137
FXUS63 KOAX 040426
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1126 PM CDT Mon Jun 3 2024

.KEY MESSAGES...

- A few spotty thunderstorms possible (10-15% chance)
  this afternoon in far southeast Nebraska and far southwest
  Iowa.

- Higher storm chances Tuesday afternoon (60-90%) with a
  15-20% chance of severe storms, mainly in southeast Nebraska
  and southwest Iowa. Large hail and damaging winds are the
  primary threats.

- Saturated soils continue to keep flooding a concern as showers
  and storms move through northeast Nebraska tomorrow afternoon.

- Mostly dry Wednesday into the weekend with highs in the mid
  70s to mid 80s.

&&

.DISCUSSION...
Issued at 316 PM CDT Mon Jun 3 2024

Today and Tomorrow:

Water vapor imagery this afternoon features a vigorous shortwave
trough entering the Pacific Northwest, with a broad band of ascent
stretching ahead of it from CA to WY/MT. To the east, an MCV
over Kansas continues to power an MCS traveling the ArkLaTex
region while additional shortwaves continue to waft to the north
and east. Drilling down to the surface, a local surface low was
analyzed over far northwest Kansas with a surface
trough/convergent boundary stretching north/northwest into
eastern Montana. To the direct south of the forecast area, the
aforementioned MCS has turned over much of eastern Kansas, but
has left southeast Nebraska into southwest Iowa with leftover
instability on the order of 1500-2000 J/kg. A combination of
convergence in those areas and some northward component of the
advection of the MCV to the south will help create a few pop up
showers and storms in extreme southeastern Nebraska and
possible into southwest Iowa. While there is some decent
instability, shear will be on the low end with HRRR forecast
soundings depicting around 3 kts of shear, giving storms little
to work with and maintain healthy updrafts for any meaningful
amount of time (with any chances diminishing by 7 PM). Highs
will continue to peak in the mid-to-upper 80s with light winds
and provide a splendid evening for those getting off work.

The main concern of the forecast period comes into focus tomorrow,
as the aforementioned trough moves east towards the area
dragging a cold front. Increasing warm air advection will being
to develop after 7 AM, and could help spark a few morning storms
in eastern Nebraska ahead of the incoming front, where dry low
levels could result in a stray strong gust or two due to
evaporative cooling. During the afternoon, sufficient
instability is expected to develop and strong convergence along
the front is expected to result in an increasing-in-coverage
line of showers and storms. Timing of any showers and storms
continues to lean towards an initiation time of 3 or 4 PM to the
northwest of the Omaha and Lincoln Metros, with those storms
exiting to the east by 9 PM. Weak shear of less than 20 kts will
lower the ceiling of any severe threat with storms tomorrow
afternoon. The highest potential for severe storms is expected
to occur at peak heating and shortly after when instability is
maximized, with largely straight line hodographs pushing the
main hazard towards damaging hail and wind (though a tornado
can`t be ruled out in far southeast Nebraska and southwest
Iowa). One wildcard to watch would be a slow progression of the
MCV to the south, which could increase cloud cover and limit
instability if it moves east slower than models anticipate ahead
of the front. Additionally, it won`t take much rainfall to
create flooding issues for already saturated soils and
watersheds.

Wednesday and Beyond:

With the front moving off to the east for Wednesday, we`ll find
ourselves in a northwesterly mid/upper flow pattern with the main
jet streak settled nearly overhead to just north of the area. Rain
chances for the remainder of the work week remain low, but there
could be a pop up storm or two that develops as a shortwave
moves through the flow Wednesday or Friday evening. Highs during
this time will remain nice in the upper 70s to 80s with typical
afternoon winds of 20 to 25 mph keeping things from feeling
stagnant outside. Beyond the forecast period, our next best
chance for widespread showers and storms return Monday as a more
dynamic system swings south and across the area.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1118 PM CDT Mon Jun 3 2024

Southerly winds ranging from 5 to 15 knots will prevail at all
TAF sites until the passage of a cold front tomorrow afternoon.
The front will likely move through the area sometime between 17Z
and 22Z. After 18Z, scattered thunderstorms are expected to
develop along and ahead of the front across portions of
southwest Iowa and southeast Nebraska (KLNK and KOMA). These
storms may be strong to severe, with wind gusts up to 50 knots
and hail up to quarter size. Storms should be south and east of
all TAF sites by 00Z. Winds post-front will prevail
northwesterly at 10 to 20 knots.

&&

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

&&

$$

DISCUSSION...Petersen
AVIATION...Darrah