618 FXUS65 KCYS 091741 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1141 AM MDT Tue Oct 9 2018 .UPDATE... Issued at 1115 AM MDT Tue Oct 9 2018 A Winter Weather Advisory has been issued for Cheyenne and Morrill counties in the southern Nebraska Panhandle from 12 PM until 12 AM MDT. Our concerns are growing for potentially significant snowfall across this area as a strong upper-level low ejects northeast into the Central Plains this afternoon/evening. Models are in excellent agreement with the western fringe of an impressive TROWAL over our far southeastern zones per 700-500 hpa theta-e progs. An extensive precipitation shield has already developed across eastern Colorado this morning, with snow being observed at Limon and Wray. The main concern is surface temperatures with Sidney at 35F, but it appears precipitation should commence shortly, suggesting either steady or falling temperatures through the remainder of the day. Our overall confidence in snow is increasing. HRRR/RAP forecast soundings show deep saturation, along w/ decent dendritic growth potential. A bit of a coupled upper jet will provide further dynamic support for at least light to moderate snow, w/3+ inches possible by midnight. If rates are heavy enough, there is potential for snowfall amounts at or near Warning criteria near SNY. Updates will be sent shortly. && .SHORT TERM...(Today and tonight) Issued at 242 AM MDT Tue Oct 9 2018 The upper level trough axis has moved over the region and moisture has largely been kicked east with a few light flurries continuing across the high terrain of southeast Wyoming. As the day progresses from morning to afternoon, the surface low, now located over north-central Colorado, will swing north over central Nebraska, bringing a shot at more precipitation as wrap- around moisture filters into the area. Areas affected will be along the western portion of the Nebraska Panhandle beginning late afternoon and extending through early evening. An upper level shortwave will reinforce the shower potential towards the evening hours. However, daytime highs are forecast to be just above freezing, so precipitation will fall as a rain/snow mix, but will likely melt upon contact with the surface, as surfaces heat first. Grassy areas may see signs of light flurries. Still, the bulk of the moisture will stay to the east of the region, mainly affecting areas east of a Sydney-Alliance-Chadron line, so the region seems to have been spared from a heavy dumping of wrap- around moisture this time around. A dry northwest flow aloft will move over the region by midnight as the earlier disturbance moves north and east. Cool, dry conditions will remain for the overnight hours. .LONG TERM...(Wednesday through Monday) Issued at 242 AM MDT Tue Oct 9 2018 Another upper-level disturbance will drop in from the north and swing across the region Wednesday. The system looks like it'll start off strong, supported by a bout of strong diffluence aloft, but then lose steam and tucker out just as it moves to the east of the Laramie Range around mid-afternoon. Temperatures will remain cold through this period, with most precip falling as snow across southeast Wyoming and a light rain/snow mix expected across the western Panhandle. Mountains west of the Laramie Range, including the Snowys, the Sierra Madres and the Shirley Mountains may receive an additional 6 to 12 inches of snow as this system tracks across the area Wednesday and an Advisory will need to be considered for the mountains in a future forecast package. Warmer and mostly dry conditions prevail moving into the end of the week as a southerly flow affects the region. However, by Saturday night, the next strong system looks as though it will drop out of the north, bringing the next round of cold temperatures to the region and the next shot at decent precipitation. For now, the remnants of Hurricane Sergio look like they will stay south and east of the region, but should the moisture track change and push further north, this system may spell another story for the region. This will need to be monitored as we move towards the end of the week. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1137 AM MDT Tue Oct 9 2018 IFR to MVFR conditions to persist across the terminal sites this afternoon. Brief periods of heavy snow and reduced visibilities possible across the NE Panhandle through midnight as the trowal region of precipitation moves across. KSNY expected to see worst conditions with some reduction in flight conditions at KAIA as well. Some light snow also expected across KRWL and KLAR ahead of an upcoming shortwave. && .FIRE WEATHER... Issued at 242 AM MDT Tue Oct 9 2018 A cold and active pattern will continue over the next week, significantly limiting fire weather concerns and aiding in fire containment issues. The next best chance of measurable precipitation across the mountains will arrive Wednesday. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...Winter Weather Advisory until midnight MDT tonight for NEZ021- 055. && $$ UPDATE...CLH SHORT TERM...AB LONG TERM...AB AVIATION...WM FIRE WEATHER...AB