615
FXUS65 KCYS 200443
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1043 PM MDT Tue Aug 19 2025

.KEY MESSAGES...

- Hot temperatures with more limited thunderstorm chances are
  expected Tuesday through Thursday.

- Active weather returns Thursday and continues through early
  next week as multiple days of showers and thunderstorms
  alongside cooler temperatures are expected.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 300 PM MDT Tue Aug 19 2025

Isolated showers and thunderstorms have developed west of Cheyenne
this afternoon, which are depicted decently by hi-res models. These
storms are associated with a moisture boundary, that is pushing off
to the west towards the Laramie Range. A few of these storms may
produce nickel sized hail and brief downpours, which may struggle to
reach the surface due to drier air in place in the lower levels, and
a few lightning strokes. Otherwise, for the short term, abundant
sunshine and quiet weather will prevail across most of the CWA
through Wednesday as global models indicated high pressure aloft
anchored over the Four-Corners region and associated ridging pushing
into our area. This ridge will usher in rising temperatures with
portions of the Nebraska Panhandle soaring to near triple digits and
the remainder of the CWA climbing into the upper 80s to mid 90s over
the next few days with no widespread record setting highs expected.

For most locations across the CWA, higher temperatures will come
with a decrease in moisture. This may bring an enhanced risk of fire
weather concerns, but not critical conditions, for portions of our
CWA. One of the factors that may limit the fire weather concern is a
weak gradient over the CWA, resulting in generally weaker winds
across the region. However, some areas will see some diurnally
driven afternoon and evening gusty winds. Thankfully these winds are
not expected to be co-located with portions of the region that will
experience the lowest daytime minimum RH values. We will continue to
monitor these conditions over the next few days for any watches
and/or warnings.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 300 PM MDT Tue Aug 19 2025

One more hot day can be expected Thursday across the area before a
major pattern change knocks down temperatures for Friday onward. A
strong ridge will remain locked in over the Four Corners stats on
Thursday, but we will have a potent shortwave trough moving over the
top of it well to the north. This will begin to suppress the ridge
slightly, but not before highs climb well above average once again
Thursday afternoon. While it will certainly be hot, Thursday does
not look particularly likely to challenge daily record highs,
besides perhaps Rawlins where the current forecast of 89 is just
below the daily record of 90F. Meanwhile, the shortwave trough
moving over to our north will help pull monsoon moisture over
the top of the ridge and into our area on Thursday. While
forcing doesn`t look too impressive, ample moisture and modest
instability should be enough to get some isolated to widely
scattered showers and thunderstorms going in the afternoon,
continuing into the evening hours as the surface cold front
surges southward across the area. Overrunning over the cold
front actually looks to increase during the overnight hours, so
rainfall coverage may be higher during the night compared to
Thursday afternoon.

We`ll wake up to a very different airmass over the area Friday
morning, which will be the beginning of a cooler and wetter pattern
expected to continue through the early part of next week. The
synoptic setup for this cooler pattern will be driven by a broad
longwave trough setting up over the Northern Plains and Great Lakes
region. This will force the Western ridge further west, and put our
area under a fairly active northwest flow pattern. A strong surface
high (in fact, exceeding the climatological 90th percentile of MSLP
per the NAEFS average) over the central and northern Plains will
push up against the mountains and keep a cool, moist, low-level
inversion in place over the High Plains. For Friday and Saturday,
look for highs in the mid 70s to mid 80s across the area. Then, a
reinforcing cold front is expected around the Sunday time period,
keeping highs generally in the 70s for Sunday through Tuesday.
Monday looks like the coolest day of the period, and some areas
between Laramie and Sidney may not even make it out of the 60s!
There is pretty good confidence in the cooler temperatures, but less
in the precipitation outcome. While precipitable water is expected
to surge above the 90th percentile of climatology on Friday and
remain more or less steady through at least Tuesday, there is more
uncertainty regarding potential instability. In particular, several
forecast soundings indicate the potential for the low-level
inversion to cause CIN/capping issues each afternoon. These
issues can be pretty uncertain at this lead time, so the overall
takeaway at this time is that the pattern will generally be
much more favorable to widespread showers and thunderstorms
Friday onward, but each day will likely have a failure mode due
to the low-level inversion.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1043 PM MDT Tue Aug 19 2025

Strong upper level high pressure will dominate the weather pattern
across the region through Wednesday night. Dry conditions are
expected over the next 24 hours.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail. Clear skies and
east to southeast winds expected into Wednesday evening with
occasional gusts around 20 knots.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

SHORT TERM...RZ
LONG TERM...MN
AVIATION...TJT