textproduct: Cheyenne

KEY MESSAGES

- A Marginal Risk of Severe thunderstorms expected Sunday with a Slight Risk (2 of 5) of severe thunderstorms possible Monday for eastern Wyoming and the Nebraska Panhandle, with all severe hazards possible.

- Expect a quick cool down on Monday before heat builds back into the area towards the middle of next week.

- Fire Weather Watch in effect for the eastern high plains of southeast Wyoming and all of western Nebraska Tuesday through late Wednesday, with critical fire weather conditions likely extending through late in the week.

SHORT TERM /THROUGH TUESDAY/

Issued at 235 PM MDT Sun Jun 7 2026

Current observations across the region show generally mostly sunny skies, but increasing clouds as we head towards peak heating of the day. A surface cold front, which has hardly moved in the past few hours, is currently located across central and northeast Wyoming, just a bit outside of our forecast area. Further south, a dryline-like boundary extends south of the cold front, roughly paralleling the Wyoming/Nebraska border. Dry conditions with inverted-V soundings located west of this dryline with dewpoints in the 20s to low 30s. East of the dryline is where the best instability is located with dewpoints in the 40s and 50s with SBCAPE values between 1000 to 2000 j/kg. Still fighting a little bit of CIN in the boundary layer, but expect CIN to slowly erode over the next few hours. Expect any strong to marginally severe thunderstorms to form along and east of this boundary late this afternoon and into this evening. SPC has a Marginal Risk for severe thunderstorms across most of western Nebraska, east central Wyoming, and portions of Carbon county (mainly for winds). After a mesoscale analysis, currently lacking in the shear department (0-6 and effective), but shear does increase this evening through late this evening with 40 knots of shear around sunset. This should be sufficient for a few strong to marginally severe storms across mostly the Nebraska Panhandle, but can't rule out some activity in eastern Wyoming as well. There is a small area of Slight Risk, but that's mainly across the far northern part of Niobrara County. Based on high res model data, there may be two individual times for the strong/severe thunderstorm threat. First one being this evening as the dryline-like boundary tracks east, and the second may be later this evening and into tonight as outflow from thunderstorms across eastern Montana and the Dakotas move into our eastern plains as the cold front accelerate southward. This second line of thunderstorms may linger past midnight.

Tricky forecast for Monday with another Slight Risk for severe thunderstorms expected, this time over far southeast Wyoming and the southern Nebraska Panhandle. Some models don't seem to be handling the low level moisture well with this event (especially the GFS) and/or mix it out way too early with the heating of the day. Surface cold front should move across the rest of the area by the early morning hours with thunderstorm outflow, from activity to the north and east, providing the low level moisture with some upslope flow. In fact, added some patchy fog to the east side of the Laramie Range as winds shift into the northeast later tonight. With increasing low to midlevel shear, confidence is increasing for another round of severe thunderstorms forming near the I-80 corridor and North Platte River valley. Will have to watch for all modes of severe weather, including 1 or 2 tornadoes, with 0-1km helicity between 100 to 200 and relatively low LCL's between 1500 to 2000 meters. Large hail is also a concern across the area. It will be around 5 to 10 degrees cooler compared to today behind the cold front, with highs generally in the upper 70s to mid 80s.

For Tuesday, all models show increasing southwest flow aloft as the broad Pacific trough finally tracks east into Wyoming. Increasing west to southwest winds will bring dry air advection to the whole area and greatly limit any thunderstorm threat. Tuesday will be our warmest day of the week with highs in the 80s west of the I-25 corridor, and upper 80s to upper 90s east of I-25. With very warm/hot temperatures, dry conditions, and gusty winds, decided to issue a Fire Weather Watch for far southeast Wyoming and all of western Nebraska. Since similar conditions are expected on Wednesday with poor overnight recoveries, decided to make the Watch valid through Wednesday evening.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 100 PM MDT Sun Jun 7 2026

Tuesday into Wednesday, the Intermountain West switches from southerly flow to a downsloping westerly flow as the upper level low becomes stack moving along the Canadian Border. This will lead to the continuation of warmer temperatures, but also a more likely chance to break the cap when combined with the progged frontal boundary moving through Wednesday afternoon/evening. Our windiest day looks to be Wednesday as the 700mb ramps up to about 50- 55 knots by the afternoon giving us gusty winds but possibly not enough to meet the high wind criteria if those winds stay below 55 knots.By Thursday and area of high pressure looks to build in that may stay through the weekend. Fire Weather remains a concern throughout the long term as RH values look to bounce between 15 and 20 percent and some isolated places dropping as low as 10 percent. The severe chances look minimal through the long term as the stout dry layer looks to stick around with minimal CAPE when glancing at the global model soundings. It shouldn't be a surprise if a Red Flag warning gets issued through Saturday. Another trough looks to push through Saturday evening into Sunday morning giving us another chance for some light rain to possible thunderstorm chances Sunday.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 1040 PM MDT Sun Jun 7 2026

Primarily VFR conditions for the TAF period, with low probabilities (30% chance) for a few non-severe showers and thunderstorms KAIA and KSNY from 06-08Z, hence the mention of PROB30 for these terminals. This may result in brief MVFR with visibilities down to 3SM. Similar to today, we can expect shower and thunderstorms to develop after 20Z, mainly for KCYS and the Nebraska terminals, which will have the potential to produce large hail, gusty and erratic wind gusts up to 60 knots, frequent lightning, and CIGs down to 2 kft. Confidence in exact placement and timing is low, although earliest storm initiation is expected to be in the vicinity of KCYS before storms propagate to the east.

For our winds, expect a shift from SSE to more northerly after 08Z behind the passage of a weak cold front. Can expect gusts to increase to 20-25 knots after 18Z, with some higher gusts at KRWL and KLAR.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Fire Weather Watch from Tuesday afternoon through Wednesday evening for WYZ430>433. NE...Fire Weather Watch from Tuesday afternoon through Wednesday evening for NEZ434>437.