textproduct: Cheyenne

KEY MESSAGES

- Numerous rain showers and widely scattered thunderstorms expected on Saturday. A few strong thunderstorms or an isolated severe storm possible.

- Mostly dry and warmer weather will prevail for Sunday through Wednesday, with thunderstorms possibly returning late in the week.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 152 PM MDT Sat May 9 2026

Scattered showers and some weak thunderstorms are noted on radar across the area as of this afternoon primarily for our northern zones with much stronger activity seen to the northwest moving into Central Wyoming. At the surface, a cold front is currently draped across portion of the northern Nebraska Panhandle and up into northeastern Wyoming, while aloft an upper level shortwave is making its way across Wyoming and into Nebraska through the day. Current expectation for the rest of today is in line with the morning forecast package, and expecting scattered thunderstorms with widely scattered strong to possibly severe activity today.

High resolution guidance remains largely in agreement on this continuing over the next several hours, with a few thunderstorms possible but remaining largely sub-severe. Then as the front drops across the area, we should see an uptick in thunderstorm activity along this boundary across the I-25 and I-80 corridors, with an increase in severe parameters fueling stronger to possibly severe activity. Along this area should be increasing CAPE values with pockets of 800-1200 J/kg, 0-6 KM shear values of 40-60 knots but isolated peaking at around 70-80 knots noted as well on the HRRR, and steepening low and mid level lapse rates. Storms will likely be clustered in nature with limited potential for individual supercells, though cannot rule out at least one to occur early on. By the later part of this timeframe, most CAMs agree that activity will congeal into more linear fragments as they move into Nebraska with intensity waning as the sun sets. Greatest threats will be gusty winds and isolated large hail with activity being higher based in nature.

Overnight temperatures should actually chill notably behind the cold front in tandem with clearing skies fueling radiational cooling, with widespread lows in the 30's expected Sunday morning. A building ridge will then control the weather across the area for the remainder of the short term as we see temperatures rebounding into the 60's and 70's on Sunday, and then significant warmth on Monday as highs skyrocket into the 80's and 90's. This will be knocking on the door of record highs for most of our forecast area with highs 20 degrees above normal. Alongside this record warmth brings the return of critical fire weather conditions as our RH values bottom out in the low teens to near single digits on Monday with some breezy winds possible along the I-25 corridor and along the base of the Laramie Range. Will have to take a deeper dive into fire fuels as we move into Sunday and determine if Red Flag products will be necessary or not.

LONG TERM /TUESDAY THROUGH FRIDAY/

Issued at 152 PM MDT Sat May 9 2026

The general pattern going into Tuesday is one of upper level ridging. A rather large high pressure system will be building over the Four Corners Region with an axis of it passing through. This should allow temperatures to reach the mid 70s to low 80s. We do have fire weather conditions showing up in the interior mountains near Rawlins this day. Humidities appear very low, possibly getting into the low teens with gusty conditions. Elsewhere, dry conditions may favor some elevated concerns. These conditons should persist into Wednesday where some spots in valleys east of the Laramie Range could reach the 90s and near daily record temperatures. Humidities plummet given the favorable environment for deep layer mixing. Relative humidities reaching the mid and low teens are a possibility. Attention to conditions these few days should be maintained for fire weather interests. Thursday a plume of monsoonal like moisture makes its way north from the Eastern Pacific into our area. The ridge gets pushed southeast into Texas allowing increasing chance of isolated to scattered showers and storms. PoPs are low at this time, and surface layer mixing will still be high creating dry conditions at the surface. So, the most likely outcome Thursday are the continued fire weather risk, but maybe throw in a few dry and windy thunderstorms. About this time a compact, but high amplitude trough will be passing over the northwestern Pacific Coast. Global models differ on the speed and strength of this feature. The GFS is much more aggressive with this trough and is a bit slower/south with the progression as it reaches our area Friday. ECMWF is a bit more progressive, weaker and northward with its trajectory. Both have the general negative tilt form to the trough which tend to be more dynamic than positive and flatter systems. The timing is somewhat important from a severe weather angle, a slower and more southward system may allow for the favorable left exit region of the jet to the south of the trough to be in phase with the better daytime heating. At the moment the models make this a more north and eastward event. A dry slot on the south side of the system will create sinking air and may tighten pressure gradients in the 700 mbar enough to create strong winds. Indeed our machine learning models highlight an elevated risk Friday morning and afternoon (~40%) for west to east mountain gap flow locations. Conditions area wide continue to by dry and warm, so fire weather is likely to continue, even going into Saturday. Fuels in our Nebraska Panhandle zones are not in good shape with little green up reported. The snowfall received on the eastern slopes and ridges of the Laramie Range has caused some greenup with vegetation. The periods of recent rain may stave off more critical fire concerns going into this period.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1132 AM MDT Sat May 9 2026

Showers are developing across the Nebraska Panhandle and within the vicinity of KCDR, KBFF, and KAIA. This activity is expected to become more widespread before the arrival of a mid level shortwave. Widespread showers and thunderstorms are expected to form over the mountain ranges and spread southeast into the high plains. Impacts to terminals may include variable surface winds and gusts above 50 kts, hail, lightning, and reduced visibilities down to two statue miles or less. KBFF, KAIA, and KSNY have the highest confidence of thunderstorms this afternoon. Storms are possible at all other terminals with the same threats to aviation. A few hour lull in storms is expected after sunset before more shower and storm development is possible for the Nebraska Panhandle terminals. The intensity of this convection is expected to be less than the afternoons, however ceilings could be lower. Elsewhere, weak, variable winds and high humidity may create fog near sunrise. Probabilities are too uncertain at the moment and were left out of the TAFS for this synoptic forecast period. Cloud coverage is expected to diminish going into tomorrow afternoon.

CYS WATCHES/WARNINGS/ADVISORIES

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