318
FXUS65 KCYS 032229
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
429 PM MDT Thu Jul 3 2025

.KEY MESSAGES...

- Widespread showers and scattered embedded thunderstorms along
  and west of I-25 this afternoon will spread east this evening
  and into Friday morning. A few rare AM showers and storms are
  expected to begin Independence Day.

- Temperatures drop back down closer to near normal for
  Independence Day but afternoon showers or thunderstorms could
  impact festivities.

- High pressure to the south could drive daily shower and
  thunderstorm chances in the long term while keeping us close
  to near seasonable for temperatures.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 427 PM MDT Thu Jul 3 2025

Deep moisture is streaming out of the southwest as visible on
GOES water-vapor imagery in between a shortwave trough over the
Great Basin and a strong upper level ridge over the Central
Plains. Abundant moisture in the middle to upper atmosphere is
mixing down through the dry boundary layer as
showers/thunderstorms increase in coverage. This is slowly
pushing dewpoints up across Carbon and Albany counties. While
moisture is abundant, instability is somewhat unimpressive
thanks to very warm temperatures aloft. 500-mb temperatures are
near the 99th percentile, as precipitable water values creep
towards the 99th percentile as well. The result so far is
widespread shower coverage, with scattered embedded
thunderstorms streaming from south to north across Carbon and
Albany counties, and now reaching into southern Converse county.
This activity will be capable of producing locally gusty winds,
particularly with the first round moving into a given area.
DCAPE will decrease once a round or two of showers modify the
nearby environment. Overall coverage east of the Laramie range
looks fairly limited through the evening as instability is not
impressive, but additional forcing from the surface wind shift
boundary may boost some showers or thunderstorms near or just
east of I-25, which will spread eastward with modest isentropic
lift tapping into good MUCAPE overnight. Most of this activity
is expected to be sub-severe, but isolated large hail and/or
strong winds cannot be ruled out.

The axis of the shortwave trough will pass through near or shortly
after sunrise Friday morning, which may kick off Independence day as
an unusually showery morning. This first round should be out of our
area around noon before instability has time to ramp up with
daytime heating, but don`t be surprised to see showers and a few
thunderstorms during the morning hours. We may have to watch
for this activity becoming strong to severe as it approaches our
eastern row of counties. In addition, expect an increased
pressure gradient behind this activity, which will lead to a
brief period of gusty winds in the wind prone areas and over the
High Plains during the morning. Expect thick cloud cover to
break up late morning and allow for some destabilization as we
head into the afternoon and evening hours. A second round is
then possible that may interfere with holiday festivities across
the area, kicked off by a late arriving vort-max ahead of
another trough well to our northeast. Hi-res model guidance is
fairly consistent in showing a late afternoon and evening round
of scattered thunderstorms moving across the area and possibly
linearizing ahead of a developing meso-high. This may be capable
of producing strong gusty winds, and possibly isolated
marginally large hail. The timing is inconvenient for July 4th
festivities, and may interfere with some fireworks displays, but
confidence is not very high in how this second round will play
out due to the modest forcing and marginal environment.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 427 PM MDT Thu Jul 3 2025

Water Vapor Imagery shows an active Pacific Ocean thats going to be
responsible for the multitude of shortwaves traversing The Pacific
Northwest and Intermountain West. Looking at cluster analysis the
main uncertainty appears to be where the area of high pressure will
set up.  If the high pressure system sets up further West over the
Nevada area, then the Intermountain West will be in Northwest flow.
While in Northwest flow, daily chances for evening weak to strong
thunderstorms can be more expected as these shortwaves push through
our region. The secondary scenario is if this area of high pressure
sets up over the four corners region, then a hot and dry outcome can
be more expected. The ridge axis will be pretty stout over the
Intermountain West and better deflect those shortwaves. However, we
would still have to watch for possible shortwaves to develop
thunderstorms. Ensemble guidance does keep temperatures in the 80`s
and possibly some 90`s next week east of I-25. To build some
confidence NAEFS is also showing average values for climatological
PWAT`s and Integrated Water Vapor for the Wyoming and Nebraska
areas. So the warmer/drier weather pattern may be in our favor, but
it is something to monitor for more certainty in next weeks weather
pattern.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1138 AM MDT Thu Jul 3 2025

VFR through 21z is still expected its a little uncertain how far
the ceilings will drop under these storms but model soundings
indicate ceilings will be between 5000-7000ft. However, these
showers may drop visibilities into the MVFR/IFR range especially
over KRWL and KLAR. For our Nebraska terminals the rainfall
looks to start between 12-15z and possibly end by 18z.

&&

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

&&

$$

SHORT TERM...MN
LONG TERM...MM
AVIATION...MM