Area Forecast Discussion

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.

- Much cooler temperatures expected to return on Sunday with cloudy skies and wetting rainfall expected for most locations.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 224 PM MDT Sat Sep 19 2026

A stormy Saturday is expected across the forecast area with showers and thunderstorms already appearing on radar early this afternoon. A potent upper-level closed low moving into Wyoming this afternoon will be the main driver of storms as it drags a weak surface front along with it. Ahead of the front, winds will shift more easterly in the Nebraska panhandle, allowing dewpoints to sustain in the 50s. Sunshine in the panhandle will help add to the instability, with model soundings actually showing impressive CAPE values for mid to late September. MUCAPE values will reach 1200 J/kg with good low- level shear. As a result, an isolated severe storm or two could be possible through this evening. Strong winds will likely be the main hazard, especially with Hi-Res guidance hinting at some bowing segments later this evening. But severe hail cannot be ruled out as storms initially start as discrete cells. As with the last few days, heavy rain and flash flooding are possible with PWATs above the 90th percentile for NAEFS climatology. Showers and storms will continue through the better part of the night, mainly for the Nebraska panhandle.

More of the same can be expected for Sunday. As the upper-level low tracks into eastern Wyoming, the surface low will follow with it. Models still are waffling back and forth with placement of the surface low, which will ultimately have an impact on which locations see more or less precipitation. Regardless, areas east of the Laramie Range and the Nebraska panhandle are most likely to see precipitation tomorrow. Storms could start as early as mid-morning, with strong to marginally severe storms possible in the Nebraska panhandle. The environment here will be able to hang on to instability throughout the night, so strong winds and hail will be possible. A stationary frontal boundary roughly along the Wyoming/Nebraska border will begin to pop off storms from converging winds on either side of the front during the morning hours. By the afternoon, the area will get in on some wrap around moisture, so scattered showers and storm will persist into the evening hours, but will be less intense and less numerous than the morning storms. PWATs will remain high in the morning, so heavy rain and flash flooding potential will be greatest before noon. A few showers could linger into the overnight hours, but should not cause any impacts.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 224 PM MDT Sat Sep 19 2026

The long term forecast is a little messy. The upper level low that gave us rain showers this weekend is expected to be pushing into the Northern Plains/Midwest by Monday. This will cause an area of high pressure to reside over the Intermountain West eventually building into more of a negatively canted ridge. Theres is also an area of high pressure that begins to form over the Great Lakes region as our former low pressure system enters the Northern plains causing a traffic jam over the east coast. This becomes our problem as the ridge builds over us it blocks the weak low pressure system off the west coast. Temperatures will start to climb at the 700mb level raising the temperature from 6C back to 12C thus raising our cool fall-like surface temps back into the more summer-ish 70's and 80's. This upper level low is depicted to sit and spin sending a little bit of moisture and some weak shortwaves through Wednesday night for some isolated to scattered thunderstorms and showers in the afternoon and evenings, but with the weak ridge and drier airmass moving over us this week. Don't expect to have strong thunderstorm or scattered heavy rainfall chances. By Thursday, the Intermountain west really locks into a dry southwest flow pulling dry area from the desert of California and Arizona.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1140 AM MDT Sat Sep 19 2026

Some light showers are starting to develop over the mountains south of KRWL pushing southeast and may be over KLAR in the next couple of hours. Some virga is currently pushing through KCYS and heading NNE. Stronger thunderstorms and showers are expected to develop this evening and prob30's were pushed back a couple hours for most sites. Expect overcast conditions tomorrow morning with the possibility of IFR conditions for the Panhandle sites by 12z as some patchy fog may form. Intermittent showers may also occur through the night but didn't have the TAF lines to convey all the possible timings.

CYS WATCHES / WARNINGS / ADVISORIES

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