996
FXUS65 KCYS 141851
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1251 PM MDT Sat Jun 14 2025

.KEY MESSAGES...

- The potential for PM strong to severe thunderstorms will be
  present each day over the High Plains through at least
  Tuesday.

- Warm to hot temperatures are expected over the weekend before
  a modest cool down on Tuesday. Well above average temperatures
  are expected to return late in the week.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 1246 PM MDT Sat Jun 14 2025

GOES satellite imagery shows cumulus clouds already growing over the
higher terrain at this time, with mostly clear skies prevailing
over the remainder of the area. Our area remains near the axis
of the strengthening upper level ridge, but a series of vort-
maxes continue to rotate over the top of the ridge, leading to
unsettled weather. Southwest flow aloft to our west prevails,
pulling in new upper level shortwaves. The closest is apparent
on water vapor imagery moving into western Wyoming at this hour.
To our east, a more disorganized upper level flow pattern is
visible, with a weak surface high over the Great Lakes region
continuing to supply plentiful low level moisture to the High
Plains.

The sunshine, good heating, and ample moisture are setting up potent
instability east of the Laramie Range this afternoon. The latest
mesoanalysis shows SBCAPE pushing 3000 J/kg just east of the WY/NE
state line. We also have very steep mid-level lapse rates in place
once again, and slightly higher vertical wind shear compared to
yesterday. However, substantial CIN remain in place all across the
High Plains. While the surface based CIN should burn off fairly
quickly, the MLCIN may linger into the afternoon, similar to
what we saw yesterday. Storms are already kicking off thanks to
the lifting boost from the terrain and the ripple in the 500-mb
flow aloft, with some help from the dryline parked right up
against the Laramie range. The Chugwater cyclone is also present
today, which should help initiate a storm in northern Laramie
county to southern Platte county. While the CIN will initially
cause storms to struggle east of the mountains, expect this to
be sufficiently eroded by mid afternoon to allow storms to
spread east, finally reaching the state line around 4-5PM.
Overall coverage will be scattered, with isolated strong to
severe storms expected. All severe weather hazards will be
possible once again. Low level shear is quite marginal for
tornadoes, but it is enough that we can`t rule out a few
spin-ups. Storms are expected to grow upscale as the evening
progresses, but we may see some brief windows for supercell
storm modes generally at the beginning of each new storm.
Thunderstorms should depart the area by around 10PM, but we may
see some lingering shower coverage after midnight until the axis
of the subtle shortwave clears the area early Sunday morning.

The upper level ridge will amplify somewhat heading into Sunday,
leading to temperatures a few degrees hotter compared to today.
Lingering cloud cover should clear out by daybreak, allowing for
quick heating. Yet another ripple in the flow aloft will pass north
of our area on Sunday, with a trailing axis of vorticity to the
south that should help kick off another round of PM showers and
thunderstorms. The dryline position may end up a little further east
than where it is located today thanks to the surface high getting
nudged a little further away from the area. Expect the afternoon
strong to severe weather threat to rinse and repeat for Sunday
afternoon and evening, with a similar setup once again. However,
there may be a slight east shift in the main area for storms thanks
to the dryline getting nudged closer to the WY/NE border by the mid
to late afternoon hours in some models. This is a little uncertain
though, as models have generally been too progressive in pushing the
dryline eastward the last several afternoons.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 1246 PM MDT Sat Jun 14 2025

The severe thunderstorm chances continue through mid-
week next week. Monday, An upper level low pushes through the Pacific
Northwest sending a trough through our Intermountain west. This
trough will inherently flatten our ridge as it moves through the
high plains. Accompanying this trough will be a few vort-maxes
to help amplify our severe potential. East of I-25 the airmass
has a little bit more moisture to play with so this will be the
likely domain our severe weather will occur. Due to the
southwest flow of the ridge, temperatures are expected to be in
the mid to upper 80`s allowing us to break the morning cap.
Model soundings indicate MUCAPE will be around 3,000 joules with
2000 of that being MLCAPE. Lapse rates will be around 9C
creating a very unstable and energized environment. SPC has
dropped a level 2 out of 5 Slight Risk for majority of the
Northern portion of our CWA with a Marginal Risk for the
southern portion. The only parameter that`s in our favor is the
36 knots of effective shear which gives us a pulsy messy storm
type for the afternoon and evening. This trough passage also
sets us up for severe weather chances on Tuesday. Model guidance
(3 globals) depict some cyclogenesis occurring TUesday
developing from this passage. If cyclogenesis occurs this will
likely provide enough synoptic support to kick start some storm
development in the afternoon. However, we will have a little bit
less energy but a little more moisture to play with on Tuesday.
MUCAPE is set at 2000 joules with 1800 of that being MLCAPE.
Model soundings are showing a very pronounced inverted V
sounding indicative of severe winds with 687 joules of DCAPE.
Once again our effective shear is a little lower with a progged
speed of 26 knots. Again there are a couple progged lobes of
vorticity allowing some enhancement of the storms as well.
Wednesday, we may catch a little bit more of a break as more dry
air starts to filter in as we become into a Northwest flow type
of pattern. There does look to be a shortwave however our temps
will be a little cooler in the 70`s and there wont be a whole
lot of support for severe chances especially in downsloping flow
as we start to really develop a more stout dry layer near the
surface. MUCAPE is 500 joules which is plenty of energy still to
develop a thunderstorm especially with 42 knots of alleged
shear. However, if theres no moisture to lift than we wont get
any development. Wednesday, will be still be a good day to keep
an eye on for severe weather as well.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1125 AM MDT Sat Jun 14 2025

Another round of scattered thunderstorms is expected to kick off
this afternoon. Storms will begin early afternoon in Wyoming,
with WY terminals clearing out after about 23z. Nebraska
terminals can expect storms nearby beginning around 22z near
KBFF and continuing through about 03 to 04z at KCDR, KAIA, and
KSNY. Today`s storms will have the potential to produce strong,
gusty, and erratic winds, isolated large hail, frequent
lightning, and torrential rainfall (producing brief IFR
conditions). Expect skies to clear late in the evening with
southerly winds taking over again Sunday morning.

&&

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

&&

$$

SHORT TERM...MN
LONG TERM...MM
AVIATION...MN