Storm Prediction Center Day 1 Fire Weather Outlook

Created: Tue Dec 12 15:48:02 UTC 2017 (20171212 1700Z Day 1 FireWX shapefile | 20171212 1700Z Day 1 FireWX KML)

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 121546

   Day 1 Fire Weather Outlook  
   NWS Storm Prediction Center Norman OK
   0946 AM CST Tue Dec 12 2017

   Valid 121700Z - 131200Z

   The elevated area has been expanded across parts of central/eastern
   Montana. Recent observations and high-res guidance suggest
   west/northwesterly downslope flow around 15-25 mph will combine with
   dry fuels and RH values below 20% to promote elevated to locally
   critical conditions in the lee of the Rockies this afternoon.

   ...Southern California...
   Morning observations indicate pockets of elevated/locally critical
   conditions ongoing across terrain-favored areas. Winds may weaken
   slightly during the day, but very dry conditions will maintain
   higher fire-weather concerns. The current elevated area captures the
   risk area well, and no changes are needed.

   ..Picca.. 12/12/2017

   .PREV DISCUSSION... /ISSUED 0128 AM CST Tue Dec 12 2017/

   The overall mid-level pattern across the United States continues to
   be a general west-to-east ridge-trough pattern. This will maintain a
   very dry airmass across most of the United States. Additionally, the
   pattern will maintain surface ridging across the Great Basin and a
   generally favorable pattern for offshore winds across Southern

   ...Southern California...

   The long-duration offshore-wind event will continue on Tuesday. Peak
   wind gusts should be in the 20-40 mph range as compared to the 60-80
   mph range last week. This continued offshore flow will maintain a
   very dry airmass across the region, with very poor overnight
   recovery. Thus another day of elevated-to-locally critical
   fire-weather conditions is expected.

   One note, even though the overall large-scale surface-pressure
   gradient will be weakening with time, forecast soundings indicate
   mid-level-lapse rates will be on the order of 7.5-8.0 C/km. These
   lapse rates will support plume-dominated fires. Any fire plume 
   would likely modify/enhance low-level winds in the vicinity of the

   ...North-central to Southeast Montana...

   Strong westerly downslope flow will contribute to afternoon
   temperatures warming to around 60F across the area. Surface
   dewpoints will be in the teens across the region and then should
   fall during the day. The combination of warm temperatures and
   falling dewpoints will result in minimum afternoon relative humidity
   at or below 20% across much of the area, with local areas even
   lower. Additionally, the lack of appreciable precipitation in recent
   weeks has allowed fuels to cure and ERC percentiles to rise. Thus,
   given the dry, receptive fuels, strong, gusty winds, and the warm,
   dry airmass, elevated fire conditions are likely.

   ...Please see for graphic product...


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