096
FXUS65 KCYS 122054
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
254 PM MDT Sun May 12 2024

.KEY MESSAGES...

- Trending warmer through Monday, but remaining unsettled with
  daily chances for showers and storms through mid-week. Severe
  weather is not expected.

- A cold frontal passage is expected on Wednesday, with much of
  the region returning to below-normal temperatures and
  increased chances for rain and high-elevation snow.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 249 PM MDT Sun May 12 2024

Regional radar currently shows widely scattered high-based showers
and storms across the the CWA. There is enough instability,
especially east of the Laramie Range, to possibly get pea to dime
sized hail out of some thunderstorms this afternoon. The dry low-
levels and inverted-V soundings could also lead to a few stronger
wind gusts with storms as well. Storms will continue throughout the
afternoon hours before finally dissipating this evening, per Hi-Res
guidance. Clouds will likely clear out by later this evening,
which will lead to unobstructed views of the auroras across most
of the CWA.

The CWA will sit sandwiched between two shortwaves on Monday. This
will lead to shallow ridging over the Rockies and a warmer, above
average day across the area. Unfortunately, the ridging won`t be
enough to keep unsettled weather away. Weak disturbances within the
ridge will spark another round of scattered convection across the
CWA later in the afternoon. Severe storms look unlikely based on
model soundings, however, small hail and strong wind gusts could be
possible yet again.

Potentially looking at a better chance for storms on Tuesday as the
western shortwave makes it into Wyoming. Both the GFS and ECMWF do
differ a bit, with the ECMWF showing more numerous and widely
scattered storms as the shortwave directly impacts the CWA. GFS
soundings do show CAPE values below 1000 J/kg, but continue to show
inverted-V soundings. Therefore, smaller hail and gusty winds will
be the primary threats. However, higher dewpoints across the
Nebraska panhandle and northern tier of the CWA could lead to some
marginally severe storms. Aside from storms, the incoming shortwave
will lead to cooler temperatures and windy conditions for the usual
wind prones and for areas west of the Laramie Range.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Issued at 249 PM MDT Sun May 12 2024

The long term forecast will start off active as numerous showers and
thunderstorms look possible mid-week. The weather will quiet down
towards the end of the week as a ridging pattern takes hold of
western CONUS.

A shortwave digging down from the Pacific Northwest on Tuesday will
likely spark widely scattered showers and thunderstorms during the
afternoon and into the overnight hours. A vorticity max over the
CWA, as well as a weaker 250 mb 85 kt jet streak just north of the
CWA will provide some of the ingredients needed to get
thunderstorms. Location of the jet streak puts the CWA in the right
entrance region, which is favorable for lift and the development of
potentially stronger storms. GFS soundings from Tuesday afternoon
into Tuesday evening do show areas of instability, with over 1000
J/kg of MUCAPE in parts of the CWA. There are even some impressive
effective shear values over the northern tier of the CWA, with both
Douglas and Chadron showing 35 kts EBWD. Because of this, cannot
rule a few marginally severe to severe thunderstorms. Based on
current sounding profiles, the main concern would likely be the
potential for severe hail. This would mainly be in the northern tier
of the CWA, as well as the Nebraska panhandle.

Showers will likely become more numerous Tuesday night as the
shortwave pushes into Wyoming, bringing with it more mid-level
moisture. Showers will continue into the day Wednesday with the
shortwave passing over the CWA. Cooler temperatures are expected
with this shortwave which will lead to a more stable environment
with less of a chance of thunderstorms developing. Could still hear
a rumble of thunder or two, but it will predominately be rain
showers across the area.

With the shortwave pushing off to the east Wednesday night, expect a
warmer and drier end to the week as an upper-level ridge builds over
western CONUS. Temperatures will warm up above average across the
CWA on Thursday and Friday, with minimal chances for precipitation
both days.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1140 AM MDT Sun May 12 2024

An upper level disturbance over eastern Colorado will continue to
track eastward into the Great Plains today. Showers and
thunderstorms are forecast to redevelop over most of southeast
Wyoming and western Nebraska this afternoon.

HAZARDS/WEATHER TRENDS: Overall, VFR conditions are expected through
tonight with very low probabilities for IFR or lower conditions
associated with fog or heavy rainfall. Showers and thunderstorms
will continue to develop between now (18z) and 23z, with some heavy
showers expected and brief MVFR to near IFR conditions possible. The
most favorable location to see these conditions in the near future
is KSNY, so kept the tempo group going. Otherwise, kept VCSH for
most other terminals. Probability for fog tonight is very
low...below 5 percent.

&&

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

&&

$$

SHORT TERM...SF
LONG TERM...TJT
AVIATION...TJT