974
FXUS65 KCYS 241137
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
437 AM MST Tue Dec 24 2024

.KEY MESSAGES...

- Active pattern expected mid-week onwards with daily chances
  for snow in the mountains and small chances for some snow
  across the lower elevations.

- Strong winds look to return for Thursday afternoon into
  Friday. After a brief break Friday afternoon...another strong
  wind event expected for the weekend.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 306 AM MST Tue Dec 24 2024

High pressure is in control of the weather today across Wyoming
and Nebraska Panhandle. Winds have eased quite a bit in the wind
prone areas. Arlington...south Laramie Range and Bordeaux are
only gusting in the 20 to low 30 mph range this morning...while
light and variable winds are being reported outside the wind
prone areas.

Upper ridge builds over the forecast area this
morning...bringing an end to any remaining snow shower activity.
A pretty nice day expected with 50s east of I-25 and 40s west.

Ridge axis moves east into the Nebraska Panhandle this evening.
Look for increasing clouds as a low pressure system moves into
western Colorado Wednesday. Begin to see chances for snow
showers increasing Wednesday morning in our western mountains.
Lower elevations of Carbon and Albany Counties may see some snow
showers for Christmas Day...but not expecting significant
accumulations or travel impacts. Trough axis moves through
Wednesday night into Thursday with this snow ending Thursday
morning.

Need to be on the lookout for strong winds Thursday afternoon as
Craig to Casper 750/700mb height gradients begin to rise. By
Thursday afternoon...both 850 and 700mb gradients are forecast
above 60mtrs. Random Forest showing a spike in the wind prone
areas during this time as well. Arlington up near 80 percent and
Bordeaux up to 40 percent. GFS 700 and 750mb winds up near 60kts
Thursday afternoon...so high wind headlines look like a pretty
good bet. If model guidance continues to show this...will likely
be issuing high wind watches in the next 24 hours for Thursday
afternoon through Friday morning.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Issued at 306 AM MST Tue Dec 24 2024

An active period is expected in the long term as a series of
shortwaves brings prolonged mountain snow and windy conditions to
the area.

As mentioned, the synoptic pattern for the end of the week and into
next week looks active as shortwave after shortwave barrels across
Wyoming. The first shortwave arrives Friday evening with decent mid-
level moisture. Westerly winds will favor orographic snow for the
mountains, conversely, the westerly winds may dry out the low-levels
leading to minimal precipitation chances across the lower
elevations. Advisory level snow amounts look probable across the
Sierra Madre Range during this time. Aside from high terrain snow, a
prolonged high wind event looks plausible Friday evening through
Sunday morning. The shortwave will cause MSLP gradients across the
CWA to tighten. CAG-CPR 700 mb height gradients will also increase
with the shortwave passage, with heights over 55 meters. Winds aloft
will respond by increasing in magnitude. 700 mb winds will max out
around 60 to 65 kts over much of the CWA with sufficiently strong
downward omegas to bring these winds down to the surface. High winds
will be likely in the typical southeast Wyoming wind prones, but
high wind probabilities outside of the wind prones are also
increasing per in-house guidance. If these variables stay
consistent, high wind headline across southeast Wyoming may be
needed.

A brief break from high winds is likely during the day Sunday as the
CWA sits between shortwaves. This break will be very short as the
next shortwave arrives Sunday night. Winds will increase ahead of
the shortwave with high winds possible by Sunday evening. This event
looks similar to the previous one, albeit it slightly weaker winds
and a shorter duration event. Expect another mostly gradient driven
event as the shortwave disturbance tightens MSLP gradients and CAG-
CPR height gradients. Winds aloft will be about 55 to 60 kts over
the area with great downward omegas. Again, confidence is high for
the wind prones seeing high winds Sunday night into Monday, but some
high winds could also spill over into the wind prone adjacent areas
as well. Just like the previous shortwave, this one will also have
some decent mid-level moisture which will lead to mountain snow.
Models are also a bit more excited about snow outside of the high
terrain with this system as well. However, westerly downsloping
winds may bust any precipitation chances during this time.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 437 AM MST Tue Dec 24 2024

Satellite shows some lingering low stratus in and around KRWL early
this morning. MVFR CIGs will be possible here through about mid-
morning before clouds dissipate and lift. The rest of the day at all
terminals will be relatively quiet with light winds and VFR
conditions.

&&

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

&&

$$

SHORT TERM...GCC
LONG TERM...SF
AVIATION...SF