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223
FXUS63 KOAX 290443
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1143 PM CDT Sat Jun 28 2025

.KEY MESSAGES...

- A 30-40% chance of storms exists primarily over northeast
  Nebraska after 3 AM. Some storms may be strong to severe with
  damaging winds being the primary hazard through sunrise.

- Showers and storms linger Sunday morning, with redevelopment
  likely (50-70% chance) in the afternoon and evening hours.
  Once again, a few storms could be strong to severe, and heavy
  rainfall may also occur.

- Dry conditions expected for Monday. A 20-40% chance of rain
  returns late Tuesday into Wednesday and again Thursday into
  Friday. Temperatures cool slightly Monday before warming to
  the low to mid 90s by the end of the week.

&&

.DISCUSSION...
Issued at 354 PM CDT Sat Jun 28 2025

Today:

Water vapor imagery this afternoon depicts broad, quasi-zonal flow
across the CONUS only mainly interrupted by deepening across
northern Montana. A messy surface pattern continues to be in place,
with a local center of low pressure over south-central South Dakota
that connects to a deeper low over eastern Colorado by a surface
trough, with increasingly high dewpoints as you approach
central Iowa. Dewpoints in our neck of the woods continue to
hand in the upper 60s to low 70s, making temperatures in the
upper 80s to low 90s feel more like 95-100 degrees. We`ve still
got a few hours of good heating underneath mostly clear skies
to bump up those values a bit more, with heat indices
anticipated to top out at 100-105 degrees from 4-5 PM.

The main concern of the evening and overnight will be convection
that is expected to develop across north-central Nebraska and South
Dakota between 6-7 PM, bringing severe storm chances to the area. As
we begin to lose day time heating and start decoupling the boundary
layer, surface-based convection will lose favor as a bit of 700 mb
moisture takes over as the launching point of new storms. Though
they are expected to be elevated, we`ll possess a very dry
layer at 850 mb that balloons our DCAPE value to around 1600
J/kg at midnight. Joining with that strong wind potential, a few
of the recent CAM runs (especially with the HRRR) have depicted
a more resilient storm cluster to march across southern South
Dakota, inducing a meso-high that will travel with it. That
meso-high may work with the surface trough/lower highs along it
to produce a locally strong pressure gradient that could enhance
outflow from the MCS and bring gusty winds approaching 70 mph
to areas of far northeast Nebraska. This strong outflow may also
extend well south of the convection as well, with the main
variable as to how strong winds get being how close to the
northern portions of the forecast area will be to the MCS (and
as a result meso-high and its enhanced pressure gradient force).
As of now, our best chance for those winds is well into the
morning hours, at 5-7 AM. Most of the other convection is
expected to stay the north and west.

Sunday:

CAMs become increasingly split as to the state of the atmosphere
over eastern Nebraska and southwest Iowa tomorrow morning, which
will entirely be dependent on how far MCS from the central and
western portions of Nebraska/South Dakota can push eastward. A
second hot day is becoming increasingly uncertain, we deal with
convective debris for at least portions of the forecast area.
Regarding overall storm development and progression, a couple of
scenarios do seem apparent:

Scenario 1 favors a cluster of storms from central Nebraska to
be over the forecast area 6 AM tomorrow morning, bringing
moderate rain to portions of the forecast area centered along
the Platte River, lasting into the late morning. This would sap
our instability for the latter portion of the day, keeping
afternoon convection at bay to the south while our remaining
chances occur overnight along the nose of the low-level get.
This scenario would minimize the severe risk for the area,
though a storm or two could produce strong winds or a 1"
hailstone.

Scenario 2 would have a very limited area of convection across the
forecast area, favoring widespread storms to the north and a few pop-
up storms across southeast Nebraska through the morning. Limited
reductions to the instability would favor potential redevelopment of
storms during the late afternoon hours into the evening,
eventually taking supercellular storm structures upscale into
an MCS that would then progress along a theta-e axis that
extends southwards int Kansas and Missouri. This scenario seems
the more likely out of the two, and would pose the greatest
risk for severe weather and potentially heavy rain, with the
severe risk being from 6 PM to 2 AM while the heavy rain risk
would only be during the initial development phase from 5-9 PM
before it becomes progressive in its sweep southward.

Monday and Beyond:

After the overnight convection sweeps southward, Monday`s rain
chances will entirely rest on the southern edge of the deepening
shortwave that pivots through the area during the afternoon hours.
From there, we`ll enjoy a cooler Monday with a gradual heating trend
through the rest of the week as a stubborn cutoff low spins over the
California Coast and amplifies ridging to the east of it and into
the Central Plains. Rain and storm chances look rather murky but
certainly not out of the question as convergence of the High Plains
will serve as a jumping point for MCSs that could drift east and
affect the area in some way.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
-- Changed Discussion --
Issued at 1143 PM CDT Sat Jun 28 2025

A line of storms is approaching northeast Nebraska tonight,
likely to primarily track eastward. This will likely clip KOFK
around 09Z with a burst of wind on the leading edge, and causing
a wind shift to northwesterly. Latest guidance keeps storm
activity north of KOMA and KLNK through Sunday morning with the
outflow boundary gradually dropping south leading to a wind
shift to northerly Sunday afternoon. We`ll watch this boundary
as it sinks south this afternoon for potential storm
development, but right now confidence is only around 20% that
we`ll see storms Sunday afternoon and evening along this
boundary. If weather stays quiet as guidance suggests right now,
expect VFR conditions through the remainder of the TAF period.
-- End Changed Discussion --


&&

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

&&

$$

DISCUSSION...Petersen
AVIATION...McCoy