010 FXUS65 KCYS 110502 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1002 PM MST Wed Mar 10 2021 .UPDATE... Issued at 517 PM MST Wed Mar 10 2021 Let the Winter Storm Warnings and Winter Advisories expire this evening as most of the snow has ended with the first shortwave moving into the northern plains. Will send out updates to POP, temperature, and winds over the next few hours once the snow showers or flurries end shortly. Winter Storm Watch in effect for Friday and this weekend with the most severe conditions likely Saturday, Saturday night, and Sunday morning. && .SHORT TERM...(This evening through Friday) Issued at 300 PM MST Wed Mar 10 2021 ...One winter event winding down this afternoon. Another...potentially historic event taking shape for Friday through Sunday.... Currently...Surface low near Wheatland this afternoon with cold front extending southwest into northwestern Colorado. Snow band continues across the northern Nebraska Panhandle westward to Converse County. Still getting snow reported on mountain SNOTELS in the SNowy and Sierra Madre Ranges as well as Metars up near Douglas and Chadron. Decided to clear out most of the advisories across the southern CWA with the exceptions of the Snowy and Sierra Madre Ranges and Converse/Niobrara and northern Panhandle where warnings will be allowed to continue through 5PM. Off to our west across central California...our next low pressure system is moving on shore. Evening shift will need to monitor for fog development this evening as the snow that fell today had quite a bit of moisture content to it. Would say the lower elevations of the Panhandle and maybe Laramie would be the prime areas for fog tonight. Mainly dry Thursday for most of the day...but guidance begins to hint at qpf developing across our southwestern counties late Thursday afternoon. Upper low moves into southern Nevada and northern Arizona Thursday evening with difluent upper level flow over southern Carbon and Albany Counties. NAM...SREF and GFS all showing widespread QPF Thursday evening into Friday morning in this diffluent flow. ECMWF showing similar placement...but much less QPF. Given the pretty good agreement from the GFS...NAM and SREF QPF...decided to start a Winter Storm Watch for our western counties after 00Z Friday...spreading east to the Panhandle by 12Z Friday. .LONG TERM...(Friday night through Wednesday) Issued at 300 PM MST Wed Mar 10 2021 Key messages...Heavy snowfall is likely starting Friday afternoon. Prepare for impossible travel conditions starting Saturday morning into Sunday evening. Protect livestock, people, property, and pets. IMPACTS...Whiteout conditions, low visibility levels, and possible power outages. Blizzard conditions are possible starting Saturday afternoon into Sunday evening for the Nebraska Panhandle and Albany, Laramie, Platte, and Goshen counties. Saturday and Sunday's snowfall will bring major impacts to the entire CWA across southeastern Wyoming and the western Nebraska Panhandle. Forecast confidence is medium with placement and duration of the low pressure system hovering in Colorado. The uncertainty continues for exact snowfall amounts and intensity of this system due to the forecast concerns of varying dynamics and the possibility of a barrier jet forming. Although it is still early, this system shows tight gradients and strong winds aloft will support strong surface gusts up to 35-40 MPH for the Nebraska Panhandle and southeastern Wyoming. A possible jet could develop along the Rocky mountain ranges which could enhance snowfall development especially with most models showing cold air aloft. Snowfall ratio were too high with the GFS so using a NBM/ECMWF blend, I created a sweet spot ratio across the CWA ranging from 11:1-8:1. If this set up continues on track, this will lead to record-breaking snowfall across the region. Potential 3-day storm total snow forecasts are significantly above maximum 3-day records for Cheyenne and Scottsbluff including the March 2003 snowfall event. In addition to snowfall and strong winds, temperatures continue below freezing in southeastern Wyoming and hover in the upper 30s for the Nebraska Panhandle into next week. Skies will remain overcast into Tuesday afternoon. A piece of energy cuts off the same low pressure system from the weekend which may lead to light snowfall again Tuesday although upper level moisture is not present at this time. Mild conditions are possible mid next week. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1002 PM MST Wed Mar 10 2021 Current radar imagery has indicated that the snow has finally shifted to the east, lifting the majority of terminals to VFR conditions. VFR and MVFR conditions expected to through the late afternoon tomorrow. Through the forecast period, winds are expected to remain light. Main concern for the remainder of this evening, into tomorrow morning, are the fog potentials for KCDR. Forecast soundings still look good for that terminal showing a low level moisture layer below the inversion. Still some uncertainty with the cloud deck above, which will limit fog development. Next shot for wide-spread snow is expected tomorrow evening. At this time the low pressure cell seems fairly disorganized, primarily bringing snow only for the KCYS, KLAR, and KBFF with some wrap- around moisture on the northern portion of the low. There is a chance that the snow will need to be included in the remaining terminals, depending on how this low develops over the next 12 to 18 hours. && .FIRE WEATHER... Issued at 300 PM MST Wed Mar 10 2021 Minimal fire weather concerns as we have seen widespread snow and are looking at another widespread heavy snow event Friday through the weekend. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Winter Storm Watch from Thursday evening through late Sunday night for WYZ101>103-106>108-116>119. Winter Storm Watch from Thursday afternoon through late Sunday night for WYZ104-105-109-110-113>115. NE...Winter Storm Watch from late Thursday night through late Sunday night for NEZ002-003-019>021-054-055-095-096. && $$ UPDATE...TJT SHORT TERM...GCC LONG TERM...AW AVIATION...MD FIRE WEATHER...GCC