textproduct: Cheyenne

KEY MESSAGES

- Above average temperatures dry conditions for most of Saturday. Showers & Thunderstorms possible this evening for mainly southeast Wyoming.

- A pattern change will bring a gradual cool down and increased chances for precipitation Sunday through much of next week.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 215 AM MDT Sat Oct 10 2026

A few more warm days still on track this weekend with models in pretty good agreement through Sunday night, showing a slow and gradual cool-down as we head into late Sunday and early Monday morning where temperatures will likely lower back down closer to average for this time of the year. All models are in better agreement (compared to a few days ago) and show the strong Pacific storm system digging south across the Pac NW and the Sierra Nevada Range this weekend, possibly bringing beneficial rainfall to the Great Basin. In our neck of the woods, central Wyoming will be the fringe of this activity with mainly dry and warm conditions along and east of the Interstate 25 corridor.

For this morning, Intervals of midlevel clouds pushing over the area based on the current IR Satellite loop. Some returns between 10k to 15k feet shown on KCYS radar, but based on observations across the area, it is likely still too dry for any rainfall to reach the surface. Expect this to be the case for most of the day with low to midlevel moisture advection gradually increasing through the afternoon. Not much forcing (early) today with models showing a subtle vort max lifting northeast across Wyoming later today into late this evening. A upper level jet couplet also lifts northeast colocated with the vort max. This will likely be enough to generate numerous showers and a few thunderstorms across mainly Carbon and Albany counties this evening and into tonight. Can't rule out some of this activity moving into, and east of, the I-25 corridor...but confidence is limited with low level moisture advection taking quite a bit of time. Convective parameters are marginal with 100 to 400 j/kg of CAPE and lapse rates around 5 to 7 c/km. Should be enough forcing to generate some moderate rain showers. A few thunderstorms are possible as well, so added some Prob thunder of 15% to 20% (slight chance). High res guidance is still showing some more organized bands of thunderstorms tonight, likely due to the position of the jet and the vort max pushing east. Added the potential for strong gusty winds to the forecast...mainly for Carbon and Albany counties. Remaining relatively warm for this time of the year, with afternoon highs around 70 west of I-25 and mid 70s to mid 80s across the eastern plains.

A little cooler on Sunday, mainly due to increasing cloud cover, but 700mb temperatures do lower a degree or two compared to Saturday. Pacific storm system will still be located roughly over the same area as late Saturday with the system digging into southern California. Slightly better convective parameters and forcing over most of southeast Wyoming on Sunday with more favorable lapse rates and low to mid level moisture with dewpoints increasing into the mid to upper 40s. Increased POP across most of southeast Wyoming and the far western Nebraska panhandle Sunday afternoon and Sunday evening for at least scattered to numerous rain showers and isolated thunder. May be some heavy rainfall with some of this activity as it rapidly lifts northeast. Can't rule out some high elevation snow, but snowlevels will likely be between 11,000 to 12,000 feet at the start of this event. Some cooler air will move into Wyoming Sunday night, with overnight low temperatures closer to the low to mid 40s by early Monday morning.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 220 AM MDT Sat Oct 10 2026

Monday sees the majority of the upper level support and moisture lift north of the area. Dry, sinking air on the backside of the system moves in which dampens rain potently. The best signal for rain remains to the west in Carbon County. Winds stay gusty behind the system. Global model ensembles have between 50 and 60 percent of members with wind gusts above climate average for this time of year. Our in-house high wind ML model is giving elevated wind gusts around 40-50 mph for the Arlington and Rawlins wind prone areas. Some spots along I-25 could get some of these gusts. Nothing quite reaching high wind criteria at this time, though trends are slightly increasing.

Overnight Monday the trough over the West Coast moves eastward. Ahead of the system the subtropical jet intensifies with the tightening of 250 mbar pressure gradients between the trough and an upper level ridge over TX and northern Mexico. Being on the left exit region of the jet could increase synoptic lift. PWATs are in the 90 to 99 percentile, which is about half an inch. Forecast soundings have most of this moisture residing below 500 mbar, so shallow showers are anticipated with low rainfall rates mainly in our western areas.

We see a weak return flow at the surface Tuesday in response to the Pacific system moving east and surface lee cyclogenesis starting. A lull in rain is possible given being removed from the favorable synoptic lifting provided by the jet and subtle ridging nosing in. Most shower activity, if we see it during the day, would still be kept to Carbon County. By the evening and overnight the advancing system should be close enough to start kicking off showers. The return flow could moisten the surface layer enough that we see some areas of fog develop in the central and eastern parts of our area towards morning.

By Wednesday and Thursday we hit a forecast horizon with the progression of this trough. The general trend has been towards a slower system, though models like the GFS are a little more progressive and amplified, showing a more negative tilt to the trough shape. Perhaps this increases lift and instability to produce thunderstorms over the Nebraska Panhandle Wednesday. But if you go with the Euro solution the trough is not as amplified. The Euro and Canadian model solutions are for the system to then retrograde back west and not move much through the remainder of the forecast period. Additionally, some major disagreement in the 00Z runs of global models on a clipper like system swinging southeast out of Canada. GFS, and even the Euro AIFS, do resolve the clipper and ejects the trough northeast. This has major implications to the long range forecast. If the clipper solution is correct colder air can be anticipated with the potential of some locations seeing freezing overnight temperatures. But if this is not correct, continued mild temperatures are likely. The features that cause this uncertainty appears to be the strength of the ridge to the north in Canada and if it allows a trough ejection to occur near Alaska around October 14th. So, watching the progression of these features around that timeframe in those locations should help resolve what our long term forecast.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1138 AM MDT Sat Oct 10 2026

Scattered showers and isolated thunderstorms are moving in from the southwest at this hour. Expect this to expand in coverage and spread northeast through the evening hours. All terminals except SNY have at least a PROB30 group for strong, gusty winds in the range of 35 to 50 knots, though timing differs by terminal. Confidence in impacts is highest at RWL, and decreases progressively further east. In addition to the wind, these showers have the potential to produce a VIS drop. Dry air may cut into visibility potential further east, but at least MVFR is possible. A dip into IFR cannot be ruled out. Otherwise, expect gusty southwest winds especially at LAR and RWL, where consistent gusts of 30 to 40 knots are expected.

Gusty winds will continue overnight at LAR and RWL, but should ease elsewhere. In addition, scattered showers will continue through the night and into Sunday morning, especially near RWL. Confidence is lower in VIS dropping below VFR during this phase, but later updates will need to re-evaluate this.

CYS WATCHES/WARNINGS/ADVISORIES

WY...None. NE...None.