular concern for potentially locally
   extreme fire behavior, enhanced fire spread, and explosive fire
   growth across parts of southern UT and northern AZ this afternoon
   into the evening.

   The 12Z Las Vegas NV and Flagstaff AZ soundings this morning sampled
   90th percentile to near-record (warm) 500-mb temperatures combined
   with 75th percentile to 90th percentile (enhanced) 500-mb wind
   speeds -- based upon the SPC sounding climatology. These factors
   reflect the anomalous combination of substantial mid-tropospheric
   warmth and enhanced winds. Water vapor imagery depicts subtle
   disturbances grazing the southern periphery of a broader belt of
   enhanced midlevel zonal flow across the western states -- locally
   enhancing the height gradient / winds aloft over some of the driest
   surface conditions and driest fuels (i.e., across southern UT and
   northern AZ). The aforementioned soundings indicate 30-40 mph of
   flow in the midlevels, highlighting the enhanced momentum aloft that
   will be manifest to some extent at the surface. This will be the
   result of mixed layers deepening to over 10 kft above ground in some
   areas -- aided by surface temperatures warming well into the 80s
   across the higher elevations and into the 90s to near 100F at the
   lower elevations. In addition to supporting an area of locally
   enhanced winds -- i.e., 22-25 mph sustained west-southwest winds
   with gusts of 30-35 mph across southern UT and northern AZ -- the
   deep vertical mixing will also support minimum RH of 3-8 percent.
   This anomalous combination of very warm to hot temperatures / very
   low RH at the base of deep, well-mixed boundary layers / very dry
   fuels -- and the enhanced boundary-layer and surface winds -- will
   all exacerbate the critical fire-weather risk in southern UT and
   northern AZ.

   ..Cohen.. 06/28/2017

   .PREV DISCUSSION... /ISSUED 0257 AM CDT Wed Jun 28 2017/

   ...Synopsis...
   An upper-level shortwave trough will move across the Intermountain
   West today, enhancing westerly flow aloft over much of the central
   Great Basin and Southwest.  At the surface, low pressure will
   persist over much of the West with continued hot and dry conditions.

   ...Arizona...Utah...and adjacent areas...
   A persistent hot, dry airmass over the area will allow for deep,
   well-mixed boundary layers yielding afternoon RH values in the
   single digits for most locations.  Deep vertical mixing in the
   presence of enhanced flow aloft will result in sustained afternoon
   wind speeds of 20-25 mph across much of northern Arizona and
   southern Utah, resulting in critical fire weather conditions.  For
   the surrounding elevated fire weather areas, sustained wind speeds
   are expected to remain just below 20 mph.

   Despite limited moisture across the region, sufficient instability
   will develop during the afternoon across portions of northern Utah,
   southwestern Idaho, southern Wyoming, and northern Colorado to
   support isolated thunderstorm development.  Given the expected high
   cloud bases and dry sub-cloud layers of these thunderstorms, little
   precipitation is expected to reach the ground, supporting the
   potential for isolated dry thunderstorms.

   ...Southern California mountains and adjacent foothills...
   Continued low RH coupled with modestly enhanced winds will also
   prolong elevated fire weather conditions through today across
   portions of Southern California.

   ...Please see www.spc.noaa.gov/fire for graphic product...

      

Day 2 Fire Weather Outlook

 Storm Prediction Center Norman OK
   1236 PM CDT Wed Jun 28 2017

   Valid 291200Z - 301200Z

   The Elevated area has been expanded westward across portions of
   northern AZ and southern UT, where the latest model guidance
   indicates 15-20 mph westerly winds combining with RH of 5-12 percent
   amid dry fuels. No other changes have been made to the ongoing
   forecast.

   ..Cohen.. 06/28/2017

   .PREV DISCUSSION... /ISSUED 0302 AM CDT Wed Jun 28 2017/

   ...Synopsis...
   An upper-level shortwave trough will move eastward across the
   central Rockies on Thursday with an enhanced band of westerly flow
   aloft.  At the surface, low pressure will deepen over western
   Kansas, resulting in an increased pressure gradient across New
   Mexico.

   ...Northwestern New Mexico and adjacent areas...
   A hot, dry airmass will linger over the area on Thursday.  As
   vertical mixing occurs in a deepening boundary layer, afternoon RH
   values will fall into the single digits and sustained wind speeds
   will increase to 15-20 mph.  Given the dry fuels across the region,
   elevated fire weather conditions will exist.

   ...Please see www.spc.noaa.gov/fire for graphic product...

      

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