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548
FXUS65 KCYS 250335
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
935 PM MDT Mon Jun 24 2024

.KEY MESSAGES...

- Moisture will return to the High Plains on Wednesday and
  Thursday, leading to the potential for some strong
  thunderstorms in the afternoon and evening.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 340 PM MDT Mon Jun 24 2024

Gusty showers and thunderstorms continue across the CWA this
afternoon. Current radar trends depict widely scattered coverage of
these storms, most fairly week and unorganized. Still can`t rule out
the threat of severe gust to 60 MPH this afternoon. Earlier, an
observation site gusted 50 MPH due to a collapsing storm. Current
observations from across the CWA continue to show the very dry low-
levels, with most locations under 25 percent relative humidity. This
supports the strong wind threat. RAP soundings for this afternoon
show strong inverted-V profiles, DCAPE values over 1200 J/kg, and
very high based storms. All this to say, that strong winds in
storms is the primary concern this afternoon, although, cannot
rule out some small hail. Aside from the storms, hot
temperatures continue this afternoon, with areas in the Heat
Advisory and the panhandle spiking to 100 degrees and warmer
this afternoon. Temperatures should slowly be on the decline now
with increasing cloud cover from storms. Hi-Res guidance has
storms dissipating early this evening.

Looking at a quiet day on Tuesday, as the CWA sits under the broad
ridge over much of southern CONUS. A weak back door front dropping
down from the northeast with bring "cooler" temperatures to parts of
the CWA. Biggest cool down will be north of the North Platte River
Valley. Temperatures here will be about 10 degrees cooler compared
to Monday`s high, leading to highs in the upper 80s. Elsewhere,
temperatures will only drop by a few degrees. Should stay dry on
Tuesday, however, did add slight chance PoPs to the southern border
to account for some light showers that the HRRR is showing. Most
other Hi-Res guidance remains dry.

Wednesday will be much more active. As the ridge axis slides further
east, winds aloft will shift out of the southwest. This southwest
flow will allow the CWA to tap into monsoon moisture, increasing mid-
level moisture. At the surface, southeast flow will prevail, also
increasing moisture. As a result, model soundings and the NAEFS show
PWs generally over an inch east of the Laramie Range, which is above
the 90th percentile for climatological normal. An embedded shortwave
moving through the ridge will likely spark scattered convection
during the afternoon. Luckily, cloud layer winds are rather fast, so
storms will be quick moving, but dropping torrential rains. This
could lead to flash flooding concerns Wednesday afternoon into
Wednesday evening. Sufficient effective shear and veering with
height will also support the potential for more organized and
potentially severe convection.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 345 AM MDT Mon Jun 24 2024

The long term forecast period will start out on an active note with
a good chance for showers and thunderstorms on Thursday. By
Thursday the broad ridge over the southwestern CONUS will have
broken down with as a longer-wave trough moves throughout the
central and northern Rockies. This trough will spread faster
flow aloft eastward by later in the day. Lingering surface
moisture in southeastern Wyoming and western Nebraska will again
result in enough instability for showers and thunderstorms,
with 500b flow increasing to around 30-40 knots by 0z. However,
a primary difference in the Thursday forecast compared to
Wednesday looks to be surface and lower-level flow, which seems
light and muddled at best lending to straight/shorter hodographs
and thus more clustered/outflow dominant showers and storms.
Still, will have to watch the Thursday thunderstorm forecast as
several ingredients for severe weather remain in the vicinity of
the CWA.

On Friday, a frontal system will pass through the central High
Plains bringing a drier airmass with cooler temperatures for both
Friday and Saturday. Only a few isolated orographic showers look
possible on Saturday afternoon. By Sunday, expect temperatures to
rebound as height rise, however a dry airmass will remain in place
with only a few showers in the higher terrain of southeast
Wyoming.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
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Issued at 932 PM MDT Mon Jun 24 2024

West flow aloft tonight will turn northwest on Tuesday. Clear
skies will prevail, except for occasional ceilings near
1500 feet at Chadron and Alliance from 13Z to 17Z. Winds will
gust to 25 knots at Cheyenne, Laramie, Rawlins, Scottsbluff and
Sidney from 15Z to 00Z.
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&&

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

$$

SHORT TERM...SF
LONG TERM...MAC
AVIATION...RUBIN