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000
FXUS63 KOAX 232336
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
636 PM CDT Tue Apr 23 2024

.KEY MESSAGES...

- Winds decreasing tonight with a couple hours of frost possible
  tomorrow morning for northeast Nebraska.

- Several rounds of showers and thunderstorms are expected
  Thursday through the weekend, potentially leading to localized
  flooding. Some severe weather is also possible with the
  greatest threat being Friday afternoon and evening.

&&

.DISCUSSION...
Issued at 250 PM CDT Tue Apr 23 2024

This afternoon - Tonight:

Skies have mostly cleared while some fair-weather cumulus has
developed across far northeastern Nebraska this afternoon. Winds
are fairly breezy out of the northwest gusting to 35 to 40 mph
with temperatures ranging from the mid 60s to low 70s across
eastern Nebraska and southwest Iowa. This evening winds are
going to drop off fairly dramatically after sunset, becoming
nearly calm by midnight with winds down to around 5 to 7 mph.
Clear skies will allow temperatures to fall down into the mid-
to-upper 30s in many locations by Wednesday morning which could
lead to a couple hours of frost across northeast Nebraska around
sunrise.


Wednesday:

Tomorrow we see the shift to southeasterly flow out ahead of the
developing surface low and approaching deep negatively-tilted
trough moving in from the four-corners region of the
southwestern CONUS. Skies should stay mostly clear during they
day as high pressure remains over the region, but we`ll see
increasing clouds during the evening hours as we start to see
moisture advect into the region with the advancement of the
low-level jet northward into eastern Nebraska and western Iowa.

Thursday - Friday:

This system has a very impressive, broad LLJ out ahead of the
upper-level wave which will bring a lot of moisture northward
out of the Gulf of Mexico northward into the Central Plains. We
won`t get enough moisture for precipitation until probably
Thursday morning, but once it starts, we`ll probably have
scattered showers Thursday morning becoming more numerous
Thursday afternoon. Thursday evening we`ll see air-mass
destabilization due to heat and moisture flux associated with
the diurnal increase in the LLJ. This will lead to widespread
thunderstorm development across the region with an increased
risk for localized flooding. While the greatest risk for severe
weather will likely remain to the southwest of our area,
Thursday night we could see stronger storms produce large hail
or damaging winds overnight.

Friday morning there is some uncertainty in when shower and
storm activity exits our area, with more of our models
indicating heavier shower and storm activity ending by Friday
morning with only a few lingering showers possible. What will
likely happen is we see a dry line move through pushing more of
the heavier rainfall off to the east as the surface low moves
over eastern Nebraska. We will likely see storms re-develop
along that dry line during the afternoon around the Missouri
River which will likely be our best chance for severe weather. A
combination of low CAPE but high shear in this region could
generate a few low-topped supercells as they move into western
Iowa which could produce large hail, damaging winds, and
tornadoes Friday afternoon. Storms should be largely out of our
area by Friday evening.

Saturday - Sunday:

Saturday during the day we get a bit of a break between systems
as another upper-level trough digs down into the Four-Corners
region and we end up under the shortwave ridge between the two
troughs. Precip chances start to increase again Saturday
afternoon as we see another LLJ push back into the region
associated with the second wave, bringing moisture back to the
region. We`ll again see thunderstorms become more widespread
after sunset Saturday evening as we see air mass destabilization
from heat and moisture flux associated with the diurnal
increase in the LLJ. These storms could produce isolated reports
of large hail or damaging winds overnight Saturday night into
early Sunday.

This second wave appears to be taking a more easterly track than
the first, which would track the surface low more into Iowa with
the severe weather threat for Sunday. Still, I would monitor our
area for potential squirrelly low-topped supercells on Sunday
afternoon under the surface low which means we can`t completely
rule out severe weather for our area through Sunday afternoon.
Storms should completely exit the region by Monday morning.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 630 PM CDT Tue Apr 23 2024

Winds are on the decrease across all three sites out of the
northwest, with wind gusts expected to drop off by 01z. From
there, expect winds to very slowly begin shifting northerly,
then northeasterly by 12z. By late tomorrow morning, winds will
be out of the southeast and winds will remain light, and
generally less than 10 kts through the end of the period closing
out an all-VFR forecast.

&&

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

&&

$$

DISCUSSION...McCoy
AVIATION...Petersen