546
FXUS63 KOAX 161011
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
511 AM CDT Sat Aug 16 2025

.KEY MESSAGES...

- Scattered showers and storms (15-20% chance) are possible
  across extreme northeast NE this morning.

- Dangerous heat continues today with heat indices peaking
  between 104 and 109 degrees this afternoon. A Heat Advisory
  remains in place from 11 AM to 8 PM.

- Storm chances (15-20%) return to northeast Nebraska tonight
  and Sunday night. From then through Wednesday, periodic
  chances of storms are expected to continue with pockets of
  severe storms possible.

&&

.DISCUSSION...
Issued at 233 AM CDT Sat Aug 16 2025

Today and Tonight...

The synoptic pattern this morning features a mid- to upper-level
ridge centered over the southern Plains and lower Mississippi
Valley, flanked by weak troughing to the west and east. Surface
analysis depicts a low over south-central SD with an associated
surface front extending into eastern SD/southern MN. A
shortwave disturbance moving into the northern Plains has aided
in the initiation of an MCS over western NE/SD, which is
expected to evolve into a bowing segment and progress eastward
through the overnight period as a nocturnal LLJ helps to sustain
the system. The key question is whether the complex remains far
enough north the keep the CWA dry, or if its southern flank
clips northeast NE, bringing a threat for strong to severe
storms.

Strong instability is in place across northeast NE, with 2500-3000+
J/kg of MLCAPE. However, the 00Z KOAX sounding and subsequent model
soundings indicate a stout cap in place south of the NE-SD border.
The MCS will likely track along the surface front within a
less- capped environment, keeping most activity north of the
state line. Still, the southern end could brush extreme
northeast NE early this morning, bringing the potential for
damaging wind gusts (60-70 mph) and locally heavy rainfall. CAM
guidance remains consistent in keeping the bulk of the system
north of the CWA, so PoPs currently peak at 15-20% for northeast
NE.

Any lingering morning clouds or showers should clear by midday,
allowing for strong diurnal heating. Gusty southerly flow and warm
air advection will push highs into the 94-99 degree range, with
dewpoints in the low 70s driving heat indices to 104-109. The
highest values will occur near the Missouri River valley, where
there is the potential for a few counties to be upgraded to an
Extreme Heat Warning. For now, a Heat Advisory remains in effect
from 11 AM to 8 PM. Make sure to stay hydrated and take multiple
breaks in the shade or air conditioning if you are spending time
outdoors this weekend.

Another round of storms is possible this evening into the overnight
period as the surface front sags south, likely aligning east-west
near or just north of the NE-SD border. A weak shortwave
disturbance crossing the Dakotas may initiate isolated to
scattered convection along the boundary. Strong instability
(2500+ J/kg of MLCAPE) will be present, but limited large-scale
forcing for ascent and modest shear may hinder any widespread
severe activity. The exact placement of these storms will
depend on how this morning`s convection evolves and where the
front ultimately stalls. Guidance has trended towards bringing
this convection mainly north of the NE-SD border, with SPC
following and trimming the Marginal Risk out of northeast NE.
Current PoPs peak at 15-20% for northeast NE and western IA.

Sunday...

The aforementioned shortwave disturbance sliding across the Dakotas
Saturday evening will help to dampen the ridge, bringing subtle
height falls and providing minor improvement to the heat on Sunday.
Even so, persistent southerly flow will continue low-level warm air
advection, keeping highs in the upper 80s to low 90s. Afternoon heat
indices are expected to peak in the 98-104 degree range. Another
Heat Advisory may be warranted for parts of the area.

Another round of afternoon and evening storms is possible Sunday
near the surface front as another weak shortwave disturbance moves
through the Dakotas. The front is expected to linger near
northeast NE, though it may shift slightly north or south
depending on prior convection. This setup mirrors the previous
day, with strong instability developing above a gradually
eroding cap with weak large-scale forcing for ascent. A few
strong to severe storms are possible, with damaging wind gusts
and hail the primary hazards. SPC maintains a Marginal Risk
(Level 1 of 5) for severe weather across northeast NE and
western IA, and PoPs currently peak at 25- 35%.

Monday and Beyond...

Through the first half of the work week, the mid- to upper-level
ridge over the south-central CONUS will begin to retrograde toward
the Four Corners region. This shift will bring predominantly
northwesterly flow aloft and allow temperatures to gradually return
toward seasonal normals. Highs may still reach the low 90s on Monday
before easing into the low to mid 80s by mid-week.

Afternoon and evening storms will be possible Monday as a weak
shortwave disturbance pushes near the surface front, again likely
draped across eastern NE into western IA. SPC does place this area
in a Marginal Risk (Level 1 of 5) for severe weather, as instability
is ample enough for a few strong to severe storms. Near daily storm
chances will continue through at least Wednesday as this pattern
favors a series of shortwave disturbances cresting the ridge and
moving into the area. Periodic strong to severe storms will be
possible when favorable shear and instability overlap, a signal
supported by GEFS and ECMWF ensemble-based machine learning
guidance, which highlights a 5-15% probability for severe weather at
times through the week. Forecast confidence in the timing and
location of any specific hazards remains low at this time range
and will largely depend on how prior rounds of convection
evolve. We will also have to monitor hydrologic concerns for any
areas that receive multiple rounds of rainfall.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 507 AM CDT Sat Aug 16 2025

VFR conditions are expected to prevail throughout the forecast
period. LLWS will continue across all three terminals as a 45
kt southwesterly low-level jet persists at FL015-020. LLWS is
expected to diminish by 15-16Z. Southerly winds will increase in
speed this morning and afternoon, with sustained speeds of
12-15 kts and gusts up to 25 kts. Winds will gradually calm
under 12 kts after 00Z. Scattered mid-level and high clouds will
overspread the area through much of the forecast period.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory from 11 AM this morning to 8 PM CDT this evening
     for NEZ011-012-015>018-030>034-042>045-050>053-065>068-
     078-088>093.
IA...Heat Advisory from 11 AM this morning to 8 PM CDT this evening
     for IAZ043-055-056-069-079-080-090-091.

&&

$$

DISCUSSION...Wood
AVIATION...Wood