Riverside, Wyoming Weather Forecast Discussion

245
FXUS65 KCYS 092353
AFDCYS
Area Forecast Discussion
National Weather Service Cheyenne WY
550 PM MDT Tue Sep 9 2025
.KEY MESSAGES...
- Daily chances for afternoon showers and thunderstorms continue
  through Thursday with gusty winds, downpours, and isolated
  hail possible.
- A cold front will impact the area later this week bringing
  cooler temperatures and chances for showers on Friday and
  Saturday.
&&
.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 330 PM MDT Tue Sep 9 2025
Unsettled weather continues over the area today. An upper level
ridge is trying to build back in over the southern plains this week,
with the axis located more or less along the I-25 corridor.
Meanwhile, a broad upper level low continues to spin over the West
Coast, ejecting several shortwaves/vort-maxes out to the northeast
over our area. One of these is passing over the top of the ridge
this afternoon, supporting scattered showers and isolated
thunderstorms. The convective environment is fairly unimpressive due
to limited boundary layer moisture. MLCAPE is mostly between 250 and
500 J/kg across the High Plains with bulk shear mostly between 25
and 35 knots. Both instability and shear increase heading east
across the Nebraska panhandle, so the storms moving eastward along I-
80 this afternoon will have the potential to produce a few isolated
strong to severe wind gusts and/or hail through the early evening
hours. Elsewhere, expect mainly sub-severe convection, but brief
heavy downpours, gusty winds, and lightning will still be of
concern. A few showers may linger over the area through the late
evening hours, but the best chance for anything strong to severe
will be in the next few hours.
South to southeast winds overnight will usher in improved low-level
moisture into the area by Wednesday morning. Expect to see higher
dewpoints pushed up against the I-25 corridor. Limited cloud cover
expected over the High Plains should allow for good radiative
cooling tonight, and thus possibly some patchy radiation fog. We
will be under south to southwest flow aloft as the ridge axis shifts
east and amplifies rapidly. Additional vort-maxes moving
overhead will provide forcing for another round of widely
scattered showers and thunderstorms Wednesday afternoon and
evening. Forecast soundings are somewhat more potent tomorrow
thanks to the recovery in low-level moisture, but the modest
inversion may present some capping/CIN issues. As a result,
expect mainly sub-severe storms again, but a few strong to
severe storms cannot be ruled out.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 330 PM MDT Tue Sep 9 2025
Long term should remain active initially as a deep trough and
low pressure system moves across the region, displacing a high
pressure ridge off to our east and cooling us back off, but as
this trough weakens over the weekend we should see precipitation
chances wane and temperatures moderate themselves to near normal
to end the period.
Thursday should be the last day our region remains under the
influence of the ridge as it begins to ride eastwards in
response to an approaching Pacific trough. This trough then
moves into the region Thursday into Friday, bringing an increase
in precipitation chances and highs dropping into the 70`s with
even some upper 60`s showing up by Saturday. Meanwhile PWAT
values will max out around 125-150% of normal, allowing for
rainfall across the entirety of the CWA on Friday. While
precipitation chances do continue on Saturday, they should be
waning as the trough will broaden and less forcing makes its way
across our area. Then moving into Sunday and the beginning of
next week, a transient ridge will move across as the trough
breaks down, but another weaker low will be on the heels of this
system just beyond the short term. This overall pattern brings
cooler temperatures with the coolest conditions expected on
Saturday, with a slight warming trend for Sunday and Monday
albeit only a few degrees at best. Meanwhile the precipitation
chances start off strong, but should taper off for Sunday into
Monday prior to the next system moving in. Ensemble model
clusters are in fair agreement, but do show some discrepancies
in both the placement and strength of the aforementioned
systems, leading to a moderate (60%) confidence in the overall
forecast.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 550 PM MDT Tue Sep 9 2025
Southwest flow aloft will continue over the region for the next 24
to 36 hours. Embedded weak upper level disturbances will result in
another round of showers and thunderstorms each afternoon/evening.
HAZARDS/WEATHER TRENDS: VFR conditions will prevail as the shower
and isolated thunderstorm activity this evening comes to an end
around sunset. Might be another brief shower or thunder shower
around KLAR and KCYS until 02z. Otherwise, activity should dissipate
by 02z.
There is a slight chance for some fog (~10% to 15%) over the eastern
plains tonight as surface winds shift into the south or southeast.
Only a few of the high res models are showing this potential, with
other guidance showing fog and low CIGS well to the east. Decided to
keep out of the TAFs for now, but will monitor through this evening.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MN
LONG TERM...CG
AVIATION...TJT

NWS CYS Office Area Forecast Discussion