


Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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260 FXUS63 KFSD 091745 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1245 PM CDT Wed Jul 9 2025 .KEY MESSAGES... - A Mesoscale Convective System (MCS) will likely develop over western SD this afternoon and progress through our area this evening. The primary hazards with this activity will be damaging winds up to 75 mph and up to half dollar size hail. - Additional chances for showers and storms will continue into the late week with the focus being between Thursday and Friday. Mixed storm modes could bring a variety of severe weather risk, but slower storm motions may also bring a locally heavy rain risk. && .DISCUSSION... Issued at 350 AM CDT Wed Jul 9 2025 TODAY & TONIGHT: Taking a look across the area, mostly quiet conditions continue as of 4 am this morning. The forecast still remains on track for a few isolated thunderstorms to develop across southcentral SD through daybreak as pieces of vorticity interact with a 20-30 kt LLJ. However, the severe risk with this activity will likely stay on the lower side with only around 500-750 J/kg of instability to work with. As the LLJ weakens, should see this activity weaken and diminish by mid-morning. Shifting gears here, another warm day is ahead as increasing southeasterly winds and increasing mid-level warm air advection (WAA) lead to temperatures in the 80s to low 90s with the warmest conditions closest to the warm/stationary front situated along and west of the Missouri River Valley. From here, the focus turns to our next precipitation chances this evening and overnight. Taking a look aloft, a quick mid-level wave will push across the state and intersects the previously mentioned surface front triggering semi-discrete clusters of showers and thunderstorms across western and central SD. While this developing activity will have access to an unstable environment characterized by 2000-3000 J/kg of instability and 25-35 kts of bulk shear, model soundings continues show a stabilizing boundary layer as this developing activity moves into our CWA. As a result, most high- resolution guidance has this developing Mesoscale Convective System (MCS) weakening as it progresses eastwards towards the I-29 corridor. With this in mind, the majority of the severe risk (if any) will likely be isolated to areas west of U.S. Highway-281 where remnant thunderstorms could produce damaging winds up to 65 mph and half dollar sized hail. Lastly, as the LLJ strengthens across areas east of I-29 overnight; some potential redevelopment will be possible mainly in northwestern IA. While this activity will likely be sub-severe due to waning instability, can`t completely rule out the potential for a few additional thunderstorms with some smaller hail. THURSDAY-FRIDAY: Looking into the latter parts of the week, could see the previously mentioned activity lingering across areas east of I-29 through the mid-morning hours on Thursday before things progress out of our area. From here, quieter conditions temporarily return through the late afternoon as temperatures peak in the 80s to low 90s for the day. More shower and thunderstorm chances will return during the evening to overnight hours on Thursday as a strengthening shortwave lifts through our area and intersects a few lingering surface boundaries left behind from the previously mentioned MCS. While there is still some uncertainty regarding where things will set up, the high CAPE/low shear environment associated with this system; will likely support an isolated to scattered severe risk with stronger storms potentially develop up to 2 inch hail (Hen Egg) and damaging winds up to 70 mph with strong cold pools. As instability wanes overnight, slower storm motions along with PWATs between 1.50 to 1.75 inches (90th percentile) will promote a locally heavy rainfall risk into Friday morning. Nonetheless, with the variety of convective scenarios its still a bit difficult to pin point an area of focus for the overall severe risk and subsequent heavy rainfall threats at this time. Lastly, there will be additional chances for showers and thunderstorms by Friday afternoon as a cold front swings progresses through the area. However, the severity of those storms is still uncertain at this time. SATURDAY ONWARDS: Heading into the extended period, quieter conditions return to the area as surface ridging moves in by Saturday to replace the departing system. With backing surface wind profiles and increasing warm air advection (WAA) in the mid-levels, expect temperatures to trend near to above normal over the next few days with highs increase from the upper 70s to mid 80s by Saturday to the mid 80s to low 90s by Monday. From here, our next shower and thunderstorm chances likely return by Tuesday as a cold front swings through the region. While the severity of this activity is still uncertain, some of the machine learning guidance has started to show some weak signals for stronger activity so this period will likely be one to watch moving forwards. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1241 PM CDT Wed Jul 9 2025 Very isolated showers/storms are possible over northwest Iowa and southwest Minnesota this afternoon, but chances of impacts to KSUX are less than 15% and thus no need to mention in the TAFs. A better chance of storms arrives this evening as a linear complex of storms develops over western South Dakota and crosses the Missouri River around 02-03Z. These storms will be capable of 50+ kt gusts as they move through the K9V9, KHON, and KMHE areas. Storms will bring MVFR visibilities, potentially briefly IFR west of the James River where storms are at their strongest. The storm complex looks to weaken a bit as it approaches the I-29 corridor, and this adds a bit of uncertainty to the storm threat for KFSD and KSUX. Left the PROB30 groups for both sites for now, though slightly adjusted the timing for both sites and added a 45kt wind gust potential for KFSD. Storms will continue weakening as they move west of I-29 through daybreak Thursday. Outside of thunderstorms reducing visibilities, VFR conditions are expected through the period. Winds will be mainly out of the southeast, gusting as high as around 20 kts this afternoon before weakening overnight (except in storms), and then gusting back up to around 20 kts Thursday afternoon. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...05 AVIATION...Samet