textproduct: Omaha/Valley

KEY MESSAGES

- Sunday and Monday will be days to watch very closely if you live within the Omaha area of forecast responsibility. Multiple rounds of severe thunderstorms are expected bringing the potential for large hail, damaging winds, tornadoes and flash flooding.

DISCUSSION

Issued at 142 PM CDT Sun May 17 2026

This afternoon, an elongated sfc low will be in place from SE Colorado/SW Kansas up into the Dakotas. A dryline is set up toward the KS/CO border and a warm front is located across central Nebraska. Temps are currently in the 80s in the warm sector with dewpoints in the mid-60s. SBCAPE values of 3500+ J/kg, MLCAPE values of 3000+ J/kg and DCAPE values of 1200+ J/kg are expected. Expect good instability through the afternoon/evening and fairly steep lapse rates, particularly down into central and eastern Nebraska.

Portions of northeastern Nebraska in particular are showing potential for an environment favorable for strong updrafts and potentially some longer lived supercells. Any storms that are able to get going and become sustained in that favorable environment would have the best chance of developing a tornado, with some potential to be strong. Storms are expected to develop into a line, posing a damaging wind threat along with hail and tornadoes possible.

Heading into Monday, a broad trough extends from the PACNW up into eastern Nebraska/western Iowa. Another system moves in through the day, bringing additional chances for strong to severe storms, particularly for areas along and south of Interstate 80. There still remain some questions as to how far north the warm front and system get. The environment is expected to be primed with strong instability and deep layer shear conducive for supercell development and maintenance. With this type of set up, large hail and damaging winds are to be expected in addition to the possibility for a few strong and potentially long-lived tornadoes. Flash flooding will be possible, particularly in areas that have also received a few inches of rain over the last 48 hours.

Expect cooler temperatures for much of the week as a cold front pushes into the region Monday. Tuesday and Wednesday bring relief from the recent storms.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 637 PM CDT Sun May 17 2026

A line of severe thunderstorms is observed at this hour from near KOFK to KJYR to KHJH. These storms have a history of producing large hail, damaging winds, and tornadoes. The line will continue progressing eastward this evening, eventually turning into more of a damaging wind threat as it approaches KOMA and KLNK. Have continued mentions of -TSRA at terminals this evening, refining timing at KOMA with the line expected to arrive by 01z per latest model guidance. Expect frequent updates and amendments. Background winds will switch to the west northwest once the line moves through, and remaining at 12 kts or less after 06z. Ceilings will deteriorate to MVFR and IFR at terminals tonight behind the line of storms and persist through much of the TAF cycle. After 20z, will see more redevelopment of showers and thunderstorms, with chances over 50% late in the TAF period. These storms will once again become strong to severe with all hazards possible.

OAX WATCHES/WARNINGS/ADVISORIES

NE...Flood Watch through Tuesday morning for NEZ065-066-068-078- 088>093. IA...None.