038 FXUS63 KFSD 260431 AFDFSD AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 1031 PM CST Mon Jan 25 2021 .SHORT TERM...(This Evening through Tuesday) Issued at 304 PM CST Mon Jan 25 2021 A large winter storm system will continue to spread snow northward this evening and overnight. Afternoon observations and radar show well-defined bands of light to moderate snow along and south of the Hwy 20 corridor in Nebraska and Iowa. These bands are being formed by the robust synoptic and frontogenetic lift ahead of a shortwave trough currently moving northeast across Kansas and Nebraska, and these snowbands are expected to persist through the overnight hours. After shifting accumulating snow northward yesterday, high-resolution models have been fairly consistent in their portrayal of this system over the past 18 hours, with locations such as Sioux City IA likely to receive another 3 to 5 inches of snow. Locations a bit further north such as Vermillion SD, Le Mars IA, and Storm Lake IA are more likely to see 1 to 3 inches of accumulation by sunrise Tuesday. The gradient on the north side of this snowfall event is expected to be tight, as dry northeasterly winds create a much less conducive environment for snow generation just north of the aforementioned area. Winter Weather Advisories cover the locations most likely to receive 3 to 6 inches of snow. Snow amounts and impacts to the south towards Omaha NE and Des Moines IA will be much greater, so take extra care if headed that direction tonight or tomorrow morning. Once snowfall ends Tuesday morning, a surface high over North Dakota and northern Minnesota will continue to drive cold, dry, 10-to-15-mph north winds. Daytime temperatures remains suppressed about 10 degrees below seasonal averages. .LONG TERM...(Tuesday Night through Monday) Issued at 304 PM CST Mon Jan 25 2021 On Wednesday an open shortwave travels across the central Plains. Models have shifted the orientation of the jet stream associated with this wave, and now any accumulating light snow looks to remain well south of the region. Highs remain chilly, generally topping out in the teens. A notable pattern change begins on Thursday, with its effects not being fully felt until Friday and Saturday. A strong upper-level ridge builds over the central CONUS Thursday, and the surface high to the east encourages breezy southerly winds Thursday and Friday. This increases temperatures to near normal readings on Thursday, and then 5 to 10 degrees warmer than normal (mid 30s) Friday and Saturday. Even though temperatures will be mild, added low level moisture advection over the snowpack is likely to lead to abundant low-level stratus clouds, so don't expect much sunshine. Over the weekend, models show a deep trough moving across the Plains. For now, the focus of forcing with this system is south and east of Siouxland, but this will be the next winter weather system to monitor. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1030 PM CST Mon Jan 25 2021 MVFR and brief IFR conditions near the Missouri River into the KSUX area will gradually improve during the overnight hours as the moderate to heavy snow that fell during the evening shifts southeast. Dry air in the low to mid levels will wrap south and bring mostly VFR conditions to the area after about 10-12z. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...Winter Weather Advisory until 9 AM CST Tuesday for SDZ070-071. MN...NONE. IA...Winter Weather Advisory until 9 AM CST Tuesday for IAZ020>022- 031-032. NE...Winter Weather Advisory until 9 AM CST Tuesday for NEZ013-014. && $$ SHORT TERM...VandenBoogart LONG TERM...VandenBoogart AVIATION...08