550
FXUS65 KCYS 160615
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
Issued by National Weather Service Rapid City SD
1215 AM MDT Wed Jul 16 2025

.KEY MESSAGES...

- There is a Slight Risk (2 of 5) for severe thunderstorms
  Tuesday and Wednesday.

- Temperatures should cool for Wednesday behind a cold front.

- 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 118 PM MDT Tue Jul 15 2025

As usual, convection and some thunderstorms have begun across
the region. Expecting coverage of this to increase a bit this
afternoon, with a chance for some thunderstorms including a
marginal to slight risk of some stronger activity including
hail and winds. The main show however occurs this evening as the
upper level trough begins approaching and the jet kicks in,
with wind shear rising as bulk shear values of 30-50 knots,
locally nearing 60 knots, are expected. High resolution guidance
has been consistent since early runs Monday showing a line of
activity forming and moving across Wyoming and into our region
later this evening and into the nighttime hours. While the
overall intensity that models are showing has fluctuated,
guidance is largely in agreement that these storms will move
across Converse and Niobrara Counties and possibly the northern
fringes of counties just to the south sometime between 10 PM and
1 AM. This system continues eastwards into the Nebraska
Panhandle, but agreement on the strength of it as it moves in is
much lower. Strong winds gusting in excess of 65-70 mph are
expected with this line, but with our region you can never rule
out some hail as well.

CAMs indicate some scattered convection remains possible through
the morning hours, but should largely wane. Then Wednesday
during the day brings another round of thunderstorms, and
looking better and better with each model run. Bountiful
instability with MUCAPE values exceeding 2500 J/kg alongside
bulk shear values into the 50-60 knot range will contribute to
widespread thunderstorm development along the I-25 corridor
during the afternoon. All severe hazards are possible with these
storms with initial supercells then forming into clusters as
they evolve eastwards later into the afternoon and evening,
with hail and winds then becoming the much more predominant
threat. And with activity both today and tomorrow training
storms alongside potentially heavy QPF from PWAT values of
0.6-1.0 inch will bring a marginal risk of flooding. But behind
the front we should see a cooler day on Wednesday with highs
only into the 60`s and 70`s outside of our western zones which
should remain a bit warmer with highs into the 80`s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 118 PM MDT Tue Jul 15 2025

Thursday...With temperatures warming aloft and a decrease in
available moisture, we expect only isolated to scattered afternoon
showers and thunderstorms near the Colorado state line from Laramie
to Kimball. Will see a warming trend.

Friday...The warming trend continues under zonal flow aloft. 700 mb
temperatures near 16 Celsius will yield high temperatures from the
mid 80s to mid 90s. Expect isolated to scattered late day showers
and thunderstorms.

Saturday...With an increase in low and mid level moisture, and a
passing shortwave trough aloft, we should see an attendant increase
in afternoon and evening shower and thunderstorm coverage. Slightly
cooler with additional cloud cover and more precipitation coverage.

Sunday...A low amplitude shortwave ridge aloft will move overhead,
and with warmer temperatures aloft and drier air aloft, expect less
coverage of late day showers and thunderstorms. 700 mb temperatures
near 16 Celsius will yield maximum temperatures in the mid 80s to
mid 90s.

Monday...Hot temperatures continue with 700 mb temperatures near 18
Celsius, yielding highs in the mid 80s to mid 90s. Perhaps enough
moisture for isolated late day showers and thunderstorms near the
southern Laramie and Snowy Ranges, though warm temperatures aloft
may produce enough convective inhibition to limit thunderstorm
development, and keep it dry.

Tuesday...Zonal flow aloft and limited low and mid level moisture
will produce another mostly dry day, though cannot rule out isolated
late day showers and thunderstorms if the convective inhibition can
be overcome. 700 mb temperatures near 18 Celsius will yield maximum
temperatures in the upper 80s to upper 90s.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1210 AM MDT Wed Jul 16 2025

A complex aviation forecast is on track for the TAF period.
Lingering thunderstorms are moving through the northern NE
panhandle, and may bring lightning, gusty winds, and VIS drops
to KCDR over the next few hours. This should clear out by around
09z.

Meanwhile, low clouds are pushing southwestward, and MVFR to
IFR CIGs are expected through Wednesday morning at all High
Plains terminals. IFR is expected at KCYS, KSNY, and KCDR, and
possible at KBFF and KAIA. Additionally, temporary VIS
reductions as the cloud deck intersects the ground at times will
be possible, particularly at KCYS. Expect conditions to
gradually improve Wednesday morning, reaching VFR by the late
morning or early afternoon hours.

Attention then shifts back to thunderstorm activity as fairly
widespread thunderstorms are anticipated along the I-80 corridor
Wednesday afternoon and evening. This is handled with PROB30
groups at this time. Strong, gusty winds, heavy rainfall, and
hail will all be possible with Wednesdays storms.

&&

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

&&

$$

SHORT TERM...CG
LONG TERM...RUBIN
AVIATION...MN