819
FXUS65 KCYS 200820
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
220 AM MDT Wed Aug 20 2025

.KEY MESSAGES...

- Hot temperatures continue through Thursday with near record
  highs possible in the northern Nebraska Panhandle.

- 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 THURSDAY NIGHT/...
Issued at 220 AM MDT Wed Aug 20 2025

Expecting a quiet day on tap as the Four Corners ridge continues
to hold strong for today. Dry conditions and strong subsidence
will encourage a lack of precipitation, alongside critically dry
conditions for our far western and northern zones. For the most
part we shouldn`t see red flag conditions due to winds not
lining up with our driest areas, but portions of the northern
Nebraska Panhandle as well as Niobrara and Converse Counties
could briefly see gusts line up with 15% RH values during the
late afternoon before RH`s begin to climb again. Hot temperatures
expected as well with near record tying highs possible mostly
for our far northeastern zones where temps will be the hottest
(100+ degrees).

Thursday will also be another warm day, but thankfully this will
be the last of significant warmth as we begin a pattern change
late in the day. Highs in the NE Panhandle and just along the
border of WY should still reach the upper 90`s, but the rest of
the region should see mid to upper 80`s as the ridge begins
breaking down and a cold front starts moving into the CWA. The
aforementioned front should be just on our doorstep to start
the day, passing across through the early evening hours and also
bringing back precipitation chances. Currently the best
precipitation chances lie in our northern zones and with severe
parameters including instability remaining meager, it`s unlikely
we`ll see stronger to severe thunderstorms for the day. But
that should change as we move into the long term.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 220 AM MDT Wed Aug 20 2025

A deep upper-level low pressure system moving across Central
Canada and then slowing as it moves east-southeastwards and
approaches the Great Lakes will help to drive the Four Corners
ridge southwestwards, bringing a northwesterly flow to our
region that should persist through the end of the long term
forecast period. This low should also begin deepening and
overspreading with most of the Central and Eastern US expected
to be under troughing by early next week. With how strong this
system is expected to be, we should see multiple smaller
embedded shortwaves riding the periphery and across our CWA
while also helping to bring monsoonal moisture up around the
notably weakened ridge, causing daily shower and thunderstorm
chances. Storm total QPF starting with Thursday and continuing
through the end of the forecast period suggests we could see
a noteworthy amount of rainfall, with Laramie County expected
to receive 1.25-2 inches of new rainfall. Ensemble guidance
(ECMWF Ens & GEFS) is a bit more modest compared to the NBM,
with only a 20-50% chance of greater than 1 inch of new rainfall
for our southern zones east of the Laramie Range. Still any
rain helps for our now critically dry CWA.

And of course these numbers could locally spike based on the
strength of thunderstorm activity, with severe thunderstorms
possible starting on Friday. Current analysis indicates a
marginal risk (1 of 5) of strong to severe thunderstorms for the
end of the week, with modest instability and steep lapse rates
supporting both hail and winds. Thereafter, we may see similarly
marginal risks during the weekend, but instability should begin
to wane by early next week at latest, so don`t expect a
widespread and multi-day outbreak but rather the first of a more
fall-like pattern of rain and cooler temperatures with some
thunder expected. And finally on the note of temperatures, if
you`re a fall fan then this is the first sign of cooler
conditions to come, as Friday will be the warmest day of the
long term with highs in the mid 70`s to low 80`s, with
widespread 70`s then expected over the weekend and into next
week, and Cheyenne itself only expected to peak in the upper
60`s to start next week.

&&

.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...CG
LONG TERM...CG
AVIATION...TJT