


Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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672 FXUS63 KFSD 271951 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 251 PM CDT Fri Jun 27 2025 .KEY MESSAGES... - Periodic thunderstorm chances return late this afternoon through the weekend. Storms could become strong to severe at times. Continue to monitor the forecast if you have outdoor or travel plans. - Strong to severe storms are possible after 5 PM this afternoon west of I-29, with initial development across south central South Dakota. Large hail to 2 inches and wind gusts to 70+ mph are the main threats. An isolated tornado cannot be ruled out. - Additional strong to severe storms are possible Saturday and Sunday during the afternoon/evening hours. Though each day`s storm threat will be determined by the previous days storms. - Warming temperatures and increasing humidity this weekend bring a risk of heat indices near 100F in some areas Saturday afternoon. Otherwise seasonably warm temperatures prevail much of next week. && .DISCUSSION... Issued at 251 PM CDT Fri Jun 27 2025 Quiet conditions persist through the first half of the afternoon hours today. However, things will change over the next few hours as thunderstorms develop along a boundary across south central South Dakota. These storms may be capable of large hail up to about 2 inches in diameter as the storm mode will be discrete during initial development. Storms look to quickly grow upscale into a mesoscale convective system (MCS) as they push eastwards which will transition the threat from large hail to damaging winds. Given steep low level lapse rates, and very high DCAPE values exceeding 1,500 J/kg, damaging winds to 70+ mph will then be the main threat. This damaging wind threat looks to be the main hazard for the forecast area though the large hail threat will coincide with it if a discrete storm can develop ahead of the line. At the same time, there could be an isolated tornado as well with 0-3 km shear vectors with magnitudes of about 25 knots oriented perpendicularly off the MCS. Once the storms push into and east of the Missouri River Valley, they should weaken with eastward extent as capping will strengthen via nocturnal stabilization. The low level jet will also be strengthening during this period of time as well. That said, this cap will not be moist and lifting will above the cap results in little to no instability. Thus, think that if any showers or storms persist through tonight, they will not be severe. Overnight low temperatures will fall to the 60s. Severe weather chances continue through Saturday though there remains uncertainty in this potential. The general consensus for severe storms amongst the 12z guidance is for storms to develop along the warm front but the location of this front is driving the uncertainty. The front looks to end up just northeast of the area. However, this can still change depending on how tonight`s storms shake out. With mean flow paralleling the boundary, storms look to quickly grow upscale into a line. At the same time, a stout elevated mixed layer (EML) will be in place with mid level lapse rates approaching 9C/km. This will present large capping across the forecast area and could inhibit convection to a large degree. The main question will be if diurnal heating will be strong enough to mix out the cap. While high temperatures will reach into the upper 80s and 90s across the area, questions still remain if highs will warm a bit more to potentially the mid to upper 90s or even low 100s. However, both the REFS and HREF show a near 0% chance for highs to exceed 100F. IF storms are able to develop, they would likely be in a line spanning back from the previously mentioned boundary down the dry line. Large hail will be possible with initial updrafts but quick upscale growth will quickly transition the main hazard from large hail to damaging winds. To account for this potential, did keep broad chance PoPs across the area. The other aspect to Saturday is that it is going to be hot and humid. With highs warming to the upper 80s and 90s while dew points moisten to the 60s and 70s, heat indices will be up into the 90s to nearing 100F. Did think about issuing heat headlines but given how borderline the environment is, decided to hold off on issuing headlines at this time. Will continue to monitor this potential. Low temperatures will fall to the mid to upper 60s overnight. Severe threat looks to continue into Sunday though this looks be a more isolated threat. This potential will be contingent on how fast the boundary is able to push out of the area. Per the GFS, Canadian, and Euro ensembles, the front looks to be pushing just southeast of the area during the early to mid afternoon hours. This looks to keep convection just out of the area. This is supported by the NBM as it shows the highest probabilities for exceeding a tenth of an inch of rain off to the southeast. Will still monitor the potential for convection to develop earlier than currently anticipated though. Outside of rain and storm chances, Sunday will be a cooler day with highs only warming to the 80s with northerly winds keeping a light breeze in place. Lows will fall to the 60s overnight. Next week looks to begin on the dry side as the shortwave responsible for the end of week and weekends storms will push east of the region. This will keep high temperatures near to just above normal for this time of year in the 80s to low 90s. Upper level ridging over the southern CONUS could result in ridge riding shortwaves that may bring storm chances back to the Northern Plains. However, too far out to say for sure about any details just yet. Will continue to monitor this potential. Aside from rain chances, highs will remain in the && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1226 PM CDT Fri Jun 27 2025 Morning low level stratus continues to clear the area as it burns off/pushes northeast. A few showers and weak thunderstorms are present west of the James River. The northern showers are close to KHON so have included a PROB30 group in KHON`s TAF for the first few hours of the TAF period. Otherwise southerly flow will persist this afternoon with gusts up to 10-25 knots, strongest west of the James River. Additional showers and thunderstorms are expected to develop across south central South Dakota and north central Nebraska later this afternoon. Current thinking is that the storms will weaken with eastward extend so have not included any mention of thunder in any TAFs as this time. The low level jet (LLJ) will strengthen this evening, leading to low level wind shear (LLWS) across the area tonight. The LLWS will weaken as the LLJ weakens by tomorrow morning. This will leave increasing southerly flow to finish out the TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Meyers AVIATION...Meyers