textproduct: Omaha/Valley

KEY MESSAGES

- There is a conditional threat for severe weather through this evening and overnight with potential for damaging winds, large hail, tornadoes, and heavy rain/flooding.

- A Flood Watch is in effect through Tuesday morning. If additional storms Tuesday evening look like they'll impact the same areas, the watch may need to be extended.

- A wet pattern continues through the week with daily shower and storm chances. While the threat for hail, damaging winds, and tornadoes will diminish, repeated rounds of rain may lead to an increasing flooding threat.

DISCUSSION

Issued at 211 PM CDT Mon Sep 14 2026

A somewhat conditional severe weather threat remains in the forecast for later this afternoon into this evening and overnight with the big questions being how unstable we can get and how many surface-based storms we can get. Early afternoon analysis showed a warm front stretching from north-central KS, east-southeast into northeast KS and western MO. This will surge northward into southeast NE through this afternoon while a stream of shortwave energy starts pushing through leading to storm development. 18Z KOAX sounding did show a very stout cap, though obviously was well north of the boundary. In addition, satellite showed quite a bit of cloud cover across the area aside from some decent clearing across far southeast NE where temperatures had climbed into the mid 80s with dewpoints approaching 70. And you don't have to go very far south and west to see upper 80s and lower 90s. So while much of the area remains capped now, the unstable airmass is on the way, though questions remain as to how far north it'll get.

As for model guidance, there's very good agreement in developing a southwest to northeast line of thunderstorms. SPC objective mesoanalysis shows sufficient effective layer shear to yield some supercell structures, but with the line going up quickly, think it could become somewhat of a messy storm mode as we go into the evening. As storms first develop, all severe weather hazards would be possible, including tornadoes and even a strong tornado, owing to large, looping low level hodographs. However, threats should transition to mostly damaging winds and heavy rain/flooding with guidance suggesting potential for training thunderstorms. In addition, guidance shows 1.75-2" of precipitable water with warm cloud depths exceeding 4 km. Low level moisture transport will also ramp up this evening and overnight and point toward the NE/KS border, where 3+ inches of rain fell in some locations last night/this morning. While short term guidance doesn't produce much precip in those areas, there remains the possibility that an outflow boundary surges southeast out of the line of initial convection owing to line- parallel 0-3 km shear. This could provide a focus for storm development near the NE/KS border as the aforementioned moisture transport ramps up. Therefore, ended up issuing a Flood Watch for much of southeast NE and southwest IA, pairing areas where training thunderstorms are most likely with areas that will require less rain to see flooding.

The remainder of the week is looking relatively wet with pretty much daily shower and storm chances. The surface boundary will push just south of the area by Tuesday morning, but rain chances will persist, especially near and south of I-80, as additional shortwave energy passes through. While the damaging wind, hail, and tornado threat should remain to our south with the higher instability, we will see a heavy rain/flooding threat with potential for training showers and storms, though still some questions as to how far north those will extend. In addition, NAEFS precipitable water values look to be in the 1.75-2 inch range, good for the 99th+ percentile of climatology for this time of year, so anything that does develop will be a pretty efficient rain producer. Should it look like heavier precip will end up in our area, may need to extend part or all of the Flood Watch.

A steady stream of shortwave energy will continue Wednesday into Thursday while the surface boundary slowly meanders back north, eventually reaching SD by Friday. At least on and off showers and storms will be possible through that period, with potential for repeated rounds of rain to lead to flooding concerns. Friday is generally favored to be a drying period, though still looking at 20- 30 percent chance of rain in the afternoon with a few various ensemble members a little slower with the northward advancement of the front. However, any dry period looks to be short-lived as a cold front pushes in from the northwest for the weekend and gives us continued 30-50% chances of rain. Machine learning severe weather guidance keeps severe weather potential below (under 5%) through this active period, though again, potential heavy rain and flooding will remain a concern with each successive round.

Otherwise, temperatures may be a bit of a roller coaster through the week and will hinge on precipitation on a given day. Currently, upper 60s and 70s are favored Tuesday and Wednesday before the front moves back north and marks a return to the 80s Thursday and Friday. Behind the weekend cold front, expect to be back down in the 70s to lower 80s. But again, lots of moving parts, so confidence in exact temperatures on a given day is relatively low.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1243 PM CDT Mon Sep 14 2026

Main forecast concern remains timing of strong to severe storms this evening. Still looking like 23-03Z at LNK and OMA with primary TS threat staying south of OFK. Expect 50 kt winds and perhaps some hail with the strongest storms. Additional showers and a few storms may linger overnight behind the main line, but TS coverage should be less with that. Otherwise, expect MVFR ceilings to scatter out this afternoon before potentially returning as storms move through. Winds will remain southerly, gusting 25-35 kts into early this evening, eventually becoming lighter and northwesterly to northerly.

OAX WATCHES/WARNINGS/ADVISORIES

NE...Flood Watch from 6 PM CDT this evening through Tuesday afternoon for NEZ052-053-066>068-089>093. IA...Flood Watch from 6 PM CDT this evening through Tuesday afternoon for IAZ069-079-080-090-091.