645
FXUS63 KOAX 180137
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
837 PM CDT Mon Aug 17 2026

.KEY MESSAGES...

- Strong to severe thunderstorms are expected tonight into the
  overnight hours with hail, damaging winds, heavy rain, and an
  isolated tornado possible.

- Overnight storm activity will linger through much of Tuesday
  morning, bringing chances for a few strong to severe gusts,
  small hail, and additional rainfall.

- Cooler temperatures return to the forecast Wednesday, with a
  gradual warming trend expected heading into the weekend. Periodic
  chances for showers/storms are expected Wednesday through
  Friday.

&&

.UPDATE...
Issued at 837 PM CDT Mon Aug 17 2026

A severe thunderstorm watch has been issued for portions of
northeast Nebraska. A few severe thunderstorms have developed in
a weak area of convergence between O`Neal and Ord. In the
short-term, these thunderstorms may spread east with a large
hail, damaging wind, and isolated tornado threat. These
thunderstorms may struggle to persist as the environment becomes
less favorable across our area. A separate severe weather hazard
is anticiapted later tonight with additional thunderstorms from
farther west.

&&

.DISCUSSION...
Issued at 155 PM CDT Mon Aug 17 2026

Today Through Tomorrow:

Water vapor imagery this afternoon shows a belt of ascent
overspreading the northern High Plains as a shortwave moves into the
region while quasi-zonal flow mid/upper flow remains laid over the
eastern half eastern half of the CONUS. We`ve trended warmer and
drier than the initial guess from the NBM this afternoon, which
likely has some bias correction from our recent rainy and humid
pattern.

Warm conditions and modest moisture pooling have developed across
north-central Nebraska into South Dakota ahead of a surface trough
laid from northwest Nebraska into eastern North Dakota where it
meets the main cold front. Further destabilization is expected
to occur over the course of the afternoon and early evening
hours, with isolated storm development possible along it shortly
after 5 PM before shifting into northeast Nebraska closer to
midnight. As it approaches the area, it will grow into an MCS
that forecast soundings indicate will be cold pool-driven and
gusty, with a few hailstones possible as well. Speeds of 60-70
mph seem plausible as it moves through, with additional activity
building behind it off of the nose of the LLJ. As the
convection trains over the same areas, flooding will become an
increasing threat. PWAT values aren`t overly impressive at 1.7",
but much of that area has already seen 4" or more in the last
4-5 days. After the initial MCS, that training convection will
be capable of marginally severe wind and hail through the
overnight hours as it shifts slowly southward. By sunrise
tomorrow morning, that shower and storm activity will continue
to carry marginal severe potential (owing mostly to the better
shear we`ve seen over the past couple of months). The evolution
from 6 AM onward is still a bit murky, where the longevity of
the activity will limit afternoon potential. Ambient shear
values and instability will be sufficient for supercellular
structures, while boundary-parallel shear values will promote
upscale growth. Southeast Nebraska has a narrow shot at seeing
the initial development of the evening storms that could carry
some large hailstones, damaging winds, and an isolated tornado.
It is more likely that the main boundary will have pushed south
and they miss out on those chances. Lingering light rain showers
in the belt of ascent will linger into the overnight hours, as
we dip into the low- to-mid 60s.

Wednesday and Beyond:

With the passage of the early week action, things will start
quieting down heading towards the weekend. Mid/upper ridging will
take further hold over the western CONUS, with the area being on the
eastern fringe of it, dodging the warm temperatures. A few
shortwaves will also round the top of the ridge and move through the
area, with the most likely one occurring Wednesday afternoon
into the evening hours where storms (some severe possible)
develop to the west and waft into eastern Nebraska. Thursday
onward sees precipitation chances decrease, with temperatures
that peak Friday in the mid-to-upper 80s before settling back
down in the low 80s for the remainder of the weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 550 PM CDT Mon Aug 17 2026

VFR condition and light south winds start the period. Multiple
clusters of thunderstorms have developed over central and
western Nebraska into South Dakota. These thunderstorm clusters
are forecast to continue to move southeast. These thunderstorms
will move northwest to southeast through the region overnight.
Latest forecast guidance has a round of thunderstorms moving
into OFK vicinity between 05-07Z. These thunderstorms may
continue southeast to OMA, but confidence remains low on this
scenario. A second round of thunderstorms arrives at OFK between
10-12Z and LNK/OMA around 12-14Z. Additional thunderstorms are
possible between thunderstorm clusters, but forecast confidence
on thunderstorm coverage and location is low. With any
thunderstorms, northwesterly wind gusts are anticipated. These
wind gusts may exceed 40-50 kts with any severe thunderstorms.
Visibility reductions to MVFR are likely due to rainfall with
further reductions to IFR possible in the heaviest rainfall.
Thunderstorms move out of the region Tuesday morning with winds
returning to the south. A front will gradually move through the
area, shifting winds to the northwest, but the timing of this
and any additional thunderstorm development remains uncertain
and will depend on tonight`s thunderstorms.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.

&&

$$

UPDATE...Chehak
DISCUSSION...Petersen
AVIATION...Chehak