982
FXUS65 KCYS 310455
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
955 PM MST Thu Jan 30 2025

.KEY MESSAGES...

- High wind warning in effect tonight for the wind prones aside
  from Laramie Summit where watch remains in effect as strong
  winds are expected through Saturday evening.

- Mild temperatures continue into Saturday for areas along and
  east of I-25, but areas to the west will remain cold,
  especially at night.

- Widespread elevated to strong winds continue through Sunday,
  but low confidence outside of this from model discrepancies.

&&

.UPDATE...
Issued at 942 PM MST Thu Jan 30 2025

After taking another look at the wind potential for the weekend,
decided to expand the High Wind Watch to include Converse county
and eastern Platte County. The latest guidance shows a strong
SW to NE oriented surface pressure gradient, strong 700-mb winds
oriented due west to east, and the presence of a modest
inversion around 700-mb supporting downslope acceleration. Such
a set up can be conducive to strong winds expanding northward to
portions of I-25 between Wheatland and Casper. While the next
shift can take a closer look, there was enough confidence to
expand the watch at this time.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 240 PM MST Thu Jan 30 2025

As low pressure continues to progress eastwards into the south-
central Plains, our region is expected to be overtaken by high
pressure ridging aloft, thereafter transitioning to a more zonal
flow Friday into Saturday. Under this pattern, the region is
expected to see mostly clear conditions through Friday
afternoon, but moisture aloft streaming in with the upper level
jet will begin to bring cloudy skies overspreading through the
beginning of the weekend. As this jet makes its way over the
region, surface winds will also begin to increase as we see
another spell of high winds. Warnings have been issued for our
windy prone zones including I-80 near Arlington, Bordeaux, and
north Carbon County beginning tomorrow morning, with in house
guidance remaining in good agreement on probabilities of gusts
60+ mph around 60%. The Laramie Summit region remains under a
watch for high winds as well beginning Friday evening, with both
watches and warnings continuing through Saturday evening.

As the aforementioned moisture begins to spread into the region,
we should see an increase in precipitation chances for our
southwestern zones through the day. The bulk of this activity
should be limited to the higher terrain as flow becomes westerly
to southwesterly, keeping upslope the primary mechanism for
development. Several inches of snow may be possible for both the
Sierra Madre and Snowy Ranges across the higher terrain of these
areas moving into the weekend and early next week.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 240 PM MST Thu Jan 30 2025

No major changes to the long term forecast with zonal flow
transitioning to weak upper level ridging by midweek. Some concerns
with elevated winds through Sunday with shortwave disturbances
traversing within the zonal flow, kicking up wind speeds across the
I-25 and I-80 corridors. Local in-house model guidance keeps higher
probabilities (around 60%) through the early morning hours before
decreasing to 20% by Sunday afternoon.  Latest GFS runs for the
Craig to Casper gradients max out at 54/58 meters at 850mb/700mb
from at 06z Sunday and decrease slowly into the morning hours. As a
result, can see elevated winds with speeds up to 50 mph possible and
a few gusts hitting around 58 mph. However, would like to see better
agreement between local in-house model guidance and the GFS for high
wind criteria based winds. Otherwise, can see winds getting close to
high winds but remaining just under criteria. Strong winds are
possible to continue into Monday, with those same gradients showing
a reverse low level gradient setup with values dropping to -45
meters at 850mb and will need to monitor for elevated winds to
continue.

Other than wind, main concern in the long term forecast will focus
on precipitation potentials throughout the week. Models remain in
disagreement with the GFS placing more widespread precipitation
across southeast Wyoming and western Nebraska, whereas the Euro
keeps much of the precipitation confined to the mountain areas. Some
concerns with the GFS solution, with the southeasterly flow being
much more favorable for mountain snow and generally shadowing
adjacent areas. Regardless, high PWATs will take little to get
precipitation going with PWAT standardized anomalies up to 3.0 sigma
above climatology are being reported through Tuesday, with a fairly
decent moisture advection signature evident flowing from the Pacific
to the Intermountain West. Will continue to advertise NBM and GFS
solutions, with weak disturbances contributing towards the
instability needed to provide enough lift for precipitation to
develop, until the model solutions come into better focus.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 933 PM MST Thu Jan 30 2025

North flow aloft this evening will back to west flow Friday
afternoon. Mostly clear skies will prevail through Friday
afternoon, then ceilings will be near 15000 feet Friday evening.
Expect low level wind shear at Sidney until 15Z. Winds will gust
to 25 knots at Cheyenne, gust to 38 knots at Rawlins and Laramie
after 12Z to 15Z Friday, and gust to 22 knots at Sidney after
15Z Friday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from Friday morning through Saturday afternoon
     for WYZ101.
     High Wind Warning from 11 AM Friday to 5 PM MST Saturday for
     WYZ104.
     High Wind Warning from 2 AM Friday to 5 PM MST Saturday for
     WYZ106-110.
     High Wind Watch from Friday afternoon through Saturday
     afternoon for WYZ107-116-117.
NE...None.

&&

$$

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