textproduct: Cheyenne

KEY MESSAGES

- Winter Weather Advisories have been issued for the Sierra Madre, Snowy, and North Laramie Ranges, as well as the I-80 Summit today and tonight through 5 PM Tuesday.

- Isolated to scattered showers and thunderstorms possible today with above average temperature and moisture present.

- Another round of accumulating snow is expected Thursday morning through Saturday morning. Exact accumulations uncertain at this time.

- Upper-level blocking pattern may start this weekend, leading to the potential for multiple rounds of precipitation across the region.

SHORT TERM /THROUGH THURSDAY/

Issued at 221 AM MST Mon Mar 2 2026

An active weather period starts this morning as an upper-level trough across the Pacific Northwest pushes towards the Intermountain West this morning and through early Wednesday morning. Westerly flow aloft is expected to turn southwesterly throughout the morning hours, helping usher in ample Pacific Moisture associated with this incoming system. Several vorticity maxima will eject out ahead of the approaching trough, with strong 700-500mb differential cyclonic vorticity advection, favoring continued synoptic lift and forcing throughout the day and into the overnight hours. West of the Laramie Range, southwesterly 700mb flow is expected through early Tuesday morning with locations east of the Laramie Range experiencing westerly 700mb flow. Additionally, weak 700mb warm air advection will develop across Carbon County later this morning and into the afternoon hours, leading to additional synoptic ascent across this region and 700mb temperatures increasing from about 0C to 2C. With temperatures this afternoon expected to increasing into the upper- 50s to mid-60s everywhere and elevated dewpoint values from continued moisture advection into the region, an active day is expected with everything from heavy snow in the mountains to the potential for thunderstorm this afternoon. Looking first at the thunderstorm potential, the 00Z and 06Z HRRR both suggested surface CAPE values of around 200-300 J/kg this afternoon across northern Carbon County and points east through at least southeastern Converse County. While 200-300 J/kg of SBCAPE is not expected to give severe storms across the area, especially not in early March, but this instability should enable a few isolated thunderstorms this afternoon with the potential to produce gusty winds and heavier rainfall, definitely not something typically expected in early March and especially not across northern Carbon County in early March. The Storm Prediction Center has outlined much of southeast Wyoming in a General Thunder risk for this afternoon. These showers should spread eastward throughout the afternoon and evening hours, though likely not expecting much thunder in the eastern portions the CWA due to a relative lack of CAPE this afternoon. At the same time as isolated showers and storms are ongoing across the region, upslope flow is expected across the Sierra Madre, Snowy, and North Laramie Ranges, leading to snowfall in the mountains as 700mb temperatures should remain cold enough to get snowfall, rather the rain, in the higher terrain. Late Monday night into early Tuesday morning, 700mb temperatures will start to fall as a weak cold front pushes through, dropping temperatures into the -4 to -2C range, with -3C temperatures expected over the lower elevations of southeast Wyoming. With 700mb temperatures at and below -3C in Southeast Wyoming, rain showers should mix with snow and become all snow throughout Monday night into early Tuesday morning and throughout the day Tuesday as 700mb temperatures remain cold. Heavier snowfall accumulation on Monday into early Tuesday morning are expected in the higher terrain, as well as the I-80 Summit. 6 to 10 inches of snow is possible for the mountains, while 2 to 4 inches are possible for the I-80 Summit. As a result, decided to issue Winter Weather Advisories for the Sierra Madre, Snowy, and North Laramie Ranges, as well as the I-80 Summit through Tuesday evening.

The upper-level trough will continue its eastward progression throughout the day Tuesday, keeping broad synoptic forcing across the region. 700-500mb differential cyclonic vorticity advection will remain strong Tuesday, further assisting the broad synoptic forcing expected across the region. Northerly 700mb flow develops Tuesday afternoon as a 700mb low attempts to develop across northeastern Colorado and the overall 700mb trough axis moves to the east of the CWA. Northerly 700mb flow remains a favorable direction for the mountains to see ongoing upslope and snowfall, with the Sierras now not blocking the Snowies as is typical with the southwesterly flow expected on Monday. At the surface, a surface low develops late Monday night into the early morning hours Tuesday across eastern Colorado before being absorbed by a secondary low developing across eastern New Mexico and the Panhandle of Texas. Despite the shorter life cycle of the initial low over eastern Colorado, this placement is very favorable for snowfall across the CWA as it is in the northern, colder portion of the surface low. With 700mb temperatures within the favorable range for snow, rather than rain, and cooler surface temperatures, in the mid-30s to low-40s across the southern portions of the CWA, snow is expected to continue and become more widespread south and west of the North Platte River Valley early Tuesday morning and into the early afternoon hours. With surface temperatures in the mid-50s north and east of the North Platte River Valley, precipitation is expected to remain primarily rain, despite the cooler 700mb temperatures. Starting in the mid-afternoon hours, the initial low will start to be pulled south and absorbed by the developing low over New Mexico. Once this low starts being pulled southward, precipitation chances will end north to south across the CWA, with all precipitation chances expected to be gone by very late Tuesday night/very early Wednesday morning. Light snow accumulations are expected in the lower elevations, likely only around trace to maybe 1 inch, especially with how warm ground temperatures continue to be. The Winter Weather Advisories end at 5 PM Tuesday as the initial low is pulled south and absorbed, all while synoptic forcing weakens as the upper-level trough moves out of the region.

