textproduct: Cheyenne

KEY MESSAGES

- Critical Fire Weather conditions expected Sunday and again Monday as humidities dive into the single digit values.

- Pattern change alongside a chance at some precipitation including storms and snow expected mid through end-week timeframe.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 242 AM MDT Sun Apr 19 2026

Benign weather is expected over the next few days as upper-level ridging moves into the Rockies. Temperatures will return to being mild and above average on Sunday as the ridge axis moves into Wyoming. 700 mb temperatures will climb to about +4C, leading to high temperatures in the 60s across the forecast area. Highs are expected to be even warmer on Monday as the ridge axis moves into the CWA. 700 mb temperatures will reach +8C, leading to highs in the 70s and 80s, which is roughly 15 to 20 degrees above average. The ridge will also ensure that mostly sunny skies dominate the area, with no precipitation chances anticipated. As a result, conditions over the next few days are expected to be extremely dry. With dry desert air being advected into the region, relative humidity values will fall into the single digits on both days. The extremely low relative humidity poses fire weather concerns, especially on Monday when winds become more breezy as a weak disturbance passes to the north. Red Flag Warnings are currently in effect both days for areas east of the Laramie Range. Overnight humidity recoveries are also expected to be poor both nights.

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 328 PM MDT Sat Apr 18 2026

A high amplitude upper level ridge will be responsible for the prevailing conditions to start off Tuesday. Unsurprisingly, this ridge will bring along with it dry and sunny conditions. We start off the day in the upper 30s to low 40s across much of the area. Temperatures reach the 70s in the mountain interior and mid 70 and 80s over SE WY and the NE Panhandle. This is a good 20 degrees above average for this time of year and within the 90th percentile of 700mb climate per the NAEFS. Some sites, particularly in valley regions of the Nebraska Panhandle, may overperform and tie their record highs. As usual with unseasonable warmth our relative humidity values are also expected to be low during the day, reaching the low teens. Winds should be on the lighter side given the ridge passing overhead, but given the dry preceding conditions and the tall mixing heights of nearly 14 kft, the fire threat is still a concern. RH recoveries overnight are poor.

Ensemble models are in good agreement of a closed low moving in over the Pacific Northwest Wednesday and our upper level ridge moving east. We will be in the southwesterly flow regime of the low pressure system by this point. We can expect increasing upper level cloud coverage from west to east overnight Tuesday and through Wednesday. Temperatures appear to be about the same as Tuesday, perhaps slightly cooler with the increased cloud cover. Dry conditions continue as well, with minimum RH values reaching the teens once again in the afternoon and evenings. However, the winds are a much bigger concern when talking about fire potential. ML high wind products are indicating an elevated probability of high winds over our wind prones (~40% of exceedance). Meaning gusts of 40 to 50 mph are likely to be felt over portions of our CWA, particularly over the interior mountain ranges. Meteorologically this increase in winds is in response to lee cyclogenesis to the north of the area. A dryline may take shape in the evening across the Nebraska Panhandle. While we are at long range here, some ML guidance are starting to pick out elevated thunderstorm potential along this dryline, with numerical grand ensemble giving about 50% chances of MUCAPE reaching above 100 J/kg currently. The vertical profiles in this environment are trending towards dry at the surface with deep layer mixing. Inverted-v soundings may support a wind threat with any high based convection. Again, we are a ways away, so guidance may change. This may also have further implications on anticipated fire weather conditions as little precip is likely to make it to the surface. Additionally any thunderstorms may increase the threat of dry lightning or influence on surface winds.

Overnight winds increase as the mid level low moves off to the northeast and a Pacific cold front moves through. Aloft we are still at the base of the upper level trough. Along this base are likely to be a few embedded vorticity maxima that may provide more forcing for ascent for the next few days. There is a bit more uncertainty on the amplitude of the remaining troughing. Cluster analysis of ensembles seem to paint GEFS members as being more supportive of deeper maximums and ENS and GEPS members with weaker lobes where most of the energy parts with the Wednesday system to the northeast. What this means to us is a slight increase in precipitation probabilities tied to stronger upper level solutions. Regardless, probabilities of seeing measurable precipitation over a large portion of our CWA remains low, except for maybe the mountains. Temperatures are likely to cool in combination of increased cloud cover and the Pacific front which hopefully will keep us out of widespread fire weather conditions, though portions of the southern NE Panhandle may have RH values in the 20s during the day.

Models are advertising an arctic front sometime overnight Thursday which may push us towards more seasonable temperatures Friday. Model spread remains high at this range in terms of upper-level features. Thus while precip chances remain elevated, the amount is still in question. Saturday appears to be much the same as Friday weather wise.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 515 AM MDT Sun Apr 19 2026

An upper level ridge axis will build over the Great Basin and move east into Wyoming and Colorado over the next 24 hours. Mostly clear skies and dry weather expected to continue. VFR conditions will prevail through Sunday evening. Gusty winds up to 25 knots possible for KRWL, KLAR, and possibly KCYS this afternoon.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning from 11 AM this morning to 8 PM MDT Monday for WYZ417-418-430>433. NE...Red Flag Warning from 11 AM this morning to 8 PM MDT Monday for NEZ434>437.