Flash Flood Warning 4, NWS Cheyenne, WY

779 
WGUS75 KCYS 080610
FFSCYS

Flash Flood Statement
National Weather Service Cheyenne WY
1210 AM MDT Mon Jun 8 2026

NEC033-123-080620-
/O.EXP.KCYS.FF.W.0004.000000T0000Z-260608T0615Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cheyenne NE-Morrill NE-
1210 AM MDT Mon Jun 8 2026

...FLASH FLOOD WARNING WILL EXPIRE AT 1215 AM MDT EARLY THIS MORNING 
FOR EASTERN CHEYENNE AND SOUTHEASTERN MORRILL COUNTIES...

Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

&&

LAT...LON 4163 10286 4169 10264 4140 10264 4140 10261
      4109 10261 4100 10324 4134 10289 4141 10310

$$

CG

Area Forecast Discussion
National Weather Service Cheyenne WY
536 PM MDT Sun Jun 7 2026

.KEY MESSAGES...

- A Marginal Risk of Severe thunderstorms expected Sunday with a
  Slight Risk (2 of 5) of severe thunderstorms possible Monday
  for eastern Wyoming and the Nebraska Panhandle, with all
  severe hazards possible.

- Expect a quick cool down on Monday before heat builds back into
  the area towards the middle of next week.

- Fire Weather Watch in effect for the eastern high plains of
  southeast Wyoming and all of western Nebraska Tuesday through
  late Wednesday, with critical fire weather conditions likely
  extending through late in the week.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 235 PM MDT Sun Jun 7 2026

Current observations across the region show generally mostly sunny
skies, but increasing clouds as we head towards peak heating of
the day. A surface cold front, which has hardly moved in the
past few hours, is currently located across central and northeast
Wyoming, just a bit outside of our forecast area. Further
south, a dryline-like boundary extends south of the cold front,
roughly paralleling the Wyoming/Nebraska border. Dry conditions
with inverted-V soundings located west of this dryline with
dewpoints in the 20s to low 30s. East of the dryline is where
the best instability is located with dewpoints in the 40s and
50s with SBCAPE values between 1000 to 2000 j/kg. Still fighting
a little bit of CIN in the boundary layer, but expect CIN to
slowly erode over the next few hours. Expect any strong to
marginally severe thunderstorms to form along and east of this
boundary late this afternoon and into this evening. SPC has a
Marginal Risk for severe thunderstorms across most of western
Nebraska, east central Wyoming, and portions of Carbon county
(mainly for winds). After a mesoscale analysis, currently
lacking in the shear department (0-6 and effective), but shear
does increase this evening through late this evening with 40
knots of shear around sunset. This should be sufficient for a
few strong to marginally severe storms across mostly the
Nebraska Panhandle, but can't rule out some activity in eastern
Wyoming as well. There is a small area of Slight Risk, but
that's mainly across the far northern part of Niobrara County.
Based on high res model data, there may be two individual times
for the strong/severe thunderstorm threat. First one being this
evening as the dryline-like boundary tracks east, and the second
may be later this evening and into tonight as outflow from
thunderstorms across eastern Montana and the Dakotas move into
our eastern plains as the cold front accelerate southward. This
second line of thunderstorms may linger past midnight.

Tricky forecast for Monday with another Slight Risk for severe
thunderstorms expected, this time over far southeast Wyoming and
the southern Nebraska Panhandle. Some models don't seem to be
handling the low level moisture well with this event (especially
the GFS) and/or mix it out way too early with the heating of the
day. Surface cold front should move across the rest of the area
by the early morning hours with thunderstorm outflow, from
activity to the north and east, providing the low level moisture
with some upslope flow. In fact, added some patchy fog to the
east side of the Laramie Range as winds shift into the northeast
later tonight. With increasing low to midlevel shear,
confidence is increasing for another round of severe
thunderstorms forming near the I-80 corridor and North Platte
River valley. Will have to watch for all modes of severe
weather, including 1 or 2 tornadoes, with 0-1km helicity between
100 to 200 and relatively low LCL's between 1500 to 2000
meters. Large hail is also a concern across the area. It will be
around 5 to 10 degrees cooler compared to today behind the cold
front, with highs generally in the upper 70s to mid 80s.

For Tuesday, all models show increasing southwest flow aloft as
the broad Pacific trough finally tracks east into Wyoming.
Increasing west to southwest winds will bring dry air advection
to the whole area and greatly limit any thunderstorm threat.
Tuesday will be our warmest day of the week with highs in the
80s west of the I-25 corridor, and upper 80s to upper 90s east
of I-25. With very warm/hot temperatures, dry conditions, and
gusty winds, decided to issue a Fire Weather Watch for far
southeast Wyoming and all of western Nebraska. Since similar
conditions are expected on Wednesday with poor overnight
recoveries, decided to make the Watch valid through Wednesday
evening.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 100 PM MDT Sun Jun 7 2026

