textproduct: Omaha/Valley

KEY MESSAGES

- Dense fog potential overnight tonight for northeast Nebraska.

- Have trimmed northern counties out of the Flood Watch due to latest guidance trending heavy rainfall farther south. Still expect a broad swath of 3-5 inches of rain through Thursday. - Cooler, dry conditions through the weekend with temperatures trending back warmer next week.

DISCUSSION

Issued at 1136 PM CDT Tue Sep 29 2026

Clouds across eastern Nebraska and western Iowa tonight as a plume of moisture continues to stream in from the remnants of Hurricane Polo as well as the Gulf. An upper-level trough over Arizona is helping to pull this moisture northward as well as track these remnants toward our area. Overnight, drier conditions over northeast Nebraska as well as some potential clearing of clouds will lead to significant fog development over a large portion of northeast Nebraska. We could potentially need a dense fog advisory for this portion of our area by daybreak on Wednesday.

Overall models have been trending farther south with the track of the remnants of Polo which takes the band of heaviest rainfall now more through Pawnee City, Falls City, Nebraska City in southeast Nebraska, and Shenandoah, Clarinda, and Red Oak, in southwest Iowa. A couple models continue to hold on to a more northerly trajectory so I'm not trimming the Flood Watch quite as far south as I want to, but I am taking out all of our northeast Nebraska counties. I think the greatest concern for flooding over the next couple of days will be for rivers such as the Little and Big Blue Rivers, Turkey Creek, the Big Nemaha, and West and East Nishnabotna Rivers.

Now for the weather discussion. As the western trough approaches we'll see shortwaves bring additional rounds of showers and storms overnight through the day on Wednesday. A stationary boundary sets up southwest to northeast across our area overnight with light or even northerly winds to the north and southerly winds south. As the remnants of Polo approach from the southwest we see increased WAA along the strengthening warm conveyor belt overnight. This will lead to some elevated instability over the surface stable layer potentially allowing for some heavier showers or even thunderstorms overnight across southeast Nebraska into southwest Iowa. CAMs depict this pretty well as a band of storms really ramping up between 1-3 AM and exiting east of our area towards 7AM. Rainfall rates under heavier storms could lead to some localized flash flooding early Wednesday, especially in towns with more pavement.

We're likely to see at least a short break Wednesday morning after 8AM before the next round starts to push into southeast Nebraska around 11AM. This will be associated with the isentropic upglide north of the warm front from Polo interacting with another weak shortwave moving across eastern Nebraska.

The round I'm most concerned about for heavy rain and flash/river flooding arrives Wednesday night as we see Polo move into north-central Kansas injecting additional moisture into the region with a band of mid-level 850-700-mb frontogenesis setting up across southeast Nebraska into southwest Iowa overnight into early Thursday. This could further enhance rainfall rates with a swath of 1-3 inches of rain likely just overnight across a good portion of southeast Nebraska and southwest Iowa. Locally higher amounts very possible. This all falling on already saturated ground from previous rounds of rain will mean most of this will end up as runoff into local rivers and creeks. Flash flooding will be the immediate concern overnight, but flooding on the bigger creeks and rivers will be likely through the day on Thursday, possibly even lingering into Friday depending on how long it takes to completely flush through our system.

Though still potentially heavy through Thursday morning, rain should taper off through the afternoon on Thursday, clearing out by the evening. Behind this system, a Canadian High slides down over the Northern Plains keeping cooler air in place going into the weekend with dry, quiet weather. Highs over the weekend stay in the lower to mid-60s, with a reinforcing dry cold front bringing another shot of cooler air in on Sunday.

The upper-level pattern quiets down going into next week with a ridge building along the West Coast and broad high pressure centered over the Great Lakes forcing the moisture axis from the Gulf west of our area. I'd expect the transition to northwesterly flow across our region to start bringing in more shower/storm chances toward the latter half of next week once we can bring the moisture plume back east over our area. While weather stays quiet we do see temperatures trend back up into the low-to-mid 70s toward midweek next week.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 547 AM CDT Wed Sep 30 2026

A band of showers and a few scattered storms are ongoing at the KOMA and KLNK terminals this morning resulting in IFR ceilings and brief IFR visibility reductions, while fog has overspread KOFK. Expect LIFR conditions to prevail for a few more hours at KOFK with fog burning off in the late morning hours. There will also be a break in shower activity at KOMA and KLNK by 14z, but it will be short lived as more activity overspreads the terminals after 16z and persists for most of the TAF cycle. Expect continued IFR ceilings and visibilities with the heaviest shower activity. Winds remain under 10 kts for the duration of the TAF cycle, becoming northeasterly in the afternoon and evening hours.

OAX WATCHES/WARNINGS/ADVISORIES

NE...Flood Watch through Thursday evening for NEZ044-045-050>053- 065>068-078-088>093. Dense Fog Advisory until 10 AM CDT this morning for NEZ011-012- 015>018-030>033-042-043. IA...Flood Watch through Thursday evening for IAZ055-056-069-079- 080-090-091.