textproduct: Cheyenne

KEY MESSAGES

- Southwest winds will increase Thursday across the area, leading to critical fire danger over the High Plains and the potential for high winds in portions of Carbon county.

- A very strong cold front will sweep through the area between the late afternoon and evening hours Thursday, bringing rapidly dropping temperatures and an abrupt wind shift.

- Snow squalls and a flash freeze will be possible Thursday evening, primarily in Carbon and Converse counties.

- Widespread snowfall is expected Thursday evening through Friday, though exact accumulations remain uncertain.

- Winter-like temperatures in the teens to low 20s are expected by Saturday morning, creating a risk for outdoor irrigation and sensitive vegetation that has emerged from winter dormancy early.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 335 PM MDT Wed Apr 15 2026

Active weather will continue across the area for the next several days with multiple different hazards anticipated. This will be driven by a powerful Pacific trough which is already apparent on GOES satellite imagery moving inland this afternoon. As this feature dives into the western CONUS tomorrow, it will amplify the downstream ridge over our area. This will strengthen the southwest flow aloft beginning tonight and continuing through the day tomorrow. Median 700-mb wind speeds per the LREF climb to around 45 knots late this evening and remain there through midday Thursday over much of Carbon County. These values are around the climatological 99th percentile. The latest probabilities for wind exceeding high wind criteria from the NBM are in the 50 to 70% range for much of Carbon county including Rawlins, Elk Mountain, Arlington, and Muddy Gap. In addition, the wind direction is favorable for some downslope winds into the Upper North Platte River Valley. While confidence is lower for that zone, it was enough to include the Saratoga area in a High Wind Watch. The best window looks like mid morning through the early afternoon on Thursday, but the watch covers a longer time period beginning midnight tonight and continuing until a few hours after the frontal passage on Thursday to account for a few overnight mountain waves, and higher than expected wind gusts with the cold front. We will also need to keep an eye on the Converse County area for a potential expansion of the high wind threat, but probabilities are lower there (10-40%).

By mid morning, gusty southwest winds will mix down the surface across the entire area. Widespread gusts of 30 to 40 mph are anticipated over the High Plains, which will increase the fire weather threat. A Red Flag Warning has been issued for all of the High Plains once again. The increased cloud cover may provide a failure mode for critical conditions, but confidence was high enough to upgrade across the board.

Big changes will be on the way as a powerful cold front arrives late Thursday. Expect this to arrive around 3 to 4PM for our northern and western zones, including western Carbon and western Converse counties. The Sidney area will be the last to see the front push through, with expected timing around 10 to 11PM. As the front passes through, expect an abrupt wind shift and rapid rise in surface pressure. Extremely strong frontogenesis will support precipitation immediately behind the frontal passage. Modest instability will be present ahead of the front, so we will need to watch for convective enhancement, particularly due to the late afternoon timing. The very strong mechanical forcing (as much as 3 mb per hour pressure rises) and potential for a few hundred J/kg of CAPE will put snow squalls on the table. While temperatures will be spring-like ahead of the front, look for a very rapid drop in temperatures which could add flash freeze concerns. Rain may flip over to snow very quickly, especially in Carbon County. Rawlins, for example, should see a high around the lower 60s Thursday, but may be below freezing by 7 to 8PM, if not sooner. Travelers across Albany, Carbon, and Converse counties should be prepared for hazardous, rapidly changing conditions including low visibility in falling and blowing snow and icy surfaces especially as the sun goes down. Overnight, model guidance remains a little split concerning whether some post-frontal overrunning lift will manage to develop. Forecast soundings for Rawlins show about 6 hours of a warm nose developing right in the middle of the dendritic growth zone between about 9PM and 3AM. A few ensemble members try to bring low-level dry air in underneath this very promptly, and cut into precipitation totals. Taken all together, there was enough confidence in at least some impacts from snow to issue a Winter Weather Advisory for most of Carbon and Converse counties. These are the areas where impacts will occur Thursday evening.

