Text Products for AFD Issued by CYS

Area Forecast Discussion
Issued by NWS Cheyenne, WY
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FXUS65 KCYS 221039
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
439 AM MDT Mon Apr 22 2024

.KEY MESSAGES...

- Elevated to high winds possible for areas west of the Laramie
  Range Monday afternoon. Low relative humidities will also lead
  to fire weather conditions in certain areas.

- Relatively mild temperatures are expected for Wednesday and Thursday
  along with a chance of late day showers and thunderstorms.

- Cooler and unsettled weather is likely for Friday and the
  weekend.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 430 AM MDT Mon Apr 22 2024

An approaching cold front with jet energy aloft will lead to a windy
day for areas west of the Laramie Range. Current observations show
gusts between 30 and 40 MPH, but this will steadily increase through
the morning hours, with the strongest winds expected this afternoon.
Low-level MSLP and height gradients remain unremarkable with the
progressive nature of this front. Even the GFS has backed off on 700
mb wind speeds from previous runs, only maxing out at about 45 kts.
NBM continues to show strong winds gusts this afternoon at 45
to 50 MPH. The NBM also shows a roughly 70 percent chance around
the Arlington/Elk Mountain area for 48 kt wind gusts. This is
likely due to the potential for mountain wave activity as
indicated by the omega field. Although the NBM might suggest
high winds, in-house guidance for high winds only gives the
usual wind prones a 20 percent chance of high winds. Given that
this event is outside of the typical high wind season, it will
likely be difficult to see widespread and frequent gusts over 58
MPH. However, it will still be very windy for areas out west
with gusts of 40 to 55 MPH. Cannot rule out an occasional gust
to 60 MPH, especially between Laramie and Rawlins along
Interstate 80.

With the approaching cold front from the north, the northern
zones of the CWA will be a few degrees colder than Sunday. The
southern portion of the CWA will be warmer as the FROPA doesn`t
occur until late Monday night/early Tuesday morning. Warmest
temperatures will generally be along the Interstate 80 corridor.
With the mild and windy conditions out west, fire weather
conditions are also expected. Relative humidities will likely
drop below 15 percent for areas out west. However, increased
cloud cover from both mountain wave activity and the cold front
may limit relative humidities from dropping below critical
threshold.

With the front through the CWA by Tuesday morning, expect a cooler
but seasonable day across area. Highs will be in the 50s to low 60s.
Increasing clouds are expected throughout the day with a weak
disturbance approaching from the west. This will increase low-level
moisture and may lead to some scattered showers and a few rumbles of
thunder Tuesday evening into Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 300 AM MDT Mon Apr 22 2024

CWA on the east side of a broad flat ridge located over western
Wyoming Wednesday. Southerly low level winds east of the
Laramie Range Wednesday morning transporting low level moisture
into the Panhandle and eastern high plains. Ridge amplifies
Wednesday afternoon...forcing the low level moisture eastward
into central Nebraska through the afternoon. ECMWF and GFS
showing some low QPF over the Laramie Range and west Wednesday
afternoon...so can not rule out some scattered showers and
isolated thunderstorms Wednesday. Overall...a pretty nice day
with afternoon highs in the mid 70s across the Panhandle and
upper 60s to low 70s in southeast Wyoming.

Upper ridge axis shifts east Wednesday night into Thursday with
the approach of next in series of upper shortwaves from the
desert southwest. This system expected to bring increasing
chances for showers and storms Thursday afternoon.

This vort max shifts east Friday morning...but on it`s heels is
another vort max moving in from the west and southwest Friday
afternoon. This system looks a bit more organized with a surface
cold front and upper level jet support. Front looks to stall out
near the Colorado/Wyoming state line Friday evening. Good
chances for showers and storms (70-80 percent) coverage. Still a
pretty warm system...with 700mb temperatures of +2C...so
snow levels looking to be pretty high (8500 to 8800 feet). Right
now...snow does not look to be an issue...but if system comes in
colder...we may be dealing with heavy snow at some locations.

Colder air arrives Sunday as a vertically stacked low tracks
across southeast and east central Colorado. This may be the
system that brings heavy snow to our CWA as 700mb temperatures
fall to -4C to -6C. Stay tuned to later updates in the forecast.


&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1140 PM MDT Sun Apr 21 2024

VFR conditions expected across area terminals through the
forecast period. High clouds continue to move over the region
tonight into Monday. A cold front currently over northwest WY
will drop south early Monday morning turning surface winds
northwest for terminals east of the Laramie Range.
Additionally, low ceilings will be possible for portions of
east-central WY, but looks to stay away from TAF sites. Stronger
west winds are expected for terminals west of the Laramie Range
Monday with gusts up to 40 kt possible at KRWL and KLAR.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from noon today to 7 PM MDT this evening for
     WYZ428.
NE...None.

&&

$$

SHORT TERM...SF
LONG TERM...GCC
AVIATION...MB
National Weather Service Regional Headquarters
