505 FXUS65 KCYS 281104 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 404 AM MST Sat Feb 28 2026 .KEY MESSAGES... - High Wind Warnings remain in effect for the wind prone locations through 11 AM Saturday morning. - Red Flag Warnings have been expanded to include southern Converse County, and northern Platte and Goshen counties through 5PM Saturday evening. - Precipitation chances start increasing Sunday morning and continue throughout most of the upcoming week. && .SHORT TERM /THROUGH MONDAY NIGHT/... Issued at 205 AM MST Sat Feb 28 2026 One more day of active weather before the region with see some calmer weather on Sunday. The upper-level ridge over the western CONUS will slowly move eastward before being absorbed into the broader upper-level ridge developing over the Desert Southwest. Northwesterly flow wil continue aloft, leading to another dry day across the region with continued gusty winds. However, later this evening into the overnight hours, a fairly strong band of 500mb vorticity will start pushing into southwestern portions of the CWA as a subtle 500mb shortwave traverses across southern portions of the CWA. Further down at 700mb, height gradients will finally begin to weaken later this morning with downward omega values decreasing as well. Craig to Casper gradients will finally dip below 50m by 8 to 11 AM this morning, leading to the end of the high wind concerns for the next several days. As gradients weaken and 700mb winds switch to more westerly east of the Laramie Range, 700mb winds west of the Laramie Range switch to southwesterly. This favors upslope flow along the Sierra Madre and Snowy Ranges. Assisted by the 500mb shortwave and cyclonic vorticity advection, precipitation chances in the mountains start to increase very late tonight into very early Sunday morning. Precipitation in the Sierra Madres looks to start around 11PM tonight and continue throughout much of the next several days. Snow accumulations do not look to be all that high at this time, with the current forecast of only 4 to 6 inches in the mountains through Monday evening. Temperatures will be warm once again Saturday, with highs expected to be in the mid-50s to mid-60s across the region. Critical fire weather conditions are expected to continue this afternoon across much of the region. Afternoon minimum humidity values will drop into the 10 to 20% range with strong wind gusts from ongoing downslope flow. The worst conditions look to be along the I-80 corridor through the southern Panhandle. However, northern portions of the region may also see critical fire weather conditions with strong winds, namely along the I-25 corridor in Converse County. Decided to add fire weather zone 418 to the Red Flag Warning for this afternoon as critical conditions may develop this afternoon. With how warm and dry it has been, it will not take much to get a fire going and with breezy winds, rapid fire spread is expected. Humidity recoveries Saturday night into Sunday morning will be very good, likely into the 60-75% range. With additional moisture moving into the region, critical fire weather conditions will end Saturday evening. Elevated fire weather conditions are not expected to return until mid-week. On Sunday, the upper-level ridge starts to quickly accelerate off to the east as an incoming upper-level trough pushes into the western CONUS. Multiple lobes of 500mb vorticity will eject out ahead of this trough and will continue to do so all day on Sunday, with the main trough impacting the region Monday into Tuesday. 700mb flow on Sunday will remain largely westerly along and east of the Laramie Range and southwesterly west, suggesting continued upslope flow along the Sierra Madre and Snowy Ranges. With surface flow also remaining mostly southwesterly, continued snowfall is expected in the mountains. However, the best moisture doesn't arrive until mid- day Sunday, so significant snowfall is not expected to begin until then. A brief lull in the precipitation looks possible late Sunday night into early Sunday morning ahead of the next push of upper- level forcing Monday onwards. Temperatures Sunday will be warm again, with highs in the low- to upper-50s area wide. On Monday, the upper-level trough will start to approach the region, leading to continued 500mb vorticity lobe ejection and increase upper-level synoptic forcing. The best forcing looks to arrive Monday evening throughout the day Tuesday. Monday afternoon, a 700mb shortwave looks to propagate across northern portions of the CWA, leading to brief increase in winds west the the Laramie Range. High Winds are not expected given the fairly weak 700mb jet Monday afternoon. For more information regarding Monday night into the day Tuesday, please see the long term discussion below. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Issued at 205 AM MST Sat Feb 28 2026 No major changes. See previous discussion... The work week will begin under the influence of a weak ridge located downstream of a rather vigorous shortwave trough situated over Northern California, resulting in a continuation of the anomalously warm conditions across SE Wyoming and the Nebraska Panhandle. There is weak isentropic ascent located over our area Monday morning into the afternoon, which is also reflected in the omega fields. 700 mb flow remains quasi-zonal and forecast soundings indicate some dry air in the low levels, so the Sierra Madre and Snowy ranges will be the favored areas for QPF, although there will still be a chance for a few rain or snow showers at lower elevations, though it may be more of a virga event, resulting in more wind than precipitation. Monday night into Tuesday is when we have the highest confidence of seeing the majority of our precipitation, as there is some 700 mb frontogenesis across Southern Wyoming helping to provide some forcing for ascent, hence increasing our chances for more widespread precipitation. The NBM has mean QPF ranging from 0.15-0.20 inches for areas east of the I-25 corridor, whereas our mountain ranges should see an additional 0.10 inches given the mid-level flow regime. NBM probabilities of seeing 0.1 inches of liquid or greater is a near certainty for the Snowy and Sierra Madre ranges, whereas east of the Laramie Range areas have a 50% shot at seeing QPF exceeding this threshold. 50% probabilities also exist at achieving WWA criteria for the Snowy and Sierra Madre ranges, so stay tuned for future updates as this event gets closer. As this system is rather disorganized and the majority of the synoptic-scale forcing for ascent is located well to our south over Colorado, this event unfortunately won't put much of a dent in our ongoing drought conditions. On Tuesday, temperatures at lower elevations are progged to be in the upper 40s to lower 50s, so any precipitation in extreme Eastern Wyoming and our Nebraska counties will likely fall as rain. On Wednesday high temperatures rebound into the mid to upper 50s for areas east of the Laramie Range as a weak mid-level ridge builds in ahead of the next shortwave trough, therefore conditions will remain dry. Thursday our next system of interest should impact our area as it moves in from the west. This system digs in more so from the north compared to the system earlier in the week, so we can expect a dip in our temperatures and increasing chances for beneficial moisture for Southeastern Wyoming and Western Nebraska. Our winds will also ramp up at this time especially in the usual wind-prone areas of Bordeaux and Arlington thanks to 40-50 knot 700 mb flow rounding the base of the shortwave trough in addition to anafrontal gradient flow as this system lifts to the north and east away from our area. In-house guidance has maximum probabilities of around 50% of seeing 60 mph gusts or greater in these areas, so while not as impressive as what we have seen most recently, high winds will return to the picture for the end of the forecast period. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 403 AM MST Sat Feb 28 2026 VFR conditions expected through the period with clear skies turning partly cloudy to mostly cloudy throughout the evening. A weak front will move through the region today, shifting winds to be out of the north. Expecting the front to pass through all terminals between 16 and 20Z. Precipitation chances increasing late in the period. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Red Flag Warning until 5 PM MST this afternoon for WYZ430>433. Red Flag Warning from 11 AM this morning to 5 PM MST this afternoon for WYZ418. High Wind Warning until 11 AM MST this morning for WYZ106-110- 116-117. NE...Red Flag Warning until 5 PM MST this afternoon for NEZ436-437. && $$ SHORT TERM...AM LONG TERM...NB/AM AVIATION...AM