FXUS65 KCYS 122355 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 455 PM MST Fri Dec 12 2025 .KEY MESSAGES... - Recent strong winds across southeast Wyoming will continue to diminish Friday. However, additional High Winds likely for the wind prones late Friday into Saturday morning. - Arctic cold front will brush eastern Wyoming and the northern Nebraska Panhandle Friday and Saturday. Much colder temperatures expected. - Warming trend expected Sunday through early next week with strong winds possibly returning to southeast Wyoming on Tuesday and Wednesday. && .UPDATE... Issued at 455 PM MST Fri Dec 12 2025 Upslope flow across the southern portions of the Nebraska panhandle is leading to areas of fog via upslope. Uncertain how far up the higher elevations this may push up but limited to 4500ft for now which mainly keeps it in the panhandle for now but does locally bring across the Wyoming border along the North Platte river. && .SHORT TERM /THROUGH SATURDAY/... Issued at 119 PM MST Fri Dec 12 2025 The brief break in high winds continues through the afternoon before the next round starts up again this evening. Although it technically hasn't been a true break with sites in the Arlington zone occasionally hitting 60 MPH gusts, it has not been the constant barrage of winds it has been for the past several days. Aside from the winds, observations clearly show where the arctic front has stalled. Temperatures along a line from Douglas to Alliance are currently in the teens and 20s early this afternoon, signaling the location of the front. South and west of this boundary, temperatures range from the upper 30s to low 50s. Hi-Res guidance has really toned down the precipitation behind this front, however, still cannot rule out some light snow showers around the Chadron area this afternoon. High winds pick up again this evening as a surface trough develops in lee of the Laramie Range. MSLP gradients will increase west of the Laramie Range as well as 850 and 700 mb CAG to CPR height gradients. This will increase winds aloft to about 60 kts overnight. Strong subsidence will be the main driver in getting these winds down to the surface. Did go ahead and upgrade the High Wind Watches to Warnings for the South Laramie Range and Bordeaux as in-house guidance gave them fairly good probabilities of hitting high winds. However, the GFS has the trough positioned nearly over the Laramie Range which prohibits a strong MSLP gradient from developing. This could prevent these zones from seeing high winds. Strong winds should keep overnight lows around freezing in the wind prone areas. Did go ahead and adjust overnight low temperatures underneath the arctic front. Given that the current placement of the front this afternoon is a bit more further west and south than anticipated, went ahead and spread overnight lows in the teens and 20s further west to Douglas and further south to Scottsbluff. The Wyoming Wind Machine will turn off by late Saturday morning as winds turn more northerly. High Wind Warnings will expire at 8 AM, but blustery conditions can be expected at the wind prones throughout the day. Northerly winds will funnel more cold air into the CWA, however, the extent of the arctic air still needs to be ironed out. Most ensembles keep the arctic air around the Chadron area, but there are members from both the GFS and ECMWF that show it creeping into Alliance and Douglas. For now, kept the coldest air in the northern Nebraska panhandle. For the rest of the CWA, high temperatures in the 30s and 40s are expected, with the warmest temperatures expected west of the Laramie Range. A pleasant day is expected Sunday as strong upper-level ridging builds into the Rockies. Southwest flow aloft will usher in 700 mb temperatures as warm as +8C! These temperatures will approach climatological max of NAEFS climatology so expect an unusually warm mid-December day! High temperatures across the area will be in the 50s and 60s, which is about 20 degrees above average. These temperatures will put Cheyenne and Laramie within a degree of tying their record highs. Mostly sunny skies with lighter winds will make for a great end to the weekend. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 119 PM MST Fri Dec 12 2025 There remains strong agreement from global ensemble based clusters regarding the evolution of the ridge currently over the western half of CONUS. The main differences between ensembles would be in the amplitude of any shortwave activity traversing the weakening ridge early next week with more southerly tracking waves bringing stronger low level pressure gradients to the forecast region and high potential for strong winds in the wind prones areas early in the week (Monday/Tuesday). Looking towards the mid week the is signal even in the ensembles for a strong hybrid type low to track across the Canada/US border with a zonal flow in the central/northern Rockies allowing strong low to mid level flow to push south into our area bringing strong winds to the wind prones and adjacent areas. Currently this event does not look to have the ceiling as the event we just concluded but 70kt 700mb flow is certainly in the cards which when paired with favorable negative omega in the lee of the higher terrain and an increasing sfc pressure gradient along the front range as the attendant cold front pushes south through the high plains the ceiling remains higher somewhere between Saturday's high winds in the wind prones and last Tuesday's peak gusts which were widely 60-80mph even outside the wind prones. Aside from the typical threat of wind this transient early week shortwave activity does look to bring a chance for high elevation snow (likely below advisory thresholds) and will prevail the downslope airmass through the mid week period when that reinforcing cold front moves south along the front range dropping highs from the early week 50s and 60s to late week 40s and 50s behind the front. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 455 PM MST Fri Dec 12 2025 Fog across the Nebraska panhandle looks to be the main concern tonight with widespread 1/4sm to 1sm already occurring and likely to continue amid this upslope regime. Winds of 10-15mph will do little to mix the fog out and may actually work to just push it further west up the valleys. IFR to LIFR cigs are common as well with a few sites showing only 100-200ft of vertical vis. For Wyoming terminals gusts remain the primary hazard at 30-40kts through the period. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning until 8 AM MST Saturday for WYZ106-110-116. NE...None. && $$ UPDATE...WFOCYS SHORT TERM...SF LONG TERM...WFOCYS AVIATION...WFOCYS