textproduct: Omaha/Valley

KEY MESSAGES

- Widespread rainfall of 2 to 4 inches expected through Thursday, with locally higher amounts. A Flood Watch has been issued for Tuesday evening through Thursday. - If we get any clearing on Wednesday, a few strong to severe thunderstorms will be possible during the afternoon and evening, mainly in southeast Nebraska. - Rain will end Thursday night, with cooler, dry conditions expected through the weekend.

DISCUSSION

Issued at 226 PM CDT Tue Sep 29 2026

Today through Thursday:

Water vapor imagery this afternoon features largely zonal flow across the northern half of the CONUS with a positively-tilted shortwave trough extending from the Dakotas/northwest MN southwest to a cutoff low over the southern Great Basin. This cutoff low/shortwave and the remnants of the former hurricane Polo remain the focus for the forecast period, with strong moisture advection expected to contribute to efficient rainfall processes that will be present through the first half of Thursday. Hidden in higher river/flash flooding threat, severe weather will also be possible Wednesday with a 5% chance of damaging hail/wind or an isolated tornado near that reaches from Kansas into far south-central Nebraska.

Taking a look at the synoptic setup for this period, the remnant MCV from Polo will join the Great Basin low as they eject to the northeast. This will help initially deepen the mid/upper lows, and promote a stronger mass response across the Southern and Central Plains that will amp up warm air advection and moisture transport from the Gulf in addition to the remnants from Polo. Already, a cold front stretches from eastern ND to southeast CO, while a warm front extends from there towards LA. That aforementioned cold front will shift into the forecast area later this evening, stalling out/becoming increasingly positively-tilted, and remaining in the area through the first half of Thursday. Convergence along the front as moisture transport runs into the frontal interface along with deeper lift associated with the large-scale height falls will help "skinny" CAPE profiles to be realized and lead to efficient rainfall processes.

Looking at the periods of peak rainfall, the first wave of healthy rainfall is set to occur this overnight tonight into the morning hours (4 AM to 10 AM). After a lull in activity, strong convergence in the lowest levels will help to spread stronger storm activity northward from Kansas into southern Nebraska after 3 PM tomorrow. We'll see our best instability of the forecast to go along with modest shear that could organize some of the stronger storms to make severe activity a possibility. That modest shear and curvature in the low-level hodograph will keep all hazards on the table. Those showers and storms present the highest rainfall potential as the move across southeast Nebraska into Iowa from 3 PM to 3 AM, and amounts during this time could exceed 2" alone. Once that period ends, we'll be dealing with exiting rainfall across far southeastern Nebraska into southwest Iowa that will leave us high and dry by Thursday night.

Most of southeast Nebraska are set to receive 2-4" of rainfall, with an narrow band of 5-6" or more possible where the strong storms track Wednesday evening. This should translate to areas of flash flooding, several area streams and rivers hitting action stage, and a handful of locations hitting minor flood stages south of the Platte River. River levels should peak Friday and Saturday according to ensemble river guidance, and could complicate rural travel if conditions do reach minor flood stage.

Friday and Beyond:

Friday onward in the forecast will see the area dry out considerably, much to the joy of those hoping to harvest. West- northwesterly flow will move into the area and we'll see temperatures hang in the 60s through the remaining forecast that warms a tad bit towards the end of next week. Very few ensemble models output any QPF for eastern Nebraska and southwest Iowa, making for a well-timed dry period that will carry us into meteorological fall with excellent weather.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1225 PM CDT Tue Sep 29 2026

VFR conditions are in place this afternoon across all three terminals, with an initial round of showers and storms moving off to the northeast of KOMA, while lighter showers continue near KOFK. An additional round of rain is expected to develop near 21z near KLNK, spreading northeastward during the early evening hours with a few embedded rumbles of thunder that are hard to pin down as well (40% chance). As those showers push through, expect ceilings to fall into MVFR territory, before moving into IFR territory overnight. Lower visibility values are expected to develop as IFR conditions arrive, and KOFK and KOMA should see the worst of them at 2SM. Winds will otherwise turn southeasterly over the course of the TAF, with speeds of less than 10 kts settling in.

OAX WATCHES/WARNINGS/ADVISORIES

NE...Flood Watch from 7 PM CDT this evening through Thursday evening for NEZ015-018-030>034-042>045-050>053-065>068- 078-088>093. IA...Flood Watch from 7 PM CDT this evening through Thursday evening for IAZ043-055-056-069-079-080-090-091.