FNUS21 KWNS 161632

Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1131 AM CDT Wed Jun 16 2021

Valid 161700Z - 171200Z

Major change to the isolated dry thunderstorm area was an expansion
eastward to include more of Colorado and into far southeast Wyoming
and southwest Nebraska Panhandle where PWAT values are forecast to
be less than 0.75 and thus dry thunderstorms are most likely.
Otherwise, the largest change was to expand the northern Plains
elevated southeastward into northwest South Dakota. Morning forecast
guidance indicates 15+ mph winds and RH of 20 to 25 percent
extending farther southeast than previous guidance had indicated.

Strong offshore flow continues in San Luis Obispo and Santa Barbara
counties with multiple RAWS sites showing 30 to 40 mph winds and
relative humidity between 20 and 30 percent. Expect these winds to
subside through the day.

..Bentley.. 06/16/2021

.PREV DISCUSSION... /ISSUED 1257 AM CDT Wed Jun 16 2021/

Partial upper-level ridge breakdown will continue for today as an
upper-level trough, currently moving east over the northern Rockies,
continues to translate into the northern Plains. An attendant
surface low and trailing cold front/trough will likewise continue to
the east through the day. The displacement of stronger upper-level
flow and tighter surface pressure gradients from the drier air mass
and favorable fuels to the west will limit the potential for a
robust fire weather threat. But the diurnal deepening of a thermal
low over the lower Colorado River Valley and building high pressure
along the West Coast will support several areas of elevated fire
weather concerns. 

...Great Basin into the northern Rockies...
Areas of elevated fire weather conditions appear likely this
afternoon for much of the Great Basin and parts of the northern
Rockies as RH values fall into the single digits and low teens area
wide. Downslope winds in the lee of the Sierra Nevada will drive
15-20 mph winds along the CA/NV border, and similar sustained winds
are expected further east/northeast across the Great Basin and
northern Rockies as the regional pressure gradient tightens. Areas
of east-central NV, northeast UT, and southwest WY may see frequent
gusts upwards of 25-30 mph in terrain-favored locations by early
afternoon. This may support periods of critical wind/RH conditions,
but the potential for widespread critical conditions is low given
weak flow aloft. 

...Northern Montana...
Post-frontal winds are forecast to be sustained at 15-25 mph across
northern and northeast MT early this morning, but are forecast to
gradually abate through the day as the surface low shifts east into
the Plains. Diurnal warming will drive RH reductions into the 20-30%
range by mid/late afternoon, but winds by this time will most likely
be near 15 mph across the region. This temporal displacement of
stronger winds and low RH suggest low potential for sustained
critical conditions, but elevated wind/RH combinations seem likely
with localized critical combinations possible. 

...Southern California...
The thermal low across the southern CO River Valley is forecast to
extend along the CA coast as temperatures climb into the upper 90s
and low 100s. Building high pressure across CA's Central Valley will
support an offshore wind gradient with 15-25 mph winds likely. RH
values falling into the 15-20% range and dry fuels will support
elevated fire weather conditions. 

...Four Corners...
Mid-level moisture lingers over the southeastern quadrants of the
Four Corners region as sampled by 00Z regional soundings and recent
GOES PWAT imagery thanks to modest moisture advection within a mean
easterly flow regime. This moisture, combined with deep
boundary-layer mixing from strong diurnal heating, will support
thermodynamic profiles favorable for convection again this
afternoon. Isolated to scattered thunderstorms will be driven
primarily by orographic ascent. With dry lightning observed in
recent days under similar conditions, another day of dry lightning
strikes seems likely. 

To the south along the AZ/NM border, southeasterly winds will
increase in response to the deepening thermal low to the west. Winds
will likely increase to near 15 mph by early afternoon and support
elevated fire weather conditions given single digit to low teen RH

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