823
FXUS65 KCYS 282254
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
454 PM MDT Sun Apr 28 2024

.KEY MESSAGES...

- A High Wind Watch has been issued for strong winds early
  Tuesday morning through Tuesday afternoon across the Laramie
  Range.

- Active extended forecast period with multiple rounds of rain
  and snow showers with occasional thunder possible daily
  through the weekend.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 245 PM MDT Sun Apr 28 2024

As the low continues to remain nearly stationary along the NE/SD
border, a shortwave embedded in the flow is kicking off some showers
across areas along and west of the Laramie Range, these will likely
fall as rain at lower elevations and snow at the highest peaks in
the mountains. A rumble of thunder is possible, but strong or severe
storms are not expected with little to no additional precipitation
accumulation. After the showers have died off this evening, and
skies begin to clear, temperatures are expected to drop with a low
chance of areas of patchy fog and low clouds in the far eastern
Nebraska panhandle. As a messy, weak, low amplitude ridge moves over
southeast Wyoming and western Nebraska tomorrow, mostly dry
conditions are expected with afternoon highs in the 60s to 70s.
Monday late afternoon/evening though, a low passes to the north of
the forecast area, but the trough dips just low enough to kick off
more precipitation chances, and bring in cooler temperatures.
Precipitation type this time will be mostly rain with snow in the
mountains. However, areas of Carbon County and the Laramie Valley
may briefly transition over to snow or at least a rain/snow mix
early Tuesday morning. Precipitation accumulation is expected to be
minimal with 2 to 5 inches of snow possible in the mountains and
less than 0.02 to 0.25 inches of rain at lower elevations. In
addition to increasing precipitation chances, winds will also begin
to increase. Refer to the long term discussion for further
details.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 245 PM MDT Sun Apr 28 2024

Tuesday will begin with an upper level low across the PacNW
with multiple shortwaves passing in the flow through the middle
of the week. The initial vort max passage with a surface low
positioned neat the WY/MT/SD border will likely lead to gusty
winds across the CWA with this bora wind event. Additionally,
strong downward omega fields develop across the Laramie Range as
the 110 kt jet exit shifts just to the north. Decided to go
ahead with a High Wind Watch starting early Tuesday morning for
much of the Laramie Range in southeast WY, including Interstate
25 between Cheyenne and Wheatland and Interstate 80 between
Cheyenne and Laramie. Wind gusts around 60 mph will be possible,
especially late Tuesday morning in the wake of the trough axis
passage. However, this event will likely be short in duration.
Local in-house guidance is hinting at the high wind potential,
but probabilities are slightly lower than typical high wind
events. Latest GFS has delayed the timing of the trough by 3-6
hours compared to 24 hours ago, which is also highlighted by in-
house guidance. Will need to continue to monitor these trends
as they will have significant impacts to the timing of this
potential for high winds.

With Tuesday mornings frontal passage, a few light showers will be
possible. However, the next best chance for precipitation will come
Wednesday afternoon into Thursday as the secondary vort max swings
through our area associated with the same larger scale upper level
low now over the north-central CONUS. Favorable isentropic lift with
this system could lead to widespread showers, likely as rain east of
I-25 and snow farther west. We could even see a few thunderstorms
Wednesday afternoon with the surface low deepening across eastern
CO. However, high uncertainty remains with timing of magnitude of
colder air worked into our CWA. 60% of GEFS membership favors a
colder solution, but still disagree on exact timing of the upper
level trough passage. Most EC members are favoring a more
progressive solution.

An active pattern looks to continue into the weekend and early next
week with multiple shortwave passages and possibly another Pacific
wave approaching from the west. This will bring numerous chances for
showers, but coverage will likely remain scattered. Should see a
gradual warm up headed towards early next week with temperatures
climbing 10-15F degrees above normal for early May.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 454 PM MDT Sun Apr 28 2024

Scattered showers and thunderstorms possible this evening in and
around southeast Wyoming terminals. Although prevailing VFR
conditions are expected at these terminals, cannot rule out a brief
drop in visibility from light to moderate rain. Some low clouds
continue to linger around Nebraska panhandle terminals this evening.
Clouds will gradually raise, leading to clearer skies by Monday
morning.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from Tuesday morning through Tuesday afternoon
     for WYZ106-107-116-117.
     High Wind Watch from late Monday night through Tuesday
     afternoon for WYZ110.
NE...None.

&&

$$

SHORT TERM...LEG
LONG TERM...MB
AVIATION...SF