textproduct: Cheyenne

KEY MESSAGES

- Slight risk of severe weather Wednesday as monsoonal moisture flows into the region. Showers and thunderstorms continue on Thursday but severe risk will decline and move southeast.

- Warm again today but cooler than the start of the week, with much cooler temperatures through the weekend.

- Warming trend early next week may bring us back to near normal late summer warmth.

SHORT TERM /THROUGH FRIDAY/

Issued at 230 AM MDT Wed Aug 12 2026

Monsoonal moisture will now move into the region as we undergo a pattern change bringing daily chances of showers and thunderstorms for our entire CWA alongside an initial risk of severe weather, followed by an increased flooding risk. This morning the upper level ridge that has been controlling our weather pattern will begin shifting eastwards, turning our flow aloft to southwesterly and allowing much needed moisture to begin infiltrating our area. At the surface, a backdoor cold front will slowly descend across the area through the day, allowing flow behind it to shift to southerly to southeasterly and aiding in moisture return at the surface. This front will lead to cooler temperatures during the later half of the week and into the weekend, but for today we will get one more round of above normal. While not as hot as the past several days, highs will range in the 80's to 90's, which is around 3-6 degrees above average. Meanwhile, storm initiation is expected from both this boundary and upslope flow beginning as early as late this morning and continuing into the evening hours. Steep lapse rates of 8-10 C/km alongside MUCAPE of 1000-1500 J/kg west of the I-25 corridor and some patchy bulk shear in the neighborhood of 20-40 knots could support stronger initial supercells or clusters capable of large hail and damaging wind gusts. The problem will be the continued use of the atmosphere and numerous showers and storms streaming into the region through the afternoon hours. This activity will likely use up these favorable parameters and by the evening hours expecting storms to relax and become sub-severe as widespread rainfall becomes the dominant concern. PWAT values will rise considerably, and by this evening we'll be looking at values between 1-1.6", roughly 150-175% of normal on average. The NBM paints a 20-60% probability of 0.5"+ of new rainfall, heaviest in the Nebraska Panhandle. Now while not an absolute soaker of a day, our incredibly dry ground can present a concern for being hydrophobic, and if we get any training storms of heavier downpours from stronger activity, then storms will have a marginal risk of flooding.

Moving into Thursday our risk primarily shifts from severe weather to flooding. While not completely gone, our severe risk will be mostly relegated to Laramie County through the southern Nebraska Panhandle. CAMs develop a fresh batch of convection during the afternoon into the early evening across this area that could take advantage of modest instability and decent wind shear, creating another risk of large hail and damaging wind gusts for the day. Otherwise, precipitation totals should jump up notably today as moisture hits its peak for this event. PWAT values are expected to rise to 160-180% of normal by the evening, with the NBM up to a 25-50% probability of 1" or more of new rainfall for the day, this time highest across the I-25 corridor south of Douglas. Once again any stronger storms or training rainfall alongside ground that may become saturated could lead to an increased flooding threat, with a slight risk overall expected across our entire CWA. Finally, the first notable cooldown from the summer will occur as temperatures bottom out in the mid 70's to low 80's for the day thanks to the cold front and widespread cloud cover.

Friday however we may get enough clearing east of the I-25 corridor that temperatures will jump up just a tad for the day. Highs are still expected to sit in the mid to upper 70's for our western zones outside of the mountains, but widespread low to upper 80's should occur east of the mountains. But that's not to say our precipitation chances are done yet, as another round of of showers and thunderstorms will occur during the afternoon and into the evening. PWAT values do drop back down to around 130-150% of normal, still higher than normal though, and this activity could once again fuel a flooding risk. With the most likely area for stronger or multiple rounds of storms being Laramie County through the southern Nebraska Panhandle again, a slight risk for flooding is yet again expected for this area, while a widespread marginal risk elsewhere is anticipated. The best parameters for severe activity will also drift a bit further southeastward from our area, allowing a potential reprieve from stronger activity (though never ruling it out with how this region likes to over perform!) Overall though we'll finally see beneficial moisture, and precipitation chances should linger into the weekend, hopefully making at least a small dent into this potent drought.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

Issued at 103 PM MDT Tue Aug 11 2026

Thursday evening starts off this long term period with monsoonal moisture moving in, and a shortwave moving through the area. With precipitable water values in the 1-1.5 range, RH values 60-90%, and the shortwave, its safe to say our area will be getting some much needed moisture. This moisture sticks around through Monday, bringing daily afternoon chances of precipitation. This precipitation looks to mainly be showers, but an isolated thunderstorm cannot be ruled out especially near the NE panhandle with CAPE values near 1000J/kg. Winds do not appear to be out of the ordinary, staying below 15 knots most of the time. Temperatures cool off as a cold front moves over the area Thursday. 700mb temperatures stay near 12C during the daytime Thursday-Sunday, with nighttime temperatures getting near 10C. This means temperatures will cool off nearly 20F from what we have been experiencing. Typically our area has daytime temperatures near 83F this time of year. This is a welcomed break from our hot temperatures the last few weeks. With all of this monsoonal moisture coming in, fire weather is not a concern through this long term period.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1138 AM MDT Wed Aug 12 2026

West southwest flow aloft will continue, while a shortwave trough aloft moves from north central Wyoming at midday to northwest South Dakota this evening. Meanwhile, at the surface, low pressure will deepen across eastern Colorado with a few low level convergence axises developing across southeast Wyoming and western Nebraska. Isolated to scattered thunderstorms will develop across southeast Wyoming this afternoon and develop and propagate eastward across western Nebraska this evening. Some of the storms across the eastern tier of southeast Wyoming counties and the Nebraska Panhandle, will become strong to severe this afternoon and evening.

Wyoming TAFS...Inherited TAFS from our midnight shift forecaster were in good shape, with only some minor tweeks needed. Based on the 12Z NAM and the consistent runs of the HRRR, high confidence in isolated to scattered thunderstorms developing mainly east of a Rawlins to Lusk line through 21Z, with storms intensifying from 21Z to 00Z along and east of a Lusk to Cheyenne line, and ending by 01Z, before more isolated to scattered showers and a few thunderstorms occur this evening. Thunderstorms will produce erratic winds and gusts up to 40 knots, with a few storms from Lusk to Cheyenne possibly seeing higher wind gusts. Storms will produce occasional MVFR, otherwise VFR prevails. Widespread MVFR ceilings and visibilities due to fog will develop from 08Z to 15Z along and east of Interstate 25. Typically gusty diurnal winds to near 30 knots will occur until sunset.

Nebraska TAFS...Inherited TAFS from our midnight shift forecaster were in decent shape, thus only some minor tweeks needed. Using the 12Z NAM and the consistent past few runs of the HRRR, high confidence in isolated to scattered thunderstorms developing along the Wyoming-Nebraska state line around 20-22Z and strengthening and propagating eastward across the panhandle well into the evening hours. Some of the storms will become strong to severe this afternoon and evening, producing erratic winds gusting up to 45 knots, with a few storms, most likely across the northern Panhandle, producing winds gusts in excess of 50 knots along with some hail of one inch diameter or larger, along with locally heavy rain. The strongest storms will produce localized MVFR ceilings and visibilities this evening. Widespread IFR and MVFR ceilings due to low clouds and fog will form from roughly 06Z to 15Z. Typically gusty diurnal winds to near 25 knots expected until sunset.

CYS WATCHES/WARNINGS/ADVISORIES

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