A briefly calm day is expected Wednesday as an upper-level ridge develops between the departing trough to the east and the next incoming trough to the west. Northerly flow aloft will turn westerly throughout the day as the weak ridge axis remains in place across the region. Mostly sunny skies are anticipated under the subsidence from the ridge aloft along with 700mb temperatures warming back into the 0C to 2C range, enabling surface temperatures to warm significantly for Wednesday afternoon. Highs are currently forecast to be in the low-50s west of the Laramie Range and upper-50s to mid- 60s east of the Laramie Range. There is some uncertainty with the high temperatures on Wednesday. If the system Monday/Tuesday over performs, as some systems have been doing this year, and more snow accumulation occurs than currently forecast, high temperatures may be cooler across southeast Wyoming. With current forecast expectations, temperatures should warm nicely on Wednesday, but there is a chance that forecast highs of Wednesday start to decrease over the next couple of days as exact snow accumulations are known.

The brief lull on Wednesday starts to end late Wednesday night into the very early morning hours Thursday. The next upper-level trough will move closer to the region Wednesday evening, with the trough axis likely over western Idaho and Nevada. Upper-level flow turns southwesterly as this trough approaches the region and ample Pacific Moisture will advect into the region, along with multiple 500mb vorticity maxima ejecting out ahead of the incoming trough. Generally positive, or cyclonic, differential vorticity advection is expected to develop early Thursday morning. When combined the much of the CWA being under the influence of the left exit region of the upper-level jet late Thursday morning and being downstream of the trough axis in eastern portions of the CWA, synoptic forcing looks fairly strong for this incoming system. Southwesterly 700mb flow strengthens late Wednesday night into early Thursday morning, favoring upslope development along the Sierra Madre Range once again. Southerly to southwesterly surface flow should develop early Thursday morning as the surface low develops across northern Wyoming and pushes southeast across the CWA throughout the afternoon hours. Brief warm air advection is anticipated at 700mb as the low develops, but will quickly switch over to cold air advection. Once cold air advection starts across the region, 700mb temperatures will quickly drop back into the -4 to -2C range late Thursday night. Surface temperatures are expected to max out around the mid-40s to low-50s west of the Laramie Range and low-50s to mid-60s east. Colder air starts to move into the region Thursday afternoon and evening, so temperatures are expected to drop quickly. With ample forcing throughout the day, snow showers are expected to start across the Sierra Madre and Snowy Ranges, with rain transitioning to snow expected across the lower elevation. All snow is expected by late Thursday night as a strong 700mb cold front pushes through, dropping 700mb temperatures into the -5 to -2C range. Exactly accumulations are uncertain at this time, but the mountains look to get another shot of beneficial snow with current accumulations forecast to be between about 9 and 12 inches, with the potential for 0.5 to 3 inches in the lower elevations. This forecast will change over the next several days, but any precipitation is beneficial after the dry winter we have had so far.

LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/

Issued at 221 AM MST Mon Mar 2 2026

Late Thursday night into early Friday morning, the CWA will remain under the upper-level jet with the trough axis still off to the west over Utah. Multiple vorticity maxima will continue to eject out ahead of this trough Thursday night into Friday morning, with strong differential cyclonic vorticity advection anticipated across the region. Therefore, synoptic forcing will continue throughout the day Friday, along with ample moisture advection into the region. Messy 700mb flow is expected as the 700mb closed low over southern Utah late Thursday night is interrupted by the Rocky Mountains then tries to form again to the east Friday afternoon. However, 700mb flow will be favorable for continued upslope flow along the Sierra Madre and Snowy Ranges, though likely not as stout as would occur if winds remained largely the same. The strong cold front associated with this system will push through Friday morning into the early afternoon hours, leading to additional snow showers likely to develop along the front. 700mb temperatures cool to the -10 to -8C range by Friday afternoon, leading to a much cooler day across the CWA with highs in the mid-30s to mid-40s in the lower elevations of western Nebraska. Snowfall comes to an end by Saturday morning, as the best forcing moves out of the area.

Skies will begin to clear for Saturday as subsident flow starts behind the departing trough and a strong upper-level ridge moves towards the West Coast. The ridge does not look to move into the western CONUS much, as an upper-level low develops over northern Mexico, potentially resulting in an Omega Block across the western CONUS. Luckily, for the precipitation starved areas along the Rocky Mountains, northwesterly flow aloft remain in place with this potential Omega Block, opening the door for multiple shortwave to push through the flow and give multiple precipitation chances for the CWA. Exact timing on any potential shortwave is unknown at this time, as there is still several days between now and then. High wind chances may also return with the northwesterly flow currently expected for this upcoming weekend and early into next work week.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 404 AM MST Mon Mar 2 2026

Isolated to scattered showers are ongoing this morning and expected to continue through most of the day. KRWL and KCDR may see some isolated thunderstorms impacting the terminals this evening, but confidence on exact location of these storms is low. With ample moisture in the area, cloudy skies are expected through the day, but should remain in VFR conditions, except under and shower or storm. MVFR conditions possible under any storm that impacts a terminals this afternoon. Lower ceilings expected late in the TAF period, likely dropping to IFR as rain turns to snow across the area.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Winter Weather Advisory from 5 PM this afternoon to 5 PM MST Tuesday for WYZ103. Winter Weather Advisory from 11 AM this morning to 5 PM MST Tuesday for WYZ112-114. Winter Weather Advisory from 11 PM this evening to 5 PM MST Tuesday for WYZ116. NE...None.