893 FXUS63 KABR 211128 AAA AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 528 AM CST Thu Dec 21 2023 .KEY MESSAGES... - High confidence on above average temperatures continuing through the weekend. - Patchy to areas of fog to remain over eastern SD Friday morning. Uncertainty is increasing on how widespread fog will be Saturday, with patchy fog possible near the Watertown area Saturday morning. - Next 20-80% chance of precipitation from late Saturday night into Sunday morning, continuing though Monday before diminishing west to east Tuesday. Rain will transition to a wintry mix from Sunday on. This remains a low confidence forecast. && .UPDATE... Issued at 521 AM CST Thu Dec 21 2023 Updated aviation discussion below. && .SHORT TERM /TODAY THROUGH FRIDAY AFTERNOON/... Issued at 327 AM CST Thu Dec 21 2023 The potential for dense fog over the eastern half of the CWA late tonight into the morning hours on Friday will be the main forecast challenge in the short term. As of 8Z, the weather pattern across the region is fairly quiet with mid and high level clouds crossing the area. The clouds and southerly winds is keeping temps mild, with readings in the upper 20s and low 30s. Low level temps remain mild for this time of year, thus highs should once again warm into the 30s and 40s. Low 50s will be possible over the far western CWA as a warm front approaches the region from the west. Southerly winds will continue across the eastern CWA, which will draw low level moisture into the region later this afternoon and through the overnight hours. Dew points may reach the low to mid 30s, which is about 10 degrees above normal high temperatures today. The added low level moisture, along with light winds should cause fog to develop, mainly over the eastern half of the CWA. The 6Z run of CONSShort highlights the potential for visibility to fall below a half mile in and around the Watertown area. Kept the mention of fog in the forecast through the mid morning hours, per CONSShort and other Hi-res models. It will be interesting to see how long the fog, and potential low clouds hang on, and the impacts on high temperatures. Highs in the mid 30s can be expected if the clouds and fog remain throughout the day. Highs in the mid to upper 40s with little to no fog. && .LONG TERM /FRIDAY EVENING THROUGH WEDNESDAY/... Issued at 327 AM CST Thu Dec 21 2023 A wintry mix of precipitation will be the main concern this period. However, fog on Saturday could also be a driving hazard. However, the latest model runs are downplaying the widespread potential for fog a bit. The high temperatures near 50 degrees for Saturday are no longer near the NBM 75th percentile, but closer to the 50th, giving a bit more confidence in their occurrence. Even the NAM, which has a tendency to be too high on the very near surface moisture/indicating low visibility from fog, is not as widespread. At this point, we'll put patchy fog in the most likely location, near the Watertown area as dewpoints rise into the 30s on winds out of the south to southeast, and wait to see how this trends as the time nears. Similarly to 12 hours ago, the trend for this update has been a slightly more easterly move to the precipitation, ranging from 0.10- 0.75" (lowest over north central SD). We will have to wait and see when more of the 00Z ensemble data arrives if this trend continues. As for precipitation type, using deterministic solutions to forecast specific precipitation types for Saturday night-Monday night is a difficult idea at best. There is just too much variability at this time. EC ensemble precipitation type meteograms still show chances for rain, snow, or freezing rain for much of the event, with a slight more of a push to snow over central SD. We're still looking for the surface low to eject out of CO on Sunday. To get a better understanding of the variability you only need to look at the 00Z operational runs of the EC, GFS, and Canadian models, putting the surface low anywhere from the eastern half of NE to IL by 00Z Tuesday. This is a 500mi difference, which leads to significant differences in the temperature profiles and where precipitation will even fall, and low confidence in the forecast beyond 12Z Sunday. Will keep with a general blended forecast at this point, with high temperatures expected to stay in the 30s Sunday through next Thursday, and dry weather returning for Wednesday and Thursday. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 521 AM CST Thu Dec 21 2023 Terminals KABR,KATY,KPIR,KMBG IFR visibility in fog will impact KPIR early in the TAF period with improvement to VFR by 14Z. All terminals will see VFR conditions through most of the valid TAF period. KABR and KATY could see MVFR and IFR cigs and visibility later tonight and into the morning hours on Friday. KATY could see 1/4SM as soon as 9Z, or perhaps starting at 12Z Friday. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...SD SHORT TERM...SD LONG TERM...KF AVIATION...SD