050 FXUS63 KFSD 311119 AFDFSD AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 519 AM CST Tue Dec 31 2019 .SHORT TERM...(Today and Tonight) Issued at 356 AM CST Tue Dec 31 2019 Final lobe wrapping around the deep Great Lakes upper-level closed cyclone brought areas of very light snowfall and a few flurries overnight, but should be dwindling to nothingness by daybreak across the area. Advection of drier air from the north will work to break the lower clouds going through the morning from the northwest, and should also assist in decoupling stronger winds away mainly early this morning as well. However, winds will remain somewhat stronger and gusty through the early morning around the Buffalo Ridge, and should see continued drifting of snow, at least early in the day. The bulk of the day will be quiet and seasonably cool as we say goodbye to 2019, with temps up to a half-dozen degrees below normal (and actually cooler than most 09z readings) after falling well through the morning before steadying recovering a few degrees, mostly thanks to the new snow cover and weakening gradient under a stabilizing lapse rate. Tonight, there will be continued warming aloft, which will set up potential for some elevation dependent temperatures, and at least a weak mountain wave wind enhancement for areas near the Buffalo Ridge. Neither inversion nor wind direction are optimal for downward transport, so likely to only see a minor increase in winds, perhaps a few gusts to around 25 mph. Heading out to ring in the New Year? Should be a lot of wind chill readings from around zero to 10 degrees. .LONG TERM...(Wednesday through Monday) Issued at 356 AM CST Tue Dec 31 2019 Wednesday and most of Thursday look to remain quiet as the strong west-northwest flow aloft kicks a couple of waves into the region, but mainly skirting the periphery. The first will move through Wednesday with an increase in mid- and high-level cloudiness, which will make for a little challenge in how warm temps could reach given the very warm temps aloft along with the west-southwest near surface flow. Should end up with a lot of temps from the upper 20s to lower 30s, but those spots with lesser snowfall across northwest Iowa should make it well into the 30s, as well as some higher elevation sites in the south central. A second wave should split moving into the Plains on Thursday, enough to drive a cold front southward through the area during the morning and midday hours. Should be mainly dry, but by Thursday night, could begin to see the northern edge of the southern stream wave brush parts of northwest Iowa with a snowfall threat, as well as a small chance for snowfall ahead of the kicker wave in northwest flow diving into the northern plains. This fairly dynamic wave digs into the back side of the split trough across the central/northern Plains during the day on Friday. Depending on the longitude of baroclinicity, there is a good chance that a fairly narrow band of light snowfall will occur given the tight frontal forcing and favorable dendritic range. In fact, had to coordinate to actually add in PoPs on Friday afternoon, and likely that they will go higher as the location of the PV/frontal overlap becomes more certain, as well as QPF amounts. Northwesterly winds could become a bit blustery during the afternoon, perhaps strong enough for a little drifting of the expected fluffier snowfall. The precip threat pulls out pretty quickly by early evening Friday, and this will bring a return to quiet weather heading through the end of the forecast period. Temps mainly waffle either side of normal through the period, with highs warmest and likely above normal Sunday in the upper 20s and 30s, surrounded by mainly 20s Saturday and Monday. Lows will be in the teens. One thing to watch is a digging and amplifying wave progressing along the International Border and toward the Great Lakes on Sunday. Not likely to produce any precip in our area, its track does place this area into a very wind-favored quadrant of the wave. Almost all guidance at this range indicates that there may be as much as 40-45 knots of wind near the top of the mixed-layer, and generally a bit stronger winds for areas north of a KHON-KSLB line than south. Pushed winds up 5-10 knots from the initial blend, and will be keeping a watchful eye on this period. It is good that most of the recent snowfall has been compacted by the strong winds, and that most of the snow Friday should fall south and west of the strongest wind corridor. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) Issued at 518 AM CST Tue Dec 31 2019 Strongest winds gusting at times around 25 kts will continue to decrease slowly this morning east of Interstate 29, as MVFR to IFR ceilings also gradually erode eastward. VFR conditions are expected to remain through the remainder of the period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...Chapman LONG TERM...Chapman AVIATION...Chapman