textproduct: Cheyenne

KEY MESSAGES

- Chances for afternoon and evening thunderstorms continue until mid week.

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

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 409 AM MDT Sat Sep 5 2026

A deepening upper level low is pushing into the Pacific NW near the border of California and Oregon. This upper level low will help feed moisture into the Intermountain West. The model soundings show the Intermountain West classic inverted V sounding. With the improving the surface moisture will slowly increase however, gusty showers will always be a possibility as this region is not known for having saturated soundings like in the southern United States. DCAPE is roughly 1500-1900 joules with MUCAPE of 1500-2000 joules to match. The upper level low will send a shortwave through this region this afternoon and evening. There is a pretty strong CAPE in the morning and a convective temperature in the upper 80's to low 90's across the forecast area. Hi-res guidance shows the showers happening in two phases. The first phase is light showers along the WY/NE border between the 15-18z. This phase has low confidence because there is a lot of CIN in the morning and we won't have the diurnal heating to erode the Cap like we would have at around 21z or 3pm today. Which is the timing of the second phase. The HRRR, NAM Nest, and the RRFS initiate convection at this time. However, the initiate it all in different places. The HRRR has the most northern track with storms popping off around the Scotts Bluff, Box Butte, Morrill county intersection and quickly pushing east. NAM nest has the storms starting in Logan/Sedgwick/Phillips county area in Colorado and moved into Cheyenne county then the storms quickly move out of my area and into Garden county. The RRFS-MPAS version is a blend of the of the two previous models with a cluster of storms starting near the eastern edge of Morrill/Cheyenne county along with other storms in the cluster of Colorado counties near the Wyoming/NE border. Looking at the GFS and Euro, they depict a stream of strong vorticity stretching from Weld county to Goshen county that pushes eastward. This stream of vorticity may be the key to helping our storms busting through the cap. SPC has highlighted the Nebraska Panhandle with a Marginal Risk for severe thunderstorms today. The main threats with these storms would be wind gusts up to 60 mph and hail up to 1 inch. The hail size may be more up to ping pong balls or 1.5 inches if a thunderstorm can sustain itself. The effective shear looks to be around 24 knots with the overall bulk shear of 30- 40kts which may end up getting the job done. We start to lose most of our synoptic forcing between 06-09z and most of the high-res models have those storms just east of our forecast area so not really expecting lingering overnight showers but we may have storms continue into the night. Sunday, that upper level low slowly pushes against our ridge creating a slight tightening of the height gradient for a breezy afternoon and evening. With the continual feeding of moisture there will be a little bit more moisture for storms to utilize. Otherwise it's pretty much a cut, copy, paste of Saturday afternoon. The bulk shear will remain about 30-40 knots with Vort-maxes as the primary means for synoptic lift. The difference is the CAPE values really start to die off as the sun goes down and the stronger CAPE values become located in South Dakota by the evening instead of the Nebraska panhandle. Also the expected initiation location is also further west starting in Platte, Goshen, and Eastern Laramie county. SPC also draws the marginal for tomorrow in these locations as well. Again it will be for hail and wind. Honestly in our neck of the woods, the wind component is almost always a safe bet. The hail is kind of hit or miss with either we get large hail or accumulating pea size hail. So we have a fun weekend to look forward to. The daily high temperatures will be in the 80's and 90's this weekend as 700mb temperatures remain between 15 and 17C. The overnight temperatures will also continue to be in the 50's and 60's making the nightly experience rather enjoyable if its not storming over you.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 409 AM MDT Sat Sep 5 2026

Our upper level ridge starts to break down as the Low continues to push inward from the Pacific Northwest. The low starts to move northward over our ridge as it moves into Montana/Canadian Providences to the north of us. This low will continue to push shortwaves through our region Monday and Tuesday for afternoon and evening showers. The ridge starts to build back over us Wednesday and THursday starting a drying period as we go into a more westerly downsloping flow. The global models show the upper level low over the hudson bay area at this time which is far enough east to not influence the weather pattern over us. However, each of the global models do want to bring in another system into the Pacific Northwest at the end of the week so more precipitation may be on the way next weekend we just will have to wait to see how the models trend.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 511 AM MDT Sat Sep 5 2026

VFR conditions will technically prevail when considering ceilings and visibility requirements. However, high-based thunderstorms will be most likely between 23z and 05z for KBFF, KSNY, and possibly KAIA. KCDR looks to sit out on this day for once. Showers look possible for KLAR and KCYS between 22z and 01z. Some of the HI-res models even keep storms over KSNY until 0800z. The estimated visibility may be below 3sm briefly with some of the stronger storms but generally should stay between 4 and 6sm. Most likely threats from these storms are wind guts 60mph and greater along with hail possible up to 1.5 inches or ping pong balls.

CYS WATCHES/WARNINGS/ADVISORIES

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