textproduct: Cheyenne

KEY MESSAGES

- Near record warmth and critical fire weather conditions will continue through Monday evening.

- A few high-based virga showers will be possible this evening, with more widespread activity possible Monday, bringing the potential for gusty and erratic winds and isolated lightning.

- A strong cold front arriving Monday night will bring cooler temperatures and a chance for rain and snow Tuesday into Wednesday.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 310 AM MDT Sun Mar 29 2026

The last of yesterday evening's virga shower activity is beginning to dissipate on radar early this morning, but we will be ready to rinse and repeat Saturday's weather for both Sunday and Monday, with a few minor differences each day. The powerful upper level ridge has moved back into the area, although this iteration is much flatter and broader than previous iterations this month. Still, 700-mb temperatures are hovering around the 97.5 to 99.5 percentile of climatology. All Wyoming sites set daily record highs on Saturday, and most can expect additional records both today and tomorrow. While these values would have been remarkable pre-2026, the high bar of monthly records set on 3/21 and 3/25 are expected to remain safe through this round of warmth. Today's highs will be very close to yesterday in Wyoming, and perhaps 1-3 degrees warmer in Nebraska. This will be due to the surface trough pulling east into central Nebraska this morning, allowing for westerly downslope winds to develop across the entire area. The other impact of that will of course be an increase in the fire danger for Nebraska. Most of southeast Wyoming remains under a Red Flag Warning until 9PM Monday, but Nebraska zones will join at 10AM today, and continue through Monday evening. In Wyoming, winds will be a little lighter than yesterday, generally gusting 30 to 45 mph. Another vort-max is expected to push through the area this evening, providing synoptic lift to support another round of virga showers. Today's activity will probably less widespread than yesterday. Lightning is a little less likely too, but it cannot be ruled out. Showers will bring gusty and erratic winds, with a slight chance (20%) for gusts exceeding 60 mph in the typical wind prone areas, and little to no rainfall.

By Monday, our area will begin to experience some influence from a Pacific trough finally breaking into the northern Rockies region. This system will support potent lee cyclogenesis over the Black Hills region, with surface pressure falling rapidly through the day. Stronger westerly winds will overspread most of the area. Look for wind gusts of 35 to 55 mph in Wyoming, and 30 to 40 mph in Nebraska. This will keep fire danger quite high again as temperatures creep up a few more degrees in the Nebraska panhandle. In addition, the late afternoon and evening virga shower activity looks slightly more widespread on Monday. Lightning probabilities will also be a touch higher, perhaps around 10-20%. As elevated moisture increases ahead of the next system, we may actually see some rainfall reach the ground. While the chance for wetting rainfall (0.10" or more) remains quite low Monday evening, there is about a 20-30% for 0.01" over much of the area. There is about 30% chance for winds exceeding high wind criteria in the typical wind prone areas. Parameters for synoptic winds are largely unimpressive, but the boost from the virga shower activity could be enough to get a few gusts exceeding 60 mph.

Big changes will finally arrive with a powerful cold front Monday night. The lee cyclone will begin to race eastward around sunset, allowing rapid pressure rises to push down from the north along a frontal boundary. Expect an abrupt wind shift to the north behind this boundary. Winds could be quite strong right along the front as well, with potential for gusts of 45 to 55 mph during a brief window behind the frontal passage. Shower activity will continue along and behind the front, continuing into Tuesday morning. Rapid cold air advection will also change precipitation type from rain over to snow by daybreak Tuesday for most of the area. The front will stall just west of the Laramie Range, allowing milder air to remain in Carbon county. The frontal passage may bring a dusting to an inch or so of snow to portions of the area and a rapid drop in temperatures end up just below freezing by Tuesday morning.

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 300 AM MDT Sun Mar 29 2026

A strong surface high pressure will settle in over the northern Plains Tuesday behind the cold front Monday night. The boundary will remain stalled against the terrain barrier with winds transitioning from northeast to east or southeast through the day as the surface ridge axis passes by. Meanwhile, another upper level shortwave will traverse across the Great Basin and approach the area. Models are now consistently showing decent isentropic lift developing around midday Tuesday, overrunning the stalled frontal boundary. This signal continues through Tuesday night until sometime Wednesday, when the upper level trough axis passes overhead and forcing flips to descent. The combination of good moisture (NAEFS mean PW values around the climatological 90th percentile), low level upslope flow, and isentropic lift suggests some reason for cautious optimism on portions of the area actually receiving decent precipitation from this system. Current NBM probabilities for 0.10" or more of liquid precipitation are above 50% for areas south of a roughly Elk Mountain to Wheatland to Sidney boundary. This region is where southeast low-level winds are favorable for lift and frontogenesis from the stalled boundary looks the most potent at this time. There is some model disparity in timing, mostly concerning whether this will be a Tuesday PM into Wednesday morning event or if it disorganized lift will keep unsettled weather and chances for showers into Thursday morning. In addition, precipitation type will be very tricky with this event. On one hand, we have a sufficiently cold airmass parked up against the Laramie Range, but with warm air advection aloft contributing the primary lifting mechanism, we could see precipitation mixing with rain and times. This also won't be strictly tied to elevation, as the airmass over the higher elevations will be considerably warmer than the airmass further off to the northeast. Forecast soundings suggest we may be seeing more snow than rain, but snow will be wet with very marginal temperatures right around or even just above freezing.

This system will depart by Wednesday night, after which time ridging will briefly recover. Expect temperatures to climb back to around 10 degrees warmer than average for Thursday, with some potential for strong southwest winds over Carbon and Albany counties, and strong southerly winds over the High Plains as the surface high pressure system retreats to the east. While relative humidity will drop for Thursday, there should be enough moisture in this return flow to keep values above critical. Still, due to the winds, this will warrant a close watch in the coming days. Currently there is a 30 to 50% chance for high winds in Carbon and Converse counties with the pre-frontal southwest flow on Thursday.

The next upper level trough will push in from the west late Thursday. Models are beginning to come into a little better agreement regarding this system. Most LREF members (about 75%) now support the upper level low tracking just north of our area, which would mean a faster, drier, and windier storm for us. There are still 25% of members holding onto the slower, more southerly closed low scenario which would have a higher probability of widespread snowfall, but the current forecast favors the scenario supported by the majority. In the more likely scenario, we could expect a powerful cold front moving in from the west Thursday night, bringing exceptionally strong frontogenesis and rapid cold air advection. The second system looks considerably colder than the first, which would support rain ahead of the front, quickly changing over to snow behind. While this scenario provides a much shorter window for precipitation, it will still be quite potent. There is already a very strong frontogenesis signal showing up in most ensemble members. For this system, probabilities for 0.10" or more of precipitation range from 30 to 50% for the entire area. It is too far out to narrow down regional variability in precipitation. In addition to the chance for snow, there will be a chance for another round of high winds, this time from the northwest, as the storm system departs. This would be either on Friday or Saturday, but again there is some disparity in the timing and speed of departure of the second system too.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1120 AM MDT Sun Mar 29 2026

VFR conditions are expected for the TAF duration. Model guidance has shifted to shower development further south near the Colorado border so all showers were taken out of the TAF. If the showers do move north they are most likely to be in the vicinity of KLAR and KRWL between 00z and 08z. Other than that the winds look to be fairly breezy but nothing out of the norm here.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning until 9 PM MDT Monday for WYZ417>423-425- 427>433. NE...Red Flag Warning until 9 PM MDT Monday for NEZ434>437.