textproduct: Cheyenne

KEY MESSAGES

- Dry conditions and above average temperatures are expected to continue through mid-week.

- The next chance for precipitation and temperatures closer to seasonal averages will be late week, Thursday night, into the weekend.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 131 PM MDT Tue Oct 20 2026

Another beautiful day is in store across a majority of the CWA with ample sunshine under a west-southwesterly flow regime aloft that will remain dominant through today. This flow will support warm-air advection into our region, bumping 700-mb temps back into the 4 to 8C range, which reflects nicely at the surface. So, expect highs this afternoon to top out in the low to mid 60s west of I-25 and the upper 60s to low 70s east of the corridor. Heading into the overnight hours, the lows look seasonable as they dip down to around 40 degrees for many locations. Taking a look at the latest water vapor imagery, within the flow regime there is a weak shortwave that is moving across the Central Rockies, this feature will provide sufficient ascent for some isolated to scattered showers later this afternoon primarily over the Snowy Range. Confidence in precipitation development and coverage remains low given the relatively weak forcing and dry air that is in place. In reality, all we may see from this system is increasing cloudiness with the possibility of breezy winds underneath. Therefore, kept PoPs 15 percent or less so it doesn't show up in the forecast due to the low confidence. Jumping ahead a day, for Wednesday, looks to be another beautiful day as the aforementioned shortwave will be a distant memory as it moves off to the east. It will be replaced as a transient upper-level ridge quickly moves in overhead. High temperatures will top out mid 60s west of I-25 and low 70s east of the corridor. With the ridge remaining the dominant upper-level feature and little in the way of appreciable forcing for ascent, dry conditions are expected through Wednesday afternoon. As the ridge pushes off to the east, weather conditions begin to change late Wednesday evening as another weak shortwave slides closer to the CWA, this will bring a surge of clouds that will keep our nighttime lows a tad warmer with temperature only dipping into the 40s to 50s.

LONG TERM /THURSDAY THROUGH TUESDAY/

Issued at 131 PM MDT Tue Oct 20 2026

Thursday...The beginning of an unsettled and wetter pattern will commence as the initial negatively tilted shortwave trough aloft, emanating from the parent upper trough over southern Nevada, moves northeast across our counties during the daylight hours. Dynamics associated with this perturbation aloft and orographic effects will produce scattered showers in the afternoon across Carbon County, including our Snowy and Sierra Madre Ranges. A lull in shower coverage is expected Thursday night as the southeast Wyoming is somewhat dry slotted. Brisk southerly low level winds will persist Thursday night, along with cloud cover to keep minimum temperatures rather mild.

Friday...The parent shortwave trough aloft, negatively tilted, moves from northern Utah near dawn, to northeast Wyoming by suppertime, with the majority of our forecast locations being dry slotted, as the bulk of the shortwave trough moisture and lift will be over western Wyoming and central Montana. Although, with the approach of the Pacific origin cold front and frontal lifting, as well as some mid level moisture, you can anticipate, scattered afternoon showers for areas bounded roughly by Laramie, Wheatland, Torrington and Cheyenne, with the showers moving and/or developing into far eastern Wyoming and the Nebraska Panhandle in the evening, before showers mainly dissipate late as the rather potent Pacific origin cold front sweeps eastward across southeast Wyoming and western Nebraska, with orographically driven showers falling across the Northern Laramie, Snowy and Sierra Madre Ranges.

Saturday...A windy and colder day is in tap in the decent thickness packing behind the Pacific origin cold front, with winds decreasing in the afternoon as pressure gradients slacken off. The next closed low aloft moves near the Four Corners by early evening, and with orographics combined with diffluence aloft and adequate low and mid level moisture, you can expect scattered afternoon showers from the Sierra Madre Range eastward across the Snowy Range and across the Laramie Valley including Laramie, and to the southern Laramie Range. Dry elsewhere, though with cloud cover.

Sunday...Confidence in model solutions is rather low to moderate, at this juncture, as an initial spoke of shortwave trough energy is progged to move north and northeast across our counties, possibly producing scattered to numerous showers dynamically driven, with cold air damming near the low levels producing low level mechanical lift over and east of the Laramie Range. FOr now, we will blend with our neighboring offices early in the day, keeping POPS relatively low and mainly southeast of a Laramie to Alliance line. Although model trends will need to be watched closely for a possible rain/snow scenario early in the day. A cool, overcast afternoon looks quite plausible as the shortwave trough aloft opens up over central Wyoming with cold surface air upslope remaining underneath the southwest flow aloft, which may make for a colder day, than currently forecasted, as model trends come into better agreement.

Monday...A decent shortwave trough aloft, positively tilted, moves across the Dakotas, with cold surface high pressure remaining dammed up along and east of the Interstate 25 corridor and the Laramie Range. Confidence in precipitation forecast is minimal in this progressive pattern, although with forecast experience, believe there is a distinct possibility for colder temperatures than currently forecasted if current model trends continue.

Tuesday...Day seven shows the typical model discrepancies in this progressive synoptic pattern, leading to a fairly low to moderate confidence forecast. Likely a dry scenario with cold northerly flow at mid and upper levels and relatively low precipitable water values. Again, with 700 mb temperatures progged near -1 Celsius, if true, our maximum temperatures will need to be lowered eventually as models come into better congruency.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1130 AM MDT Tue Oct 20 2026

A rather diffuse and weak negatively tilted shortwave trough aloft, or atmospheric perturbation, stretching from central Wyoming to central Colorado at midday, will move slowly across western Nebraska and western Kansas by this evening, then to eastern Nebraska and eastern Kansas by dawn Wednesday, as a transitory shortwave ridge aloft builds across our forecast area overnight. A weak, dry cold front, or surface trough, will slide southward across our forecast area late this afternoon and tonight, shifting winds to a north and northeast direction, but with little, if any, sensible weather effects.

Wyoming TAFS...High confidence in VFR prevailing. Associated with a shortwave trough aloft, the HRRR past few runs are hinting at isolated to widely scattered showers possibly developing during the late afternoon and early evening. Inherited PROB30s for Laramie and Cheyenne, and confidence not high enough to remove these PROB30s for continuity sake as the models may be underdoing convective shower potential. Typical diurnal wind gusts to near 25 knots through early evening due to low level pressure gradients and differential heating effects caused by orographics.

Nebraska TAFS...VFR prevails, with high confidence. Clear skies will prevail, with scattered clouds near 10000 feet through the afternoon near KSNY. Typical diurnal wind gusts to near 22 knots through early evening due to low level pressure gradients and orographically driven differential heating effects.

CYS WATCHES/WARNINGS/ADVISORIES

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