textproduct: Cheyenne

KEY MESSAGES

- Chances for afternoon and evening thunderstorms continue until mid week. Strong gusty winds and brief heavy rainfall are the primary threats.

- A temporary drying trend begins Mid-week and possibly continues through the end of next week.

SHORT TERM /THROUGH MONDAY/

Issued at 235 PM MDT Sat Sep 5 2026

Not too many changes to the previous forecast package with shower and thunderstorms, some strong with heavy rainfall, remaining the primary concern today. Overall, strong upper level ridge axis is forecast to remain across the central Great Plains for much of the weekend. Fall-like upper level trough will meander its way across the Pacific NW coastline and move inland on Sunday. Ahead of this trough, some shortwave energy will eject northeast over Colorado and Wyoming along with a 100 knot jet max nudging east into the northern Front Range Sunday night and Monday. Generally expect a slow cooling trend Sunday and Monday as some cooler air makes its way into Central Wyoming. Further east, surface winds are expected to shift into the east or southeast, resulting in some upslope flow and minor cooling over mainly southeast Wyoming.

Shallow convection from this morning has lifted northeast of the area and dissipated. However, radar loop shows activity starting to fire up again over the northern and central Nebraska panhandle early this afternoon. Expect this trend to continue through late this evening as coverage is likely going to increase across the entire Nebraska Panhandle. Convective parameters look favorable for scattered to numerous showers and thunderstorms, which may linger past midnight across portions of the southern panhandle. Meso Analysis shows MLCAPE of 1000 to 2000 j/kg (slightly higher SB) over mostly western Nebraska, with values increasing a bit more through the afternoon as we near the peak heating of the day. Severe thunderstorm potential looks limited today, but can't rule out a few marginally severe multicell clusters developing into this evening. Main limiting factor is shear with 0-6km and overall effective shear around 20 to 25 knots, maybe up to 30 knots. Hodographs are fairly straight, with some curvature across the southern Panhandle this evening. Generally expect some very heavy rainfall with gusty winds as high res guidance shows clusters of thunderstorms forming and then building upshear into this evening. Can't totally rule out some hail producers (including large hail) in this area, but its not the most favorable environment this time of the year. There is some considerable concern for some areal flooding or localized flash flooding. Area of concern is not generally known for flash flooding issues however. Kept POP above 35 percent through midnight for Alliance, Sidney, and Kimball Nebraska.

Another warm day for Sunday, but not quite as warm as guidance suggests due to east to southeast upslope winds across the plains. Similar weather pattern during the day with even higher dewpoints due to some low level moisture advection. Model soundings show some lingering CIN in the low to midlevels on Sunday, likely due to the nocturnal convection early Sunday morning. Upper level shortwave/vort max is not as strong as today's forcing and arrives a bit later in the day, so expect more isolated coverage of thunderstorms. Shear looks even more marginal with around 20 knots of Bulk Shear by mid to late afternoon. A few strong thunderstorms are possible, but having a hard time with the severe potential with such limited 0-6 km shear. Further west, may say some gusty winds associated with shower and isolated thunderstorm activity as the leading edge of the Pacific cold front and jet max aloft moves into central Wyoming by late Sunday evening. Increased POP across the whole area, but mainly for later in the day (after 6 PM) due to the better forcing.

Drier air forecast to push into the area on Monday behind the front with some cooler air. Expect a lower coverage of thunderstorms, mainly located south along the I-80 corridor and the mountains. High temperatures in the mid 70s to mid 80s are expected for most of southeast Wyoming, with highs in the low 90s for western Nebraska. It will be windy during the day with southwest winds between 25 to 35 MPH with gusts around 45 MPH likely along and west of Interstate 25.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Issued at 200 PM MDT Sat Sep 5 2026

The very persistent low pressure system loitering in the Pacific Northwest will finally be ejecting eastward on Monday and Tuesday. The models are trending towards a slightly more eastward and amplified evolution of this low's passage, possibly influenced by a stronger shortwave just ahead of it. Moisture content ahead of this system seems to be on track with previous forecasts. PWAT values are running about 2 to 3 standard deviations above climatology. The few CAMs that go out to Monday evening do not show much in the way of rainfall with most of the synoptic forcing staying well north of the area. Regardless a few showers and storms from the afternoon will linger through the early evening. Tuesday the western most lobe of the upper level system will swing southeast to pass just north of our area. With it a weak cold front will pass through. There is enough moisture ahead of the front that a few storms are possible, particularly for the southern NE Panhandle areas. No severe weather is anticipated at this time for this round of storms before they depart to our east. The front should cut afternoon highs by about 5 degrees, so that is nice. What isn't nice are the low humidity and gusty winds behind it which could elevate fire weather conditions.

Post cold front Wednesday is also slightly cooler and drier. The ridge that has been patiently waiting for its chance to build back west will do so by Thursday. Downsloping flow from the Intermountain West will act to heat us back up and keep us dry. Continued gusty winds does mean fire weather will be the topic of upcoming forecast. The type of pattern will continue until our next Pacific upper level system arrives in the very long term, hopefully with more rain.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1123 AM MDT Sat Sep 5 2026

Scattered thunderstorms are anticipated for the Nebraska Panhandle terminals this afternoon and evening as a complex of storms develops from north to southeast. Storms will be capable of producing variable wind gusts to 50 knots, lightning, and reduced vis from heavy rain, down to 2SM. The earliest onset is around 20z at KBFF and KCDR and ending around 06z at KSNY. At KLAR and KCYS the chances of storms is slightly lower, but the latest high resolution model guidance does support at least a few showers and storms in the vicinity. VFR conditions outside of this storm activity at terminals through the rest of the forecast period, though lowered CIGs behind storms may occur. Breezy conditions at KRWL possible to 35 knots out of the southwest this afternoon. Highly variable wind directions possible post storms and during the overnight hours at KCDR, KBFF, KAIA, and KSNY.

CYS WATCHES/WARNINGS/ADVISORIES

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