textproduct: Cheyenne

KEY MESSAGES

- Elevated to Critical Fire Weather conditions expected again Tuesday as humidities dive into the single digit values with light winds. A Red Flag Warning remains in effect for all areas east of the Laramie Range until Wednesday evening.

- There is a Marginal Risk (Level 1 of 5) for severe weather Wednesday afternoon. The primary concerns will be damaging winds gusts caused by microbursts.

- The potential for high winds will return Wednesday afternoon into Thursday. This may event spread outside of the wind prone areas. A High Wind Watch has been issued for Wednesday afternoon through Thursday evening.

- A cooler weather pattern with more frequent chances for precipitation will take over Thursday and last into early next week.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 151 AM MDT Tue Apr 21 2026

Clearing skies tonight as temperatures continue to drop across the region. Mostly light winds are ongoing as dry air continues to move in. Dewpoints remains quite low tonight, in the 9 to 20F range, leading to poor overnight humidity values nearly everywhere as temperatures remain in the mid-30s to mid-40s. Clear skies will continue today, with very dry conditions expected to continue this afternoon and into the overnight hours and Wednesday evening.

Upper-level ridging continues today ahead of an upper-level trough pushing into the western CONUS this afternoon and evening. The incoming trough will take a day or so to organize as it slowly meanders eastward Tuesday evening through Wednesday afternoon. Under the ridging Tuesday and most of Wednesday, clear skies and warm temperatures are anticipated as 700mb temperatures warm into the 10 to 15C range, leading to surface highs in the upper-70s to upper-80s Tuesday and upper-70s to possibly the low-90s for Wednesday. Precipitation chances remain little to none Tuesday through Wednesday morning. With very warm temperatures and largely dry conditions across the CWA, relative humidity values will be extremely low Tuesday and Wednesday, likely in the 5 to 12 percent range, especially east of the Laramie Range.

Wednesday afternoon looks to be quite interesting as the upper-level trough starts to push into the region and multiple 500mb vorticity lobes eject out ahead of the approaching trough. 700mb flow starts to switch southwesterly across western portions of the CWA and westerly across eastern portions of the area as the 700mb system starts to deepen over northern Idaho and western Montana. 700mb height gradients begin to increase, leading to a strengthening 700mb jet to 50 to 55kts across western portions of the area. Surface winds respond as modest subsidence is expected. Winds will likely approach high wind criteria by late Wednesday morning into the early afternoon hours, so a High Wind Watch has been issued for much of the area west of the Laramie Range from 9AM Wednesday through 6PM Thursday. Additionally, strong subsidence combines with strong 700mb flow and increasing surface gradients across the Snowy Range, suggesting very strong winds at the Arlington/Elk Mountain wind prone area along I-80. Craig to Casper 850mb gradients increase to 75 to 80m late Wednesday evening into the overnight hours, with a very strong surface pressure gradients across the zone as well. Therefore, a High Wind Watch has been issued for this zone for the same time, with wind gusts up to 75mph possible in this zone. Winds are expected to expand eastward as a 700mb shortwave develops across the Laramie Range and a very strong surface pressure gradients develops with the approaching cold front. A 3 to 4mb gradients is expected across the Laramie Range, with a 12mb gradient from western Carbon County eastward to the Laramie Range. Very strong winds are anticipated at Bordeaux, the I-80 Summit, Central Laramie County, and Converse County. Therefore, High Wind Watches are in effect for these areas as well, with Bordeaux and the I-80 Summit expected to gust upwards of 80mph. As strong winds kick up to the west of the Laramie Range, east of the Laramie Range will see increasing lift as vorticity maxima push overhead and cold front pushes towards the area, leading to increasing shower chances. However, very dry surface conditions are expected so precipitation will likely evaporate before hitting the ground. RAP soundings suggest a stout Inverted-V signature across the Panhandle, with CAPE values around the 500 J/kg mark. Therefore, isolated showers and storms are possible, leading to increasing dry lightning concerns with virga showers across the Panhandle. Red Flag Warnings remain in effect through Wednesday evening and the Storm Prediction Center has highlighted eastern portions of the Panhandle in a Marginal Risk (Level 1 of 5) for severe weather (mainly wind) Wednesday afternoon and evening. West of the Laramie Range is expected to see mostly snow as the strong cold front pushes through, leading to snow accumulations between 3 to 6 inches for the mountains and trace to half an inch of snow in the lower elevations west of the Laramie Range.

