


Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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992 FXUS63 KFSD 110005 AAA AFDFSD Area Forecast Discussion...UPDATED National Weather Service Sioux Falls SD Issued by National Weather Service Aberdeen SD 705 PM CDT Thu Jul 10 2025 .KEY MESSAGES... - Scattered strong to severe storms are possible this evening, capable of damaging wind gusts and large hail, and potentially a tornado. Greatest threat locally is along and south of Highway-20. - A marginal (level 1 of 5) risk of severe storms continues Friday afternoon and evening, as a front brings scattered thunderstorms southward into the evening and early overnight hours. Marginal risks of 1" hail, brief strong winds, and brief heavy downpours possible. - Temperatures cool Saturday, but return back to above normal levels Sunday and Monday. Humidity is expected to build each day. - Thunderstorm risks return late Monday through Tuesday, with signals for severe weather potential present in most data. && .DISCUSSION... Issued at 258 PM CDT Thu Jul 10 2025 A line of elevated thunderstorms is crossing the Missouri River in South Dakota this afternoon in an environment characterized by around 3000 J/kg of MUCAPE and mid-level lapse rates of 7.5-8 C/km. Hail would be the main threat with this activity if an updraft along the line is able to sustain itself long enough. These storms also have around 1000-1500 J/kg of DCAPE to work with; however, the elevated nature of the storms may make it difficult for strong winds to make it to the surface. So overall, this activity looks mostly like a heavy rain and lightning threat over the next few hours as it lifts slowly east-northeastwards and fades as it closes in towards I- 90. The bigger question going into late this afternoon will be storm development that is expected to occur somewhere in north-central Nebraska. The aforementioned storms crossing the Missouri may act to suppress the greater thermodynamics south of the area through this evening, keeping the greatest threat of severe weather closer to the I-80 corridor. Still, the greater severe weather threat locally will be mainly along and south of Highway-20. These storms will be capable of all modes of severe weather, mainly large hail and damaging winds, though a brief tornado cannot be ruled out. Heavy rain and urban flooding may also be possible, more on that below. FRIDAY: Lingering showers are likely to continue moving east or southeast in the morning as rapid subsidence develops behind departing upper trough. A light and variable wind could lead to a bit of patchy valley fog into mid-morning. Recent CAMS and lower resolution guidance have backed off PoPs through mid-day, holding off on any diurnally based convection until mid-afternoon in most locations. Better focus for convection is expected to develop along a slowly advancing cold front sinking through central and northern South Dakota in the morning along with a weak pre-frontal trough bisecting the CWA. Soundings within the warm sector ahead and near these features continue to indicate modest MLCAPE of 1500-2000 J/KG, but unidirectional shear remains very limited. This would suggest any activity that develops will be pulsy in nature, but also capable of smaller hail and brief downburst winds. FRIDAY NIGHT: The front and accompanying convection will slowly drift through the CWA overnight, with isentropic downglide clearing out precipitation quickly by daybreak. Temperatures Saturday morning expected to fall into the middle 50s to lower 60s. SATURDAY-SUNDAY: A perfect Saturday will be in store for the region as high pressure drifts across the area. Combined with light winds and temperatures only in the upper 70s to lower 80s, the afternoon may feel quite comfortable. Some isolated high based showers and thunderstorms may develop west of the James River early Sunday morning, signaling the return of warmer air aloft. Temperatures Sunday are expected to climb back into the mid 80s to lower 90s. MONDAY-WEDNESDAY: As we`ve been discussing the past days, we`ll keep our eyes on a frontal boundary dragging across the Dakotas Monday into Tuesday. Dew points will likely surge higher Monday afternoon given the southerly flow but also increasing evapotranspiration of the season. Will likely continue to need to bump dew points upwards from NBM values. A mid-lvl wave moving through early Tuesday will bring our next risk of convection, possibly strong to severe, to the region. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 655 PM CDT Thu Jul 10 2025 The best chances of thunderstorm impacts will be from KYKN to KSUX through the evening hours, and thus have a TEMPO group in KSUX from 00Z to 03Z to account for this. The strongest storms will bring IFR visibilities and the potential for severe wind gusts in excess of 50 kts. After the storms, showers may continue for areas mainly south of I-90, but guidance varies largely regarding any activity through the early morning hours. We`ll dry out heading into Friday morning, before another round of showers and thunderstorms move into the area Friday afternoon. Held off on mention pcpn in the TAFS for now. Winds will shift to the north behind the passage of a cold front during the afternoon and evening hours on Friday. && HYDROLOGY... Issued at 258 PM CDT Thu Jul 10 2025 Thunderstorm are expected to track eastward through portions of northeastern Nebraska and northwestern and western Iowa this evening. PWAT values approaching 2.0" along with storm motion along an elevated boundary will lead to an increased potential for excessive rainfall later this evening and overnight. HREF PMM indicate potential for localized 2 to 5" of rain along, but especially south of Highway 20 during this event. While probabilistic models suggest lower river flooding in southern CWA basins the greatest risks may rise from urban and small stream flooding given potential for 1 to 3" per hour rainfall rates. Thus have issued a narrow flood watch for the Highway 20 corridor this evening into early overnight. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...Flood Watch from 7 PM CDT this evening through Friday morning for IAZ031-032. NE...Flood Watch from 7 PM CDT this evening through Friday morning for NEZ013-014. && $$ DISCUSSION...Dux/Samet AVIATION...SD HYDROLOGY...Dux