FNUS22 KWNS 161956

Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0255 PM CDT Wed Jun 16 2021

Valid 171200Z - 181200Z


Expanded the elevated area to include the Snake River Plain based on
forecast 15 to 20 mph winds amid less than 10 percent RH. 

In addition, added a critical area to southern Wyoming. Sustained
winds are forecast 25 to 30 mph with gusts as high as 45 mph along
the I-80 corridor in southern Wyoming. Guidance regarding fuel
receptiveness has been mixed, but recent 1000+ acre fires near the
Big Horn mountains in areas showing similar fuel receptiveness lend
support for more critical fuels. Therefore, based on this evidence
and collaboration with fuels guidance, local WFOs, and regional
GACCs, it was deemed fuels are sufficiently dry to warrant a
critical delineation. 

Finally, added an elevated area in northeast Nevada where winds are
forecast to be 15 to 20 mph with relative humidity in the single

Expanded the isolated dry thunderstorm area westward to include much
of southern Nevada into the Sierra and parts of southern California.
Lightning may be very isolated across this region, but there appears
to be enough of a mid-level moisture push to support at least some
convection capable of lightning production.

..Bentley.. 06/16/2021

.PREV DISCUSSION... /ISSUED 0203 AM CDT Wed Jun 16 2021/

Strong zonal flow aloft will persist over the northern Rockies into
Thursday. This will support strong mid-level winds from Wyoming into
Montana and western North Dakota, which will help support areas of
elevated fire weather concerns given the receptive fuels. Mid-level
moisture will continue to linger across the Four Corners region
under an upper-level high, supporting another day of dry
thunderstorm potential. 

...Northern Rockies and northern High Plains...
Westerly surface winds are expected across the northern Rockies and
northern High Plains as a surface trough stalls to the east across
the Plains and high pressure builds over the Pacific Northwest.
Sustained winds near 15-20 mph are probable, and strong mid-level
flow may mix down as frequent gusts to 25-35 mph given sufficiently
deep boundary-layer mixing. With afternoon RH values in the teens to
low twenties expected and receptive fuels already in place, elevated
conditions appear likely. Locations along the I-80 corridor in
south-central WY will see the highest potential for critical
conditions as downslope winds support strong warming/drying as well
as wind gusts up to 45 mph. However, recent fuel reports from this
area suggest fuels are not as receptive as areas further north,
precluding a critical risk delineation at this time (though an
upgrade is possible pending new fuel reports).

...Four Corners...
A persistent upper-level high over the Four Corners will continue to
allow mid-level moisture return from the southern Plains into
central AZ, NM, and central CO. Forecast soundings show sufficient
instability above deep, well-mixed boundary layers with mean
boundary-layer RH values near 20% and PWAT values between 0.4 to
0.6. This suggests a mixture of wet and dry storms is possible, and
given recent dry lightning activity under similar thermodynamic
conditions in recent days, at least a few dry strikes seem likely. 

...Great Basin...
Dry conditions will persist across much of the Great Basin for
Thursday. Afternoon RH values in the single digits are expected, and
fuels will remain receptive after several days of hot/dry
conditions. Weak upper-level flow aloft will limit the potential for
widespread fire weather concerns, but winds up to 15 mph are
possible, especially in terrain-favored locations, which should
support patchy elevated conditions.

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