textproduct: Cheyenne

KEY MESSAGES

- Warmer and drier weather returns today and will continue through Sunday, leading to elevated fire weather conditions.

- Cooler and more unsettled weather is expected to return Monday through Wednesday. Rain showers, snow showers, and thunderstorms will be possible.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 310 AM MDT Fri May 1 2026

Skies continue to clear across the area this morning as yesterday's weak storm system pushes well to our south. GOES water vapor imagery shows significantly drier air in the middle to upper atmosphere overhead. A little bit of surface moisture still remains, which has lead to fairly widespread radiation fog in the Laramie Valley. This should burn off within a few hours of sunrise. A narrow ridge will attempt to fill in over the northern Rockies today, bringing warm and dry weather back to the area for the next few days. For today, expect 700-mb temperatures to gradually warm back to around 0C by the end of the day, which will support high temperatures near seasonal averages. Dry air aloft will mix down this afternoon, and send humidity down to around 15 to 20%. North winds will also develop over the plains today, and we can expect occasional gusts of 15 to 25 mph. Thus, fire weather conditions will be elevated today, but we should remain outside of critical.

The strength of the ridge overhead will peak on Saturday with 700-mb temperatures around +3 to +5C. Highs will climb to the mid 60s to mid 70s, which will be about 10F above seasonal averages. The airmass overhead will also be exceptionally dry. NAEFS mean precipitable water values are around 0.10 to 0.25 inches, which is as low as the 2.5 percentile for portions of the area. Humidity will easily drop below critical thresholds, with single digit RH expected to show up over the High Plains. With the ridge axis close to overhead, winds should remain fairly light, but northwest flow on the periphery of the ridge could produce wind gusts of 15 to 25 mph over the High Plains. The most likely scenario keeps us out of critical due to winds remaining too light, but with humidity as low as it is expected to be, we will need to watch Saturday closely for fire weather conditions. Sunday will be another warm day, but the ridge overhead will begin to weaken as a powerful, closed upper level low moves into the West Coast and weak shortwaves drop down from the north. Forecast highs are fairly similar to Saturday, but moisture will begin to recover fairly rapidly. While a weak boundary will improve dewpoints along and north of the North Platte River Valley, the moisture recover will be primarily aloft for those further south. As a result, we can expect to see a return of the afternoon and evening virga showers, with potential for gusty winds.

LONG TERM /MONDAY THROUGH THURSDAY/

Issued at 310 AM MDT Fri May 1 2026

A very complex and messy synoptic weather pattern is setting up for the early part of next week. The weekend ridge will fade to the south as the sprawling upper level low elongates and spread inland. Meanwhile, the broad upper level low over the Hudson Bay region will retrograde westward, pushing the storm track of weak upper level shortwave troughs closer to the northern Rockies. While there will be potential for widespread beneficial precipitation, the realization of this potential will depend on the complex interaction between these two features. By Monday afternoon, most ensemble members show an elongated band of elevated moisture stretched across roughly the entire I-80 corridor through the western US from California to Nebraska. This is spread between the closed low to the west and the main broad upper level low to our northeast. Ensemble mean precipitable water values climb above 0.5 inches for much of the area by Monday afternoon as well. Monday's precipitation chances look to be mainly convective, but this will gradually become more synoptically driven heading into Tuesday as frontogenesis associated with the northern branch train of shortwaves moves into the area. Moisture is plentiful, but forcing is much more muddled, which increases the uncertainty regarding precipitation outcome Monday PM through Tuesday night. There is reason for cautious optimism concerning the potential for beneficial precipitation, with the highest odds generally along the I-80 corridor. Still, we are still several days out and we have seem many promising systems this season fizzle into nothing in the last few days leading into the event. Without a clear signal for widespread lift, the official forecast is somewhat conservative on both PoPs and QPF.

Ensembles (particularly the ECMWF ensemble) made a fairly significant shift towards a wetter solution across the I-80 corridor last evening. Looking at total QPF between Monday afternoon and Wednesday morning, the ECMWF ensemble jumped significantly in the 00z suite. The highest probabilities for beneficial moisture are along the I-80 corridor. Currently, Laramie and Cheyenne have roughly a 60-70% chance for 0.25" or more, and a 40% chance for 0.5" or more. Rawlins, Wheatland, Scottsbluff, and Sidney all have around a 40-50% chance for 0.25" or more, and a 20-30% chance for 0.5". Further north, these probabilities drop off more. The ensemble members in the wetter clusters generally have lower 500-mb heights on the western periphery of the broad ridge over central North America, whereas members with a more powerful ridge over the Pacific northwest positioned further east keep the area drier. Another caveat to this system is that the wetter ensemble members are also the colder ensemble members. This would mean that in the wetter scenario, we would likely see rain changing over to snow Monday night into Tuesday. Tuesday would likely be considerably colder than the current NBM mean. If the drier scenario plays out, temperatures would also likely remain warmer. In this scenario, we could expect spotty rain showers, with snow mainly confined to areas above 7000 ft or so in elevation.

The unsettled weather pattern will move out of the area by Wednesday morning. After this, ensembles are in good agreement showing strong ridging working back into the area and thus pushing high temperatures back above seasonal averages for the second half of next week.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 525 AM MDT Fri May 1 2026

LAR is dealing with dense fog this morning. Expect fog to burn off between 13z and 15z. VFR conditions will prevail after that.

Elsewhere, expect VFR for the forecast period. Northerly winds will occasionally gust to around 20 knots late this morning into the early evening hours. The wind direction may be variable at times overnight.

CYS WATCHES/WARNINGS/ADVISORIES

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