880
FXUS65 KCYS 180939
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
339 AM MDT Sun Aug 18 2024

.KEY MESSAGES...

- Hot and (generally) dry conditions will persist across much of
  the area today. A couple of high based showers or storms
  cannot be entirely ruled out later this afternoon or this
  evening across southern and eastern areas. While strong gusty
  winds would be the primary hazard, any developing storms in
  western Nebraska could be associated with a risk for small
  hail as well.

- A break down in the upper-level ridge will yield a good chance
  for showers and storms across much of the area on Monday. The
  threat for widespread organized severe storms is low, but a
  strong storm or two is still possible.

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

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 314 AM MDT Sun Aug 18 2024

Hot and generally dry conditions will persist across much of the
area today w/ upper-level ridging remaining in control with 700-
millibar temperatures of +16 to +18 deg C across the CWA. Should
see the majority of areas along/east of I-25 in the 90s again w/
80s west, although there will be at least some potential for mid
and upper level cloud cover to hold us back a few degrees as 500
millibar vort energy undercuts the ridge. Profiles look to be on
the dry side today w/ notable subsidence present on all guidance
and little support for convection from the CAMs as a result. NBM
guidance remains quite puzzling with 40+ percent PoPs across our
southern zones this afternoon and evening, but do not see really
any support at all for this in QPF fields or CAM reflectivities.
Have maintained some very low 15-20 percent PoPs over our south/
east between 21z-06z as a high-based shower or weak storm cannot
be entirely ruled out w/ the energy aloft, or in the vicinity of
the retreating dryline over the western Nebraska Panhandle later
this evening. If any storms can manage to develop, would believe
the primary hazard would be strong wind gusts 55-65 MPH with the
high cloud bases, but MLCAPEs around 1000-1500 J/kg and vertical
shear profiles could support a stronger/organized updraft or two
capable of producing hail as well. This threat is expected to be
highly conditional. Larger-scale ridging will break down Monday,
with strong southwest flow aloft giving way to improved moisture
profiles and cooling thermal profiles aloft contributing to much
weaker capping. As such, numerous showers and storms appear very
likely on Monday and Monday night. The overall threat for strong
to severe storms is low, but not zero as continued steep low/mid
level lapse rates support sufficient instability for more robust
updrafts. Shear profiles will not be quite as good as Sunday but
flow aloft should still support around 35 knots of 0-6 km shear.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 314 AM MDT Sun Aug 18 2024

Tuesday...Atmospheric moisture decreases to 0.4 to 0.8 inches.
With less atmospheric moisture, ridging and warm temperatures aloft
producing convective inhibition, it looks mostly dry. High
temperatures from the mid 80s to upper 90s with 700 mb temperatures
near 18 Celsius.

Wednesday...Although ridging aloft continues, precipitable water
values will increase to 0.8 to 1.4 inches. Thus, it looks like
widely scattered to scattered late day showers and thunderstorms,
most numerous near the Colorado state line and west of a Douglas to
Kimball line. 700 mb temperatures remain near 19 Celsius, yielding
maximum temperatures from the mid 80s to near 100 degrees.

Thursday...The ridge axis aloft moves further east over the Central
Plains states, with an increase in atmospheric moisture for our
counties, thus providing more fuel for scattered afternoon and
evening showers and thunderstorms, most numerous near the Colorado
state line. With more cloud and precipitation coverage, temperatures
will be somewhat cooler.

Friday...Moist southwest flow aloft continues with another round of
scattered afternoon and evening showers and thunderstorms, most
common near the Colorado state line. Slightly warmer with 700 mb
temperatures near 15 Celsius.

Saturday...Southwest flow aloft continues, though atmospheric
moisture decreases slightly, thus coverage of late day showers and
thunderstorms will decrease somewhat. Maximum temperatures will be
similar to those of Friday.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1133 PM MDT Sat Aug 17 2024

Ridging aloft will continue. Scattered to broken clouds from
9000 to 25000 feet will prevail. Winds will gust to 20 knots at
Chadron until 17Z, to 22 knots at Rawlins and Laramie from
18Z to 03Z, and to 26 knots at Alliance and Sidney after 22Z.
Low level winds shear occurs at Scottsbluff until 08Z.

&&

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

&&

$$

SHORT TERM...CLH
LONG TERM...RUBIN
AVIATION...RUBIN