-- Discussion containing changed information from previous version are highlighted. --
249
FXUS65 KCYS 100446
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1046 PM MDT Thu May 9 2024

.KEY MESSAGES...

- Scattered rain/snow showers expected to continue this evening
  as well as Friday afternoon. Severe weather is not expected
  at this time.

- Warming trend likely headed into the weekend with the return
  of above normal temperatures for mid-May.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 144 PM MDT Thu May 9 2024

Tonight...With a rather moist airmass, and mesoscale lift provided
by daytime heating and shortwaves rotating around the upper low over
Utah, we expect scattered evening showers and isolated
thunderstorms, with less coverage across southwest Carbon County and
the southern Nebraska Panhandle. With the loss of heating, showers
will decrease in coverage later tonight and occur near the
mountains. Boundary layer progs and narrowing temperature/dewpoint
depressions suggest a decent bet for areas of fog to once again form
mainly across southeast Wyoming after midnight. Most low
temperatures will remain above freezing due to available low level
moisture.

Friday...The upper trough retrogrades further west across Nevada and
Utah, which should limit the scattered shower and isolated
thunderstorm coverage further west than today, to the west of a
Douglas to Kimball line. Coverage of showers will be greatest over
and near the Snowy, Sierra Madre and Southern Laramie Ranges due to
differential heating. 700 mb temperatures near 0 Celsius will yield
a warming trend with maximum temperatures mainly in the mid 50s to
mid 60s.

Friday night...With minimal dynamic lift and evening cooling, we
expect showers and thunderstorms to end in the early evening. Cloud
cover should decrease somewhat from north to south overnight. Low
temperatures will be similar to the previous night.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 144 PM MDT Thu May 9 2024

The long term forecast period remains fairly consistent from
overnight guidance. The weekend looks to end up mainly dry, thanks
in large part to dry northwest flow moving down over the northern
Rockies and into the high plains. Expect temperatures to recover by
at least 10 degrees on Saturday compared to Friday, and add another
5 on top of that for Sunday. This will result in an above-average
weekend over the entire CWA. The only caveat to the weekend forecast
will be the movement of the broad upper-level low over the Four
Corners region. This system remains just close enough to southeast
Wyoming that a few isolated showers and possibly a thunderstorm may
develop over the higher terrain. Will have to watch this system
carefully as any trend farther north and east with the center of the
low pressure system may result in a better chance of showers,
especially by Sunday afternoon.

After a weak ridge moves through on Monday, the next system dives
southward through the northern Rockies by Monday evening. This
system will ride the overall pattern of northwest flow over the
Rockies and high plains which has been consistently modeled in
ensemble guidance over the last several days. Showers and
thunderstorm chances will increase each day through Wednesday before
a stronger vort max riding through the northwest flow passes
through. Isolated instances of small hail and perhaps gusty outflow
winds will be the primary threats for thunderstorms, especially on
Wednesday. However, any larger widespread severe weather outbreaks
are not expected through the entire long term given a general lack
of low-level moisture and very weak to nonexistent upslope flow at
the surface. Beyond Wednesday, some differences in guidance begin to
emerge with the GEFS supporting continued northwest flow and the
ECMWF flattening this pattern somewhat by the end of the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
-- Changed Discussion --
Issued at 1043 PM MDT Thu May 9 2024

Terminals in southeast WY will shift from VFR to MVFR quickly
after 6Z. Expect fluctuations between MVFR/IFR through 12Z for
all terminals in southeast WY. LIFR is anticipated for KLAR
between 12Z-15Z before improving to IFR/MVFR while FG is present.
NE Panhandle terminals will see low end VFR overnight, with
gradual improvements on Friday. Wind gusts should remain at 12
knots or below for terminals, except KRWL, where Friday morning
after 15Z, there will be occasional gusts to 25 knots through
the afternoon hours.
-- End Changed Discussion --

&&

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

&&

$$

SHORT TERM...RUBIN
LONG TERM...MAC
AVIATION...BW