textproduct: Cheyenne

KEY MESSAGES

- Multiple, weaker cold front will push through over the next couple of days, leading to slightly cooler temperatures and increasing precipitation chances heading into the weekend.

- The first strong thunderstorms could arrive as early as Saturday afternoon to the western Nebraska Panhandle.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 129 AM MDT Thu Apr 9 2026

Zonal flow returns to the region for Thursday as a broad, flat trough moves across central Canada. An upper-level low just west of California slowly moves eastward and stalls briefly today as a weak ridge attempts to develop out ahead. Multiple lobes of 500mb vorticity will eject out ahead of the trough, traversing through the upper-level ridge this evening. Weak, synoptic lift will be associated with this CVA, mainly along and east of the Laramie Range. 700mb flow remains largely light and zonal through the morning hours before shifting northerly this afternoon and evening as a weak cold front pushes through. Warm air advection will develop this morning and afternoon, along and east of the Laramie Range, leading to warmer temperatures and supporting synoptic ascent. With the cold front pushing through and meeting WAA across much of the CWA, focused, mesoscale ascent is expected this afternoon along the front. Precipitation is more favored today due to Perceptible Water values increasing into the 90th percentile, per the NAEFS Climatological Percentile, and ample lift associated with the approaching front. While widespread precipitation is still not expected, more locations are favored to see at least a trace of precipitation this afternoon and evening. Instability will be fairly modest this afternoon, so strong, organized storms are not expected. Additionally, forecast RAP soundings suggest a stout, Inverted-V signature, so very gusty winds will be possible with any showers that develop today. Temperatures will warm into low-60s to mid-70s before the cold front pushes through the afternoon. Southerly to southwesterly flow is progged to return late tonight into the early morning hours Friday as the upper-level trough slowly approaches the region.

Southwesterly flow continues Friday afternoon as the upper-level trough pushes into the western CONUS and digs across central and southern California. The upper-level ridge out ahead of the approaching trough will push through the CWA by early afternoon, leading to southwesterly flow throughout much of the atmosphere. The fetch of southwesterly flow originates over the Pacific Ocean, so ample Pacific moisture will move into the region throughout the day today and into the morning and afternoon hours Saturday. PW values are progged to increase above the 90th percentile, per the NAEFS, especially across western Nebraska on Friday. Multiple lobes of 500mb vorticity will continue to traverse across the region as the eject out ahead of the approaching trough. 700mb warm air advection increases significantly Friday morning into the early afternoon hours, with even stronger WAA expected overnight Friday into the day Saturday. With a surface high over Minnesota and lower pressure west of the Rocky Mountains, a strong east/west surface pressure gradient will develop by midday Friday. As a result, moist, upslope flow is expected east of the Laramie Range, increasing precipitation chances, especially along and just east of the Laramie Range. Isolated to scattered showers are expected throughout the afternoon and evening on Friday. Significant precipitation totals are not anticipated at this time, but another 0.03 to 0.10 inches of rain is possible, with higher amounts possible under any heavier showers that develop. Temperatures will only increase into the mid-50s to mid-60s, with the coolest temperatures east of the Laramie Range where the cooler, upslope flow will be ongoing as well as increasing cloud coverage.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 129 AM MDT Thu Apr 9 2026

No major changes to the longer term forecast. Please see previous discussion for more details.

Unsettled weather will continue into the early part of next week across the region. By this weekend, the weather pattern on the synoptic scale will feature a broad, strengthening upper level ridge over the central and eastern CONUS, with troughing over the West Coast. A series of upper level shortwaves moving through the southwest flow aloft across the Rockies will keep precipitation chances and the potential for stronger winds in the forecast.

First, Saturday is continuing to be a day to watch for the potential for a few strong thunderstorms. The ridge axis will peak overhead on Saturday before starting to shift eastward later in the period. 700- mb temperatures peak around +6 to +8C. Look for Saturday to be the warmest day of the period as a result, with widespread upper 60s to 70s expected. A few low 80s could show up in the lowest elevations too. At the surface, we will open up Saturday with south to southeast flow over the High Plains around the periphery of a very large surface high pressure system positioned well to the east. Gulf moisture advection looks to be excellent for this time of year, with dewpoints expected to reach into the low 40s for all along and east of I-25. Morning low clouds and/or fog look like a good bet, but fog was not added to the forecast yet since we are still a few days out. Forecast soundings show a fairly potent subsident dry layer on top of the shallow surface moisture, which will play a role in the potential for afternoon convection. Broad southwest flow aloft will support lee cyclogenesis across central Wyoming during the day on Saturday. As this advances eastward, we should see the dryline which will be positioned along the Laramie Range move eastward through the day. How far the moisture retreats to the east will be the main uncertainty concerning thunderstorm potential. An approaching vort- max will enhance synoptic lift during the afternoon and evening hours, which should kick off some scattered PM showers and isolated thunderstorms. The right balance between the capping inversion weakening, and the boundary layer not drying out too much will need to be struck in order to get more organized thunderstorm potential. This is possible, but far from a guarantee. With good vertical wind shear in place, a few strong thunderstorms will be possible, but uncertainty is considerable at this lead time.

Sunday will be a few degrees cooler than Saturday behind the initial shortwave trough aloft. There will still be a chance for PM showers and thunderstorms, but coverage and intensity looks to be more limited. There will also be a short window for high winds in the wind prone areas Saturday night into Sunday morning as we see a brief surge in 700-mb height gradients and winds behind the departing vort-max. Low-level moisture will be reduced significantly for Sunday, such that elevated to near critical fire weather concerns may return to the picture too. Precipitation chances will increase again Monday into Wednesday next week as the broad upper level low over the West Coast finally moves inland. While there is good agreement on the overall synoptic evolution, the devil is in the details. The exact track and strength of the upper level low combined with the potential for interference from other shortwave troughs either ejecting ahead of the main system or riding to the north will determine precipitation amounts. Unfortunately for our drought stricken area, the probability for significant, widespread rainfall or snowfall continues to decrease. While the deterministic ECMWF continues to show a promising track with plentiful precipitation, it appears to be an outlier amongst its own ensemble system. Cluster analysis suggests that the probability of a system capable of meaningfully improving the drought (0.5" or more over a large area) is only around 10 to 20% per the LREF. Depending on the exact track of the upper level low, there will also be a potential for high winds in the wind prone areas during this period.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1135 PM MDT Wed Apr 8 2026

Winds will be all over the compass over the TAF period, especially over the High Plains. Winds are southeast this evening, with a brief surge in southerly winds Thursday morning, before winds ease and turn southwest mid morning, and then west to northwest by the early afternoon. Winds then return back to north or northeast by Thursday evening, becoming easterly again into Friday morning.

A few mid to upper level clouds are expected going into Thursday with a return of precipitation expected. Thursday's shower activity will be more widespread, kicking up mid afternoon. PROB30 groups continue for gusty and erratic winds. Rain may actually reach the ground, so a brief VIS/CIG drop and a few rumbles of thunder can't be ruled out on Thursday afternoon and evening, with activity tapering off into the nighttime hours.

CYS WATCHES/WARNINGS/ADVISORIES

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