Marine Weather and Tide Forecast for Yankton, SD

UPDATE
Issued at 408 AM CDT Sat Jun 13 2026

Taking a look across the area, we're continuing to watch a growing altocumulus field across northcentral Nebraska this morning. While we're a little early, as this field continues to expand eastwards; this will likely become the focus for where our next shower and thunderstorm chances (40%-60%) develop across northwestern IA.
With this in mind, the forecast remains on track for showers and thunderstorms to develop starting around 5 am as weak shortwave intersects a lingering cold frontal boundary. With a weakening LLJ overhead, a few developing storms could become severe with large hail up to half-dollar size (1.25") being the primary threat.

While the focus continues to be across the Highway-20 corridor, the only significant change in the forecast is that SPC has introduced a Day 1 slight risk (Level 2 of 5) to the same areas due to the increasing potential for larger hail. Otherwise, newer runs of short- range guidance has continued to expand the coverage of showers and potentially thunderstorms northwards into early afternoon. As a result, decided to follow suit with our POPs using a blend of the latest NBM and CONSshort. Lastly, its worth noting that the 06z HRRR has started to hone in on additional redevelopment in the early afternoon mainly along the cold front. If this proves to be true, can't rule out a narrow window for a few additional stronger storms carrying larger hail mainly across our far southeastern-most zones (Woodbury, Ida, Cherokee, and Buena Vista counties) during the early afternoon timeframe (12pm-4pm).

DISCUSSION
Issued at 155 PM CDT Fri Jun 12 2026

Mostly clear skies, WAA on breezy southwest winds, and deep mixing will help our high temperatures this afternoon warm into the 80s. Looking aloft we see a strong upper low over eastern Canada. A cold front drapes southwest through northern Minnesota, through North Dakota, and into Montana. This front will drift southeast bringing chances for showers and thunderstorms with it. As the front approaches our western border this evening, an area of surface convergence will form ahead of it. Increases in low- level Theta-e contributes to a modest increase in instability, though MUCAPE remains on the low side, around 500-800 J/kg. At the same time mid-level lapse rates increase, and 0-6 km bulk shear will be in the 50 kt range. While severe weather is not anticipated, the stronger shear could allow a few isolated updrafts to organize enough to produce small hail. Though, with cloud base heights of 8000-10,000+ ft AGL the chances small hail will survive to the surface is low. Tall, skinny CAPE profiles on soundings indicate that some brief heavy downpours are possible. Soundings also indicate a deep, very dry subcloud layer. Evaporational cooling could result in wind gusts to 45 mph, and is the most likely threat with any stronger storms. Convection is expected to begin as a weak mid- level short wave intersects the front around 6-8 pm. The strongest storms are expected along the Highway 14 corridor from roughly Huron east into Minnesota. Weaker, more showery storms may drift as far south as I-90. Storms should be east of the CWA around midnight.

As the cold front continues to progress southeast through the overnight, another surface low and attendant warm front will be moving northeast out of Colorado/Wyoming. Between the two fronts will be a slightly stronger area of convergence. Similar to Friday evening, instability increases as an area of rich Theta-e moves north into the region. Mid-level lapse rates increase into the favorable range for stronger storms, as well as bulk shear at 40-50 kts. However, several questions remain. First, the environment is strongly capped, for storms to form they will have to fire along the 925 mb front. The second question is how far north the richer Theta- e air will advect. The CAN and NAM12 have higher values working into the area as far north as Highway 18 and east into northwest Iowa, while the GFS and EC are more conservative and higher values remaining south of Highway 20. Third, when will the mid- to upper wave arrive? There is enough variance in guidance to leave confidence in strong storm formation low (10%). Enough forcing looks to be present to initiate isolated to scattered elevated showers and thunderstorms. The main threat will again be wind gusts to 45 mph and brief heavy downpours.
Unlike Friday, the cloud base heights are around 900 ft AGL. So while small hail is still unlikely, it has a better chance surviving to the surface should it form. Any stronger storms are most likely to occur as convection initiation begins around daybreak, 5-7 am. Storms will weaken and gradually move east through the early afternoon Saturday.

Behind the cold front, winds will become northwesterly and cooler air will flow into the region. Highs for Saturday will depend on where you are within the CWA For those north of I-90 low to mid 70s are expected. To the south, mid to upper 70s. Clear skies Sunday with a couple of dry short waves reinforcing the CAA limit highs to the low to mid 70s. Monday a return to westerly flow and mostly sunny skies will bring highs back into the mid 70s to low 80s.
Monday evening a stronger shortwave will work through the pattern, bringing chances for showers and thunderstorms. While some thunder is possible, severe weather is not anticipated at this time. Tuesday will be mostly sunny with a stronger push of WAA. Highs will be in the mid 70s to mid 80s along the Missouri River Valley. Highs for the second half of the week will remain in the 70s and 80s for the most part. From here guidance begins to diverge. Multiple chances for showers and storms exist, though details are uncertain at this time.

One final note: Those with outdoor plans, rejoice! This weekend through the first half of next week will not only be on the cool side of average for this time of year, but relative humidity values will also be low. Get out and enjoy the pleasant weather!

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
Issued at 1223 AM CDT Sat Jun 13 2026

Showers and a few thunderstorms continue to push eastwards and weaken mainly across southwest Minnesota. Some low level wind shear (LLWS) begins the TAF period at KSUX but this will quickly diminish.
Another round of showers and storms is expected to develop late tonight and persist into the morning hours tomorrow. These storms will mainly be around the highway-20 corridor, including KSUX. There is some potential for additional showers to develop northwards towards KFSD but confidence is not high enough to include in their TAF at this time. Could see some showers persist into the afternoon hours across parts of northwest Iowa as well. Winds will also strengthen out of the northwest with gusts up to 20-35 knots for the afternoon. Winds will weaken this evening to end the TAF period.

FSD WATCHES/WARNINGS/ADVISORIES
SD...None.
MN...None.
IA...None.
NE...None.