textproduct: Omaha/Valley

KEY MESSAGES

- Scattered showers and thunderstorms are expected mainly Sunday afternoon and evening. A few storms may become strong to severe, with isolated strong winds, hail and heavy rainfall the main hazards.

- Above-average temperatures continue through Tuesday, with highs generally in the low to mid 90s.

- A cold front will move through Tuesday into Wednesday, bringing high temperatures in the 80s along with periodic chances for showers and thunderstorms.

DISCUSSION

Issued at 1027 PM CDT Sat Sep 5 2026

Tonight and Sunday...

Water vapor imagery and objective analysis late this evening depicts a high amplitude mid-level ridge over the central CONUS, with a cutoff low moving onshore over the Pacific Northwest. At the surface, high temperature peaked in the low to mid 90s under the persistent ridge, approximately 10 degrees above average for early September. Dewpoints soared into the low 70s, pushing heat index values into the 102-107 degree range. As temperatures cooled through the evening, the Heat Advisory was allowed to expire.

Overnight, convection is expected to develop along a lee trough over western Nebraska before gradually progressing eastward along the LLJ into the mid to late morning hours. Some questions remains regarding storm coverage and intensity as they progress towards the area, given the rather unimpressive bulk shear (20 kts). Intermittent CAM guidance also sparks more isolated storm development in northeast NE/southeast SD overnight along the LLJ nose, though confidence in this scenario remains a bit lower given the subtle forcing. However, storm coverage is expected to become more widespread through the late morning and early afternoon as increasing low-level warm air advection noses into a surface front draped near the mid-MO Valley as mid-level disturbance pivots over the area. A corridor of modestly improved bulk shear around 25 kts will overlap steepening lapse rates and modest instability across far eastern Nebraska and western Iowa, supporting some potential for strong to severe storms.

The primary hazards will be pockets of hail and damaging wind gusts as individual cores quickly pulse within a broader, more upscale cluster. Potential also exists for pockets of heavy rainfall given that storms may train over the same for an extended period of time. Efficient rainfall processes will be in place with PWAT values of 1.75-2.00" (above the 90th percentile of sounding climatology for early September) and warm cloud depths of 4-4.5 km. CAM guidance hints of pockets of 2-4" rainfall totals, particularly over northeast Nebraska into western Iowa where convection is more persistent.

Although cloud cover and precipitation chances will increase through the day, high temperatures will still make a run at hitting the upper 80s and low 90s prior to convection becoming more widespread, bringing yet another above-average early September day. Heat index values are expected to peak in the 95-100 degree range, just shy of Heat Advisory criteria. Precipitation chances will taper off through the overnight period into Monday morning.

Monday and Tuesday...

Into the work week, the aforementioned mid-level low positioned over the Pacific Northwest will gradually deepen and pull east along the US/Canada border, helping to flatten the ridge in place and push a cold front through the area. Long range guidance varies on the exact timing of the frontal passage, though it looks to sweep southward across the area through the day Tuesday and into early Wednesday. Ahead of its arrival, Monday will be yet another day of widespread highs in the upper 80s to mid 90s, with heat index values around 100. A tightening surface pressure gradient ahead of the approaching system and mixing into stronger winds aloft will bring southerly wind gusts of 25-35+ mph on Monday.

High temperatures on Tuesday will depend on how quick the northeast- to-southwest oriented cold front pushes southward across the area. Highs are expected to reach the mid to upper 90s, with heat index values around 105, across southeast NE and southwest IA, with values peaking in the upper 80s further north where the front passes through before peak daytime heating. Chances for showers and storms exist along the front, with machine learning guidance placing a 5- 15% probability of severe weather. With the better large-scale forcing for ascent displaced to the northeast, details will likely hinge on mesoscale features that come into focus with time, though sufficient instability and improved bulk shear will be in place for a few stronger storms. For now, PoPs of 60-80% exist through Tuesday and early Wednesday as the front pushes through.

Wednesday and Beyond...

Zonal flow aloft will return by mid-week, pushing high temperatures back into the 80s. Periodic PoPs of 15-30% remain in place through the remainder of the week as shortwave disturbance traverse the area. Good news for the fall-lovers, looking further ahead, most GEFS and EPS-AIFS members bring a potent trough across the northern Plains next weekend. This system will bring a push of cooler air into the region and could knock highs in the 70s by the end of next weekend, though details on timing and extent will still need to be ironed out.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 546 PM CDT Sat Sep 5 2026

VFR conditions are favored through the forecast period. South- southeasterly winds at 8-12 kts, with a few gust up to 20 kts, will gradually calm under 12 kts this evening. Winds will become more easterly through the morning hours. Scattered showers and thunderstorms will push in from west to east after 06/18Z. This chances has been left out of the current forecast package due to the low confidence in timing and coverage. The highest probability of impacts (30-40%) is at KOFK and KOMA during the final few hours and just past the end of the forecast period. Patchy MVFR conditions, brief gusty winds, and small hail will be possible under any stronger storms.

OAX WATCHES/WARNINGS/ADVISORIES

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