312
FXUS65 KCYS 101039
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
439 AM MDT Fri May 10 2024

.KEY MESSAGES...

- Daily isolated to scattered afternoon and evening
  thunderstorms are possible into next week. Severe weather is
  not expected this time.
- Temperatures will remain warm through Tuesday
  before a cold storm system moves in on Wednesday bringing
  cooler temperatures.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 337 AM MDT Fri May 10 2024

Isolated to scattered showers and thunderstorms are possible
Friday afternoon across southeast Wyoming and western Nebraska.
As conditions start drying out today, areas most favored for
showers and thunderstorms are the mountains and higher terrain
that will have the lift needed to support development. HiRes
guidance is not very robust in terms of dynamic support with
cool temperatures, limited instability (50-100 J/kg of CAPE),
dewpoints in the low 30s, and shear values 5 to 15 knots. Due to
the main thunderstorm ingredients being limited, confidence is
low in any widespread shower/thunderstorm development.

Saturday, as a low in the Four Corners Region shifts eastward,
some moisture wraps around back north into areas along and south
of the Interstate-80 corridor, increasing precipitation chances
in the afternoon. While the shear is still very weak in the 5 to
10 knot range, with the moisture increase and instability being
more widespread and stronger near 200-800 J/kg across the High
Plains, scattered to numerous showers and thunderstorms are
possible. They will likely not be very strong thunderstorms, but
the chance of them being more widespread is higher.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 337 AM MDT Fri May 10 2024

The long term forecast continues to show chances for isolated
afternoon thunderstorms beginning by the weekend, with better
chances for more scattered showers and thunderstorms next week.
Temperatures are also expected to increase beginning this weekend
into next week with temperatures likely to remain in the upper 60s
to low 70s Monday and Tuesday. The biggest change noted is for a
potent cold core system to move into the region on Wednesday and
bring colder temperatures and more widespread precipitation chances
and the possibility for high elevation snow showers.

Precipitation chances on Saturday and Sunday will be driven by a
slow moving and large upper level low moving across the Four Corners
region. Models have been consistent over the past 24 hours in
advertising a setup where this upper level low is south of a ridge
building across the northern Pacific northwest with another upper
level low sitting in near northern Michigan. This overall setup of
upper level low and high pressure systems looks like a messy col
setup across the Front Range states. The wind fields show the col
pattern better as light easterly winds in close proximity of light
westerly winds suggest that some type of stationary or quasi-
stationary front will be located across SE Wyoming and the Nebraska
Panhandle. This boundary will be the focal point for potential
convective initiation Friday and again on Saturday. These storms
that do develop will be in a weakly shear and low CAPE/instability
environment so not expecting much in the way of deep convection, but
towers that go up along the boundary or are orographically supported
could be deep enough to foster the development of some small hail.

This overall pattern remains in place well into Saturday evening
before the closed upper low across the Four Corners begins to weaken
and open into an open wave trough as it crossed through southern
Colorado. Remaining stationary boundary should still be draped
somewhere across the Front Range and we will also have lingering
outflow boundaries in play on Saturday IF we can get a few deeper
convective cores going on Friday. This system begins to speed up on
Sunday but the threat for some afternoon diurnal convection will
again be possible.

Monday may be quiet day across the region as a weak upper level
ridge axis moves but this too will quickly move east of the region
throughout the day on Monday. We will see the benefits of some
warmer 700mb temperatures which will allow for temperatures to jump
into the 70s across much of SE Wyoming and the Nebraska Panhandle.

Heading into Tuesday models have shifted a bit on the overall
pattern across the region. Models are now showing a deeper trough
developing across western Montanta which will have a downstream
transition to to a SW flow across much of Wyoming, this deeper
trough also means the ridge will hold in place longer before getting
ejected to the east. The evolution of this trough becomes quite
messy with models initially pushing this feature in as a positively
tilted trough before pinching off a weak closed low over central
Utah with strong shortwave pushing out of eastern Montanta on
Wednesday. This secondary shortwave looks to push a cold front north
to south across the region bringing with it colder temperatures and
more widespread precipitation chances with the potential for some
high elevation mountain snow showers. While the exact evolution of
the main 500mb height needs to be watched, overall confidence
remains that we will stay unsettled for much of next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 337 AM MDT Fri May 10 2024

While MVFR to IFR conditions remain possible due to low CIGS and
fog through mid-morning, high cirrus clouds moving in from the
south will limit the fog potential across portions of far
southeast Wyoming. The primary concern one the CIGS lift will be
gusty winds 20 to 30 knots and a few showers and thunderstorms
this afternoon across southeast Wyoming. The Nebraska panhandle
terminals can expect FEW to SCT high clouds with generally light
winds less than 12 knots.

&&

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

&&

$$

SHORT TERM...LEG
LONG TERM...AW
AVIATION...LEG