


Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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346 FXUS63 KFSD 112010 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 310 PM CDT Fri Jul 11 2025 .KEY MESSAGES... - A low end (level 1 of 5) risk of severe storms develops by late this afternoon, as a cold front brings scattered thunderstorms southward into the region. The main threats with the strongest storms will be up to quarter sized hail, strong winds up to 60 mph, and heavy downpours. An isolated funnel cloud or landspout is possible, mainly along the cold front itself. - Temperatures cool Saturday, but heat and humidity build back in for Sunday through Tuesday. Cooler temperatures return for the middle and end of next week. - Thunderstorm risks return for Sunday through Tuesday, with some threat of severe storms possible. && .DISCUSSION... Issued at 309 PM CDT Fri Jul 11 2025 A few showers and weak thunderstorm persist east of I-29 this afternoon. Should see these showers and storms drift east/southeastward over the next couple of hours. At the same time, a cold front has pushed into the area from the northwest. This front will serve as the focal point for new showers and thunderstorms to develop on with convective initiation expected over the next 2 to 3 hours or so. Storms look to be initially discrete before some upscale growth leads to a broken line/cluster of storms. CAPE value will be sufficient at around 1,500 J/kg of instability but shear will be quite weak on the order of 25 knots or less. That said, still think an isolated chance for quarter size hail and damaging winds to 60 mph is possible. The other aspect to the storms is the potential for funnels or even a landspout. This potential is being driven from the vorticity along the front itself. Despite the fronts vorticity, LCL`s are decently high at around 4,000 to 5,000ft so it may be a bit more difficult to any funnel to touch the ground. Any chance for storms will come to an end by midnight as the showers and storms push east of the area. Low temperatures will fall to the upper 50s to low 60s. High pressure will push into the Northern Plains on Saturday, delivering dry and quiet conditions for the area. 850 mb temperatures will warm to the teens aloft. Mixing these temperatures to the surface will result in high temperatures in the upper 70s and 80s. Dew points will lower to the 60s to low 60s, which will keep humidity values down to 30-60%, lowest west of the James River. Thus, Saturday will be a nice day though there could be some wildfire smoke both aloft and at the surface. Low temperatures will fall to the upper 50s to low 60s overnight. Sunday will be a hotter day as highs warm to the 80s to 90s, warmest west of the James River. Southerly return flow on the backside of the previously mentioned departing surface high. Dew points will moisten to the 60s to even up to about 70F. This will increase humidity values and also result in CAPE values up to 1,500 to 2,000 J/kg. Effective shear value will be sufficient on the order of about 30 knots but lift is questionable. A shortwave trough will reside east of the forecast area, providing upper level subsidence across the Northern Plains. However, a weak shortwave trough at 700 mb will push into the area. A weak surface trough will push through the area which could result in another chance for showers and thunderstorms. This potential is quite uncertain though given the weak forcing that is in place. As of now, the ensembles only show a low 10-30% chance for rainfall amounts to exceed a tenth of an inch throughout the day. Have left model blended PoPs at this time but trends will be monitored. Zonal flow sets up for the beginning of next week. This will promote broad southerly flow into the Northern Plains, promoting humid conditions across the area. High temperatures will remain near to above average in the 80s and 90s. With weak shortwave troughs passing through the upper level flow, chances for showers and thunderstorms are possible. As of now, it looks like storm chances will increase heading into Monday evening as forcing for ascent strengthens. This chance for storms will persist through Tuesday as a cold front passes through the forecast area throughout the day. Given sufficient instability and enough shear in place, this could lead to additional chances for showers and storms, some of which could be strong to severe. Machine learning guidance also supports this possibility as these models show about a 5-15% chance for strong to severe storms. Will keep an eye on this potential over the weekend. Rain chances look to continue for Wednesday and Friday next week as shortwave trough continue to track through the upper level flow. Details of these waves is uncertain at this time so have left model blended PoPs. In terms of temperatures, highs look to cool to near to below average in the 70s to up to about 80F. Lows will fall to the 50s and 60s overnight. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1239 PM CDT Fri Jul 11 2025 Mainly VFR conditions begin the TAF period. Light rain persists this afternoon along and southeast of a KSLB to KSUX line and should slowly push southeastwards over the next several hours. To the west, a cold front has begun to push into the area, turning the winds at the surface to out of the northwest in its wake. Some brief reductions in visibility is being observed behind the front but confidence is too low to include in a TAF at this time. Will keep an eye on the lowered visibilities though. Showers and thunderstorms are expected to develop along the front later this afternoon. While storms look to develop along and east of the James River, have decided to include a PROB30 group in KHONs TAF for trailing light rain showers. Showers and storms will push eastwards through the rest of the afternoon and evening hours before sliding east of the area around midnight. This will leave clearing skies and light northwest winds for the rest of the night and TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Meyers AVIATION...Meyers