textproduct: Cheyenne

KEY MESSAGES

- Locally dense fog will persist over portions of the High Plains Friday morning. Another round of fog is possible Friday night into Saturday morning.

- Mild conditions are expected for Halloween (Saturday), though a few showers will be possible along and west of I-25.

- A complex but disorganized storm system will move into the area Sunday night, bringing cooler temperatures and a chance for rain and high elevation snow showers.

- Widespread blustery conditions are anticipated Monday into Tuesday along and east of the Laramie range.

SHORT TERM /THROUGH SUNDAY/

Issued at 300 AM MDT Fri Oct 30 2026

GOES satellite imagery this morning shows plentiful mid to upper level cloud cover streaming across the area with moist southwest flow continuing aloft. At the surface, a broad high pressure system over the northern Plains is supporting low-level south to southeast winds over the High Plains. This moisture flux has lead to the development of areas of dense fog along and east of I-25 once again. Fog is expected to clear out in the next few hours right around the immediate vicinity of Cheyenne as winds turn more westerly, but should hold on further north and east into the mid to late morning hours today. A Dense Fog Advisory has been issued for portions of the area, and may need to be expanded northward later this morning as fog spread further. Low clouds will be slow to break today in the Nebraska panhandle, keeping temperatures closer to seasonal averages. The most sunshine is expected to be found along the I-25 corridor to the WY/NE border, which should see temperatures warm into the low to mid 60s today.

Moisture return is expected again this evening into the overnight, leading to another chance for areas of fog across the High Plains, kicking off Halloween Saturday with spooky conditions. Trick-or- treat conditions look largely pleasant across the area this weekend. Temperatures will cool a few degrees Saturday compared to Friday due to increased cloud cover, but we should still comfortably reach the mid 50s to lower 60s for all areas. Model guidance is in good agreement showing a more notable vorticity maximum pushing into the area out of the southwest Saturday morning. This feature should support a few showers moving into Carbon county during the morning hours, and then spreading into Albany county, and possibly as far east as the I-25 corridor during the afternoon hours. Widespread rainfall is not anticipated, but expect to see occasional light shower activity, particularly in Carbon and Albany counties. Keeping an umbrella handy may not be a bad idea for trick-or-treaters along and west of I-25. Due to the high humidity, mild temperatures are expected once again Saturday night. Most areas will only drop to the mid 40s by 9PM before bottoming out in the upper 30s to lower 40s (a little chillier in Laramie as usual) Sunday morning. Sunday's highs will knock off a few more degrees with skies expected to become mostly cloudy by the afternoon. Southerly winds will be on the increase in advance of the next storm system which will approach the area Sunday night.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Issued at 300 AM MDT Fri Oct 30 2026

A complex storm system will bring a change in the weather for our area Sunday night into the early part of next week. This will be a fairly large and potent weather system, but two or even three upper distinct upper level low pressure systems moving across the west will make for a very messy setup. While a deep but somewhat narrow trough approaches from the west, another moisture-laden system will race into southern California along a potent sub-tropical jet stream. This system will get pulled into or around the primary trough as it moves through the area. Meanwhile, there is potential for another upper level low over the northern Rockies to drop down simultaneously, interfering further with each system. While moisture will once again be extremely abundant (NAEFS mean precipitable water values exceed the 99th percentile of climatology Sunday night!), this system will have the same issue as most others this fall: a lack of strong forcing to actually extract this moisture as precipitation.

Recent model guidance has trended largely towards the scenario where each of these upper level low pressure systems remain independent, with their forcing and lift interfering with one another. The overall evolution of the storm system has also trended more progressive and faster The net impact for our area is a decrease in the probability for widespread precipitation. While most areas can still expect some rain/snow showers with this event, the most likely scenario for QPF is fairly modest at this time. Greater than 75% of ensemble members have QPF under 0.25" for most areas inside a roughly Laramie to Glendo to Sidney triangle. There is still potential for between 0.25" and 0.75" liquid precipitation in Carbon county and along the Douglas to Chadron corridor, where forcing may be slightly more favorable. Still, about 25% of ensemble members keep the storm system too disorganized to deliver decent precipitation even to the Douglas to Chadron corridor, leaving most of the High Plains dry. Overall, confidence in expected QPF is highest for Carbon county at this time. There, extremely moist southwest flow can produce favorable orographic lift in the first phase of the storm system Sunday night into Monday morning, even if the second phase (the potential for wrap-around moisture) fails to materialize. Temperatures will be quite warm in advance of this system, meaning that snow levels will probably be as high as 9000 ft. Snow levels will gradually fall Sunday night and Monday, but there is a bit of uncertainty in seeing any precipitation at all after the colder airmass moves into the area. Probabilities for advisory criteria snowfall remain around 50/50 in the Snowy and Sierra Madre ranges, and about 25% in the northern Laramie range.

Regardless of the precipitation outcome, a cold front will sweep through the area Sunday night and cooler and windier conditions for most areas on Monday. Look for a rapid increase in northwest winds Monday morning behind the frontal boundary. There is fairly high confidence in widespread wind gusts of 40 to 55 mph along and east of the Laramie Range through much of the day Monday. Most of these areas have about a 20 to 30% chance for winds exceeding high wind criteria at this time. Temperatures will actually be several degrees below seasonal averages, only reaching the mid to upper 40s for most areas. Tuesday will bring temperatures closer to seasonal averages and continued northwest winds, but they should not be as strong as Monday.

Midweek onwards, disorganized ridging is expected to build back into the area. Temperatures look generally close to remain fairly close to seasonal averages with lighter winds, though breezy conditions may remain in the typical wind prone areas. There is potential for at least one if not two additional closed low systems later in the week towards next weekend, which may bring another chance for precipitation. However, confidence is extremely low at this lead time.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 543 AM MDT Fri Oct 30 2026

Fog and low clouds remain the primary aviation concern this morning. Now that CYS has cleared, expect VFR to prevail at WY terminals, though VCFG was still included for CYS due to fog close by. Winds will be generally south to southwest, and gusty at RWL. Another round of low clouds or fog may dip back into CYS late this evening or overnight.

Nebraska panhandle terminals will still be dealing with fog and low CIGs for several more hours. For AIA and SNY, there is high confidence in LIFR to IFR conditions for much of the morning, improving to MVFR late morning, and perhaps briefly VFR this afternoon before coming down again this evening. Confidence is lower in IFR conditions at BFF and CDR, where MVFR may prevail, but periods of IFR are still probable. There, VFR is expected this afternoon, though both may still return to MVFR later this evening.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Dense Fog Advisory until 10 AM MDT this morning for WYZ119. NE...Dense Fog Advisory until 10 AM MDT this morning for NEZ020-054- 055.