185 FXUS63 KFSD 101128 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 628 AM CDT Wed Oct 10 2018 .SHORT TERM...(Today and Tonight) Issued at 348 AM CDT Wed Oct 10 2018 The primary short-term concern is snowfall west of the James River into early this afternoon. Strong upper level low and PV anomaly were moving north into southeastern South Dakota this morning. To the west of the track of the PV anomaly from near Gregory SD toward Huron SD an area of 700 mb frontogenesis has set up. This area of frontogenesis is expected to move slowly northeast through the morning with the upper low. This will allow precipitation to continue to focus along and west of this boundary. This is also an area where temperatures are in the 30s and these temperatures are expected to remain steady or drop until precipitation ends later this morning. Precipitation is already all snow around Gregory and Platte and has been a mix of rain and snow in Chamberlain. The location of snow is elevation dependent and it is likely that the higher terrain in Jerauld County has also switched over to snow while much of the Missouri River Valley from Chamberlain to Pickstown remains a mix. With the frontal forcing for ascent, additional QPF of up to 0.25" is possible from Wessington Springs to west of Huron. When snowfall rates are high, this snow will likely stay on the ground and even some roadways. As the snow rates decrease, the warm ground should melt the snow from below. As for total snowfall, looking for an additional 1-3" in the western portions of Jerauld, Beadle, and Brule Counties with less than an inch elsewhere. So will continue the winter weather advisory or this morning in Brule and Gregory counties and through 4 pm in Beadle and Jerauld Counties. As the low lifts north this afternoon, precipitation will end along and south of I-90 but is expected to linger into this evening across portions of southwestern Minnesota north along and north of Hwy 30. Near Highway 14, a rain and snow mix is possible as temperatures cool but no accumulation is expected. Once the snow ends, expect the strong cyclonic flow around the low to keep stratus in place over much of the area through this evening with only a slow clearing along and west of the James River after midnight. Winds will also remain between 15 and 25 mph east of the James River with gusts over 30 mph much of the night in southwestern Minnesota. Highs today will be 20 to 25 degrees below normal in the upper 30s in most of southeastern SD and southwestern Minnesota to the mid 40s in northwestern Iowa. The clouds and wind will prevent temperatures from falling too far but most places will likely be at or below freezing by Thursday morning. A freeze warning may be needed across the area but will hold off on any warning until after the snow ends and also have a better idea if clouds may keep temperatures closer to freezing than we are currently expecting. .LONG TERM...(Thursday through Tuesday) Issued at 348 AM CDT Wed Oct 10 2018 More tranquil but cool weather is expected in the long-term forecast. Clouds with the upper low will continue to slowly clear from southwest to northeast on Thursday but for southwestern Minnesota, expect little if any sun on Thursday as it is likely the clouds will remain through sunset. Farther to south and west toward Brookings, Sioux Falls and Spencer, IA, skies are expected to clear by early to mid afternoon. Am a little concerned that clouds could linger longer even in these areas as cyclonic low level flow and cold temperatures aloft may cause stratocumulus to form on the western edge of the clouds during the late morning and afternoon. This could delay clearing in the aforementioned areas adjacent to southwestern Minnesota until late afternoon or evening. High temperatures will continue to be very cool from the upper 30s along Highway 14 to the mid 40s in the Missouri Valley. Any clearing that occurs Thursday afternoon and evening will be short-lived as another shortwave moves southeastward from Canada toward the central Plains. The GFS is the farthest north with this system having the axis of heaviest precipitation in the Missouri Valley while the NAM and ECMWF keep the heaviest precipitation across Nebraska which is closer to the track of the upper PV anomaly. Have sided with this solution although the potential for light precipitation extending as far north as Chamberlain, Yankton and Sioux City will mean keeping a chance of precipitation. Precipitation type is more difficult. Current thinking is that if the clouds are delayed and the low moves farther south such that no precipitation falls then temperatures will cool close to or even below freezing. However, if thicker low level clouds move into the area Thursday night prior to precipitation, the clouds will prevent radiative cooling and temperatures will remain above freezing all night or rise above freezing after the clouds move in and thus keep precipitation rain or at worst a rain/snow mix. With either no precipitation or a mix of rain and snow, expect little if any accumulations with the possible exception of Gregory County where a dusting accumulation may be possible in higher terrain away from the Missouri River. Any precipitation is expected to end by Friday afternoon leaving dry weather for the area this weekend and into early next week. Temperatures will remain well below normal through the period. After another day in the 40s on Friday, strong mixing along and behind a cold front on Saturday will allow temperatures to rise into the 50s. If enough warm air comes north and the frontal passage is later in the day, some places in northwestern Iowa and far southeastern South Dakota could even hit 60. Following the front, winds will increase. At this point, have forecasted gusts as high as 30 mph Saturday afternoon and evening but these winds could be another 5 to 10 mph stronger if the frontal passage in the early afternoon - especially west of I-29. Sunday will be another cold day with highs again struggling to reach 40 degrees. Sunday night is expected to be the coldest of the period with lows in the mid to upper 20s. Temperatures will slowly warm into the mid 40s to lower 50s Monday and Tuesday ahead of another front that will move through Tuesday afternoon. The good news: After a brief shot of cold air Tuesday night and Wednesday, all models are showing a warming trend for the end of next week with temperatures closer to normal or possibly above normal. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 628 AM CDT Wed Oct 10 2018 Snow continues to fall west of a Huron to Lake Andes line in South Dakota. This snow will slowly lift northeast through the day with snow possible as far east as Brookings and Marshall. Snow is not expected in either Sioux Falls or Sioux City. Snow will reduce visibility as low as 1 mile in Huron this morning. The snow should move north of Huron by mid afternoon. The low visibilities with fog and drizzle around Sioux Falls and Sioux City should also improve by early afternoon. After that, the main concern is stratus. The stratus is expected to persist through Thursday morning across the entire area. Ceilings will only rise to 1000 to 2000 ft in Huron and Sioux Falls and around 2500 at Sioux City by 12Z Thursday. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...Winter Weather Advisory until 1 PM CDT this afternoon for SDZ050- 057. Winter Weather Advisory until 4 PM CDT this afternoon for SDZ038- 052. MN...None. IA...None. NE...None. && $$ SHORT TERM...Schumacher LONG TERM...Schumacher AVIATION...Schumacher