Flash Flood and Hail in Wyoming, June 1, 2026

Area Forecast Discussion
National Weather Service Cheyenne WY
1233 PM MDT Mon Jun 1 2026

.KEY MESSAGES...

- Monday & Tuesday bring another chance for strong to severe
  thunderstorms in the afternoon and evening. There is a slight
  risk (level 2 of 5) across the eastern high plains on both
  days. Large hail, severe wind, and an isolated tornado
  possible.

- A warming and slight drying trend appears likely after
  Wednesday with temperatures climbing into the 80s by later in
  the week and during next weekend.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 1230 PM MDT Mon Jun 1 2026

After some morning showers and thunderstorms that produced hail,
storminess will continue into the afternoon as daytime heating
begins to further destabilize the atmosphere. A stagnant upper-level
low over the Montana/Canada border will allow the CWA to tap into
moisture from the Gulf. Moisture-rich low-level southerly flow will
usher in the necessary humidity needed to fuel storm development
during the afternoon and evening. Lift will come in the form of
vorticity maxes streaming through the area from the trough to the
north. Moderate instability this afternoon with MUCAPE values around
1500 J/kg will create an environment capable of producing severe
storms east of the Laramie Range. Hi-Res guidance shows initially
discrete cells, with effective shear and steep mid-level lapse rates
supporting a large hail threat. As the afternoon progresses into
evening, more outflow dominant storms will lead to a severe wind
threat. Storms will move out of the Nebraska panhandle rather
quickly this evening, with most storms expected to be out of the
area by 9 PM. A few lingering storms could be possible overnight,
but the severe threat will be long gone by then.

With the upper-level low still stuck over the Montana/Canada border,
a similar set up is forecast for Tuesday. The environment remains
largely the same, although with a few small, but important changes.
Model soundings show a lot more instability in the Nebraska
panhandle Tuesday afternoon with MUCAPE values of 2500 J/kg and
higher. However, shear values are rather unimpressive with weak low-
level and effective shear. On top of that, a strong capping
inversion seems to persist through most of the afternoon. Hi-Res
guidance shows storms forming off the high terrain per usual, but
not necessarily strengthening as they enter the more favorable
environment. They are likely also catching onto the cap that
may be in place. Soundings do show the cap eroding by the
evening hours. This is also when the HRRR shows another round of
convection developing off the high terrain and pushing eastward
into the Wyoming high plains, and into the Nebraska panhandle
overnight. These storms do appear stronger, as instability will
persist into the overnight hours. As a result, cannot rule out
severe nocturnal convection from about 8 PM Tuesday through 1 AM
Wednesday. Primary hazards will once again be large hail in
initial discrete cells, transitioning to more of a wind threat
as convection becomes a bit more organized.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 150 PM MDT Sun May 31 2026

We remain under SW flow aloft upstream of a high amplitude
positively-tilted ridge centered over Ontario and the Great Lakes
region, resulting in mostly dry and above-average temperatures
heading into the second half of the week. Thanks to trajectories
stemming from the Gulf of Mexico, PWAT over SE Wyoming and W
Nebraska will be in the 80th-90th percentile relative to
climatology. This will allow for daily chances of showers and
thunderstorms despite the absence of any large-scale forcing for
ascent. Despite anomalously high PWAT, long range ensemble
forecast soundings continue to show large dewpoint depressions
at the surface and inverted-V profiles, so any showers or storms
will likely produce far more wind than any beneficial moisture.
The threat for any severe weather looks to remain low towards
the end of the week as deep-layer shear is weak due to the lack
of mid and upper level flow. Going into the weekend, high
temperatures are expected to push 80 degrees west of the I-25
corridor, with even a few 90s for our Nebraska counties as we
remain under longwave ridging through the end of the long term
period.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1145 AM MDT Mon Jun 1 2026

Primary forecast concern today will be the potential for strong and
severe thunderstorms for the high plains terminals. Upper level
disturbance over the Great Basin region will rapidly eject eastward
over the area this afternoon and this evening. Scattered showers and
thunderstorms are expected ahead of this disturbance with strong
winds, hail, heavy rainfall, and frequent lightening possible.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail until 09z late
tonight (low CIGS). Brief IFR or LIFR conditions expected with the
heaviest thunderstorms, but will keep in PROB30 groups until
convection develops over the next few hours with increasing
confidence.

For tonight, attention shifts to low CIGS and possibly some fog,
depending on how much rain (and how widespread) falls today. Added
IFR CIGS for KSNY, KAIA, KBFF after 09z Tuesday. These conditions
are possible at KCDR and KCYS as well, but confidence is lower.

&&

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

&&

SHORT TERM...SF
LONG TERM...NB
AVIATION...MM