576
FXUS65 KCYS 161142
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
Issued by National Weather Service Rapid City SD
542 AM MDT Wed Jul 16 2025

.KEY MESSAGES...

- Scattered strong to severe thunderstorms are expected
  Wednesday afternoon and evening in southeast Wyoming and
  southwest Nebraska. Large hail is the primary threat, but all
  severe weather hazards are possible.

- Warmer temperatures and isolated to scattered late day
  showers and thunderstorms will occur for Thursday through
  early next week.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 344 AM MDT Wed Jul 16 2025

An active period of weather is anticipated across the area over
the next 24 hours or so. Water vapor satellite imagery shows a
potent upper level shortwave trough moving across the northern
Rockies. Plentiful moisture is streaming out ahead of this
system over much of Wyoming and Nebraska. Meanwhile, a surface
high over the norther Plains is pushed up against the eastern
edge of the Rockies, supporting substantial low level moisture
advection. Precipitable water values exceed 1 inch for most
along and east of I-25, which is pushing the 90th to 97.5
percentile of climatology. Nearly saturated boundary layers are
resulting in low clouds and fog pushing in to cover most of the
High Plains. The latest mesoanalysis shows fairly potent
isentropic lift over much of the area ahead of the upper level
shortwave. This is supporting scattered shower and thunderstorm
activity lingering well into the night. Activity is tapping into
some modest elevated instability, which is strongest in the
general vicinity of the Laramie range. This will continue
through the morning hours today, with isolated storms capable of
producing small hail. Large hail cannot be ruled out through
the morning.

Abundant moisture and instability continuing will set the stage
for an active Wednesday. Capping could present an issue for
surface based convection, but forcing looks to be strong enough
to allow for storms to tap into elevated instability thanks to
continuing overrunning flow. Capping looks weaker on the Wyoming
side. This will put the most potent severe weather environment
over Albany, Platte, Goshen, and Laramie Counties Wednesday
afternoon, with ample deep layer shear, steep mid- level lapse
rates, and plentiful instability. This points to large hail as
the most widespread threat, but all severe weather hazards will
be possible. Storm motions should be fairly fast, but there is a
possibility for training storms. With the plentiful moisture in
place, isolated flash flooding will be on the table too. The
low-level inversion will be stronger in the Nebraska panhandle,
while forcing is overall weaker. This puts a little more
uncertainty into the forecast for southwest Nebraska. Overall
coverage will probably be more isolated in NE, but an isolated
strong to severe thunderstorm will still be possible. Forcing
will continue well into the evening once again, but drier air is
expected to move in aloft after midnight. This should end
thunderstorm activity for all except the southern NE panhandle,
which may continue for a few hours, but wind down by about 3AM
Thursday morning as another round of low clouds/fog moves into
the area.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 344 AM MDT Wed Jul 16 2025

A zonal flow pattern will take over aloft on Thursday and
dominate much of the northern half of the CONUS into the
weekend. Drier westerly flow aloft will reduce the risk for
storms on Thursday, but isolated thunderstorms will still be
possible, mainly along the I-80 corridor. Monsoon moisture will
be pulled into the flow on Friday, causing precipitable water
and mid-level moisture in general to recover. While mid to upper
level moisture should improve for Friday, the dryline is
expected to be positioned further east, resulting in fairly
steady precipitable water Thursday into Friday. Expect to see
some high-based showers and thunderstorms with gusty winds
possible on Friday along with warm to hot temperatures.
Ensembles indicate that the dryline will move back to the west
on Saturday while decent mid to upper level monsoon moisture
remains in place. Expect this to then bring the highest chance
for more widespread shower and thunderstorm coverage of the long
term period. For Sunday through Tuesday or so, expect decent
monsoon moisture to remain in place aloft, but we may lose the
boundary layer moisture for several days, leading to more
isolated PM thunderstorm activity each of those days.
Additionally, an upper level trough digging into the northwest
will amplify the downstream ridge over the central plains,
leading to another warm trend to carry through the middle part
of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 540 AM MDT Wed Jul 16 2025

Low CIGs and areas of fog/mist have moved in over most of the
High Plains, leading to MVFR to IFR conditions this morning at
all terminals east of the Laramie range. Occasional LIFR will
also continue for the next few hours at KCYS and KSNY. In
addition, showers will produce areas of moderate rainfall near
KCDR and KAIA for a few more hours. CIGs may temporarily lift
during periods of rainfall. Expect gradual improvement to MVFR
by mid morning, and VFR by early afternoon as CIGs lift and
break up.

Attention shifts back to thunderstorms for the afternoon hours
with several rounds of storms expected across the area. The
highest probability for storms is at KCYS and KLAR, but all
terminals will have the potential to see aviation impacts due to
thunderstorms this afternoon and evening. The strongest storms
will be between about 21z and 03z. Heavy rainfall, gusty/erratic
winds, lightning, and hail are all possible. Expect this
activity to clear out late in the evening, before low CIGs surge
in again towards Thursday morning.

&&

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

&&

$$

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