textproduct: Omaha/Valley

KEY MESSAGES

- Showers and storms likely this evening (60-80% chance). Storms may be severe with large hail and damaging winds.

- Additional rounds of strong to severe storms possible Saturday through Monday with large hail, damaging winds, tornadoes, and flash flooding all possible.

- Pattern quiets down Tuesday and beyond with highs in the 60s Tuesday and Wednesday, warming into the 70s later in the week.

DISCUSSION

Issued at 1226 PM CDT Fri May 15 2026

Clear skies this morning with some scattered cu starting to develop over south-central Nebraska. Water vapor satellite imagery shows the deepening trough over the West Coast which will lead to the development of our active pattern going into the weekend. Over eastern Nebraska, RAP objective analysis shows a front situated along the western extent of our area, from a few miles east of Yankton south to around Hastings. This boundary will continue to slowly move southeast, eventually stalling from around Onawa, IA southwest to around Red Cloud, NE. This corridor will be the focus for initial storm development as the upper-level wave arrives this evening.

Temperatures are forecast to get very warm today, with highs in the 90s. In northeast Nebraska, we will again expect humidity to drop to 20 to 25 percent this afternoon leading to very high fire danger. Fairly weak winds of 5 to 10 mph should limit Red Flag conditions.

Through the afternoon we'll start to see moisture pooling along the surface front with an upper-level shortwave kicking off storm development around 6-7pm this evening. We're expecting 2000-2500 J/kg of SBCAPE to develop, combined with 0-6 km of bulk-shear of 35 to 40 kt should favor supercell development initially. Dry low-levels in the soundings indicate high-base hailers initially evolving into a damaging wind threat as storms converge into clusters or more into a line. The tornado threat at this time is very low due to high LCLs along with little low- level curvature in the hodograph, but SPC has bumped a good portion of our west-central Iowa counties up into an Enhanced Risk (level 3 of 5) for increased damaging wind and hail threat.

As previously mentioned, storms should initially develop along the northeast to southwest frontal boundary which will stall across our area this afternoon. The general consensus of the CAMs suggest that these storms will congeal into clusters or a line and move southeast through the evening, clearing out by around midnight-2am. With increased confidence in placement of these storms, have increased PoPs to around 60-80 percent this evening in areas with the greatest chance of seeing storms.

Saturday will be another warm day, though a few degrees cooler due to starting out the day with the post-frontal air mass in place across our area. With the approach of our next upper-level wave, we'll see a warm front lift back north into our area through the afternoon. CAM guidance is still not confident in any convection developing along this front during the late afternoon into the evening. The HRRR and RRFS, though, (both notorious for over- convecting at times) give us at least an idea of what it may look like if we get storms along this front. 3000-3500 J/kg of MLCAPE develop along and south of the warm front with 40-50 kt of bulk shear. If storms develop, they'd likely be severe developing into discrete supercells initially, congealing into a east-west line with potential for large hail, damaging winds, a tornado or two, and flash flooding. Over western Nebraska an upper-level wave will kick off convection during the afternoon, developing into a few different segments of storm clusters that travel eastward across the state through the evening. These segments grow into bowing segments tracking eastward into our area by late evening with a damaging wind and hail threat persisting through around 3-5am as they move across our area.

Sunday's severe potential may at least initially be greatly impacted by any lingering showers, storms, and cloud cover from the early morning system. As H5 troughing deepens over the Intermountain West, we'll see a strong low-level jet set up, nosing into eastern Nebraska and western Iowa during the afternoon. This will help to bring in more low-level moisture. Surface winds could get fairly strong on Sunday, gusting 35 to 45 mph out of the south, enhancing low-level shear. Instability of 3000-4000 J/kg combined with 40-45 kt of bulk shear should support supercells as the cap erodes during the afternoon. With greater low-level moisture and shear, all modes of severe weather will be possible including large hail, damaging winds, flash flooding, and tornadoes.

Monday will have a similar set-up as the H5 longwave trough nudges eastward, closer to our area, with similar values of instability and perhaps even more shear expected to develop. The area of greatest threat on Monday will be a bit farther east than Sunday, more directly across eastern Nebraska and western Iowa.

The rest of the week next week looks quiet with cooler temperatures moving in on Tuesday and Wednesday (highs in the 60s). Temperatures trend back upward later in the week.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1226 PM CDT Fri May 15 2026

VFR conditions this afternoon with storms forecasted to develop around 00Z this evening just northwest of KOMA and KLNK. Expect storms to impact the terminals from around 01-03Z with potential for large hail and damaging winds. Cloud bases should be fairly high, around 6000-8000 ft with any storms. Once storms clear, winds will shift to the north or northeast, becoming more easterly toward daybreak on Saturday. We'll see winds increasing out of the east toward the end of the TAF period with additional strong to severe storms possible Saturday evening into the overnight hours.

OAX WATCHES/WARNINGS/ADVISORIES

NE...None. IA...None.