230
FXUS65 KCYS 041208
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
600 AM MDT Fri Jul 4 2025

.KEY MESSAGES...

- Widespread showers and scattered embedded thunderstorms will
  continue to spread east early 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. Hot temperatures are
  possible by mid to late next week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 305 AM MDT Fri Jul 4 2025

Current KCYS radar loop shows the band of nocturnal
thunderstorms, which developed late last night, pushing eastward
into the southern Nebraska Panhandle. This ended up being a few
hours earlier than expected, but not too far off as it was
a concern over the last few forecast packages. Elevated
instability and MUCAPE of around 1000 to 1500 j/kg remain over
most of the western Nebraska panhandle as an area of
convergence remains over the area. Thankfully, this activity has
been sub-severe but very heavy rainfall rates and frequent
lightning have led to travel impacts overnight.

For the rest of today, models continue to show the slow moving
trough axis moving into the eastern plains by noon/early
afternoon today with another shortwave disturbance aloft
immediately behind the Pacific trough. After a brief lull this
morning with some sunny skies, instability will increase rapidly
as forcing remains over the area. Expect a fairly active
afternoon and evening with scattered showers and thunderstorms,
some strong to marginally severe across the Nebraska panhandle.
This activity may linger into the late evening hours, which
could impact Independence Day festivities...although the latest
CAM runs now show most of this thunderstorm activity finished by
around 9 pm late this evening.

For Saturday, models show a flattened ridge axis across the
Intermountain West as another Pacific shortwave clips northern
and central Wyoming. With low level convergence along the
mountains due to westerly winds behind the shortwave, but
upslope easterly winds ahead of it...and ample moisture across
the area, showers and thunderstorms are expected to develop in
the afternoon. These thunderstorms may become strong or severe
across western Nebraska with current MLCAPE between 1500 to 2500
j/kg and 0-6km shear of 30 to 40 knots.


&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 219 AM MDT Fri Jul 4 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 /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 600 AM MDT Fri Jul 4 2025

A series of upper level disturbances will push over the region
beginning early this morning, with the next disturbance set to
impact the area closer to mid to late afternoon. Bands of showers
and thunderstorms will develop and push east southeast through late
this evening, with a brief lull between 16z and 21z today.

HAZARDS/WEATHER TRENDS: Although VFR conditions will generally
prevail over all terminals today, a tricky forecast for
thunderstorms with timing and impact not only this morning but also
late this afternoon through late this evening. Added thunderstorms
to area TAFs, with the most confidence over the western Nebraska
terminals (prevailing and tempo groups) and somewhat lower
confidence for KRWL, KLAR, and KCYS (PROB30). Periods of MVFR
conditions in heavy rainfall are possible with occasionally gusty
outflow winds up to 40 knots possible. Conditions are not expected
to improve until after 03z.

&&

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

&&

$$

SHORT TERM...TJT
LONG TERM...MM
AVIATION...TJT