536
FXUS65 KCYS 081940
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
140 PM MDT Mon Jun 8 2026

.KEY MESSAGES...

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

- Expect a quick cool down on Monday before a quick warmup on
  Tuesday, and then temperatures moderate through the end of
  the week though still around 5 to 10 degrees above normal.

- Red Flag Warning 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 NIGHT/...
Issued at 1234 PM MDT Mon Jun 8 2026

Severe weather will once again be possible this afternoon for areas
east of the Laramie Range. Model soundings show a favorable
environment for all modes of severe weather with large hail, severe
wind gusts and an isolated tornado all possible this afternoon
and evening. Flash flooding also cannot be ruled out with high
PWs over the Nebraska panhandle. Radar already shows a few
storms over Albany County going up where a cumulus field
developed. The uncapped environment here quickly led to the
development of a few stronger updrafts with some small hail. As
these storms progress eastward, they will enter a less favorable
environment with less SBCAPE and shear, so they will likely
weaken an fall apart. Mesoscale analysis as well as model
soundings show a more favorable environment east of the Laramie
Range around mid to late afternoon. Soundings from the GFS still
indicate a strong capping inversion around 18Z that will first
need to erode away. Hi-Res guidance like the HRRR also seems to
be catching on to this, showing convection developing a little
later in the day with each new run.

Once the cap erodes and convection can actually get going, the
environment shows both good instability and shear. Model soundings
show MUCAPE values up to 2000 J/kg of CAPE with about 45 kts of
effective shear. These parameters along with steep mid-level lapse
rates will support a large hail threat for areas east of the Laramie
Range. Severe wind gusts will be a secondary threat in some of the
stronger storms with DCAPE approaching 900 J/kg. Cannot rule out an
isolated tornado or two as MLCAPE reaches about 1500 J/kg by this
evening with the favorable shear. As previously mentioned, flash
flooding could be possible with PWs around an inch in the Nebraska
panhandle. Luckily, cloud layer winds are fairly fast so storms
shouldn`t sit in any one area for too long. While convection is
already occurring and will continue for the next several hours,
Hi-Res guidance has delayed the timing of severe storms, making
the most likely window between about 6 PM and 10 PM this
evening. Once storms move out later this evening, it will be a
calm overnight.

Even though a strong trough will push into Wyoming on Tuesday, the
weather will be a bit quieter compared to Monday. Ahead of the
trough, southwest flow will dominate the low and mid-levels.
Southwest flow will advect hot and dry desert air into the CWA. 700
mb temperatures will climb to about +14C which is roughly the 90th
percentile of NAEFS climatology. This will lead to quite a hot day,
mainly for areas east of the Laramie Range. High temperatures here
will reach the upper 80s and 90s. These hot temperatures will help
dry out the eastern portions of the CWA, with relative humidity
dropping as low as the single digits. With the incoming trough, a
250 mb jet will move into the CWA creating windy conditions. This
combination of dry and windy conditions will lead to fire weather
conditions. As a result, the Fire Weather Watch in effect was
upgraded to a Red Flag Warning. The trough could also trigger
some shower and storm development across the CWA. Given the very
dry low and mid-levels, gusty showers with severe wind gusts
are possible. Dry lightning will also be possible, given a few
hundred joules of elevated CAPE.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 1234 PM MDT Mon Jun 8 2026

The long term forecast appears dry with a switch in the flow regime
from southerly flow to a more westerly. This is due to a persistent
upper level trough pattern to our north into Canada. A cold front
Wednesday will effectively cut us off from the more moist air that
has been advecting in from the Gulf. During this period we are
watching for conditions favorable for fire weather and high winds.

The high wind conditions spill over from Tuesday as flow at the 700
mb level stays elevated. The GFS is projecting winds at this level
at around 50 knots. As daytime mixing commences the risk of these
winds being mixed to the surface increases. Additionally enhancement
by mountain wave breaking is likely to occur. Taking a horizontal
cross section across our west to east ranges depict downsloping
winds approaching 55 knots during the late morning to early
afternoon hours collocated in areas of negative omega. Higher gusts
are certainly possible given the low resolution of global models.
This is not a great combination with the expected low relative
humidities values. Across most of the area values are expected to
plummet below 15 percent and temperatures in the 70s to high 80s.
This is following previous poor nighttime recoveries of about 40-50
percent.

Going into Thursday and beyond, winds start to calm down after the
departure of the mid level shortwave and ridging builds in. As
mentioned our source of moisture has been cut off by the prevailing
synoptic pattern, so humidity values remain very low. Winds are
likely to remain high enough to warrant continued fire weather
products through just about the entirety of the long term. Saturday
and Sunday may see enough moisture and a source of lift from a
clipper type system to support a few storms. Both GFS and Euro are
on board with this solution with the usual caveat being that at
this range solutions will change. If you are looking for any bit of
good news past the long term, the latest CPC outlook has our area in
below average temperatures and increased precipitation chances.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1131 AM MDT Mon Jun 8 2026

Scattered severe thunderstorms will be possible at terminals mainly
east of the Laramie Range this afternoon and evening. Main concerns
in storms will be severe winds with gusts over 50 kts and large
hail. Moderate to heavy rain will also be possible, which could
reduce visibility down to MVFR criteria at times. Storms will move
out of the area before midnight. Cannot rule out some patchy low
stratus and fog Tuesday morning from the moisture left behind from
storms, however probabilities of this occurring are currently
low.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from noon Tuesday to 9 PM MDT Wednesday for
     WYZ430>433.
NE...Red Flag Warning from noon Tuesday to 9 PM MDT Wednesday for
     NEZ434>437.

&&

$$

SHORT TERM...SF
LONG TERM...RV
AVIATION...SF