238
FXUS65 KCYS 111146
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
545 AM MDT Fri Jul 11 2025

.KEY MESSAGES...

- A strong cold front will move south across the area Friday
  morning, with potential for strong storms and heavy rain
  Friday afternoon and evening.

- Temperatures will be warming Saturday through Monday, before a
  potent cold front brings another round of cooler temperatures
  for Tuesday and Wednesday. Shower and thunderstorm chances
  will be greatest for Tuesday and Wednesday.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 240 AM MDT Fri Jul 11 2025

Current IR Satellite this morning shows the Pacific shortwave
disturbance, which brought the widely scattered thunderstorms
yesterday, continues to quickly move southeast of the area into
Kansas and Nebraska. Mid to upper level flow will continue to
shift into the northwest today with veering winds aloft. This is
area of the next relatively strong cold front for early-mid
July digging south into the Front Range today. The leading edge
of the cold front is still across northern Wyoming and is
forecast to quickly move south this morning across the High
Plains. A cluster of showers and embedded thunderstorms continue
to push across east central Wyoming, but are likely not
producing much rainfall. Frontal position will likely be through
most of southeast Wyoming and in northern Colorado around noon
today, and then the front is forecast to stall near the
Colorado/Wyoming border. This should keep temperatures across
the I-80 corridor and near the Colorado border in the upper 70s
to mid 80s for a while today...so not much lower compared to
yesterday. Further north, highs will struggle to reach the low
to mid 70s.

Another round of showers and thunderstorms expected mid to late
afternoon, but this time most of the activity should be confined
to the I-80 corridor near the front. Can`t rule out some
isolated thunderstorms north of the north Platte River Valley,
but coverage will be limited with the cooler airmass already
through the area. Frontal boundary is expected to fluctuate into
this evening before heading south tonight. Any warm air
advection in the midlevels will aid in storm development with a
good chance of at least strong thunderstorms along and south of
a line from Elk Mountain eastward to Scottsbluff and Sidney
Nebraska. Can`t rule out some severe thunderstorms in this
pattern either with very heavy rainfall, hail, and gusty winds.
Can`t rule out an isolated tornado or two as well. Current 00z
and 06z NAM shows ample 0-3km CAPE over 2000 j/kg and EHI`s
approaching 2 near the stalled frontal boundary and thunderstorm
initiation area from Elk Mountain over towards Cheyenne, and a
secondary area across the lower North Platte River valley later
in afternoon. Northwest flow at the midlevels and east to
southeast surface winds indicate decent lower level shear within
the boundary layer. However, the lack of deep 0-6 km shear and
not much CIN suggest short duration circulations and storms
quickly becoming outflow dominant through the afternoon, so
confidence is limited on this overall threat this afternoon but
should be kept in mind for portion of far southeast Wyoming and
the southern Nebraska Panhandle today.

Thunderstorm activity should end around sunset with remnant
showers near the cold front boundary mainly near the Colorado
border. Kept Low stratus and the potential of fog, and extended
the mention of patchy fog further east since we`re expecting
decent rainfall amounts and a continuation of moist east to
southeast winds tonight. Saturday is trending drier across the
area so lowered POP below 10 percent for most locations but kept
slight chance of showers and thunderstorms for the Laramie and
Cheyenne areas, including the I-80 summit, with decent low level
convergence. Most of the area will be fighting some much drier
air aloft than previous forecasts indicated, which will likely
cap most of the convection. Pleasant day with highs in the upper
70s to upper 80s...warmest north of the Interstate 80 corridor.


&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 147 AM MDT Fri Jul 11 2025

For later this weekend and Monday, a gradual warming trend will
continue as the upper level high across the desert southwest
slowly builds northward and intensifies. Thunderstorm activity
is forecast to become more isolated through by late Saturday and
Sunday as 700mb climb above 15c. Highs in the upper 80s to mid
90s will return for much of the forecast area by Sunday and next
Monday.

Tuesday...A progressive shortwave trough aloft moving across Montana
and North Dakota will send a fairly strong cold front southward
across our counties, dropping high temperatures into the mid 70s to
mid 80s. With decent low level upslope winds and plenty of low and
mid level moisture, we expect to see scattered afternoon and evening
showers and thunderstorms. Models are not quite as aggressive
with the amount of cold air behind the front compared to
yesterday, but still show 700mb dropping between 5c to 10c
across northern Wyoming.

Wednesday...Another relatively cool day for mid July with low level
upslope, plenty of cloud cover and high temperatures only in the mid
60s to mid 70s. Adequate moisture for scattered afternoon and
evening showers and thunderstorms, most numerous near the Colorado
state line where the moisture will be the deepest.

Thursday...The atmosphere will slowly moderate with 700 mb
temperatures returning to near 15 Celsius, yielding high
temperatures in the upper 70s to mid 80s. Warm temperatures aloft
will limit convection, though still should see isolated to scattered
late day showers and thunderstorms.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 545 AM MDT Fri Jul 11 2025

A strong cold front for this time of the year will move south into
southeast Wyoming and western Nebraska this morning through mid
afternoon. Showers and thunderstorms will develop along this front
as it stalls near the Colorado border.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail through 20z.
Surface cold front will begin to push into KCDR, KBFF region by
15z...and closer to 18z further south along Interstate 80. Showers
and thunderstorms will develop by mid to late afternoon...mainly
impacting KLAR, KCYS, KSNY, and KBFF. Included prevailing MVFR with
thunderstorms starting at 20z to 22z further west, and then moving
into KSNY and KBFF between 00z and 03z Saturday. Locally strong
gusty winds and very heavy rainfall reducing VIS to less than 2
miles are possible with these thunderstorms into this evening.

Patchy fog and low CIGS are possible (20% to 30%) at KCYS and KSNY
after 06z Saturday. This may result in periods of IFR conditions
overnight into early Saturday morning.

&&

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

&&

$$

SHORT TERM...TJT
LONG TERM...TJT/RUBIN
AVIATION...TJT