Tuesday into Wednesday, the Intermountain West switches from
southerly flow to a downsloping westerly flow as the upper level
low becomes stack moving along the Canadian Border. This will
lead to the continuation of warmer temperatures, but also a more
likely chance to break the cap when combined with the progged
frontal boundary moving through Wednesday afternoon/evening. Our
windiest day looks to be Wednesday as the 700mb ramps up to
about 50- 55 knots by the afternoon giving us gusty winds but
possibly not enough to meet the high wind criteria if those
winds stay below 55 knots.By Thursday and area of high pressure
looks to build in that may stay through the weekend. Fire
Weather remains a concern throughout the long term as RH values
look to bounce between 15 and 20 percent and some isolated
places dropping as low as 10 percent. The severe chances look
minimal through the long term as the stout dry layer looks to
stick around with minimal CAPE when glancing at the global model
soundings. It shouldn't be a surprise if a Red Flag warning
gets issued through Saturday. Another trough looks to push
through Saturday evening into Sunday morning giving us another
chance for some light rain to possible thunderstorm chances
Sunday.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 536 PM MDT Sun Jun 7 2026

Showers and thunderstorms are increasing in coverage early this
evening east of a pseudo-dryline located along the Wyoming-Nebraska
border. Brief MVFR conditions will be in place in proximity to the
heavier showers and thunderstorms, particularly for the Nebraska
terminals where visibility maybe briefly drop to 3SM. However due to
dewpoints in the 40s, convection will be high-based and therefore no
MVFR CIGs are anticipated. Given DCAPE values greater than 1500
J/Kg, showers and thunderstorms will be capable of producing gusts
up to 60 knots. For the prevailing winds, 15-20 knot SSE flow will
veer to NNW for the Wyoming terminals and ENE for the Nebraska
terminals following a cold frontal passage mainly after 06Z.
Although confidence is low (20%), KCYS may see patchy fog under the
northerly upslope flow regime after 08Z. Otherwise, expect gusts at
KLAR and KRWL to increase to 30 knots after 18Z.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Fire Weather Watch from Tuesday afternoon through Wednesday
     evening for WYZ430>433.
NE...Fire Weather Watch from Tuesday afternoon through Wednesday
     evening for NEZ434>437.

&&

SHORT TERM...TJT
LONG TERM...MM
AVIATION...NB

Special Weather Statement
National Weather Service Cheyenne WY
718 PM MDT Sun Jun 7 2026

NEZ021-054-055-080200-
Kimball NE-Cheyenne NE-Morrill NE-
718 PM MDT Sun Jun 7 2026

...A STRONG THUNDERSTORM WILL IMPACT WESTERN CHEYENNE...SOUTHEASTERN
KIMBALL AND SOUTHWESTERN MORRILL COUNTIES THROUGH 800 PM MDT...

At 718 PM MDT, Doppler radar was tracking a strong thunderstorm near
Potter, or 14 miles west of Sidney, moving northeast at 30 mph.

HAZARD...Wind gusts up to 50 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Sidney, Potter, Dix, Gurley, Colton, Brownson, Sidney Municipal
Airport, Lorenzo, and Cheyenne County Fairgrounds.

This includes Interstate 80 in Nebraska between mile markers 26 and
62.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4119 10362 4153 10307 4116 10282 4100 10313
      4101 10365
TIME...MOT...LOC 0118Z 210DEG 28KT 4120 10323

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

Mose

Preliminary Local Storm Report
National Weather Service Cheyenne WY
736 PM MDT Sun Jun 7 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0726 PM     Non-Tstm Wnd Gst 7 S Chugwater           41.65N 104.82W
06/07/2026  M58 MPH          Laramie            WY   Mesonet

            Produced by a 25 dBZ shower with no
            lightning detected.

&&

NB

Preliminary Local Storm Report
National Weather Service Cheyenne WY
814 PM MDT Sun Jun 7 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0804 PM     Tstm Wnd Gst     9 WSW Brownson          41.09N 103.23W
06/07/2026  E66 MPH          Cheyenne           NE   Public

            Personal weather station.

&&

NB

Preliminary Local Storm Report
National Weather Service Cheyenne WY
830 PM MDT Sun Jun 7 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0823 PM     Flash Flood      2 E Potter              41.22N 103.28W
06/07/2026                   Cheyenne           NE   Trained Spotter

            Reported flooding on I-80. Radar
            imagery/traffic cameras suggests combination
            of heavy rain and small, accumulating hail.

&&

NB

Preliminary Local Storm Report
National Weather Service Cheyenne WY
834 PM MDT Sun Jun 7 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0828 PM     Tstm Wnd Gst     8 NNW Brownson          41.27N 103.13W
06/07/2026  M62 MPH          Cheyenne           NE   Public

            Personal weather station.

&&

NB

Preliminary Local Storm Report
National Weather Service Cheyenne WY
853 PM MDT Sun Jun 7 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0824 PM     Non-Tstm Wnd Gst 19 NNE Harrison         42.93N 103.71W
06/07/2026  M65 MPH          Sioux              NE   Public

            Associated with 25-30 dBZ showers based on
            radar imagery.

&&

NB