


Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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099 FXUS63 KFSD 091956 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 256 PM CDT Wed Jul 9 2025 .KEY MESSAGES... - Severe storms this evening into tonight will be capable of damaging winds up to 75 mph and half dollar-sized hail. Greatest threat is west of the James River, with storms weakening with eastern extent. - Additional storm chances into the weekend focus around Thursday into Friday. Mixed storm modes could bring a variety of severe weather risks, but slow storm motion may also bring locally heavy rain risks especially late Thursday through Friday. - A dry weekend is expected, with cooler temperatures Saturday warming above normal by Sunday and Monday. - The next risk for thunderstorms returns to the region late Monday into Tuesday. && .DISCUSSION... Issued at 252 PM CDT Wed Jul 9 2025 THIS AFTERNOON THROUGH TONIGHT: The main story in the short- term will be a developing Mesoscale Convective System in western South Dakota that will cross the Missouri River this evening, but first a quick mention on storm potential this afternoon: A few areas of ACCAS over southwest Minnesota and northwest Iowa could develop into a very isolated storm or two in an unstable environment characterized by 2000-3000 J/kg of MLCAPE. Effective bulk shear will be less than 20 kts in these areas, thus pulse storms are expected with any development. Otherwise, expect a hot and humid afternoon on our Wednesday with highs in the upper-80s to mid-90s and dew points into the 70s. For this evening into tonight`s severe weather threat, look for storms to form rapidly into a line segment in western South Dakota and surge eastward. Look for this MCS to cross the Missouri River around the 9-10 pm and slowly weaken as it moves eastward towards I- 29. Damaging winds will be the main concern, especially west of the James River where storms look to be the strongest. DCAPE values of 1500+ J/kg combined with quick storm motion will favor the potential for damaging wind gusts as high as 75 mph. Mid-level lapse rates around 8-9 C/km will support some large hail (up to half dollar in size) especially west of the James River where storm updrafts will be at their strongest. Storms will likely weaken as they progress towards I-29 as instability wanes. Even these dying thunderstorms will be capable of at least 60 mph wind gusts as far east as the US Highway-75 corridor late tonight. THURSDAY: Shortwave energy is expected to be moving away from the CWA after daybreak Thursday, with temporary subsidence residing over the forecast area into the afternoon. A slightly cooler, but still very humid day is expected across the area, with focus turning towards the placement of residual boundaries left over by departing MCS and formation of a surface warm front over central and eastern Nebraska in the afternoon. By mid-late afternoon, increasing DPVA and convergence of increasing low-lvl flow will provide enough lift to aid in the development of convection south of the CWA along the aforementioned surface trough. While extremely uncertain, some of this convection may drift northward in the evening, producing some severe weather risks locally. However the greatest potential is likely to stay south of the MO river and Highway 20 where the majority of HREF 2-5KM updraft helicity is focused. THURSDAY NIGHT: Again, extreme uncertainty continues Thursday night into Friday, with models suggesting a stronger mid-lvl area of vorticity tracks out of the western High Plains and into the Central Plains overnight. The track of this energy remains highly in doubt, with EC/CMC pushing the wave over the Dakotas, with the NAM/GFS further south and focusing overall convective risks well south of I- 90 into Friday morning. The further north EC/CMC would instead allow for more development along a N-S frontal boundary through the Dakotas and increase the potential of MCS activity throughout the CWA Friday morning bringing isolated convective wind risks and low end hail risks. The southern solutions have the potential to lead to lower PoPs through most of the CWA, with heavier rains focused more over Nebraska and western Iowa into daybreak. FRIDAY: A larger upper trough begins to cross Central Canada early Friday, with the trough axis moving into the central Dakotas mid-day Friday. With the CWA sitting in-between these features and a slow moving cold front drifting south in the middle of the day, precipitation chances may begin to increase rapidly by mid-day through the afternoon. Pooling moisture and temperatures warming into the 80s will again serve to push moderate instability into the area. Shear however will be quite weak, owing to more possibility of brief microbursts winds and marginal hail into the evening as the front progresses southeast. The slow storm movement will lead to localized heavy rain potential. SATURDAY-TUESDAY: Cooler and dry weather is likely Saturday as northwest flow spreads throughout the northern US. By Sunday, mid- lvl heights begin to rise quickly, with southerly winds bringing a return of upper 80s to 90s to the region. A bit better agreement in medium range deterministic models into Monday, keeping deeper southerly flow in place and pushing temperatures a bit warmer. Convection risks begin to increase quickly again late Monday night into Tuesday as a frontal boundary moves into the Plains. && .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...Dux/Samet AVIATION...Samet