409
FXUS65 KCYS 071145
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
545 AM MDT Sun Jul 7 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms possible this afternoon,
  mainly along the Interstate 80 corridor from Laramie to
  Sidney.

- Gradual warming trend next week with little to no
  precipitation chances. Very hot by the weekend.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 355 AM MDT Sun Jul 7 2024

As the cold front passed through the CWA earlier Saturday night,
shower and storm activity increased. These storms continue to linger
across a good portion of the CWA early this morning. Most Hi-Res
guidance is in agreement with the majority of the shower and storm
activity diminishing by about 7 AM, as there is a brief lull in any
upper-level forcing. By mid-day, another vort max will rotate
through the trough and spark another round of isolated to scattered
convection. With a more stable atmosphere behind the cold front,
severe chances will be limited. RAP soundings max CAPE values out
below 1000 J/kg for the CWA. However, with this being Wyoming,
cannot rule out a rogue gust to 60 MPH with any showers or storms
this afternoon. Storm coverage this afternoon looks fairly confined
to the Interstate 80 corridor from roughly Laramie to Sidney and
areas south. Shower and storm activity will diminish this evening.
Besides storms, looking at a rather cool day across the area.
Temperatures will be below average, with most locations in the 70s.
Some locations west of the Laramie Range may not make it out of the
60s! This will lead to a rather chilly overnight, especially for the
mountains, which could see freezing temperatures.

Heading into Monday, the upper-level trough axis will gradually
begin to shift eastward into the center of the country. This will
help the ridge over the west coast strengthen and expand eastward.
This ridge will begin to usher warmer and drier air into the CWA.
Monday will mark the start of a gradual warming trend, with high
temperatures warming approximately 5 to 8 degrees compared to
Sunday. Subsidence under the ridge will limit any storm
potential, with sunny skies dominating throughout the day.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 355 AM MDT Sun Jul 7 2024

No changes made to the medium and long range forecast later this
week and into next weekend, with a gradual warming trend Tuesday
through Thursday, and then hot temperatures and dry conditions
to end the week. Models still show the upper level high,
currently over the western Great Basin Region, slowly drifting
east over the southwest United States. The associated ridge
axis, extending north of the upper level high, will also amplify
and translate eastward into western and central Wyoming by
Wednesday. With increasing subsidence aloft and surface
dewpoints in the 30s to low 40s Tuesday and Wednesday,
convection should be limited with a few thunderstorms over the
mountains. 700mb temperatures will approach +18c across Carbon
County on Wednesday, and range between +12 to +16c further
east...resulting in highs in the 80s for most of the area with
low 90s across portions of the Nebraska Panhandle and far
eastern Wyoming.

All models indicate the strong upper level high (597-599 dm)
and associated ridge axis drifting further east into the four
corners area with the ridge axis amplifying northeastward
towards the Dakotas late this week. Ensembles remain in
excellent agreement and show very little, if any, spread in POP
and temperatures. Kept POP below 10 percent for most
areas...with the exception of the Snowy, southern Laramie Range,
and adjacent high plains and high valleys where mountain
showers and thunderstorms are possible each day. Started using
the NBM 75th percentile max temperatures Thursday through next
weekend with the bulk of ensemble forecasts (GEFS and ENS)
slightly warmer compared to the ensemble mean and most
deterministic models forecasts each afternoon. This will result
in afternoon high temperatures solidly into the mid to upper 90s
across most of the forecast area with readings of 100-104
degrees below 5000 feet, such as Torrington, Scottsbluff, and
Chadron. Amazingly, these forecast temperatures are still a few
degrees shy of our daily record high temperatures since we are
near our climatological average hottest (daily) temperatures
for the calendar year (~84-91 degrees). At this time, it looks
like next Saturday will be the hottest day of the week. PWAT and
midlevel moisture do creep up by next weekend as some monsoon
moisture starts to advect northward out of the tropics...which
may help result in higher coverage for showers and thunderstorms
after next Sunday.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 545 AM MDT Sun Jul 7 2024

Northwest flow aloft will continue today as a secondary disturbance
moves southeast across the area...resulting in another round of showers
and thunderstorms this afternoon, mainly across southeast Wyoming.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail across southeast
Wyoming and western Nebraska terminals over the next 24 hours. Showers
and thunderstorms will develop in the mountains and move southeast
across the I-25 corridor...mainly impacting KLAR and KCYS, and possibly
KSNY this afternoon until 01z Monday. Brief MVFR CIGS and VIS are
possible with this activity until conditions improve this evening.

&&

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

&&

$$

SHORT TERM...SF
LONG TERM...TJT
AVIATION...TJT