textproduct: Cheyenne

KEY MESSAGES

- Widely, scattered showers and isolated thunderstorms in the afternoon and evening will bring the potential for localized strong gusty winds Monday and little to no rainfall.

- Near record high temperatures possible Monday afternoon, mainly across western Nebraska with highs around 90 degrees.

- A stormier weather pattern will setup on Wednesday and continue through the remainder of the week with daily chances for PM showers and thunderstorms.

- Increasing potential for strong to severe thunderstorms is being monitored middle to late in the week.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 1250 PM MDT Mon May 25 2026

We remain under a ridge downstream of an open wave located over the Desert Southwest, resulting in hot and mostly dry conditions. A typical diurnal warm season pattern is in store for this Memorial Day, with high-based cumulus developing over the higher terrain and eventually developing/pushing further east over lower elevations. These should rapidly dissipate after sunset given the loss of daytime heating. Latest visible satellite imagery is already showing deepening convection over Carbon County and the Laramie Range, with radar imagery also showing some weak returns aloft. Given 850-300 mb mean winds of just 5-10 knots per SPC Mesoscale Analysis, expect these showers (and perhaps a lightning strike or two) to primarily remain over the higher terrain especially given the lack of any large-scale forcing for ascent. However, a few collapsing showers may be able to drift onto lower elevations which will bring a threat of erratic and gusty winds at the surface, rather than any meaningful rainfall. This is confirmed via forecast soundings which illustrate inverted-v profiles with surface dewpoint depressions of 40-50 degrees along with skinny MLCAPE of 300-400 J/Kg rooted around 600 mb. Given the ridging, 700 mb temperatures near 10 degC, and WSW flow aloft, can expect high temperatures to reach 10-15 degrees above average today (average high for Cheyenne today is 68 degrees), with upper 70s and low 80s west of the I-25 corridor, and 80s and even a few 90s for our Nebraska counties, which will fall just short of record high temperatures. As for fire concerns, any dry lightning will need to be monitored for our Nebraska counties considering median RH values around 15%, however with maximum wind gusts around 15 mph and some recent rainfall, decided to leave out any fire weather highlights at this time.

Tonight we will remain dry and mild, especially for our Nebraska counties which will experience breezy conditions of 15-20 knot gusts and partly cloudy skies, therefore limiting radiative cooling. Low temperatures may not dip below 55 degrees, which is impressive considering climatological lows for the Nebraska Panhandle are around 45 degrees.

On Tuesday, the ridge axis shifts east over the Dakotas and Southeastern Wyoming/Western Nebraska, with a closed 500 mb low located to our west over Southern Oregon and Northern California. As the primary vorticity maximum is located to the west of the shortwave trough axis (and hence vorticity advection), this closed system should dig well to our south over California and Nevada into the middle of the week. However precipitation chances look to be relatively low on Tuesday and just slightly greater than today, with high- based convection being confined to the higher terrain. With the help of SSE flow mid-level flow, hi-res ensemble guidance has PWAT values increasing to the 90-95th percentile relative to climatology over our Wyoming counties, so we may (emphasis on the may) be able to squeeze out slightly more rainfall out of any showers and storms, although forecast soundings continue to show LCLs of 2-3 km, so gusty winds will be the main story with these. Again, with the lack of any synoptic-scale forcing for ascent over our area with the closed low located well to our west, storm coverage is expected to be primarily driven by differential heating of the elevated terrain. Breezy conditions on Tuesday night will again keep overnight lows mild, with lows in the 50s for the Nebraska Panhandle and in the 40s for Southeastern Wyoming.

LONG TERM /WEDNESDAY THROUGH MONDAY/

Issued at 1250 PM MDT Mon May 25 2026

For mid to late week, eastern Wyo and western Neb sit between the large closed low anchored near the Great Basin and the amplified ridge over the Great Plains. Low level and upper flow will primarily be south/southeasterly through the extended period for the forecast area. This pattern will maintain near to slightly above normal temperatures (highs in the 70s and 80s) and periodic precipitation chances. While the near surface flow will not be uninhibited from the Gulf, dew points will remain around 50F east of I-25 through the workweek, which can be sufficient for thunderstorm activity. The core of the upper dynamics remain west of the immediate region, but large scale ascent should extend downstream from the main low and influence the southern Wyo ranges and adjacent areas. Perhaps the greatest potential for widespread moisture comes Wednesday as a mid- level shortwave traverses the High Plains. Thunderstorm activity should increase through the afternoon, taking advantage of elevated instability/lift and a ribbon of moisture. Thunder parameters don't appear to support severe weather at this time, as overall CAPE is limited and deep layer shear is weak. Friday could be a different story, however. The upper jet swings a bit to the east, placing the panhandle in the sweet spot for increased lift. A surface low also emerges from the northern Rockies, along with a notable change in low level moisture flux over the Plains. Early indications reveal very steep lapse rates (~9C/km) and sufficient CAPE (1000+ MU j/kg) over the panhandle. Will need to continue to monitor later forecast trends regarding severe potential during the afternoon and evening. Some mechanisms remain in place over the weekend, so will hold status quo for chance PoP and seasonable temps.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 549 PM MDT Mon May 25 2026

VFR will remain in place through 00Z Wednesday, with winds being the primary concern for all terminals except for KRWL. Diurnal convection should begin to wind down shortly after sunset with the exception of KSNY which may see lingering convection move up from Colorado colocated with 850 mb theta-e advection associated with a 35 knot low-level jet, hence the TEMPO group until 04Z. Expect SE winds to increase after 16Z in response to lee cyclogenesis occurring to our north over Eastern Montana, resulting in strong gradient flow. Can expect gusts as high as 40 knots particularly for the Nebraska terminals, with sustained winds around 25 knots. Similar to today, another round of high-based showers and thunderstorms is anticipated after 18Z tomorrow, which will likely produce more rain than wind.

CYS WATCHES/WARNINGS/ADVISORIES

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