textproduct: Cheyenne

KEY MESSAGES

- Warmer and drier this weekend with temperatures around 5 to 10 degrees above normal.

- A strong Pacific storm system will bring scattered showers and storms along with seasonably cool temperatures for the start to middle of next week, with a slow warming trend into the later part of the week.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 220 PM MDT Fri Sep 25 2026

While some cloud cover lingers this afternoon from the overnight low stratus and light shower activity, mostly in Laramie County and through the Nebraska Panhandle, new development of showers and weak storms is ongoing further west in our area. These lingering clouds along with some mixed layer stability are likely contributing to stout CIN values and preventing stronger convective development, but some meager instability alongside locally notable PWAT values nearing 1.0 inch should allow for some stronger showers and storms this evening, with heavy downpours likely the strongest threat though gusty and erratic winds cannot be ruled out as well.

As the shortwave inducing this activity passes through the region, we'll see drier and warmer southwesterly flow under ridging dominate through the early part of Sunday. Highs warm above normal as 850mb temperatures bounce back into the 25-27C range, keeping us in the 70's to 80's for both Saturday and Sunday. But skies won't be completely clear and we shouldn't be fully devoid of moisture as some upper level moisture does stream into the region, with surface level RH values remaining outside of critical thresholds in regards to fire weather concerns. Sunday should start off similarly warm and dry, but moisture will begin surging back in response to an approaching Pacific trough that will become the focal point moving into the long-term forecast. Isolated to scattered shower and thunderstorm chances return Sunday evening into the overnight period through Monday morning, but with moisture still rebounding and overall severe parameters lacking, most likely scenario right now is a few meager cells promoting localized rain and thunder, with the real show expected early next week as the Pacific trough fully moves into our region.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 220 PM MDT Fri Sep 25 2026

After a warm and largely dry weekend, the weather will turn more unsettled once again as we head into the early part of next week. We will have an interesting synoptic setup across the area, with the typical upper level ridge over the southern Plains, combined with an approaching Pacific trough. The wild-card factor here will be the potential for an infusion of an exceptionally moist airmass ahead of and associated with Hurricane Polo as it moves into Baja California early next week. Unfortunately for our area which remains in drought conditions, these factors do not look likely to align and produce heavy rainfall for our area. Instead, the Pacific trough is trending towards a split trough scenario. The northern branch will move through on Monday, leaving behind a closed low in the southwest, which eventually absorbs the remnants of Hurricane Polo. Moisture will be abundant by Monday, with PW values around the 90th to 99th percentile of climatology, but forcing and instability look unimpressive at this time as the core of the northern branch of the split trough passes to our north. Still, we should have enough to at least support scattered showers and possibly a few thunderstorms. Look for increased cloud cover and slightly cooler temperatures as a result, though highs should still be a touch above seasonal averages. A cool front with the northern branch system will knock temperatures down by about 5-10 degrees for Tuesday. A chance for showers remains in the forecast, but the most likely scenario at this time leaves the closed low, and thus the potential for widespread heavy rainfall, mainly to our south.

Heading into the middle of the week, the most likely scenario supported by about 80+% of ensemble members features seasonable temperatures and dry conditions as the upper level closed low spins to our south. Cloud cover may spill into our southern zones associated with the system to the south. While the probability of a different scenario is low, it is still worth a mention. In about 20% of ensemble members (and the AI-GFS), the closed low over the southwest lifts more to the north instead of the east, which would bring abundant wrap-around moisture into our High Plains zones Wednesday into early Thursday. Regardless of the precipitation potential, there is also a chance for some strong winds behind this system. The official forecast reflects the former scenario, which is far more likely at this time, but we can't quite rule out the latter just yet. After the closed low moves out, expect another warm-up beginning Thursday, and peaking on Friday.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 522 PM MDT Fri Sep 25 2026

Little change from the previous aviation forecast. Shower and storms are drifting east near KCYS. It is uncertain if any will directly impact this terminal, but prob30 was maintained here and KBFF. Showers could hold together to impact KAIA and KSNY later this evening. Overnight ceilings drop once again, particularly at KAIA and KSNY. Dense fog is not anticipated, but a brief reduction in visibility and ceilings could send these terminals into MVFR. The shortwave bringing the showers/storms will depart east and behind it dryer and windier conditions will improve conditions around 9-13z. An area of LLWS is possible for a few hours while it passes, but the area may be north of KCYS and west of KBFF. If trends are for it to become more widespread or cover a terminal the 6z TAFs will be updated accordingly. Clear to mostly clear skies are expected through the morning and afternoon hours.

CYS WATCHES/WARNINGS/ADVISORIES

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