textproduct: Cheyenne

KEY MESSAGES

- Chilly temperatures will continue for the next several days. Another round of freezing temperatures is expected Wednesday morning in areas with snow cover, with patchy frost and fog elsewhere.

- Chances for isolated showers and thunderstorms will continue through Wednesday night. A more widespread round of showers is expected Thursday into Friday.

- Above average temperatures and pleasant weather expected for the weekend.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 300 PM MDT Tue May 19 2026

Chilly and unsettled weather will continue for the next several days as temperatures will be slow to return back to seasonal averages. Broad troughing will remain over the west through the end of the work week, with a series of weak vort-maxes providing limited precipitation potential. The cold surface high pressure system is located over the central and northern plains, keeping fairly light winds and cold temperatures over the area today. Visible satellite imagery shows plentiful snow cover lingering over portions of Carbon, Albany, and Converse counties. Meanwhile, a weak shortwave located over eastern Utah is supporting modest isentropic lift just to our south. This lift will very slowly creep north and eastward overnight and into Wednesday morning, which will support some isolated light shower activity through the period. This afternoon, expect this to be mainly in Albany and Laramie counties, but this will spread north and east overnight and into Wednesday morning. A few rumbles of thunder will be possible. As the mid-level lift pushes into our area, the surface high will retreat to the east, initiating southerly winds over much of the High Plains tonight. With moisture remaining quite elevated, we will need to watch for some fog tonight. Along and east of the Laramie Range, this will be upslope fog, whereas areas further west can expect some patchy radiation fog thanks to clearing skies, lingering moisture, and snow cover. Carbon, Albany, and Converse counties are more likely to remain clear overnight, and with the snow cover and light winds, another cold night is anticipated. Rawlins not only obliterated their daily record low this morning by dropping to 8F, but they also broke the previous monthly record low for May! Tonight will not be quite as cold, but a daily record low is still forecast for Rawlins again. Existing Freeze Watches were upgraded to a Freeze Warning for these areas. In addition, a Frost Advisory was spread one row of zones eastward. Current thinking is that further east, there will be enough cloud cover to prevent widespread frost issues, but the cloud deck edge main remain east of Platte and Niobrara counties. If clouds remain more limited than anticipated, frost could spread eastward, which will be monitored this evening.

Wednesday will remain cool relative to seasonal averages with plenty of cloud cover, especially east of the Laramie Range. Drier air will start to move into our western zones, which will set up a dry-line / wind shift boundary somewhere in between the Laramie Range and the Wyoming/Nebraska state line. Some limited instability will setup along this boundary. While forcing looks quite limited, we may manage to kick off an isolated storm or two. PoPs generally remain between 20 and 40%. With moisture remaining elevated over the High Plains, we'll be looking at another chance for some fog and low clouds Wednesday night into Thursday morning. Frost and freeze concerns will be more limited, mainly in Converse, Carbon, and Albany counties, though increasing cloud cover will keep temperatures warmer than the preceding few nights.

By Thursday, a more potent upper level low will dive down from Canada across the northern Rockies. This will be slow moving, pushing a few showers into our western zones during the morning hours. The dryline and wind shift boundary should remain in place into Thursday but it may be a little more diffuse. The main forcing with the upper level trough and strong isentropic lift looks to be fairly well timed with daytime heating, arriving in the early to mid afternoon hours. Expect numerous showers with isolated to scattered embedded thunderstorms to expand in coverage through the afternoon hours and into the evening. Instability looks relatively unimpressive, around the 400 to 800 J/kg range, but a few stronger storms cannot be ruled out. Coverage of rainfall should be fairly good with this event. Most of the area has a 60% or greater chance for wetting rainfall (0.1" or more). For once, the higher probabilities are actually located in the Nebraska panhandle thanks to the instability and ample low-level moisture present. Shower activity will likely continue well into the night, and possibly even into Friday morning before the potent upper level low clears to the east and brings precipitation to an end. PoPs are fairly aggressive now, around 60 to 80% for most of the area, but this was toned down slightly from the NBM.

LONG TERM /FRIDAY THROUGH MONDAY/

Issued at 300 PM MDT Tue May 19 2026

The long term should be a mostly quiet weather period with some initial precipitation on Friday leading to warm and dry conditions by the weekend. Friday starts on the backside of a quick moving clipper system that will see widespread shower and some thunderstorm chances across the CWA. Thankfully this activity will be mostly passing in nature with limited instability and support for stronger activity, and by peak heating later in the day the best forcing should be far enough east that activity will be lessening to dissipating across the region.

Into the weekend and early next week the upper levels will see a weak ridge of high pressure take control that will keep us mostly clear and increase temperatures. While some passing showers may be possible, it will be mostly relegated to the high terrain from orographic flow as stronger systems and better moisture are not expected until beyond the long term. Otherwise this will lead to the return of warmer conditions, with spring like temperatures in the 50's to 60's on Friday giving way to 70's and 80's by Sunday and Monday, with a chance for our eastern zones possibly peaking into the 90's on Monday. With the increasing warmth comes decreasing moisture, and enhanced fire weather concerns may return for the Nebraska Panhandle Sunday and Monday as moisture has not been notable enough to produce significant greenup as of this writing. While winds are currently expected to remain too weak to produce critical fire weather concerns, the dry nature of the region will still be conducive of problematic control problems if new fires do start up.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1141 AM MDT Tue May 19 2026

KRWL is currently experiencing IFR to LIFR conditions due to localized fog, but this should begin to clear out over the next hour or two. Thereafter, expecting light winds and VFR conditions all sites through the early night hours. Precipitation may begin to move into KCYS beginning around 22Z and continue into the nighttime hours through around 04Z, with light precipitation then possible for all Nebraska Panhandle sites except KBFF as it appears to be just outside of possible rain. This precipitation will bring lowered CIGs and VIS, which could produce MVFR to IFR conditions for all sites impacted. Winds will also begin to increase, becoming breezy starting around 12Z primarily for Nebraska sites. Finally, fog may be possible again for KRWL tomorrow morning, as well as KLAR and KCYS. Have introduced VCFG for KRWL, along with lowered decks and some BR for KCYS, with higher uncertainty for KLAR and have kept it out of this TAF for now.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Frost Advisory from midnight tonight to 8 AM MDT Wednesday for WYZ102-106-107-117. Freeze Warning from midnight tonight to 8 AM MDT Wednesday for WYZ101-115. Freeze Warning from 9 PM this evening to 10 AM MDT Wednesday for WYZ104-105-109>111-113-116. NE...Frost Advisory from midnight tonight to 8 AM MDT Wednesday for NEZ095.