646
FXUS65 KCYS 082356
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
550 PM MDT Fri Aug 8 2025

.KEY MESSAGES...

- Red Flag Warnings remain in effect through Saturday due to
  low afternoon relative humidity and poor overnight humidity
  recoveries.

- Sunday will be the coolest day of the period, with drying and
  warming next week and gusty winds returning by the middle to
  end of the week alongside potential critical fire weather
  conditions.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 340 PM MDT Fri Aug 8 2025

Today begins a break from the very hot temperatures across the area
as an unseasonably strong upper level low moves over the northern
Rockies and into the northern Plains. Most of the area is at least 5-
8F cooler than 24-hours ago at this time, with some portions of the
US-20 corridor close to 20F cooler. GOES satellite imagery
depicts a fairly potent circulating upper level low
centered over the Montana/Canada border, with a deeper moisture
plume moving over most of the forecast area. At the surface,
the post frontal airmass is not particularly moist, but also
not nearly as dry as what we saw yesterday. Dewpoints over the
High Plains generally range from the mid 40s to mid 50s.
Mesoanalysis shows modest instability over the High Plains, but
also fairly strong capping still present. However, vertical wind
shear is quite strong, with 0-6km shear around 50 to 60 knots
for most of the area. Some continued destabilization is expected
for the remainder of the afternoon and early evening hours,
which may kick off some isolated thunderstorms. There is overall
fairly low confidence in how this will play out today, but the
environment may support a supercell or two, if storms manage to
develop after all. Widely scattered showers and thunderstorms
may continue through much of the night over the High plains,
driven by modest overrunning and tapping into lingering elevated
instability.

A dry slot is also apparent on water vapor imagery moving across
central Wyoming. This will begin to push dewpoints downward again
this evening and overnight in Carbon county and our northern zones.
and increase fire weather concerns again for Saturday. Dry air
should stall out somewhere over the High Plains, with better surface
moisture lingering southeast of roughly a Cheyenne to Alliance line.
Look for very pleasant temperatures across most of the area, mainly
in the mid 70s to mid 80s. A vort-max rotating around the base of
the slow moving upper level low will help provide a little bit of
lift. While very dry mid-level air will suppress convection over
most of the area, the moist wedge to the southeast will still
contain a decent environment for showers and thunderstorms. If
storms get going, it looks like a fairly late show that may last
into the overnight hours as forcing and elevated instability
continue into early Sunday morning.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 340 PM MDT Fri Aug 8 2025

Sunday begins cool and rainy and will be our "coldest" day of
the period (widespread highs 70`s and some low 80s). The upper
level low will begin to depart, but not before another round of
activity will be possible through the afternoon with the best
ingredient for stronger to severe weather expected to remain
just to our south in Colorado. While not notably moist at the
surface, we should see moisture return enough that the
widespread fire weather danger we`ve had all week should finally
ease. With the pressure gradient relaxing allowing winds to
lessen, the warming and drying trend we can expect to start next
week should also stay just outside of critical fire weather
danger. High pressure to the west will remain in control through
at least the middle of the week, but will begin to wane due to
an upper level trough strengthening and dropping down from
Canada. This will then allow for high pressure to the east to
begin strengthening, but for our region the pressure gradient
will tighten allowing breezy winds to return. And with a lack of
surface moisture too, don`t be surprised if we see red flag
conditions returning by the middle of the week. Mid level
moisture returning should help fuel some light precipitation
chances, but we won`t see stronger precip or storms until we get
a stronger feature to pass across the forecast area, not likely
until later next week or possibly into the weekend. Otherwise
the warming will remind us that summer isn`t quite done with us
yet, with the warmest highs on Thursday as 90`s to triple digits
show up once again.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 550 PM MDT Fri Aug 8 2025

Surface cold front has pushed into Colorado this afternoon with
north winds across the high plains. The front is currently stalled
near Laramie with gusty westerly winds west of the front. A few
showers or an isolated thunderstorm are possible through this
evening.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail with a midlevel
overcast cloud deck for most terminals through late this evening.
Can`t rule out a few thunderstorms, mainly for KCDR, KSNY, and
KAIA...but confidence remains low. Will keep the PROB30 group in
these TAFs for now, but will likely need to remove them by 03z.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning until 6 PM MDT Saturday for WYZ419>429.
NE...None.

&&

$$

SHORT TERM...MN
LONG TERM...CG
AVIATION...TJT