015
FXUS65 KCYS 121127
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
527 AM MDT Wed Mar 12 2025

.KEY MESSAGES...

-  Warm, dry, and breezy weather will continue through Thursday
   with elevated to near critical fire weather conditions each
   afternoon alongside the potential for high winds in our
   western zones late tonight through Thursday afternoon.

-  The next storm system will arrive late Thursday into early
   Saturday, bringing strong winds and a chance for
   precipitation. Modest snow accumulations are possible in the
   mountains with light snowfall elsewhere.

-  Mild conditions alongside breezy winds return early next
   week.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 400 AM MDT Wed Mar 12 2025

Today will be another mild and dry day with breezy conditions
for the western half of our CWA as a quick moving upper-level
trough passes across and just south of the Four Corners with
another batch of quick transient ridging then establishing this
evening but quickly departing by Thursday afternoon. This will
allow for flow aloft to shift to a southwesterly direction with
a modest little 700mb jet establishing itself primarily over
Carbon County, with speeds around 40-55 knots. Favorable mixing
may help to bring some of this breeziness to the surface, with
the HREF showing a 40-75% probability of wind gusts 50+ mph for
locations including Rawlins, Muddy Gap, and Elk Mountain.
Because of this, have issued a high wind watch for these zones
beginning around midnight tonight and continuing through the
very late morning hours on Thursday. Meanwhile, continuing to
analyze the potential for fire weather conditions, with enhanced
potential possible for Laramie and Platte Counties again today,
as well as portions of the Nebraska Panhandle. That being said,
current guidance shows a slight amount more moisture today with
RH values expected to bottom out around or just above 15%,
which means we`re expected to see some near critical fire
weather concerns alongside the breezy winds across the area, but
values shouldn`t remain in this threshold for long enough to
produce widespread critical values. However will advise incoming
day crew to keep an eye on RH`s in case we see a bit drier
conditions than expected. Another risk of elevated concerns
expected on Thursday this time for Goshen county and the
Nebraska Panhandle once again. Similar concerns with RH values
just nearing critical values, but breezy winds will be much more
favorable, particularly for Dawes, Sioux, and Box Butte
Counties. Still confidence is too low to establish a watch at
this time.

Attention turns to the end of the week as an approaching trough
moving into the west coast then moves inland and across the
region, with a deep and stacked low expected to establish itself
across eastern Colorado. This system has been less and less
impressive with each run, but deep cyclogenesis is still
expected and should produce a stout high wind event for eastern
Wyoming and the Nebraska Panhandle. The NBM indicates a 40-80%
probability of maximum wind gusts of 60+ mph from the Laramie
Range through the Panhandle, with the aforementioned low
driving a 700mb jet of 45-60 knots across this area (which has
declined from previous runs). GFS Omega values are also showing
a much better swath just to our south in Colorado, but modest
downward mixing alongside a stout pressure gradient should drive
northwesterly winds to reach high wind criteria Friday morning
through the nighttime hours. Meanwhile stout forcing should
produce ample precipitation activity on Friday primarily in the
morning and early afternoon hours as the system quickly
propagates eastwards. However the quick moving nature of this
system will prevent widespread noteworthy snowfall with areas
east of Carbon County lucky to see a trace to an inch. Between
the low snow-ratios due to warm initial temperature profiles and
warm ground temperatures, any snow that does fall will be wet
and should melt quickly at first. Best chances for
accumulations remain the Sierra-Madre and Snowy Ranges, but even
for these locations only around 5-8 inches are expected through
Saturday morning which would promote an advisory at best. Still
any falling snowfall alongside the stronger winds could produce
brief periods of hazardously low visibilities. By Saturday
morning the region will be much cooler with sub-freezing lows in
the 20`s to teens expected, but an approaching ridge should
once again bring more mild warmth to the area into the late
weekend and early next week.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 400 AM MDT Wed Mar 12 2025

Saturday...Moist northwest flow aloft prevails, helping to produce
numerous orographic snow showers for our Snowy and Sierra Madre
Ranges, with lesser coverage for the northern and southern Laramie
Range. Continued on the cool side with 700 mb temperatures near -8
Celsius, yielding maximum temperatures in the mid 30s west of I-25,
with lower to mid 40s east of I-25.

Sunday...Turning windy and warmer as the flow aloft backs to
westerly, inducing a decent surface lee trough development. 700 mb
temperatures near -2 Celsius, combined with downslope west winds
will yield high temperatures in the mid 40s west of I-25, with lower
to mid 50s east of I-25. Dry with limited low and mid level moisture.

Monday...Fast southwest flow aloft develops with a progressive
shortwave trough aloft and associated cold front moving across
Wyoming, though timing of the cold front suggests mild temperatures
before cold frontal passage with high temperatures in the 50s west
of I-25, with mainly 60s elsewhere.

Tuesday...Colder and windy in the wake of the shortwave trough aloft
and cold frontal passage, based on the progged low and mid level
gradients. Chances for high elevation snow and low elevation rain
will increase from west to east with increasing low and mid level
moisture and cyclonic flow aloft.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 524 AM MDT Wed Mar 12 2025

West flow aloft today will turn southwest tonight. Scattered
clouds near 15000 feet will prevail. Winds will gust to 25 knots
at Rawlins after 18Z, and will gust to 25 knots at Laramie and
Cheyenne from 18Z to 01Z. Winds will remain 10 knots or less
across the Nebraska terminals.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from late tonight through Thursday afternoon
     for WYZ104-109-110.
NE...None.

&&

$$

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