A secondary surge of winds is expected to develop Thursday morning as the 700mb low continues to strengthen and moves into western North Dakota. A very strong 700mb height gradients is expected across the region, leading to a 700mb jet up to 70kts across the Laramie Range, namely the I-80 Summit. Looking at GFS Omega Values, very strong subsidence is expected west to east across the Laramie Range and expanding into central Laramie County, especially late Wednesday night and early Thursday morning. The initial portion of this High Wind Event looks to be a Bora Event behind the strong cold front, with a mountain wave likely setting up later on. The strongest gusts at many locations are expected late Wednesday night into early Thursday morning, with gusts over 80mph possible near Bordeaux and the I-80 Summit. Winds finally begin to settle down Friday evening as the 700mb low continues to move away from the region. However, a gusty 24+ hour period looks likely for much of the area. Temperatures on Thursday will be much cooler, in the upper- 40s to mid-60s across the area. With the cooler air moving into the region, any ongoing showers east of the Laramie Range are expected to quickly transition over to snow, except for the Panhandle where warmer temperatures are expected and primarily rain to a rain/snow mix are anticipated. QPF with this system looks fairly low east of the Laramie Range, so significant precipitation is not expected, but a few hundredths may fall which is better than none. For additional information, please see the modified long term discussion below.

LONG TERM /FRIDAY THROUGH MONDAY/

Issued at 151 AM MDT Tue Apr 21 2026

No major changes with the forecast update. Please see the previous, modified long term discussion...

A secondary vort-max will rotate around the longwave trough, arriving Thursday afternoon into Friday. This will knock down temperatures further, with highs expected to be about 5 to 10F below seasonal averages for Friday. In addition, the upper level disturbance will bring increased chances for widespread light precipitation. While some light snow and/or rain is probable with PoPs in the 40 to 60% range, LREF probabilities for 0.10" or more of liquid precipitation is around 30 to 50% for most of southeast Wyoming, and 10 to 30% for most of western Nebraska. Concerning precipitation type, the chilly temperatures will support snow for the majority of those areas that manage to see precipitation.

Temperatures will remain chilly through the weekend. 700-mb temperatures will be near the climatological 10th percentile. LREF means are around -4C, but the interquartile range stretches from around -7C to -1C, indicating fairly low confidence in exact temperatures. The chill will be held in place by a broad, and unseasonably strong upper level low over the Canadian prairie, which will also keep the baroclinic zone over our area. Thus, expect the weather pattern to remain unsettled through this period. Another upper level low will move in across the western US and across the Four Corners states late Saturday into early Monday. This will take a more favorable track for widespread precipitation across our area. In addition, models are in fairly good agreement showing a surface high settling in over the northern Plains, allowing for an improvement in surface dewpoints and surface winds generally out of the south to east direction. For this system, LREF probabilities for 0.1" of precipitation or more are around 50 to 70% for the entire area. This drops down to 20 to 40% chance for greater than 0.25", and a 10 to 20% for greater than 0.5". Precipitation type will be a little more complicated with this event with the large spread in 700- mb temperature shown by various ensemble members. The warmer end would be rain for most areas outside of the mountains, while the colder end would be snow for almost everyone. The NBM may be a little on the cold side for snow levels for this event, but overall the most likely scenario is a rain/snow mix. High temperatures will be 10 to 20F below average through the weekend, with lows around 5 to 10F below average due to the increased cloud cover. The positive news of the cooler weather pattern is that we can expect a break from the fire weather concerns for several days, even if the precipitation fails to materialize.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 506 AM MDT Tue Apr 21 2026

Mostly clear skies expected through much of the 12Z TAF period. Clouds will slowly increase west to east late in the period. Gusty winds are expected to return this afternoon, with gusts between 20 and 25kts for most terminals. Lighter winds return this evening.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning from 11 AM this morning to 8 PM MDT Wednesday for WYZ417-418-430>433. High Wind Watch from Wednesday evening through Thursday afternoon for WYZ101. High Wind Watch from Wednesday morning through Thursday afternoon for WYZ104-109-111-113. High Wind Watch from Wednesday afternoon through Thursday afternoon for WYZ106-116>118. High Wind Watch from Wednesday morning through Thursday afternoon for WYZ110. NE...Red Flag Warning from 11 AM this morning to 8 PM MDT Wednesday for NEZ434>437.