Marine Weather and Tide Forecast for Sergeant Bluff, IA

DISCUSSION
Issued at 218 PM CDT Tue Oct 14 2025

The radar has diminished in coverage over the last couple of hours, with further showers developing but remaining more isolated through the rest of today and into Wednesday. The forcing continues due mainly to low level WAA as surface high pressure is centered to our north near the ND/MN/Canadian border, with small lobes of vorticity adding a bit of local punch to a few of the showers. CAM forecast soundings show a saturated bottom 500mb of the atmosphere persisting through most of Wednesday, however the forcing from the WAA weakens such that we should see lower coverage and intensity of showers eventually dwindling down to a brief dry period on Thursday. Instability largely remains absent so even rumbles of thunder seem unlikely, with the activity today largely absent of any thunder activity.

An upper level ridge crosses the region Thursday with a brief burst of subsidence ahead of a developing surface low pressure system and upper level trough forming over the Rockies, allowing for a bit of sunshine and temperatures surging into the mid to upper 70s on Thursday as low level winds increase out of the south/southwest. This developing low pressure system has been consistently forecast by the global deterministic guidance to push northwards across the central Dakotas before strengthening as it stalls near the Canadian border, with a broad and diffuse cold front pushing across the forecast area late Thursday night into Friday morning. Ensembles are relatively split on QPF amounts along the front with around 25% of GEFS membership showing above 0.1 inches, with roughly 75% showing at least a hundredth or two and only a few members completely dry. The last couple of fronts have overproduced cloud cover and showers compared to the guidance in the few days leading up, so if this trend continues we can expect a tenth of an inch or two as the front passes through by 12-15z Friday. There is some additional showery activity possible on Saturday as cold air advection wraps around the now occluded upper level trough, with showers possible as long as we have the moisture to support the weak forcing, which appears likely given the forecast soundings and rain chances leading up to Saturday.

After the rain chances on Saturday, there is a significant split in the guidance for the following week, with the GFS markedly warmer as another trough develops over the Rockies and low level WAA returns. The ECMWF/CFS are much colder with a broad area of CAA and northwesterly flow aloft, with the ECMWF showing a more amplified upper level pattern which drags cooler air much farther south. Given the differences, forecast confidence is fairly low after the weekend with the only consensus being a relatively dry forecast.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/
Issued at 611 PM CDT Tue Oct 14 2025

Widespread IFR through the period with potentially LIFR late tonight into early Wednesday morning. Spotty showers will remain possible through the period, but likely be a bit more isolated than today. While showers will not be as widespread, areas of fog and drizzle will increase overnight, providing the low aviation conditions. Some improvement is expected late tomorrow morning into the afternoon.

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