025
FXUS65 KCYS 222351
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
451 PM MST Sat Feb 22 2025

.KEY MESSAGES...

- A long duration wind event is expected through at least mid
  next week in the wind prone areas. Winds may spill into
  adjacent zones Sunday PM through Tuesday AM.

- Steady warming trend through mid next week with highs
  returning to the 50s and even 60s.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 106 PM MST Sat Feb 22 2025

The short term forecast remains largely on track compared to
previous updates as we see the beginning of a high wind event
across the forecast area. Locations along I-80 near Arlington
have already seen wind gusts eclipsing 60 mph, while locations
near the Laramie Summit as well as Bordeaux have seen gusts in
excess of 50 mph. These speeds will continue to increase and
spread across more of the region over the coming days, with high
wind warnings now out for the majority of southeastern Wyoming.
The exceptions are the Laramie Valley and eastern Laramie
County, with both zones currently under a watch for potential
high winds as well. Driving this event will be a series of
shortwaves moving across the region under westerly to
northwesterly flow aloft. Models indicate a stout jet at 700mb
is developing, around 50-55 knots today but increasing to 60-70
knots tomorrow and persisting through Tuesday evening. Omega
fields also show significant downward values, with high
confidence (75-90%) that we will see these enhanced winds aloft
mix down to the surface across most of the Wyoming forecast area
through the course of early next week. Winds will not remain
this strong for the entirety of the forecast period/warning
duration though, with potential lulls generally being diurnally
driven, though even this isn`t a guarantee for a reduction in
gusts as that 700mb jet remains pronounced through the duration
of the short term period.

Aside from the winds, of note will be temperatures, with
widespread highs in the mid 40`s to mid 50`s already seen today
across areas along and east of I-25. The downsloping effect
from the winds will continue to fuel increasing warmth, with
highs on Monday for the aforementioned areas east of I-25
expected to range between the upper 50`s to mid to upper 60`s,
nearly 15-20 degrees above normal! As mentioned, this wind event
will spread into the long term on Tuesday, so please see the
long term discussion for more information on the expected end of
this event.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 106 PM MST Sat Feb 22 2025

In the long term, the southeast Wyoming and Nebraska
Panhandle areas remain mostly under amplified upper level ridges.
The ensembles still show a strong consensus of a strong positive
phase of both the Eastern Pacific Oscillation and Arctic Oscillation
for the beginning half of the work week and a weak positive to
neutral phase in the back half of the week. So what that means for
the Rocky mountain region is persistent warmer temperatures as the
arctic air stays relatively contained to the providences of Canada.
Also with a stronger positive EPO, the semi-permanent high pressure
system moves closer to the west coast to keep the region a little
bit drier than when that high pressure system was over the Bay of
Alaska. However, there are a few Low pressure systems that will be
migrating through the Canadian Providences to give us some
precipitation chances for the Converse and Niobrara counties as well
as the Northern Portion of the Nebraska. A shortwave looks to move
through our area Tuesday morning to give precipitation chances to
our Northern counties and the Sierra Madres. There is a plume of
moisture that is available as pieces of the atmospheric river makes
it past the mountains. With this shortwave, models indicate some
weak isentropic lift and some weak streams of vorticity to slightly
enhance the forcing to produce some precipitation. However, I kept
low pops over the Northern portions of our CWA because of our
overall westerly flow favoring warm downsloping. The forcing overall
while present doesn`t seem sufficient to counteract our strong
downslope regime for the day. However, in a westerly flow the Sierra
Madre and the Snowy range favor a strong upslope for those two
ranges. The Sierra Madres will shadow the Snowy Range and end up
stealing most of the moisture. No headlines are expected as the snow
accumulations look to be a few inches which is negligible almost for
the mountains. Given that the moisture looks to persist over the
Northern areas longer, no dramatic increases are expected for the
mountains to prompt headlines as of right now. There is some cooler
(not arctic) that follows behind the shortwave to drop temperatures
a little cooler than the previous days. However, temperatures look
to still be in the 40`s during the day and upper 20`s at night.

Our high wind festival looks to end Tuesday as the shortwave pushes
the area of high pressure that resided over northwest Colorado
further south. Looking at the Craig to Casper height gradients
during this period, the gradients drop from the 50`s to the 20`s and
30`s giving us a break from the winds. To support this break our in
house machine learning algorithm only gives a 10 to 15 percent
chance for high winds for Wednesday into Thursday.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 418 PM MST Sat Feb 22 2025

VFR conditions will continue at all terminals this evening.
Expect clouds to remain high, well above any MVFR levels. Some
wind shear is possible at CYS and LAR overnight as faster flow
aloft moves in above slower surface winds. Surface winds will
increase on Sunday at all terminals with gusts over 40 mph
possible at RWL, CYS and LAR. VFR will continue at all terminals
Sunday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning from 8 AM Sunday to 11 PM MST Tuesday for
     WYZ101-107-109.
     High Wind Warning from 2 AM Sunday to 11 PM MST Tuesday for
     WYZ104-105.
     High Wind Warning until 11 PM MST Tuesday for WYZ106-110.
     High Wind Warning from 11 AM Sunday to 11 PM MST Tuesday for
     WYZ108-118.
     High Wind Watch from Sunday morning through Tuesday evening
     for WYZ115.
     High Wind Warning from 11 PM this evening to 11 PM MST Tuesday
     for WYZ116-117.
     High Wind Watch from Monday morning through Tuesday evening
     for WYZ119.
NE...None.

&&

$$

SHORT TERM...CG
LONG TERM...MM
AVIATION...MAC