NZUS93 KABR 141903 LLLABR MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-150703- Public Information Statement National Weather Service Aberdeen SD 103 PM CST Thu Nov 14 2024 Deterministic models and clusters show an upper-level trough stretching from MT to the west coast of CA Saturday morning, which pushes a surface low pressure through western and central SD during the day Saturday. The jet along the westward side of the trough starts to weaken, and by Sunday afternoon/evening it causes the low pressure over AZ/NM to break off from the trough. This upper-level low starts to move east/northeast as a shortwave with a surface low pressure connected to it. The mid-levels move moisture over central SD Saturday evening which helps surface precipitation to develop. The deterministic models have precipitation forming around the surface low pressure, however, only the Canadian show a small bit of precipitation moving through northcentral SD, mainly Corson county. The NBM has PoP values around 35% over Corson county Saturday morning decreasing to 20% by the evening, with the clusters having mean 24hr precipitation of 0.01 falling over northcentral SD. The mid-levels have WAA occurring over southcentral SD, which leads to surface temperatures Saturday and Sunday being 10-20 degrees warmer than normal. These warmer temperatures are above freezing, which will decrease the chance for snow (only a few ECMWF members show snow potential), so the precipitation, if any falls, will likely be rain. Through the day Sunday into Monday, the clusters and models show the upper-level shortwave move northeast, with variations in its location and strength. The Canadian has a more northerly track, while the ECMWF and GFS have a southerly track to the lows in the upper-level and surface. The timing of the precipitation is very similar, with it moving in Monday afternoon, give or take 6 hours, with the heaviest precipitation occurring Monday evening and overnight. The only difference comes in how widespread the precipitation is over central and eastern SD. The location of the upper-level trough following the precipitation Tuesday causes some models and clusters to continue precipitation develop through Wednesday and Thursday. NBM generally has PoP values between 30-60% Monday evening through Tuesday, with values between 20-40% Wednesday and Thursday. With Monday’s temperatures being 10-20 degrees warmer than normal, the precipitation looks to start as rain as it moves into central and eastern SD, which the clusters and NBM agree on. However, as the temperatures start to drop to around normal early Tuesday, variations in the models and clusters start to occur in the p-types as a few members start to show sleet and snow occurring starting Tuesday evening/ overnight into Wednesday. Areas around and to the west of the Missouri River have more members showing snow than rain Wednesday, though less than 40% show any precipitation occurring on the ECMWF. Areas to the east of the Missouri River show an equal number of members with rain or snow, though it is still less than 40% of members showing any precipitation occurring. The clusters that have rainfall show mean rainfall amounts around 0.35in occurring west of the James River Valley, with around 0.75in of rain to the east of it. The members with snowfall have mean snowfall amounts around 2in over central and eastern SD. The GFS and Canadian 0.5km model winds and lapse rates show strong winds over central and eastern SD likely reaching the surface Monday evening into Thursday, the NBM shows surface winds and gusts increasing overnight Monday with widespread areas of 30kt gusts with pockets of 35kts. These winds look to die back through the day Thursday. If snow does fall during this time, it could become blowing snow and impact visibilities. $$