389
FNUS21 KWNS 191506
FWDDY1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1005 AM CDT Tue Aug 19 2025

Valid 191700Z - 201200Z

Very low RH will continue across much of the Great Basin, West
Slope, northern/western Arizona, western Wyoming, and southwest
Montana and remaining below Elevated thresholds for 18-24 hours
during the outlook period. This will lead to long burning periods
once again, and multiple large fires remained active last night in
similar conditions. Minor modifications were made to the Elevated
area based on the latest observations and high-resolution forecast
guidance.

Dry thunderstorms are possible in portions of north-central and
northeast Arizona on the fringe of monsoonal moisture. However, PWAT
values and dewpoints increase slightly today while deeper moisture
is expected in the coming days precluding an IsoDryT area.

..Nauslar.. 08/19/2025

.PREV DISCUSSION... /ISSUED 0156 AM CDT Tue Aug 19 2025/

...Synopsis...
An amplifying mid-level ridge over the Four Corners region will
support a large area of hot and dry conditions over much of the
Intermountain West. On the northern periphery of the ridge,
southwesterly flow aloft will increase ahead of a shortwave trough.
This will allow a dry cold front to approach and stall over the
northwestern Great Basin. Ahead of the front, very warm and dry
conditions are expected. With the increased flow aloft, forecast
guidance shows south-southwest surface winds increasing to around 15
mph with gusts to 20-25 mph. The stronger winds amid a very dry
airmass will support minimum RH of 5-15%. With regional fuels very
dry, elevated fire-weather conditions appear likely.

...Northern Rockies...
To the northwest, the mid-level trough and remnant monsoon moisture
may support isolated thunderstorm potential across the higher
terrain of the northern Rockies. Some lightning is possible, though
the highest storm chances are expected over western MT and
northeastern ID where less receptive fuels are present. This
suggests the threat for ignitions is modest and below 10% coverage
for IsoDryT highlights.

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

$$