The storm system will slowly migrate eastward Thursday night into Friday morning, spreading cold air and snow with it. While precipitation should be more or less right behind the front when it first moves into the area, the surface front will race ahead overnight. East of a Laramie to Lusk line, forcing for ascent will not really get going until after midnight, several hours behind the initial frontal passage. For determining impacts, the exact start time will be fairly critical. Snow beginning pre-dawn should easily stick, and create icy and slick conditions for the Friday morning commute. However, if forcing holds off just a few hours later until around 9AM or so, after the strong April sun takes hold, road impacts in particular may be more limited. Due to this uncertainty, decided to hold off on expanding the Winter Weather Advisory east of Laramie. The most likely scenario still includes 1 to 4 inches of snow in Albany, Platte and Laramie counties, with a dusting to 2 inches further to the east. In addition to the snow, blustery north winds are expected with this event. This will lead to chilly wind chill values and the potential for some blowing snow. Snow might actually be a little lighter and fluffier than typical for this late in the season as forecast soundings show a fairly deep, saturated dendritic growth zone. So, while some melt on contact is anticipated with the warm ground temperatures, this probably won't be a typical late April heavy wet snowfall. Ratios are expected to be around 12:1 to 15:1 in Wyoming, and 8:1 to 12:1 in Nebraska.

The last impact of this system will be the expected cold temperatures. After a historically warm start to spring, vegetation has progressed much further out of dormancy than typical for mid April. This event will not be record challenging cold by any means, but we will have temperatures far below average. In fact, 700-mb temperatures will be below the 10th percentile of climatology on Friday. High temperatures will struggle to get above freezing for some areas, and all remaining below the lower 40s at the warm end. As skies clear and winds die down, we should have time for rapid radiative cooling. Widespread lows in the teens to lower 20s can be expected by Saturday morning, which will cause issues for outdoor irrigation systems and sensitive vegetation. Those with such vulnerabilities to the cold temperatures are encouraged to make preparations for the cold weather while the warm temperatures last on Thursday.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 335 PM MDT Wed Apr 15 2026

Saturday...With decent low and mid level gradients and northwest flow aloft, it looks breezy to windy. 700 mb temperatures near -7 Celsius will yield maximum temperatures in the mid to upper 40s west of I-25, with upper 40s to mid 50s east of I-25.

Sunday...Ridging aloft moves over western Wyoming with a surface lee trough developing over our counties. With 700 mb temperatures near 5 Celsius, maximum temperatures will climb into the upper 50s and lower 60s west of I-25, with mid 60s to lower 70s further east.

Monday...The warming trend will continue as ridging aloft strengthens and becomes more pronounced over western Wyoming. 700 mb temperatures near 7 Celsius will produce high temperatures in the mid 60s to near 80 degrees.

Tuesday...Dry conditions continue as ridging aloft transitions to eastern Wyoming. Slightly warmer as 700 mb temperatures warm a degree or two.

Wednesday...As the ridge axis aloft moves to the northern high plains, our flow aloft will turn southwest with strengthening surface lee troughing. Temperatures slightly cooler due to more cloud cover. Slight chances for afternoon showers and a few thunderstorms due to an increase in low and mid level moisture and low level convergence.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1055 PM MDT Wed Apr 15 2026

Upper level ridge axis will linger around the region for one more day on Thursday, but it will become windy late in the morning and afternoon, especially the southeast Wyoming terminals. A cold front is expected to move into the area Friday evening.

HAZARDS/WEATHER TRENDS: VFR conditions expected over the next 18 hours, with the first bands of snow entering the KRWL vicinity after 00z Friday. Added PROB30 group mainly due to timing differences, but do expect it to snow with IFR conditions likely after 06z Friday (50% to 70% probabilities). Otherwise, increasing and lowering cloud bases are expected for all other terminals through 00z Friday with a gradual wind shift to the north.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning from noon to 8 PM MDT Thursday for WYZ417>419- 430>433. Winter Weather Advisory from 6 PM Thursday to noon MDT Friday for WYZ101. Winter Weather Advisory from 6 PM Thursday to 3 PM MDT Friday for WYZ103>105-109>111-113. High Wind Watch from midnight MDT tonight through Thursday evening for WYZ104-109-110-113. NE...Red Flag Warning from noon to 8 PM MDT Thursday for NEZ434>437.