Expires:No;;166633 FXUS63 KFSD 242343 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 543 PM CST Wed Dec 24 2025 .KEY MESSAGES... - Areas of fog, some dense, will continue through tonight especially east of I-29 over northwest Iowa and southwest Minnesota. Locally dense fog is possible all the way westward into south-central South Dakota tonight as well. - As temperatures drop to near and just below freezing tonight mainly north of I-90, patchy freezing drizzle and freezing fog could result in some patchy slick spots mainly on untreated and elevated surfaces. Use extra caution on the roads and check road conditions before traveling. - Temperatures remain above normal through the end of this week, but we turn windy and colder this weekend. Wind chills likely drop below zero by Sunday morning north of I-90 and then area- wide by Monday morning. - Precipitation chances Friday-Saturday are low, but may have to watch for scattered flurries Sunday as colder air moves in. - Elevated fire danger will be possible on breezier days in snow- free areas, mainly across south central South Dakota through the Missouri River Valley. && .DISCUSSION... Issued at 315 PM CST Wed Dec 24 2025 Areas of dense fog will continue through this afternoon into tonight underneath the current stratus deck, located from roughly Arlington to Sioux Falls to Le Mars and points east. This area of stratus will continue to erode on its western edge through this afternoon, but expand westward again overnight. Dense fog will continue into tonight, but also expand westward as well. Most of the area sees fog tonight, though the overall "thickness" of the fog will decrease with westward extent. In other words, areas east of I-29 into portions of southwest Minnesota and northwest Iowa have the best chance of widespread dense fog continuing through tonight into tomorrow morning, hence the dense fog advisory that will be in effect through 9 am. Further expansion westward of the advisory may be needed tonight, so keep up to date with the latest forecast! As temperatures cool off tonight, many of us look to drop to around freezing mainly north of I-90, so any fog could freeze to mainly elevated surfaces such as overpasses, bridges, and trees. Another thing to watch for tonight will be the chance of drizzle and freezing drizzle. Reports of drizzle today have been spotty at best as the stratus layer is only marginally supportive of it. However, confidence was high enough to at least continue the mention of drizzle overnight tonight. Still some uncertainty as to how widespread any drizzle, including freezing drizzle, will be, but any freezing drizzle that does form (again mainly north of I-90), may cause a glaze of ice to form mainly on untreated surfaces. All this to say, for those with travel plans either late tonight or on early Christmas morning, be sure to use extra caution on the roads and check road conditions before you leave! Most of the area will be stuck under stratus Christmas Day, keeping highs mainly in the upper-30s to low-40s. So still mild for this time of year, but not record breaking. Highs will be a bit warmer as you head west of the James River, with highs in south- central South Dakota in the upper-50s to near 60. Friday and Saturday look to be mild days, but a strong cold front is still set to move in late Saturday into Sunday, bringing much cooler air to the area. Lows by Sunday morning are not looking as cold, but we still look to drop into the teens for most of the area. Sunday night/Monday is now trending towards being the coldest night over the period, with lows in the single digits and wind chills dropping to the negative teens especially north of I-90. We look to see a return to milder temperatures by Tuesday of next. Precipitation-wise, still looking at only low-end light precipitation mainly on Sunday when light snow/flurries look possible, but nothing too impactful expected at this time. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 542 PM CST Wed Dec 24 2025 Latest satellite shows low level stratus and fog sitting mainly along and east of I-29. Ceilings in the stratus are all the way down to LIFR levels with visibilities ranging from MVFR/IFR/LIFR. Thus, fog is present where visibilities have fallen below a half a mile. This stratus/fog is expanding westwards early this evening and is expected to reach KHON. To go along with the stratus and fog, light drizzle and freezing drizzle is possible beneath the stratus/in the fog, mainly late this evening through the overnight hours. Currently think any freezing drizzle will most likely be confined to areas north of I-90 where temperatures are expected to drop below freezing. Fog and low stratus will persist through the morning hours tomorrow before the fog looks to retreat eastwards come the afternoon. However, this reduction in the fog looks to only work eastwards to about I-29 before stopping and remaining settled for the rest of the period. Given a slight strengthening of the winds along with temperatures warming, think that the fog may lift, though still leave visibilities down to MVFR levels. Ceilings look to remain persistent at LIFR thresholds to end the period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...Dense Fog Advisory until 6 PM CST this evening for SDZ040-055- 056-062. MN...Dense Fog Advisory until 9 AM CST Thursday for MNZ071-080-081- 089-090-097-098. IA...Dense Fog Advisory until 9 AM CST Thursday for IAZ001>003- 012>014-020>022-032. NE...None. && $$ DISCUSSION...Samet AVIATION...Meyers