978
FXUS63 KOAX 271623
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1123 AM CDT Fri Jun 27 2025

.KEY MESSAGES...

- Early morning fog will dissipate after sunrise today.
  Otherwise, will see sunny skies for most of the day with highs
  in the mid 80s to low 90s. Storms may develop this evening
  across northeast Nebraska (15-30% PoPs), and some could be
  strong to severe.

- Another round of showers and storms returns Saturday afternoon
  and evening and again for Sunday. Some storms may be strong to
  severe and produce heavy rainfall.

- Dry conditions expected for Monday with off and on shower and
  storm chances beyond Tuesday.

&&

.DISCUSSION...
Issued at 435 AM CDT Fri Jun 27 2025

.SHORT TERM/Today through Saturday Night/

Mostly clear skies are observed across the OAX forecast area
early this morning as convection from yesterday evening has now
congealed into an MCS pushing southeastward across the EAX/LSX
forecast area. 08Z RAP sfc objective analysis shows a 1007 mb
sfc low currently centered over northwestern Wisconsin, with the
cold front draped along a line from near La Crosse, Wisconsin
southwestward to Des Moines, Iowa to near Falls City, Nebraska.
Aloft at H5, a shortwave trof is currently centered over north
central Minnesota, with a ribbon of vorticity extending down
south along the main shortwave axis toward central Iowa into
southeast Nebraska. Given the large amounts of rainfall/moisture
we have received over the last few days coupled with the clear
skies leading to effective radiational cooling, areas of patchy
fog will remain possible early this morning. The fog should burn
off after sunrise.

The wave and associated sfc low will track to the east toward
the Great Lakes area today while a weak sfc high moves over
eastern Nebraska and western Iowa. This will result in mostly
sunny skies with afternoon highs reaching the mid 80s to low
90s. Breezy southwesterly winds will also be observed,
primarily over northeast Nebraska.

A weak H5 wave will develop across the western Dakotas/Nebraska
Panhandle region this afternoon and traverse the South
Dakota/Nebraska border. Ahead of the wave, a plume of 1000-850
mb moisture from the Gulf will advect into the Central Plains.
This moisture coupled with 2,500 to 3,500 J/kg of SBCAPE seen
from BUFKIT soundings will result in an unstable air mass,
although bulk shear will remain modest at 25 to 30kts. Although
forcing looks rather weak with this wave, CAMs do generate an
MCS looking feature in the late afternoon across north central
Nebraska into south central South Dakota, eventually tracking
east into northeast Nebraska after 00z. By this point, expect
any convection across northeast Nebraska to become elevated as a
rather deep EML overspreads the region. Shear tends to become
weaker too by this timeframe. CAMs seem to give a wide range of
solutions regarding the MCS feature, most likely due to the
capping in place and also the lack of forcing observed from the
wave. The 00z run of the HRRR and HiRes FV3 dissipate the
feature as it enters northeast Nebraska, while the NAM 4km Nest,
NSSL WRF, and HIRes ARW sustain the MCS a little longer before
dissipating as it enters western Iowa. Given the wide range of
solutions, have opted to only have PoPs at 15 to 30% across
northeast Nebraska from 00z to 06z, then gradually tapering off
overnight across west central Iowa. Given the abundant
instability available, storms may become strong to severe, with
damaging wind the primary threat with the MCS although some
small hail is also possible. This has resulted in the SPC
highlighting far northwest portions of the forecast area in a
slight risk of severe weather, with a marginal risk encompassing
the rest of northeast Nebraska.

Saturday will see yet another shortwave disturbance approach
from the west inducing a sfc low across central South Dakota,
leaving OAX within the warm sector of the sfc low. With
southwesterly flow at H8 resulting in increasing warm air
advection, highs will reach the low to mid 90s areawide. Heat
indices may reach the mid 90s to near 100F briefly in the
afternoon, making for a rather uncomfortable airmass. In
addition, will see instability creep back up to around 2,000 to
3,000 J/kg of SBCAPE. Shear once again is weak at 20 to 25 kts,
but if low to mid level forcing from the wave is observed, then
could again see some severe weather with this activity as noted
by the SPC Day 2 outlook. At this point, CAM guidance is rather
limited, but for what its worth, the NAM 4km tries to spawn
another MCS feature Sunday evening across a good chunk of the
forecast area. PoPs for late Saturday afternoon into the
overnight hours currently peak at around 40%, but expect to see
further refinements to this forecast once we get more CAM
guidance.

.LONG TERM/Sunday through Thursday/

Sunday will see the sfc low track northeast across the Northern
Plains, dragging along the sfc cold front across the forecast
area during the day. The front will trigger scattered showers
and thunderstorms, with NBM extended PoPs indicating a 50 to 70%
chances mainly along and south of Interstate 80 Sunday evening.
Modest shear and instability will be available, so a few strong
to severe storms cant be ruled out. This has resulted in yet
another marginal risk of severe weather for a large chunk of the
forecast area.

Heavy rain may once again be of concern, as LREF output shows a
normal PWAT distribution peaking around 1.6 to 1.8 inches for
Sunday. Warm cloud depths will also remain > 3,500 meters,
indicating efficient rainfall processes. Thus, the WPC has
issued a marginal risk of excessive rainfall for Sunday. Highs
Sunday will be in the upper 80s across northeast Nebraska and
the low to mid 90s south of Interstate 80. Some areas south of
Interstate 80 could see heat indices once again reaching the mid
90s to near 100F in the afternoon hours.

An H5 shortwave and vort max will eject from the Manitoba region
early  Monday morning toward the Northern Plains, but current
thinking is that we will remain dry with the bulk of the forcing
over Minnesota and Wisconsin where a sfc low is generated. Our
next low en PoP chances return late Tuesday through Thursday as
several weak waves move across the area. NBM PoPs during this
period range from 15 to 30%. Highs Monday through Thursday will
be in the mid 80s to near 90F.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1118 AM CDT Fri Jun 27 2025

VFR conditions are expected to prevail throughout the forecast
period. South-southeasterly winds will continue with a few
gusts up to 16 kts possible at KOFK this afternoon. Skies will
remain mostly clear with a few high clouds passing by. A
thunderstorm complex is expected to track across northern
Nebraska this afternoon and evening, but confidence is too low
in the system holding together by the time it reaches KOFK (20%
chance). If the system does hold together, gusty winds and
thundershowers will be possible from 01-05Z.

&&

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

&&

$$

DISCUSSION...Castillo
AVIATION...Wood