textproduct: Western and Central Wyoming

KEY MESSAGES

- Showers and thunderstorms continue for eastern portions of the area today, with locally heavy rain and flooding possible.

- Drying out across the western half of the area, with only a small chance of an afternoon shower or thunderstorm.

- Other than a chance of showers and thunderstorms Tuesday night into Wednesday, mainly dry weather is expected next week with above normal temperatures.

DISCUSSION

Issued at 237 AM MDT Sun Sep 20 2026

Rain continues to be ongoing across portions of the area, mainly central Wyoming as low pressure continues to move across the area, It is now fairly close to our office just after midnight with moisture wrapping back into the Wind River Basin. Some area had a lot of rain yesterday afternoon and evening, with some street flooding in Lander. Most of the convective rain is done now, it now mainly of the stratiform variety. The main area of rain will continue move slowly east through the night and into tomorrow with gradually drying as the low tracks to the east. We will still have the chance of some flooding today as well, especially later in the day if there is some destabilization of the atmosphere to get some thunderstorms to fire. However, the impacted area will be more restricted. Precipitable water values remain over 150 percent of normal along and East of the Bighorns. So, we will maintain the flood watch here for the rest of the day. Across the western zones, with the deeper moisture moving away, we will cancel the watch with issuance this morning. There will be enough moisture for isolated showers and storms to fire back into the Basins East of the Divide and the adjacent mountains, but coverage looks rather sparse (generally less than a 1 out of 3 chance). Showers should gradually end this evening across the eastern zones this evening with all areas dry by midnight. Some locations in Johnson and Natrona Counties could pick up 0.75 to 1.50 inches of additional rain today, especially where storms persist. However, not all areas will see heavy rain.

Once we get past this evening, it looks like we will enter a quieter pattern. Monday looks like a nice last day of astronomical summer for 95 percent of the area with near normal temperatures and a sunny to partly cloudy sky. There may be just enough moisture leftover for an isolated, and this means isolated with a capital I, shower or thunderstorm in and near the mountains East of the Divide. The chance is at most 1 out of 6 though, and nothing strong is expected. The only fly in the ointment is an upper level low moving northeastward from the Desert Southwest that will open into a trough and pass through Tuesday afternoon through Wednesday morning. The GFS has trended toward the European, so the chance of showers and maybe a few thunderstorms looks better. This system is a fast mover so no heavy rain or flooding is expected out of it at this time. Any precipitation from this system should clear the area by sunset on Wednesday. Following that, ridging should build across the area and bring dry weather for the rest of the workweek and possibly into the start of next weekend. And with generally southwest flow across the area, temperatures should average above normal, in some cases well above normal. Some of the warmer spots may see highs in the mid or even the upper 80s from Thursday through Saturday.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 951 PM MDT Sat Sep 19 2026

Areas of rain and isolated thunderstorms continue tonight east of the Continental Divide, mainly from KLND and KRIW to KCPR. Conditions will drop to MVFR/IFR when showers and storms impact terminals. Rain will continue east of the Continental Divide through Sunday afternoon and mainly impacting only KCPR beyond Sunday morning as the weather system pushes east into the Plains. Low clouds are likely (70%) east of the Continental Divide tonight into Sunday morning, with prevailing MVFR conditions in general. Skies should mostly clear out west of the Continental Divide tonight, which will allow for fog development, especially where rain fell today. The best chance will be at KBPI and KPNA with mentions of VCFG and SCT001 at this time. Confidence in prevailing Fog remains too low (30%) to include in the TAFs at this time.

Wind will average 5-10 knots through the TAF period, with gusts up to 20 knots at KCPR Sunday afternoon. Mountain obscuration will improve across the west tonight as clouds clear out and deteriorate east as low clouds develop overnight.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts.

RIW WATCHES/WARNINGS/ADVISORIES

Flood Watch through this afternoon for WYZ007>011.