Flash Flood and Hail in Nebraska, April 24, 2025

Area Forecast Discussion
National Weather Service Omaha/Valley NE
255 PM CDT Thu Apr 24 2025

.KEY MESSAGES...

- Scattered to numerous showers and storms will move through the
  area this afternoon and evening. Isolated severe weather and
  locally heavy rainfall are possible.

- Friday afternoon through Saturday morning looks dry.

- Thunderstorm chances return Sunday into Monday, with some
  severe weather threat, especially on Monday.

&&

.DISCUSSION...
Issued at 255 PM CDT Thu Apr 24 2025

...Remainder of this afternoon through tonight...

Synthesis of radar and satellite imagery as of 230 PM indicates
a vorticity maximum over central NE, which is supporting a
loosely organized shield of showers and thunderstorms across
portions of eastern NE. More vigorous convection has recently
developed just north of Hebron along an apparent surface
boundary that extends east-northeast through portions of
southeast NE and southwest IA. While considerable cloud debris
and marginal boundary-layer moisture content have limited air
mass destabilization so far today, filtered sunshine should
allow for further destabilization this afternoon along and south
of the surface boundary. That notion is consistent with latest
CAM guidance, which indicates a gradual uptick in thunderstorm
intensity later this afternoon into evening along or just south
of the I-80 corridor.

Locally backed surface winds along and just north of the surface
boundary are resulting in enhanced low-level hodograph curvature
with the current KOAX VWP indicating 0-1-km SRH of 200-250
m2/s2. A number of the CAM solutions indicate updraft helicity
swaths with the simulated storms, which is consistent with the
currently observed wind profile. So, despite the marginal
instability, the potential exists for embedded supercell
structures capable of hail up to quarter size, locally strong
wind gusts, and perhaps a brief tornado or two through 7 or 8
PM. Locally heavy rainfall is also possible.

Another round of showers and a few thunderstorms could move
through the area late tonight; though no severe weather is
expected with that activity.

...Friday and Saturday...

Mid-level ridging will build over the central U.S. while a
surface high progresses from the northern Plains into Great
Lakes region. That pattern evolution will allow a drier low-
level air mass to filter into the region Friday and Friday night
with no precipitation expected during that timeframe. By
Saturday, low-level moisture will begin to increase on the
backside of the surface high, with the forecast indicating 15-20%
PoPs across our western counties. High temperatures are expected
to be mainly in the 60s both days.

...Saturday night through Sunday night...

A prominent mid-level trough will progress through the Interior
West, encouraging the development of a surface low over the
northern or central High Plains on Sunday. As mentioned above,
low-level moisture will begin to increase by Saturday, with
that process being hastened by the development of a low-level
jet (LLJ) during this timeframe. The 12z global models suggest
that moisture increase coupled with steepening mid-level lapse
rates will promote air mass destabilization, with the potential
for periodic thunderstorm chances (peak PoPs of 40-60%) during
this time period. While specific details remain uncertain, a few
strong to severe storms appear possible.

Gusty south winds on Sunday will draw a warmer air mass into the
region with forecast highs in the 70s.

...Monday and Monday night...

The 12z models indicate a complex upper-air pattern evolution,
with an apparent lead shortwave trough progressing through the
northern Plains into upper MS Valley early in the day Monday.
That lead disturbance will then precede a neutral to positively
tilted trough, which will overspread the northern and central
Plains later Monday into Monday night. In response to those
upper-air developments, the primary surface low is expected to
develop from the northern Plains into upper Great Lakes on
Monday with a trailing cold front progressing through the mid MO
Valley. The cold front will serve as the focus for thunderstorm
development Monday afternoon and evening.

The early-day passage of the lead shortwave trough to our north
may result in the veering of low-level winds within the pre-
frontal warm sector, potentially reducing low-level hodograph
curvature and resultant SRH. Nonetheless, ample deep-layer
shear will combine with a moderately unstable air mass to
create a favorable environment for supercells capable of all
hazards. That notion is supported by various machine-learning
systems, which highlight far eastern NE and IA with some of the
highest severe-weather probabilities.

...Tuesday and Wednesday...

Surface high pressure is forecast to build through the region
Tuesday and Tuesday night, ahead of another frontal system,
which is expected to move into the area Wednesday night. As
such, the forecast will indicate a dry forecast Tuesday and
Tuesday night with increasing PoPs Wednesday afternoon into
Wednesday night.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1200 PM CDT Thu Apr 24 2025

A cluster of showers and thunderstorms has entered the region,
and is expected to slowly drift east-northeastward through this
afternoon and evening. The greater chance for thunderstorms this
afternoon is at KOMA and KLNK, though a brief thunderstorm
can't be ruled out at KOFK. This convection will reduce
visibilities at times, and as the rain moves further into the
region, ceilings will decrease to MVFR then VFR later this
evening. Ceilings are currently expected to improve around the
end of the current TAF period, though confidence on when exactly
is low and has been left of the TAFs for now.

&&

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

&&

DISCUSSION...DeWald/Mead
AVIATION...DeWald

Hazardous Weather Outlook
National Weather Service Omaha/Valley NE
425 AM CDT Thu Apr 24 2025

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-242330-
Monona-Harrison-Shelby-Pottawattamie-Mills-Montgomery-Fremont-
Page-Knox-Cedar-Thurston-Antelope-Pierce-Wayne-Boone-Madison-
Stanton-Cuming-Burt-Platte-Colfax-Dodge-Washington-Butler-
Saunders-Douglas-Sarpy-Seward-Lancaster-Cass-Otoe-Saline-
Jefferson-Gage-Johnson-Nemaha-Pawnee-Richardson-
425 AM CDT Thu Apr 24 2025

This Hazardous Weather Outlook is for portions of southwest
Iowa...west central Iowa...east central Nebraska...northeast
Nebraska and southeast Nebraska.

.DAY ONE...Today and Tonight

Scattered to numerous thunderstorms are possible today and
tonight. Overall, the severe weather threat is low, but a few
storms could still produce small hail this afternoon and evening,
gusty winds, and locally heavy rainfall. Due to multiple rounds of
storms, there is a small risk of localized flooding in southeast
Nebraska.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Thunderstorm chances return Sunday into Monday. There appears to
be increasing chances for severe weather Monday afternoon and
evening across southwest Iowa and southeast Nebraska.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected today or tonight.