604
FXUS65 KCYS 190714
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
114 AM MDT Wed Aug 19 2026

.KEY MESSAGES...

- Warmer and drier conditions begin to return today, with warm
  warm temperatures expected Thursday and Friday.

- Elevated fire conditions anticipated Thursday through the end
  of the week.

- Warm and dry conditions continue through the weekend, though
  slightly cooler temperatures are expected.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 113 AM MDT Wed Aug 19 2026

Upper-level ridging continues to build across the western CONUS
Wednesday and Thursday, leading to much drier conditions with warmer
temperatures returning to the region. 500mb vorticity advection will
continue throughout the day both Wednesday and Thursday, but, with
the monsoonal moisture tap largely cut off, precipitation chances
remain near-zero. 700mb flow will remain benign through mid-week
with only a brief wind enhancement expected Wednesday afternoon
across western portions of the CWA. In addition to benign 700mb
flow, much warmer 700mb are on tap with temperatures topping out
around 10 to 16C on Wednesday. Slightly warmer 700mb temperatures
are expected Thursday when the ridge is reaching peak strength and
starting to shift more directly overhead, rather than off to the
west. 700mb temperatures peak around 15 to 17C for Thursday. With
much warmer air aloft, surface temperatures will start to rise,
especially on Thursday. Cooler temperatures continue Wednesday with
highs in the 80s everywhere, with temperatures in the mid-80s to mid-
90s for Thursday. This warming trend will continue through at least
Friday. Precipitation chances will be minimal to none throughout the
middle of the week, due to to the much warmer and drier airmass
pushing into the region. However, warmer and drier conditions with
little to no precipitation will act to increase fire concerns
Wednesday onwards. Afternoon minimum humidity values on Wednesday
will be in the 15 to 25 percent range everywhere, though winds
remain largely light outside of Carbon County. There is a potential
to see a brief period of critical fire conditions in central Carbon
County this afternoon, but confidence is fairly low on this
persisting for 3 or more hours after a fairly moist past couple of
days. Similarly, on Thursday, afternoon humidity values remain in
the 15 to 25 percent range, but winds will be significantly calmer,
especially across Carbon County.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 113 AM MDT Wed Aug 19 2026

Friday...The mid level, 500 mb, or about 18,000 feet MSL, ridge axis
moves to a Grand Junction, Colorado to Great Falls, Montana axis,
with its dominance continuing across our forecast area of southeast
Wyoming and western Nebraska, continuing the dry conditions for our
neck of the woods. Warming trend continues as 700 mb temperatures
rise to near 19 Celsius, producing maximum temperatures from the
upper 80s to mid 90s.

Saturday...With the upper ridge axis, near 500 mb, or 18,000 feet
MSL, transitioning into the western Great Plains states from the
Dakotas southward to eastern Colorado, west southwest flow aloft
will develop over our counties, helping the pseudo monsoonal
moisture to creep back into our forecast area from western Colorado
through primarily our western counties west of I-25. Afternoon
thunderstorms will be most prevalent across our Snowy, Sierra Madre
and southern Laramie ranges, with evening thunderstorms, isolated to
widely scattered, spreading across our entire forecast area, with of
course the greatest areal coverage over our mountainous zones due to
differential and orographic effects. With additional cloud cover and
precipitation coverage, high temperatures will be tempered somewhat
despite the warm mid level temperatures.

Sunday...More scattered beneficial showers and thunderstorms will
occur in a carbon copy type day compared to Saturday, with broad
northwest flow aloft over southeast Wyoming and western Nebraska,
and pseudo monsoonal moisture over the counties. Carbon copy day
temperature wise to Saturday, for the aforementioned reasons from
Saturday.

Monday...Looks like the best chance for measurable rainfall, of 0.01
inch or more, with scattered to numerous afternoon and evening
showers, and scattered thunderstorms due to increased monsoonal
moisture, light steering winds and PWATs, Precipitable water
increases. Slight cooling in maximum temperatures due to lowering of
mid level temperatures and additional cloud and precipitation
coverage.

Tuesday...Ridging aloft amplifies over the Rockies, though with
monsoonal moisture trapped under the ridge from western Colorado
through the western half of Wyoming, and to a lesser coverage over
eastern Wyoming and western Nebraska, expect to see another carbon
copy type day with scattered to numerous showers, and scattered
thunderstorms during the afternoon and evening hours. Similar
maximum temperatures compared to Monday, with clouds and
precipitation coverage tempering highs, with readings peaking i the
80s to lower 90s.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1140 PM MDT Tue Aug 18 2026

An upper level disturbance and a surface backdoor cold front will
push into the region tonight. Expect a continuation of scattered
showers and embedded thunderstorms until 09z with clearing skies by
sunrise.

HAZARDS/WEATHER TRENDS: With shower and thunderstorm coverage
lowering over the next few hours, most terminals will see dry
weather and VFR conditions. A fast-moving thunderstorm may impact
KBFF between 07z and 08z, but it is expected to weaken as it moves
east. Therefore, added a PROB30 group for this low-end threat. Off
and on showers will likely push over KCYS and KSNY until 09z, but
VFR conditions are expected to continue. Drier weather for Wednesday
with probability of precipitation lowering below 10%. Breezy
westerly winds for the southeast Wyoming terminals after 17z with
gusts up to 25 knots possible.

&&

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

&&

$$

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