185 FXUS65 KCYS 082252 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 352 PM MST Wed Feb 8 2023 .SHORT TERM...(Late this afternoon through Friday night) Issued at 230 PM MST Wed Feb 8 2023 Mid/upper level trough axis extended from central MT south along the WY/ID border. A surface cold front reached from central ND through northern and western WY. Regional radars were detecting scattered snow showers, with a couple snow squalls developing to the north of Casper. The latest high-resolution model indicates a continued south-southeast progression of these snow squalls impacting the I-25 corridor from Douglas to Cheyenne late this afternoon through early evening. Another prime area for snow squall formation is along I-80 from Rawlins to the I-80 Summit. Ahead of the front and trough, westerly winds have been strong and gusty, particularly near Bordeaux and between Laramie and Rawlins during the morning and early afternoon. Winds behind the front remain strong from the northwest, and the High Wind Warnings will continue until early this evening. Snow showers will continue through the night into Thursday morning before tapering off in the afternoon. Accumulations during this time will average less than a half inch with the lighter showers, to 2 to 4 inches along the Pine Ridge, North Laramie Range and North Snowy Range Foothills. The Sierra Madre Range can expect 3 to 6 inches, with 5 to 10 inches over the Snowy Range. Winter Weather Advisories for snow and blowing snow remain in effect until late Thursday morning. After average high temperatures this afternoon, high temperatures Thursday will be 10 to 20 degrees colder. Strong northwesterly flow in the low/mid levels on the backside of the departing trough Thursday will primarily affect the high plains (east of I-25) through at least early afternoon with gusts of 45 to 55 MPH. The winds will gradually subside late in the afternoon and evening. Clear skies and snow cover will maximize radiational cooling with the mercury plummeting into the single digits and lower teens Thursday night. Wind chill temperatures will bottom out in the teens to lower 20s below zero along and west of the Laramie Range. Westerly winds will increase once again by Friday morning, especially along I-25 between Chugwater and Wheatland, and I-80 between Laramie and Rawlins as low level gradients exceed 60 meters. Confidence for high winds is low to moderate given the 30 to 35 kt 700-800mb flow. Peak gusts in these wind-prone areas will be 45 to 55 MPH. The winds will remain elevated through Friday night. The influence of a mid/upper level ridge building over the CWA and downsloping winds east of the Laramie Range will result in high temperatures from the upper 30s to middle 40s Friday. Friday night will not be as cold with lows in the teens and 20s. .LONG TERM...(Saturday through Wednesday) Issued at 230 PM MST Wed Feb 8 2023 Very few changes remain in the extended weather pattern. Upper level ridging will persist on Saturday, despite being on the western fringe of this feature. A 567 dm upper level high will reside across our forecast area for the majority of Saturday. Surface temperatures should remain above average for daytime highs by up to 10-15 degrees as 850mb temperatures east of the Laramie Range warm to thresholds of +3C to +12C aloft. Upper level steering flow will trend down as the day persists, so any mixing in the lower levels of the atmosphere that does occur will help bring the temperatures up quickly on Saturday morning. Daytime highs will range from the 30s to middle 40s west of the Laramie Range, and the middle 40s to middle 50s for areas east of the Laramie Range. Some locations may approach 60 degrees if westerly winds persist for a short time longer than guidance is signaling at this time of inspection. This will be the warmest day for the next week, so any outdoor recreational activities planned should be well received with the mild temperatures and sunshine for a good portion of the day. Cloud cover will build from the west late Saturday afternoon into the early evening period. Upper level flow is modeled to split on Saturday night into Sunday as an Upper Level Low (ULL) shears off from an upper level longwave trough. The trough will propagate from the Pacific Northwest, and quickly bring a weak surface cold front to the region on Sunday. A weak shortwave embedded within the flow aloft will assist with widespread cloud cover. However, surface temperatures will not be affected by more than 5-15 degrees. This looks to be a pretty dry air mass, with little to speak on regarding precipitation. A few light snow showers may be observed, but accumulation is unlikely. Daytime highs near 30 to the middle 40s can be expected, with the warmest temperatures observed east of the Laramie Range and the NE Panhandle. Early next week looks to remain quiet as seasonal temperatures are progged to occur. Upper level flow will transition from zonal to weak ridging Monday and Tuesday. In-house probabilistic data is pinpointing elevated wind gusts Monday afternoon into Tuesday. The main weather pattern that we are keeping an eye on regarding a potential winter weather event is progged to take shape by the middle to latter portion of next week. Model guidance is struggling to come into better agreement with respect to timing and placement of a Colorado Low. A strong cold front has the highest confidence at this time with respect to temperatures, but the location of where snowfall accumulations are heaviest remains to be seen. We will continue to monitor the trends of the weather pattern shift next week, but until that time, we can expect daytime highs remaining near or above average for our area. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 349 PM MST Wed Feb 8 2023 VFR can be expected through the initial timeline at most terminals, and then -SHSN will move into the SE WY. Snow squalls are expected in portions of SE WY between 0Z-4Z, but it will be tricky to pinpoint if they impact the SE WY terminals. Have gone with an aggressive approach for SE WY terminals this evening to reflect this tricky aviation forecast. The likely scenario is low end VFR will quickly shift to MVFR/IFR/LIFR as the -SHSN moves from west to east- southeast. Wind gusts of 20-40 knots for SE WY terminals can be expected through late this evening. NE Panhandle terminals will see VFR transition to MVFR by this evening as -SHSN slowly moves into the region. The most likely scenario is that the NE Panhandle will remain in high-end MVFR until the -SHSN and CIGs decrease flight category to IFR at times. Wind gusts of 20-35 knots will occur the NE Panhandle, with wind gusts increasing in the NE Panhandle on Thursday morning near or shortly after 12Z. && .FIRE WEATHER... Issued at 230 PM MST Wed Feb 8 2023 No fire weather concerns through Thursday with snow showers, colder temperatures and elevated humidities. Strong and gusty west winds this afternoon ahead of a cold front will shift to the northwest behind the cold front. Winds will remain strong with gusts of 45 to 55 MPH through early Thursday afternoon across the high plains. Warmer and drier conditions are forecast Friday and Saturday with minimum humidities between 20 and 30 percent. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning until 8 PM MST this evening for WYZ106-110-116- 117. Winter Weather Advisory until 6 AM MST Thursday for WYZ110. Winter Weather Advisory until 11 AM MST Thursday for WYZ114. NE...None. && $$ SHORT TERM...MAJ LONG TERM...BW AVIATION...BW FIRE WEATHER...MAJ