036
FXUS65 KCYS 301112
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
512 AM MDT Mon Jun 30 2025

.KEY MESSAGES...

- Cooler temperatures are expected Monday with only a few
  isolated showers or thunderstorms in the afternoon, mainly
  near the higher terrain of southeast Wyoming.

- Warm temperatures and daily chances for PM showers and
  thunderstorms will return for Tuesday onwards.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 102 PM MDT Sun Jun 29 2025

Mesoscale analysis shows an environment prime for some strong to
severe thunderstorm development as of this writing, with CAPE
around 1000-2000 J/kg and bulk effective shear of 20-40 knots. A
severe thunderstorm watch is in effect through 9 PM tonight for
areas east of and around I-25 not including Converse County. The
environment is supportive of large hail and damaging wind gusts,
but wind may become the more predominant threat as storms shift
eastwards through the evening hours. High resolution guidance is
in pretty solid agreement on this timeframe, with clustered
storms departing the Nebraska Panhandle around 9-10 PM.

Overnight activity should wane though a few lingering showers
or weak storms may be possible for these areas through the
morning hours. Ceilings may also lower and some mist or weak
fog could be possible for areas including Cheyenne and Sydney,
though confidence is overall low in this. For Monday a few
upslope showers or storms may develop off of the high terrain in
Wyoming, but probabilities are overall on the low side and we`ll
see this quickly wane with the setting of the sun. Otherwise
today and tomorrow will be the coolest days of the period, with
highs today in the 70`s to 80`s with widespread highs on Monday
in the 70`s to low 80`s thanks to the cold front. That will
change as we move into the long term though as summer warmth
returns.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 102 PM MDT Sun Jun 29 2025

Tuesday...A warming trend develops as 700 mb temperatures rise to
near 15 Celsius. Adequate moisture aloft for isolated to widely
scattered late day showers and thunderstorms, mainly over and near
the mountains.

Wednesday...The warming trend continues as 700 mb temperatures reach
16 Celsius. Moisture availability looks less than Tuesday, thus we
anticipate less shower and thunderstorm coverage.

Thursday-July 4th...Similar temperatures on Thursday compared to
Wednesday with 700 mb temperatures near 16 Celsius. A bit cooler for
July 4th, with more cloud cover and moisture aloft. Scattered late
day showers and thunderstorms each day.

Saturday...Although ridging aloft builds overhead, there should
still be adequate low and mid level moisture for scattered afternoon
and evening showers and thunderstorms. Slightly cooler temperatures
expected for most locations.

Sunday...Slightly warmer as the flow aloft turns westerly. Adequate
low and mid level moisture for scattered late day showers and
thunderstorms, mainly east of Interstate 25.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 511 AM MDT Mon Jun 30 2025

A cold front pushing westward will bring higher moisture and a
chance for reduced CIGs at all terminals. Confidence is fairly
low in the exact timing and height of these reduced CIGs.
Conditions should improve mid Monday morning.

Otherwise, expect mostly clear skies on Monday aside from a few
PM cumulus near KLAR which may bring a brief shower or storm.
Winds will be fairly light, but strong or gusty southeast winds
will increase near KLAR towards the end of the day and
overnight. This will transition into a modest low-level jet for
the High Plains with southerly winds at NE panhandle terminals
into Tuesday morning.

&&

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

&&

$$

SHORT TERM...CG
LONG TERM...RUBIN
AVIATION...MN/WFO-RIW