Marine Weather and Tide Forecast for Yankton, SD

UPDATE
Issued at 440 AM CDT Tue Jul 28 2026

Expansive mid-level clouds blanket the area early this morning, growing in coverage ahead of a subtle approaching wave. Dry air persists in the sub-cloud layer, but cannot rule out a few sprinkles as the wave slides through. Decreasing clouds are generally expected behind the departing wave, allowing for highs in the upper 80s to mid 90s this afternoon. Will have to watch for spotty showers/storms to develop along a subtle boundary from northeast SD into southwest MN by late afternoon/evening. Severe storms are not expected, but the aforementioned dry sub-cloud layer could support erratic stronger wind gusts up to 50 mph, with perhaps some small hail in stronger cores.

A quiet day Wednesday though models suggest a fair amount of smoke aloft topping the upper ridge into the northern Plains.

Fair consensus showing a stronger trough slowly pushing across the region during the latter part of this week, though not a slam dunk as the long-range ensembles do show increasing spread in the strength of the trough as it moves east across the Dakotas and Minnesota. That said, beneficial rainfall is possible, with LREF probabilities indicating moderate (50-70%) potential for 24-hour rainfall totals exceeding 0.50 inch by Friday morning. With the divergence in possible solutions, severe weather potential is uncertain. However, later Thursday/Thursday evening will be a period to watch with CAPE/Shear joint probabilities supporting a potential for a few stronger storms.

DISCUSSION
Issued at 153 PM CDT Mon Jul 27 2026

Hot and humid conditions improve behind a cold front that passed through the region this morning. Winds behind the front are out of the north and a bit breezy with gusts to around 20 mph. Dewpoints are falling rapidly to the low 60s. However, highs are still expected to climb into the 90s and low 100s, and so Heat Index values will be 100 to 104 degrees F. A Heat Advisory remains in effect for areas along and south of I-90 until 8 pm CDT.

In addition to heat there is a Marginal risk (level 1 of 5) for strong to severe thunderstorms. A shallow wave will pass through the region, triggering storms over western South Dakota late this afternoon into the early evening. These will travel east and begin to impact areas of central South Dakota some time after 9 pm CDT. As storms approach they will be encountering an increasingly stable environment. While severe weather cannot be ruled out, the area most likely to see any stronger storms will be west of the James River.
The main risk with storms will be damaging wind gusts of 65 mph.
Storm intensity will weaken as they continue east becoming scattered rain showers and weak thunderstorms. Rain accumulation will be light, a trace to a hundredth for most of the CWA West of the James River may see up to a tenth of an inch. Showers may linger into the morning commute Tuesday, but impacts should be minimal.

Tuesday surface high pressure settles over central South Dakota turning winds to the southeast. Highs will be cooler, in the 80s east of Highway 81, and in the low 90s to the west. Dew points will climb into the mid 60s to low 70s and will result in muggy conditions once again. However, Heat Index values will remain below critical. Still, it's important to maintain proper hydration and to take breaks out of the heat. Wednesday will be another quiet day with highs in the 90s.

Wednesday night a short wave will work through the upper ridge bringing chances for showers and thunderstorms. There is a very large difference in mid-range guidance on convective parameters, therefore the severity of the storms is uncertain. Thursday isolated to scattered light showers will continue periodically through the day. Thursday afternoon a stronger upper wave moves into the region. This will result in another round of showers and thunderstorms. Mid-range guidance continues to have a wide range of solutions, and severity of storms is once again in question. Over the coming days the trends will be monitored and updates issued as details become clear.

An upper level ridge will push into the region behind the wave for the weekend. Partly cloudy skies and highs in the 80s to low 90s with dry conditions are expected.

One final note: Smoke from wildfires in the western US and Canada is expected to begin to flow into the region today. This will result in milky looking skies and a decrease in air quality. You may even be able to smell smoke at times depending on how deeply we mix each day. With our current upper level pattern smoke is expected to remain in the forecast through at least the middle of the week.
People who are sensitive to air pollutants should use precautions.
For the latest on Air Quality please visit AirNow.gov.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
Issued at 636 AM CDT Tue Jul 28 2026

VFR conditions are expected to prevail through the period with variable winds generally at or below 10kt.

Cannot rule out minor visibility reductions due to wildfire smoke, though confidence in extent and timing is too low to mention FU or associated lower visibility in the TAFs at this time.

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