067
FXUS65 KCYS 152137
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
337 PM MDT Thu Aug 15 2024

.KEY MESSAGES...

- Fire weather concerns begin to increase Friday as well as
  Saturday with warmer temperatures and low afternoon humidity.

- Seasonable temperatures will continue through the period.
  Showers and thunderstorms will be most likely on Sunday and
  Monday, with less coverage for Tuesday and Wednesday.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 335 PM MDT Thu Aug 15 2024

Short range models and ensembles all show relatively quiet
weather over the next 48 hours as a mid to upper level ridge
axis strengthen over the Front Range into this upcoming weekend.
One more coolish afternoon today with highs generally in the
upper 70s to mid 80s across the area, warmest over the eastern
plains. Models show the upper level ridge amplifying over the
region on Friday with 700mb temperatures climbing above 15c.
Expect high temperatures back into the upper 80s to upper 90s
(warmest over far eastern Wyoming and western Nebraska) Friday
afternoon with slightly warmer high temperatures Saturday
afternoon.

Coverage of showers and thunderstorms will be much less compared
to the last several days as a drier airmass and increasing
midlevel subsidence, both associated with the upper level
ridge, move into the area. For today (Thursday), can`t rule out
some sub-severe thunderstorms or rain showers late this
afternoon through most of tonight. High res guidance has been
persistent today in showing some activity lingering past
midnight through 300 am local time. Forcing is limited, but
model soundings do show slightly low-midlevel warm air advection
near the top of the residual boundary layer along with a weak
shortwave slowly ejecting east out of the area. This should
provide enough elevated CAPE to initiate scattered rain showers
and a few thunderstorms through the night...mainly along and
south of the North Platte River Valley. With a relatively dry
boundary layer, especially further west, can`t rule out some
brief wind gusts of 50 mph.

Precipitation chances will decrease on Friday as the ridge axis
amplifies northward and a drier airmass moves into Wyoming. A
dry-line like feature is forecast to develop along the Laramie
Range and move eastward through the afternoon. Ahead of this
dry-line, expect another round of showers and thunderstorms to
develop with a few stronger storms possible. However, coverage
should be limited to isolated or widely scattered at best...so
kept POP between 15 to 25 percent Friday afternoon east of the
Interstate 25 corridor. This drier airmass will remain over the
whole forecast area on Saturday with the potential for
thunderstorms less than 5 percent through Saturday evening.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Issued at 218 PM MDT Thu Aug 15 2024

The main concern with this forecast is how dry things will
become under the influence of the upper level ridge next week.

The models and ensembles continue to advertise the upper level
ridge staying planted over the Rockies through the end of next
week. The big question will be the timing of the subtle shortwaves
riding over the ridge. The models/ensembles are showing deeper
moisture over the Rockies Sunday and Monday with the highest
precipitable water values ranging 0.8 to to 1 inch especially
east of the Laramie Range where the heavy rain potential could
be a factor. The models are also advertising a chance of seeing
strong to severe storms especially over the Nebraska panhandle
where the models are advertising dewpoints to be in the 55 to 60
degree range with moderate bulk shear of 30 to 40kts. Tuesday
and Wednesday the WPC clusters are favoring the upper level
ridge axis building over the Wyoming which will tend to suppress
convection and keep the bulk of the deeper moisture east of the
forecast area. As a result, temperatures will most likely be a
bit warmer on both of these days. Late next week the
ensembles/operational models showing the upper level ridge
tilting towards the east which may allow for the return of
monsoonal moisture back into the area and bring gusty winds into
Carbon and Albany counties.

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1134 AM MDT Thu Aug 15 2024

A very quiet period is expected during the next 24hrs, due to
a high pressure ridge settling over the area. This high
pressure system will be shortlived as another disturbance rides
over the ridge this evening and overnight. This disturbance may
kick off a few showers across the KRWL...KLAR and KCYS TAF sites
mainly after 00z. Otherwise, a weak boundary will pass through
the forecast area this evening causing the wind to shift to the
north briefly before becoming more variable overnight.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Fire Weather Watch from Friday afternoon through Friday
     evening for WYZ420>423-425-427-428.
NE...None.

&&

$$

SHORT TERM...TJT
LONG TERM...REC
AVIATION...REC