textproduct: Cheyenne

KEY MESSAGES

- A messy pattern is anticipated today through much of the upcoming week, allowing for ongoing precipitation chances across the entire CWA. The best chance for precipitation will be Monday night, with widespread rain and snow showers.

- A Winter Weather Advisory has been issued for the Sierra Madre and Snowy Ranges from 6PM Saturday through 6AM Monday.

- The messy, upper-level pattern continues mid-week through at least Friday before weak riding returns for the weekend.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 340 AM MDT Mon Apr 27 2026

The early morning areas of fog should be clearing up from west to east this early morning, but a few areas could be stubborn in valley areas through daybreak. A weak backdoor cold front is moving in which is dry out the area slightly and shifting winds out of the northwest. Some snow showers are occurring this morning in the northern CWA with rain/snow mix extending elsewhere. Most places will only see a dusting from this activity, though amounts up to about half an inch may be possible in Converse and Niobrara Counties. The Sierra Madre and Snowy ranges will be the exception where another 1 or 2" may be possible before noon. This shower activity will start to diminish as we go into the afternoon hours and the shortwave disturbance departs to the east. Breaks in cloud coverage may allow just enough instability in the afternoon to produce scattered shower and storm activity west of the Laramie Range. Hi-res guidance suggests that CAPE values will not be quite as high as they were yesterday. Still, a few of the stronger updrafts could produce gusty downdrafts and lightning. Highs today will be cool, reaching the 40s in our northern counties and the interior mountain basins. Low 50s for the Cheyenne Ridge and North Platte River Valley.

This evening and overnight, yet another shortwave moves in giving us a round of rain and snow. This activity will begin in the southwestern counties around 5 or 6 PM and spread northeast through the night. Rain amounts should be below half an inch at most locations. The Snowy and Sierra Madre Mountains may pick up amounts between 5-10 inches, with higher amounts. Therefore, a second winter weather advisory is in effect for this period of snowfall. Some high resolution models are depicting a swath of higher amounts for the central and northern Laramie Range, extending into Converse and Niobrara Counties. The confidence is low in this solution at this time, but we may need to revisit snowfall amounts in these areas if confidence increases later today. This disturbance moves east throughout the day and by the afternoon only a few lingering showers should be around. Conditions dry overnight with the downsloping winds. A subtle upper-level ridge begins to nose its way into the area going into the day Wednesday, keep things dry and cool to start the morning.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

Issued at 340 AM MDT Mon Apr 27 2026

Largely zonal upper-level flow is anticipated to return Wednesday through Thursday as the broad upper-level low over southern Canada moves to the east as a shortwave develops across Idaho. Ahead of the incoming shortwave trough, westerly flow will dominate aloft with a strong subtropical jet just south of the Wyoming/Colorado border. The shortwave trough remains fairly broad before slowly becoming more defined throughout Wednesday evening into the overnight hours. Weak 500mb vorticity will eject out ahead of the approaching shortwave leading to modest synoptic support for ascent across the region, though weak 500mb flow is expected. Westerly flow at 700mb will slowly turn northwesterly through the afternoon hours before becoming fairly light and variable as height gradients remain weak. Weak warm air advection (WAA) is anticipated for Wednesday afternoon as 700mb temperatures warm from about -3C to around 0C. This weak, WAA at 700mb will support some ascent across the region with isolated to scattered showers to develop Wednesday afternoon. Primarily rain is expected east of the Laramie Range where the best 700mb WAA is occurring and surface temperatures warm into the mid-50s to mid-60s, while snow is expected west of the Laramie Range during the morning hours before transitioning to rain/snow mix where weaker 700mb WAA is anticipated and surface temperatures struggle to reach the 50F mark. Significant precipitation accumulation is not expected with this system due to the average Precipitable Water values for this time of year and overall weak forcing across the area. However, another trace to 0.1 inches of precipitation will be possible Wednesday afternoon through early Thursday morning, with only a trace of snow accumulating west of the Laramie Range and 2 to 4 inches of snow accumulation in the mountains.

Precipitation chances will continue Thursday with the development of the upper-level shortwave, but the upper-level pattern becomes quite messy into Thursday afternoon. The upper-level shortwave will deepen across the Intermountain West through early Friday morning, but strong 500mb cyclonic vorticity advection (CVA) northeast of the base of the shortwave will act to accelerate the northern portion of the low, with the southern portion staying steady. The northern portion of the low looks to pinch together, resulting in the shortwave weakening significantly as the atmosphere attempts to reorganize after the trough gets pinched off. Both the GFS and ECMWF suggest this messy upper-level flow for Friday into Saturday, with a broad, weaker shortwave trough developing Friday evening and starting to advect off to the east. This increases confidence in a messy upper-level pattern dominating the mid-week weather. Luckily, with the messy disturbances aloft, synoptic support for ascent will continue throughout mid-week, enabling precipitation chances to continue. Precipitation chances start to taper off on Friday as the upper-level shortwave finally moves east of the region and a ridge develops across much of the Intermountain West. 700mb flow will remain messy through the middle of the week and into the weekend ahead of the ridge developing early Saturday morning. Another system attempts to move into the western CONUS Saturday afternoon in the GFS, but significant disagreement is present between long range models. Therefore, forecast uncertainty increases through the weekend.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1130 AM MDT Mon Apr 27 2026

Tricky forecast for this TAF period with varying CIGs and VIS, wind speed and direction changes, also precip type and timing. So, this afternoon expect the beginning of isolated to scattered snow showers, rain showers, and/or the possibility of a few thunderstorms, best chances at KRWL, KLAR, and KCYS. As temperatures cool this evening, precipitation will make the transition to all snow along with FG developing. By 13Z Tuesday, weather conditions will improve ever so slightly across the southeast Wyoming terminals and around 15Z for the Nebraska sites.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Winter Weather Advisory from 3 PM this afternoon to 3 PM MDT Tuesday for WYZ112-114. NE...None.