025
FXUS65 KCYS 281731
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1031 AM MST Fri Feb 28 2025

.KEY MESSAGES...

- Very windy conditions early this morning for the wind prone
  areas of southeast Wyoming. A High Wind Warning has been
  issued for areas south of Wheatland.

- Above average temperatures expected with highs in the 50s and
  60s with calmer winds through the weekend.

- Potential winter storm Monday and Tuesday of next week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 255 AM MST Fri Feb 28 2025

Primary forecast concern over the next 24 hours will be locally
strong winds across the wind prone areas and elevated fire
weather conditions (please see the Fire Weather Forecast for
more details). Issued a short-fused High Wind Warning for the
Bordeaux area this morning as wind gusts of 56 MPH were reported
with sustained winds over 40 MPH for over 1 hour. Current winds
are sustained of 44 MPH with a gust of 55 MPH in the last 10
minutes, and expect this to continue over the next few hours
before pressure tendencies across the central plains reverse and
become positive as a weak cool front moves south into the high
plains early this morning. The other wind prone areas have not
responded as aggressively, so will leave the Special Weather
Statement going for the next hour or so. Winds are forecast to
slowly subside after sunrise with mostly pleasant weather this
afternoon and highs in the 50s to low 60s.

Models remain in good agreement as we head into the weekend as
the upper level high pressure across the northern Great Basin
Region slides east into the Rocky Mountain Region on Saturday.
This will result in some very nice weather for the first few
days of March with dry conditions and light winds. With 700mb
temperatures climbing over 0c, afternoon highs are forecast to
be well into the 50s to low 60s for not only the eastern plains,
but the high valleys west of the Laramie Range as well.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 217 AM MST Fri Feb 28 2025

The main forecast challenge in the long range period (Sunday and
beyond) revolves around the switch from an extended mild period back
to winter weather. Sunday will be a continuation of the warm and dry
conditions, while Monday will serve as the beginning of the
transition, and Tuesday will feature the the full-on wintry setup.
Seasonable temperatures and generally low end precip chances then
round out the week.

Sunday... The axis of the upper ridge that has will have brought the
warm dry stretch finally crosses the forecast area. Meanwhile, a
closed upper low rapidly passes to the south from the Four Corners
to the Central Plains. At the surface, the primary low closely
follows the upper low, but a trough extends to a secondary low in
the northern Rockies, bisecting the CWA. Low level flow transitions
from southerly to westerly/downsloping over the course of the day,
aiding the warm air advection scheme. Considering H85 temps of 10-
12C in the panhandle and H7 temps around 2C in Wyo, see no reason to
stray from the general NBM guidance of highs near 60F. Recent model
suites have trended cloudier, particularly across the southern half
of the CWA closer to the stronger low. The upper quartile of the
envelope suggests mid 60s for highs for the eastern Wyo plains and
Neb panhandle, but confidence is low given the cloud cover and the
fact numerical guidance stays in the lower 60s. Nevertheless, these
temps are fairly anomalous for this time of year, as showcased by H7
values at the 90%ile in NAEFS climo ensembles, and max temps in the
ECM EFI reaches 0.7/1. Will also need to monitor the fire weather
component as humidity values dip into the teens across eastern Wyo.
At this time, the wind appears light enough to preclude any serious
threat of critical conditions.

Monday... The low pressure quickly scoots east into the Mississippi
Valley, but in its wake comes another, and possibly stronger,
system. The closed upper low reaches the Salt Lake area by evening
as the surface component begins to spin up over the Colorado plains.
The abnormally mild air remains over the forecast area for another
day, especially for the Neb panhandle where the brunt of the H85
thermal ridge sets up. Strengthening mid-level flow ahead of the low
and the northward push of the upper jet really increase dynamics
across the central/northern Rockies. Steady moisture advection
combined with strong lift should contribute to precip development,
first over the mountain ranges, then across much of eastern Wyo. Any
moisture for the Neb panhandle should hold off until after dark.
Thermal profiles would suggest primarily rain for the first portion
of the event except for the highest terrain. The progressiveness of
the low should place most of the forecast area in the cool sector by
Monday night. H85-7 temps rapidly drop by Tuesday morning,
indicating a switch from rain to snow from west to east. Seasonably
low SLR`s and the recent warm temps and ground conditions should
keep accumulating snow to a minimum during the overnight hours,
again except for the mountain ranges.

Tuesday... The low fully emerges onto the Plains, resulting in
northerly flow and continued cold air advection for the forecast
area. Temps at H7 fall to around -12C over Wyo and H85 values drop
back below 0C over the Neb panhandle. Expect the eastward push of
snow to continue during the day, as well as the increase in SLR`s.
The bulk of the snow accumulation for areas near and east of I-25
should occur Tuesday morning and afternoon. Potential exists for
anomalous snowfall with this system, as shown by the ECM EFI with
values surpassing 0.6/1 in spots and SoT >0 along the eastern slopes
of the Rockies. For now, agree with WPC assessment of a swath in the
neighborhood of 2-4" snow along the I-80 corridor. In addition to
the the heavy wet nature of the snow, wind will likely be an issue.
The surface pressure gradient really tightens, and mid level flow
increases alongside the powerful 130+ kt H3 jet. Surface gusts may
exceed 40 mph in the Neb panhandle and 30 mph for eastern Wyo
plains. Any snow that falls will likely be blown around, resulting
in significant visibility reductions. Will need to highly consider
winter headlines as the event draws nearer.

Wednesday and beyond... Temperatures remain near seasonal norms
(highs around 40F) as precip chances continue. A progressive upper
ridge/trough pattern brings periodic waves of energy, especially
along and west of the Laramie Range.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1032 AM MST Fri Feb 28 2025

VFR conditions will persist through the period. An area of high
pressure will move over the terminals tonight and tomorrow.
Winds are expected to be 5 to 10 knots as the high pressure
system moves over the terminal. After 06z the winds may also be
VRB05kts through the remainder of the day tomorrow. There are
also no low level wind shear concerns as well with only very
high based clouds expected (15,000ft or more)

&&

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

&&

$$

SHORT TERM...TJT
LONG TERM...DS
AVIATION...MM