266
FXUS65 KCYS 092350
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
550 PM MDT Sun Aug 9 2026

.KEY MESSAGES...

- Red Flag Warning remains in effect through 9 PM Sunday for
  all of southeast Wyoming for very low humidities and
  significant gusty winds.

- Elevated to critical fire weather conditions will likely
  persist through Tuesday with the potential for another Red
  Flag to be issued for Southeast Wyoming.

- Hot temperatures continue through the start of the week before
  a pattern change begins to occur as precipitation chances
  start to rise and temperatures fall, dropping to below normal
  by the later half of the week.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 259 PM MDT Sun Aug 9 2026

A stalled front will be the likely catalyst this evening as the
showers push through from the West. SPC has a Marginal Risk for
severe thunderstorms in the Panhandle. The Hi-res models put around
2,000 joules of CAPE east of the stalled front. DCAPE values
continue to be around 1,000-2,500 joules with moisture advecting in
at the mid levels and a stout dry layer at the surface for the
classic inverted-v Sounding. The stalled boundary runs pretty much
along the I-25 corridor. So this afternoon and evening these weak
thunderstorms/gusty showers will likely produce "virga bombs" or
frequent microburst like wind gusts pretty much west of I-25 and
through our northern counties of Converse and Niobrara. These
showers or weak thunderstorms will cross the boundary into an
environment with moisture and CAPE. It will be like when you`re
playing those popular racing games and you hit a power up, except
these showers and storms will slightly intensify but the bulk shear
will limit things a little bit being between 30-40kts and the CAPE
slowly increasing to around 1,000-1500 joules in the northern
panhandle and 2,000-2,500 joules in the southern panhandle. The HRRR
and the NAM Nest develop supercells either over Sidney or Chadron NE
indicating the locations of the most favorable environment for
severe thunderstorms if they dont fall apart before then. The RAP
also indicates some areas of weak isentropic lift along the
Colorado/Wyoming border and into the southern Nebraska Panhandle as
the evening progress. However, It also shows weak isentropic descent
in the Northern Panhandle which makes it makes it a little harder to
produce a supercell as potential drier air may entirely ruin the
chances assuming the RAP was right. Although kind of conflicting
signals depending on which models you look at, the areas to watch
this evening would be either Sidney or Chadron for a potential
severe threat that includes a tiny bit more than wind gusts greater
than 60mph. It wouldn`t surprise me if a storm does organize itself
and drops the Intermountain west special of accumulating peas or
potentially pennies with one or 2 quarter sized stones thrown in
there. Monday is looking like a copy and paste forecast tomorrow.
Looking at the WPC graphics the frontal placement remain quasi-
stationary and the SPC has a marginal risk for tomorrow as well in
the exact same place. Which honestly is fair when the catalyst is
pretty much the same and the soundings show a tiny bit lower lcl`s
but the overall inverted v is still there but a tiny bit less CAPE
values in the Panhandle with these latest runs... persistence
forecasting may actually pay off. Monday still looks like a gusty
shower/ weak thunderstorm type of day overall, but the potential for
wind gusts to exceed 58 mph exists in our environment thus
justifying the marginal severe risk. Especially when the model
soundings have DCAPE values values around 1500-2000 joules in the
afternoon and evening and the Rocky/Intermountain West region can
produce those strong microburst like wind gusts at the drop of a
hat. Temperatures and Dewpoints will be a little hard to forecast as
the models are not doing a "good job" with the stalled
boundary/dryline. They seem to be mixing out a lot more than whats
actually happening and cloud cover seems potentially underdone which
cooled us off a lot faster than the models anticipated thus the
daily high temperatures being a little cooler than forecast.
However, West of I-25 looks to still be in the 80`s and east of I-25
will still be in the 90`s with some areas still reaching 100. So in
the grand scheme of things not much of a change in impacts as it
still will be hot in the afternoon under this flatten ridge and the
global models holding onto 700mb temperatures between 15 to 20C by
the late afternoon.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 259 PM MDT Sun Aug 9 2026

As the long term forecast progresses, the 500mb jet moves from the
Pacific NW to right over our area on Wednesday. While this jet
has winds in the range of 50-60 knots, it is suppressed. As the
ridge flattens, chances of moisture increase. PWAT values
increase starting on Wednesday, with the highest values being
Friday at around 1.5" near the Nebraska panhandle. RH values
increase significantly on Thursday, ranging from 60-90%! This
moisture sticks around through Sunday, even bringing some
chances of thunderstorms with it. Shear increases Friday and
Saturday evening, supporting chances of thunderstorms. Surface
winds stay in a normal range for the area, typically staying
below 35 knots. With this moisture moving in, and winds staying
relatively slow, fire weather becomes much less of a concern
through this long term period. 700mb temperatures show Wednesday
still being quite warm, with much of the CWA being in the
15-17C range. Temperatures begin to cool down Thursday as a cold
front moves in, bringing temperatures to the 10-12C range. The
area stays cool through Sunday, below 13C.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 534 PM MDT Sun Aug 9 2026

A few strong thunderstorms in western Nebraska will impact BFF
and AIA over the next 1-2 hours with strong, gusty winds, a
brief VIS drop to IFR, and possibly some hail. Impacts may
occur at SNY and CDR, but confidence is lower there. SE winds
will stay elevated through the evening in the Nebraska
panhandle, but should become lighter and occasionally variable
later, though LLWS is possible at CDR.

Winds will turn northwest by late Monday morning across the
area with gusts increasing in Wyoming. Look for another round of
gusty showers and a few thunderstorms Monday afternoon.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Air Quality Alert until noon MDT Monday for WYZ101>119.
     Red Flag Warning until 9 PM MDT this evening for WYZ417>433.
NE...None.

&&

$$

SHORT TERM...MM
LONG TERM...ML/AM
AVIATION...MN