018
FXUS65 KCYS 152102
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
302 PM MDT Sat Jun 15 2024

.KEY MESSAGES...

- Scattered high-based showers and thunderstorms will develop
  this afternoon through early evening. Primary concern with
  these storms will be wind gusts over 60 MPH and the potential
  for dry lightning.

- A cold front will bring cooler temperatures for Tuesday and
  Wednesday, along with a chance for late day showers and
  thunderstorms. A warming trend will develop for Thursday
  through Saturday, along with daily chances for afternoon and
  evening showers and thunderstorms.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 230 PM MDT Sat Jun 15 2024

With a return of our radar earlier today, we can inspect some of
the most recent weak thundershowers across the region as of 20Z.
Additionally, there are numerous outflow boundaries present from
decaying thundershowers across southeast WY and western NE. Very
dry air is present in the lower boundary layer this afternoon,
so some of the rain shower activity showing up on radar may
actually become virga, or even dry thunder/lightning. Model
soundings analyzed earlier today depicted an inverted-V signal
for most of the cwa this afternoon. The converging outflow
boundaries from decaying showers will create new updrafts this
afternoon as most of the area has reached the modeled convective
Temperature. Prior to the onset of the weak thundershower
activity, most locations achieved daytime highs in the lower 80s
to middle 90s. The rest of this afternoon will see continued
weak thundershowers for most of the cwa. An outside chance of a
stronger thunderstorm exists, with stronger wind gusts near or
above 60mph as the main hazard. In the NE Panhandle, a more
organized thunderstorm or two could result in a heavier rain
shower and small hail, albeit brief. Gusty winds will continue
across the region through the evening hours. Dry conditions will
be expected west of the Laramie Range overnight, with overnight
humidity recoveries hovering near the 30% range due to the
higher elevations remaining in the thermal belt region.

A passing shortwave will keep daytime highs much cooler for
across our northern forecast zones on Sunday and Monday. Model
guidance has some areas potentially not reaching higher than the
upper 60s, especially Monday. Have gone with a slightly warmer
solution for now due to the potential for breaks in cloud cover.
The remaining portion of the cwa will see warmer daytime highs,
primarily south of the North Platte River Valley. Expect daytime
highs in the upper 70s to upper 80s for most of the lower
terrain, with 60s anticipated in the higher terrain. Some of the
hi-res model guidance at 12Z included the potential for
organized convection on Sunday, especially east of I-25 and
north of HWY 26. The 18Z model runs have backed off on this
trend however, so a lower confidence forecast exists for
thunderstorm activity on Sunday. Day 2 from SPC has a Marginal
and Slight Risk for portions of our cwa...will see if that is
trimmed off for the Day 1 12Z update early Sunday morning. The
timeline for any convection that develops would be later in the
afternoon to late evening at this time of inspection. Expect the
trend of possible convection to be present for similar areas on
Monday as diurnal heating destabilizes the atmosphere. The
primary hazard for both Sunday and Monday in organized
convection would be strong, gusty winds close to or exceeding
60mph.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Issued at 230 PM MDT Sat Jun 15 2024

Monday night/Tuesday...A cold frontal passage Monday evening will
help spark isolated to scattered showers and thunderstorms north of
a Douglas to Sidney line, then clearing skies and a cool overnight.
Considerably cooler for Tuesday with 700 mb temperatures near 1
Celsius yielding maximum temperatures from the mid 60s to mid 70s.
Moist upslope northeast winds and a passing shortwave trough aloft
will help produce isolated to widely scattered showers in the
evening mainly east of I-25.

Wednesday...Moist upslope southeast winds and a passing shortwave
trough aloft will produce scattered showers and thunderstorms mainly
east of I-25. Continued relatively cool with plenty of cloud cover.

Thursday...Increasing southwest flow aloft will induce surface lee
troughing and a warming trend with 700 mb temperatures near 14
Celsius yielding high temperatures in the upper 70s to mid 80s. With
adequate low and mid level moisture and convergence along the
surface trough, scattered late day showers and thunderstorms are
expected.

Friday/Saturday...The flow aloft backs to westerly, continuing the
warming trend with high temperatures mainly in the 80s. Again,
enough moisture for scattered late day showers and thunderstorms
each day.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1121 AM MDT Sat Jun 15 2024

West southwest flow aloft will continue, while a cold front
passes the terminals tonight.

Wyoming TAFS...Scattered to broken clouds from 10000 to
12000 feet will prevail, with mostly clear skies after
midnight. Thunderstorms will be in the vicinity at Cheyenne from
20Z to 00Z. Winds will gust to 35 knots at the terminals until
03Z.

Nebraska TAFS...Scattered clouds from 8000 to 10000 feet will
prevail, with mostly clear skies after midnight. Thunderstorms
will be in the vicinity from 21Z to 02Z. Winds will gust to
23 knots at Chadron and Alliance from 21Z to 06Z.

&&

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

&&

$$

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