textproduct: Cheyenne

KEY MESSAGES

- Another round of thunderstorms will bring the potential for localized flash flooding and isolated strong to severe thunderstorms this afternoon and evening, mainly in Laramie County and the southern Nebraska panhandle.

- Unsettled weather continues through at least Sunday, bringing cooler than average temperatures and daily chances for showers and thunderstorms.

- Isolated strong to severe storms and localized flash flooding will remain possible through Sunday.

- Drier weather and temperatures close to seasonal averages will return early next week.

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 220 PM MDT Fri Aug 14 2026

Active weather continues across the area as plentiful monsoon moisture flows across the area. Yesterday's shortwave trough passed through the area early this morning and brought a slightly drier airmass into the area, but total precipitable water still remains above the climatological 90th percentile over the High Plains. Values over 1 inch are pushed up against the Laramie Range, increasing eastward to between 1.3 and 1.5 inches in our far eastern zones. Overall forcing is weaker today than yesterday, but we still have a more localized area of ascent which will support storms, just not quite as widespread as yesterday. Warm air advection in the middle atmosphere is moving overtop a stalled low-level convergence boundary in Laramie county, which will be the primary focus for convective initiation today. Radar echoes are already going up at the time of this writing, and expect this to continue and grow upscale over the next few hours. Today's event is expected to evolve with continued development in Laramie County, then spreading eastward into the southern Nebraska panhandle later this afternoon and through the evening. Outside of these areas, isolated storms are still possible, but today's threat is fairly localized. Convective parameters are again marginally supportive for a few strong to severe thunderstorms along the I-80 corridor region. MLCAPE ranges from around 1000 J/kg in Laramie County up to closer to 2000 J/kg in Cheyenne county. Lapse rates are still fairly unimpressive, but are steeper than yesterday. Vertical wind shear is still marginal, but sufficient for a few strong to severe thunderstorms at around 25 to 35 knots. The primary concern today remains heavy rainfall and flash flooding, especially considering potential for back-building / training thunderstorms and storms moving over the same areas that received heavy rainfall yesterday. As a result, another Flood Watch has been issued, and remains in effect until 10PM this evening. Isolated strong, gusty winds and hail will be possible with these storms. We will also need to watch for accumulating hail. Expect most activity to be gone by around 9 to 10 PM. A few showers and maybe some rumbles of thunder will linger along and west of the Laramie range through much of the night. Low end PoPs are maintained. In addition, the NBM remains much too cold for overnight lows as it has through most of this monsoon surge, so increased overnight lows once again.

Looking ahead to Saturday, we will have another stormy day on tap as southwest flow aloft continues to advect in deep monsoon moisture. Precipitable water will remain quite high, around the 90th percentile. A shortwave trough aloft is expected to pull out of the southwest and move across the area, which will provide better forcing for lift while also increasing the wind speeds in the middle to upper atmosphere. With stronger vertical wind shear than the last few days, our severe weather threat will tick up somewhat tomorrow. In addition, the broader synoptic forcing will lead to scattered to numerous showers and thunderstorms kicking up over the extent of the Laramie Range, and moving off to the east and northeast. It may be a fairly long evening tomorrow, with storms kicking up early afternoon, and possibly a second round initiating in the middle evening hours as a secondary wave aloft brings some isentropic lift in late.

LONG TERM /SUNDAY THROUGH FRIDAY/

Issued at 220 PM MDT Fri Aug 14 2026

Sunday...Ridging becomes a bit more pronounced over Wyoming, producing warmer temperatures aloft which will tend to limit areal coverage of showers and thunderstorms, compared to Saturday. Nevertheless though, the monsoonal moisture will stretch from central Colorado through far eastern Wyoming and western Nebraska, where isolated to scattered showers and thunderstorms will occur in the afternoon and evening. Slightly warmer, but comfortable, temperatures are anticipated for this time in August.

Monday...A drier pattern ensues and is on tap as the flow aloft turns west northwest and the precipitable water values decrease, due to drying at low and mid levels and downslope southwest winds near the surface. Thus, a much drier day when compared to the weekend. A warming trend begins with more sunshine and warmer mid level temperatures near 17C at 700 mb.

Tuesday...Brisk northwest flow aloft prevails, and with a decent amount of low and mid level moisture availability as seen in the 12Z GFS run, expect isolated to widely scattered late day showers and thunderstorms, mainly east of Interstate 25 and the Laramie Range during the afternoon, with coverage everywhere in the evening. Similar maximum temperatures to Monday based on 700 mb temperatures.

Wednesday...The synoptic pattern looks more like September and early autumn with a deep shortwave trough aloft sweeping across the Dakotas into western Minnesota by evening, with a much cooler airmass moving southward across the northern Rockies, as well as the northern and central Great Plains, including the Dakotas and much of Nebraska behind a cold front. Maximum temperatures for our neck of the woods will be quite comfortable with readings in the mid 70s to lower 80s, perhaps even cooler than this if the Canadian cool surge lies further west. From experience, and from the model trends, this type of cold frontal passage is typically mostly dry for our forecast area, and for consistency sake, and matching up with our neighboring offices, we will continue with scattered showers and thunderstorms in the afternoon and evening for now, though suspect that later shifts will see far less POPS as models come to more congruency and consistency.

Thursday-Friday...Models suggest a return to bone dry and hotter conditions as the ridge aloft transitions across the northern and central Rockies and our counties. 700 mb temperatures rise from near 14C at 00Z/Friday to 18Z at 00Z/Saturday yielding maximum temperatures mainly in the 80s for Thursday, with some 5 to 10 degrees of warming for Friday. Another hot and dry period, stretching into the weekend,is on tap.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 520 PM MDT Fri Aug 14 2026

Showers and thunderstorms are rolling through and will impact KCYS, KBFF, KAIA, and KSNY this afternoon hours into the early evening. Thereafter, around 03Z, things should begin to wind down as the activity shifts off to the east. The primary hazard will be very heavy rainfall producing IFR to LIFR VIS, but there is also the possibility for frequent lightning, gusty winds, and small hail. Be alert for possible AMDs through the afternoon and evening as things evolve. Across the Nebraska Panhandle, after said activity exits, VIS reductions are possible at all the terminals between 08Z and 15Z. Then, conditions will trend towards VFR sometime after 15z Saturday before another round of activity moves back in.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Flood Watch until 10 PM MDT this evening for WYZ117>119. NE...Flood Watch until 10 PM MDT this evening for NEZ020-021-054- 055.