Cheyenne, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

027
FXUS65 KCYS 220418
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
918 PM MST Fri Feb 21 2025

.KEY MESSAGES...

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

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

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 230 PM MST Fri Feb 21 2025

The area is finally thawing out of the long period of arctic cold
temperatures as a milder and windier weather pattern takes hold this
weekend. Currently, satellite imagery shows mostly clear skies over
the area as the small and disorganized upper level low moves off to
the southeast, leaving just some low clouds lingering over the
higher terrain and in Carbon county. The arctic high is also well
off to the east at this time, and west to northwest winds have
spilled over most of the area, warming temperatures back to near
average for this time of year this afternoon.

Over the next few days, a dirty ridge will build in over the
Rockies, bringing much warmer temperatures, but also an unfortunate
return of the wind. 700-mb temperatures climb to near 0C Saturday,
supporting highs back to about 5F above average for this time of
year. Mostly sunny skies will prevail, with the exception of
increasing mid to high level cloud cover in our northern zones
through the afternoon hours as a subtle shortwave races inland from
the west. This feature will also begin to nudge up height and
pressure gradients across the area. At the start of this wind event
Saturday, the gradients look very marginal, particularly aloft.
Therefore, the start time of high winds in the wind prone areas is
still somewhat uncertain. However, the first shortwave will clear
out Saturday night as a strong jet aloft sags slowly southward
Saturday night into Sunday, spiking gradients to well above typical
criteria by midday Sunday. There is high confidence in high winds
for the wind prone areas during the day Sunday onward, and the
potential for fairly significant wind gusts exceeding 75 mph,
particularly Sunday afternoon into Monday morning. This was enough
to warrant an upgrade to a High Wind Warning, but the uncertainty on
the start time is worth mentioning. Decided to lean on in-house
guidance which pushes probabilities above 50% for high winds at
Arlington Saturday morning, and for Bordeaux Saturday evening.
Still, the first ~12 hours or so of each warning is fairly low
confidence. The watch for the I-80 summit and adjacent foothills
will be continued for one more forecast package, to allow the next
shift to be a little more precise on the timing of the beginning of
the event. By midday Sunday, the winds will ramp up considerably,
and possibly spread to adjacent zones as well. Being nearly 48 hours
out, held off on any product issuance for the adjacent areas with
this update, but expansions of the High Wind Warning will likely be
necessary with later updates.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 230 PM MST Fri Feb 21 2025

The long term begins Sunday evening in the middle of another
high wind episode with high confidence (70-80%) in this long
duration wind event. There is solid agreement from almost every
source of guidance that we should continue to see these enhanced
winds and gusts through Tuesday evening, with in house guidance
suggesting an 80% probability for high wind warning or greater
gusts (58+ mph) for our usual wind prone locations through
Tuesday morning, with probabilities dropping then through the
day. Meanwhile the ECMWF Extreme Forecast Index agrees, with
values of 0.6-0.8 across the region, which would indicate winds
above normal but not a high chance at extreme values. To support
these probabilities, we`ll continue to see a 700mb jet with
values of 60-70 knots, with strong downward omega fields helping
to bring these winds to the surface. The persistence of these
winds will finally be brought to a halt as the multiple
perturbations that have passed across our region finally exit
with the upper level ridge that has been controlling the
southwestern US beginning to amplify, but may once again break
back down just beyond the long-term forecast period. Ensemble
model clusters are also in high agreement on the pattern, with
variations generally being minor overall but otherwise all in
good agreement on how the long term forecast period will evolve.

Outside of winds, the other forecast feature of note will be
temperatures as we see a stretch of above normal conditions
across the region. Highs and lows will both see a jump by about
10 to 15 degrees above normal, leading to highs east of I-25
between 50-65 degrees Monday and Tuesday and again Thursday.
Wednesday should be the one exception due to the pattern
breakdown and we see a cooler northwesterly flow aloft, but
don`t expect a dramatic cooldown as our temperatures only
descend down into the 40`s to low 50`s. As for precipitation,
only a few passing showers into the mountains early in the week
and then perhaps a few scattered and weak echoes by Tuesday are
expected with the final in our series of perturbations moving
across the area. Overall it`ll be a bit difficult to enjoy the
warmth with all the wind, but otherwise if you`re sick of the
cold then next week is for you!

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 915 PM MST Fri Feb 21 2025

West northwest flow aloft will continue. Mostly clear skies will
prevail through Saturday afternoon, then ceilings will be near
15000 feet Saturday evening. Winds will gust to 35 knots at
Rawlins and Laramie, and to 30 knots at Cheyenne and Sidney from
15Z to 00Z.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning from 8 PM Saturday to 11 PM MST Tuesday for
     WYZ106.
     High Wind Warning from 9 AM Saturday to 11 PM MST Tuesday for
     WYZ110.
     High Wind Watch from Saturday evening through Tuesday evening
     for WYZ116-117.
NE...None.

&&

$$

SHORT TERM...MN
LONG TERM...CG
AVIATION...RUBIN