455
FXUS65 KCYS 252328
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
528 PM MDT Sat May 25 2024

.KEY MESSAGES...

- Mountain snow showers will accumulate in the Snowy and Sierra
  Madre tonight and early Sunday, with total possible
  accumulations of 2 to 6 inches above elevations of 9500 feet.
  Scattered rain showers and an isolated strong to potentially
  severe thunderstorm can`t be ruled out east of the Laramie
  Range and Nebraska Panhandle today.

- Strong winds are possible in the wind prone and gap areas of
  southeast Wyoming early Sunday morning through the mid-
  afternoon. Please see the latest High Wind Watch Statement
  for further details.

- A much warmer, milder week ahead as an upper-level ridge
  overtakes the region.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 150 PM MDT Sat May 25 2024

Radar analysis shows a band of showers with a few embedded
thunderstorm cores stretching from Cheyenne to Scottsbluff with
this whole area moving off to the northeast. A few isolated
thunderstorm cores are trying to organize but with the limited
instability available, they are remaining on the weaker side.
Still could see pea sized hail out of those cores but outside of
that, impacts a limited. Temperatures have cooled off where rain
has been observed dropping much of SE Wyoming down into the 50s.
With the passing shortwave aloft, we can expect additional
development of showers for the lower elevations through the rest
of the afternoon. Heading into the overnight hours we will see
the development of that high elevation mountain snow. Some of
the highest peaks over the Sierra Madre and Snowy`s could see
5-7" of snow.

This shortwave will move to the east of the Front Range by
tomorrow morning allow for some subsidence to advect in its
wake. Coinciding with this subsidence will be a band of 50kt
700mb winds arriving with the next shortwave trough moving west
to east through Wyoming. In-house model guidance continues to
show high probabilities for high winds primarily for the
Arlington wind prone area. The setup does favor areas along the
south Laramie Range Foothills and Summit to see some periods of
high winds as well. The current High Wind Watch seems
appropriates it captures the current forecast trends.

With a more potent shortwave trough passing aloft and some
residual low level moisture in place across SE Wyoming and the
Nebraska Panhandle, we could see more showers and thunderstorms
develop Sunday afternoon. These storms will encounter a better
environment as daytime heating and limited cloud over should
allow for some destabilization to occur with the best corridor
of CAPE values being shown across the northern Nebraska
Panhandle. A few strong storms will be possible and we can`t
rule out a storm or two becoming severe.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 150 PM MDT Sat May 25 2024

Few changes made to the long term forecast, with Memorial Day still
looking dry for those with outdoor plans. Likely a bit breezy across
the area as a shortwave passes to our northeast, but temperatures
will be average for late May with afternoon highs in the upper 60s
and 70s.

Headed into the remainder of the work week, an upper-level ridge
will build over the Rockies Tuesday into Wednesday, sandwiched
between two troughs. This will lead to warmer, above average
temperatures during this time frame as 700 mb temperatures climb
into the +10C to +14C range. By Wednesday, highs will be in the
upper 70s and low 80s. Ridging will lead to dry conditions on
Tuesday, but an embedded disturbance moving through the ridge on
Wednesday could spark some afternoon and evening convection. Per GFS
soundings for Wednesday afternoon, there is the potential for severe
storms. Soundings from across the Nebraska panhandle do show surface
CAPE values approaching 2000 J/kg. MUCAPE values are also
approaching 2000 J/kg which will primarily lead to a large hail
threat. Aside from hail, will also have to keep an eye on PWs as
these soundings are encroaching on 1 inch PWs. Cloud layer winds are
also on the slower side which could lead to the potential for minor
flooding.

After Wednesday, daily precipitation chances look possible through
the end of the work week. Although the GFS and ECMWF diverge by
Thursday and Friday, both still have afternoon thunderstorm chances.
The biggest difference between the two is temperature. The GFS sends
a trough north of the CWA, while the ECMWF dives the trough further
south with a strong cold front moving across the CWA. If the ECMWF
solution comes true, expect much cooler, below average temperatures
headed into the start of the weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 521 PM MDT Sat May 25 2024

A weather disturbance aloft will move to the east of the
terminals overnight, with northwest flow aloft developing on
Sunday.

Wyoming TAFS...Scattered to broken clouds from 7000 to
12000 feet will prevail. Showers will be in the vicinity of
Laramie and Cheyenne until 02Z. Winds will gust to 35 knots at
Rawlins, to 35 knots at Laramie and Cheyenne until 02Z, and also
after 15Z Sunday.

Nebraska TAFS...Scattered to broken clouds from 7000 to
10000 feet will prevail. Thunderstorms will be in the vicinity
of Sidney until 02Z, with showers in the vicinity of Chadron,
Alliance and Scottsbluff until 03Z to 06Z. Winds will gust to
25 knots at Sidney until 02Z, and to 30 knots at Scottsbluff and
Sidney after 15Z Sunday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from 3 AM MDT Sunday through Sunday afternoon
     for WYZ106-110-116-117.
NE...None.

&&

$$

SHORT TERM...AW
LONG TERM...SF
AVIATION...RUBIN