textproduct: Cheyenne

KEY MESSAGES

- Active with scattered to numerous showers and thunderstorms into the weekend. Strong to marginally severe thunderstorms may return to the area as a potent Pacific storm system moves into Wyoming Saturday and Saturday night.

- Friday will be the warmest day with low to middle 80s possible across the lower elevations.

- Active weather with cooler temperatures expected for much of the upcoming week.

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 200 AM MDT Fri Sep 18 2026

Current IR Satellite loop this morning shows the remnants of the tropical disturbance over South Dakota and northern Nebraska, producing moderate to heavy rainfall. In our area, we got some heavy rainfall for portions of western Nebraska, but nothing terribly widespread as many locations reported under 0.25 inches of liquid. Believe the thick cloud cover resulted in a more stable environment compared to what models were showing. The track of the tropical disturbance wasn't favorable either, with the best lift further north and east. Pretty quiet early this morning with the rainfall finished until Friday afternoon. Surface observations show areas of fog across the Nebraska panhandle and east central Wyoming, which saw the best rainfall amounts with this system. Visibilities generally range from one quarter mile to 6 miles. May need a Dense Fog Advisory, but that looks unlikely at this time with isolated and brief reports of one quarter mile. Fog and low clouds are expected to lift after 900 am.

For the rest of today (Friday), all models show the slow moving upper level trough, currently entering the western Great Basin Region, slowly meandering eastward into Idaho and northern Utah through this afternoon. Low to midlevel moisture expected to remain in place over the area. Although NAEFS PWAT isn't quite as high as yesterday, it still shows 95th to 99th percentile PWAT over most of the forecast area into this evening. A potent midlevel shortwave is still expected to eject northeast ahead of the main trough over the Front Range. With current IR Satellite loop showing clearing skies across most of central Wyoming and portions of eastern Wyoming this morning, expect higher coverage of showers and thunderstorms with more instability present due to the lack of morning cloud cover. Western Nebraska will likely be fighting some CIN due to morning low clouds and fog, but expect activity to push into the high plains later in the day as the shortwave disturbance lifts northeast. Heavy rainfall, gusty winds, and frequent lightning possible with stronger thunderstorm activity through this evening. Remnant showers are then expected after 1000 PM and past midnight. Kept POP between 50 to 70 percent today through late this evening, especially for southeast Wyoming and far western Nebraska.

For Saturday, models show some drier air starting to sneak into central Wyoming, with PWATs lowering to around 0.75 in the afternoon. Further east, still expect PWATs close to 95th percentile of climatology. Also, instability will be higher with more jet dynamics as the main Pacific upper level trough moves across Wyoming through the evening hours. Not only is another round of showers and thunderstorms likely, expect a higher chance for strong to marginally severe thunderstorms with 0-6 km shear of 30 to 40 knots and MLCAPE around 1000 to 1500 j/kg...which is solid for this time of the year. Very heavy rainfall, strong gusty winds, and even some hail possible Saturday afternoon through Saturday night. Pretty good chance for some nocturnal convection as the main trough axis moves into the forecast area late Saturday evening. Increased POP between 60 to 90 percent, especially across the eastern high plains with a good chance for widespread moderate rainfall. May see some snowfall on the highest mountain peaks as 700mb temperatures drop below 5c, but minimal accumulation is expected at this time. After a pretty warm Friday, high temperatures will be closer to average for mid September on Saturday with early afternoon highs in the upper 60s to mid 70s.

LONG TERM /SUNDAY THROUGH THURSDAY/

Issued at 1251 AM MDT Fri Sep 18 2026

An upper-level low will move west to east across the CWA throughout the day Sunday. The upper-level jet on the backside of this system will strengthen Sunday evening into Sunday night as it dives southeastward into the Central Plains. A slight intensification of the 700mb winds will be possible during this time, though the 700mb jet remains fairly weak. 700mb temperatures cool into the single digits with this low, bringing in a nice cool down with high temperatures in the 60s and 70s. The cold front will bring widespread precipitation chances to the region as moisture will be quite good with this system, with precipitable water values in the 90th percentile per NAEFS guidance. A cool, rainy day will certainly start bringing the fall vibes back to southeast Wyoming and western Nebraska. These fall vibes will continue for Monday as temperatures remain quite cool behind the system. Additionally, winds will turn easterly as a high strengthens over Iowa and Minnesota. Stout, easterly flow will result in continued upslope develop throughout the day Monday before winds turn back southerly for Tuesday.

Tuesday onwards, the upper-level pattern will remain quite progressive with multiple systems moving through the region. Daily precipitation chances will continue through much of the week. Tuesday will start off a warming trend across the region, with highs in the low- to upper-70s, followed by low-70s to low-80s Wednesday, and mid-70s to mid-80s Thursday and Friday. Luckily, winds look to remain fairly calm despite the systems moving through the region. Most of the systems will be fairly weak, with limited 700mb jet strength.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1130 PM MDT Thu Sep 17 2026

After a busy afternoon/evening with showers and thunderstorms, the overnight hours will bring winds generally less than 10 knots. However, BR and/or FG will plague the Nebraska terminals, dropping CIGs and VIS down to IFR and as possibly as low as LIFR through about 15Z, thereafter clearing out. Another round of showers and thunderstorms look to impact the southeast Wyoming sites by 00Z Saturday along with KBFF and KSNY by 03Z. Confidence is low, so introduced PROB30 groups. The main aviation hazards with this activity will be a reduction of VIS and/or CIGs down to MVFR, in addition these storms have the potential to bring gusty winds upwards of 30 knots.

CYS WATCHES/WARNINGS/ADVISORIES

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