Marine Weather and Tide Forecast for Yankton, SD

DISCUSSION
Issued at 200 PM CST Tue Feb 18 2025

THIS AFTERNOON: Temperatures slowly climbing this afternoon, with some readings above zero near Sioux City. Winds remain occasionally breezy, but wind chill readings have rising above criteria in most areas outside of the Buffalo Ridge. Dew points have also risen nearly 5 to 10 degrees over Monday afternoon values, likely signaling another cold night but perhaps not as cold as Tuesday morning.

TONIGHT: Mid-lvl vorticity will move through northern Nebraska overnight and into Wednesday morning, bringing an increase in mid- upper clouds and slowly the diurnal drop slightly. 12Z ABR sounding data again shows an extremely dry airmass with PWAT values at 0.04" sitting just above historical minimums for February 18th. While some light snow may develop and move along and south of the Missouri River, this dry air influence will limit any accumulations.
Temperatures will begin to fall after sunset, but at a slower rate than last night. However after 09Z with the gradual clearing of clouds we should see a more sudden drop in low temperatures by daybreak towards the -10s to a few -20s. Winds will again be a critical factor in determining final wind chill values and a weakening pressure gradient should keep wind chills from falling drastically areawide. Nevertheless, warning level values are likely in most areas north of I-90, with advisory levels further south.
Coldest readings channel down the James River valley and then along the Buffalo Ridge. Have refined timing of current headlines slightly, and added in a couple James River valley counties to account for the better flow of the coldest air development.

WEDNESDAY: Low level temperatures continue to rise on Wednesday, and less cloud cover should mean a faster rise in temperatures. Current end timing of headlines around 10am seems reasonable. Highs in some locations may reach above zero.

WEDNESDAY NIGHT: Surface high pressure moving through South Dakota will peak early on Wednesday, and with pressures falling with the rise in daily temperatures. Nevertheless, data continues to support some of the highest pressure values on record for February in portions of the Tri-State area. The large upper trough centered over the Western Great Lakes will finally begin to move east Wednesday night, pulling a ridge of surface high pressure into the James River valley. Overnight lows will again fall towards the -20 mark under the surface ridge, but a calm wind will keep wind chill values near the air temperatures. Areas east and west of the core of the high pressure center will see falling wind chills at the higher end of advisory levels (perhaps low warning levels near Sioux City). It's not out of the question to see the CWA split with headlines in the light wind gradient, but no headlines where winds turn calm.

THURSDAY: Another cold day on Thursday will feature a return of southwesterly winds late in the day. While overnight low temperatures Thursday won't fall nearly as far as past nights, the increase in the winds could push areas towards the -15 to -25 wind chill range by Friday morning.

FRIDAY-MONDAY: Mid-lvl ridging is still expected to develop heading into next weekend, bringing an end to the climatologically significant cold spell this week and keeping the region dry.
Southerly winds increase Friday and Saturday, but it has seemed that medium range models and ensembles are catching onto the fact that there remains 2 to 5" of snow depth that has been exposed to a very cold airmass. Gradual cooldown of forecast highs continues Friday, Saturday, and Sunday, but there remains strong potential for highs above freezing areawide by Sunday.
With dew points rising near 32 Sunday into Monday, we'll have to watch for some fog and stratus potential, which then could hamper highs on Monday. Probabilities of 40 degree or warmer highs cross the 50% threshold west of I-29 on Sunday and then climb over 70% areawide on Monday. West of the James River stands the greatest probability of highs in the 50s early next week.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
Issued at 525 PM CST Tue Feb 18 2025

Mainly VFR conditions begin the TAF period. Some MVFR ceilings and visibilities are present across parts of the Missouri River Valley, mainly in and around south central South Dakota. Light snow is accompanying the MVFR ceilings and visibilities. Could see some light snow translate towards KSUX but confidence is not high enough to include in a TAF at this time.

Any chance for light snow will come to an end during the overnight hours. Ceilings and visibilities will fully lift to VFR levels across the entire area during this period of time. Light northerly winds with speeds up to 5-10 knots and VFR conditions is expected for the entirety of tomorrow.

FSD WATCHES/WARNINGS/ADVISORIES
SD...Cold Weather Advisory from 9 PM this evening to 10 AM CST Wednesday for SDZ057-062-064>067.
Cold Weather Advisory from midnight tonight to 10 AM CST Wednesday for SDZ050-063-068>071.
Extreme Cold Warning from 9 PM this evening to 10 AM CST Wednesday for SDZ038>040-052>056-058>061.
MN...Cold Weather Advisory from 9 PM this evening to 10 AM CST Wednesday for MNZ098.
Cold Weather Advisory until 9 PM CST this evening for MNZ071- 072-080-081-089-090-097.
Extreme Cold Warning from 9 PM this evening to 10 AM CST Wednesday for MNZ071-072-080-081-089-090-097.
IA...Cold Weather Advisory from 9 PM this evening to 10 AM CST Wednesday for IAZ001>003-012>014-022.
Cold Weather Advisory from midnight tonight to 10 AM CST Wednesday for IAZ020-021-031-032.
NE...Cold Weather Advisory from midnight tonight to 10 AM CST Wednesday for NEZ013-014.