Severe Thunderstorm Warning 207, NWS Cheyenne, WY

Area Forecast Discussion
National Weather Service Cheyenne WY
203 PM MDT Tue Jul 28 2026

.KEY MESSAGES...

- Marginal Risk of Severe Thunderstorms Tuesday afternoon and
  evening. Strong gusty winds will be the primary threat.

- Monsoon moisture will remain in place through the middle of
  the week. Heavy rainfall and localized Flash Flooding
  possible Tuesday through Wednesday night.

- More heat returns this weekend through Monday, with some near
  record high temperatures possible.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 201 PM MDT Tue Jul 28 2026

Southeastern Wyoming and Western Nebraska continue to remain
under SW flow aloft beneath a 594 dam mid-level ridge centered over
West Texas and New Mexico. This is providing us with another fetch
of monsoonal moisture, with PWAT approaching the 99th percentile (as
high as 1.6" for our Nebraska counties). As we remain downstream of
a shear-induced vorticity maximum with ample deep-layer moisture,
another round of widely scattered showers and thunderstorms are
likely this afternoon into the evening.

Showers and thunderstorms have increased in coverage across the
Nebraska Panhandle early this afternoon within a theta-e ridge,
collocated with an axis of low to mid 60 surface dewpoints. Due to
the aforementioned speed maximum, SPC mesoanalysis has much of the
Nebraska Panhandle under 30-35 of effective bulk shear, resulting in
the potential for a few strong to severe thunderstorms. The main
hazards with storms today will be large hail and damaging winds,
especially with 20-25 degree surface dewpoint depressions and DCAPE
around 1000 J/Kg. Any storms that manage to rotate given marginal
deep-layer shear will have the potential to produce borderline
severe hail, especially with any discrete/semi-discrete storm modes.
Heavy rain will also be possible given anomalous PWAT, however
parched soils may limit this threat today. One exception will be
that any training convection could result in localized flash
flooding, especially with cloud-layer mean winds around 15 knots,
which is along the "borderline" threshold for favorable flash
flooding storm motion. The greatest hydrological threat is mainly
along and south of the I-80 corridor where flow aloft is weakest.

Storms should begin to exit the Nebraska Panhandle by 9-10 pm this
evening as the environment becomes overturned by earlier convection
and with the loss of any heating. Temperatures tonight along and
west of the Laramie Range will be cooler in the mid to upper 50s
with decreasing cloud-cover and light winds below 10 mph. Overnight
lows will remain mild in locations north of the Pine Ridge (i.e.
Chadron) where temperatures may struggle to dip below 70 degrees
thanks to southerly downslope flow.

Tomorrow will likely feature another round of afternoon showers and
thunderstorms, although storms are expected to be less organized and
widespread with the lack of deep-layer shear. Heavy rain and
localized flooding will remain possible tomorrow into tomorrow night
as PWAT remains within the 85-95th percentile combined with weaker
flow aloft. This may be a concern if the same areas that manage to
receive heavy rainfall today are similarly impacted tomorrow. High
temperatures tomorrow are expected to be in the mid to upper 80s
west of the I-25 corridor, with low to mid 90s further east before
cloud coverage increases later in the afternoon. A weak shortwave
trough will progress across SE Wyoming and Western Nebraska late
tomorrow evening into the overnight hours which may keep showers and
thunderstorms going well after dark. Similar to the last few days,
training convection will have to be watched closely, especially in
areas that received heavy rainfall today. Overnight lows Wednesday
night into Thursday will be similar to the previous day.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Issued at 201 PM MDT Tue Jul 28 2026

Key Messages...

-Expect scattered showers and thunderstorms for Thursday and Friday,
with drier and hotter weather over the weekend. Temperatures will
not be as hot for Monday and Tuesday.

Thursday...Northwest flow aloft develops in the wake of a passing
shortwave trough aloft, with drying noted across southeast Wyoming
and monsoonal moisture moves into Nebraska, we will see isolated to
scattered late day showers and thunderstorms across the Nebraska
Panhandle.

Friday...Monsoonal moisture plume stretches north to south across
far eastern Wyoming and western Nebraska, and with a ridge runner
shortwave trough aloft in northwest flow, we expect to see scattered
showers and thunderstorms generally east of a Douglas to Cheyenne
line.

Saturday and Sunday...Ridging prevails with a decrease in monsoonal
moisture and warm temperatures aloft will produce enough CIN,
Convective Inhibition, to prevent thunderstorm development. Hot
temperatures return with the hottest day being Sunday, and with 700
mb temperatures from 20 to 23 Celsius, high temperatures will range
from 95 to 105 degrees, with possible Heat Advisories needed east of
I-25 on Sunday.

Monday and Tuesday...Broad troughing aloft develops across the
northern Rockies with zonal flow over our counties. This will help
produce somewhat cooler temperatures as 700 mb temperatures lower to
13 Celsius. There may be enough low and mid level moisture to
produce isolated late day thunderstorms over and near the Laramie
Valley and southern Laramie Range.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1150 AM MDT Tue Jul 28 2026

Because of more daytime heating and abundant low and mid level
moisture associated with the monsoon, expect an increase in
areal shower and thunderstorm coverage this afternoon and this
evening, compared to yesterday. Coverage of thunderstorms will
be most prevalent across Laramie, Platte and Goshen Counties of
southeast Wyoming and over the central and southern Nebraska
Panhandle.

Wyoming TAFS...VFR prevails. Confidence is high in seeing
isolated to scattered thunderstorms this afternoon and evening,
mainly from I-25 eastward, with TEMPO coverage of thunderstorms
at Laramie and Cheyenne from 19Z to 22Z, producing gusty and
erratic wind gusts up to 25 knots.

Nebraska TAFS...VFR prevails. High confidence in isolated to
scattered thunderstorms developing or propagating across the
terminals from 20Z to 02Z, producing gusty and erratic winds up
to 45 knots along with brief MVFR. Based on the HRRR run, felt
confident in including TEMPO at KSNY, with PROB30s at Chadron,
Alliance and Sidney.

&&

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

&&

SHORT TERM...NB
LONG TERM...RUBIN
AVIATION...RUBIN

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