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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KOAX 150435
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1135 PM CDT Sun Apr 14 2024

.KEY MESSAGES...

- Warm, dry, and windy conditions will bring very high to
  possibly extreme fire danger to portions of northeast Nebraska
  and west-central Iowa Monday afternoon. A Fire Weather Watch
  is in effect.

- Severe storms will be possible (15-40% chance) late
  Monday afternoon into the overnight hours across much of the
  area. The greatest threat will be large hail, but damaging
  winds, tornadoes, and localized flooding are also possible.

- Additional strong to severe storms will be possible
  (15-30% chance) late Tuesday morning into Tuesday afternoon,
  primarily in far southeast Nebraska into southwest Iowa. All
  hazards will be possible once again.

- Cooler temperatures are on tap Thursday through Saturday.
  Expect highs in the 50s and lows in the 30s, perhaps below
  freezing in some spots.

&&

.DISCUSSION...
Issued at 329 PM CDT Sun Apr 14 2024

Another quiet and warm afternoon across the area with surface
high pressure off to our north and an upper level ridge axis
pushing in from the west. As of 2 PM, temperatures were in the
80s across the forecast area, with a few gusts in the 20 to 30
mph range leading to some minor fire weather concerns. However,
expect the winds to die down pretty quickly as the pressure
gradient relaxes a bit later this afternoon.

Heading into Monday, a strong shortwave trough currently just
moving onshore over CA will start cross the Rockies, with a
surface low deepening over northeast CO and inducing a
tightening pressure gradient over the forecast area. The
resulting strong southeast flow will usher in decent moisture
behind a northward advancing warm front, with surface dewpoints
in the upper 50s to lower 60s getting into much of the forecast
area while temperatures again top out in the mid to upper 80s.
As a result, expect a fairly unstable airmass over at least part
of the area, with HREF guidance showing mean SBCAPE values of
1500 to around 2000 J/kg. While model soundings do show an
elevated mixed layer/decent cap to overcome, strengthening
moisture transport and convergence along the warm front should
allow for at least a few storms to get going by late afternoon
in the vicinity of said front. However, there do remain plenty
of questions/limiting factors in addition to the aforementioned
cap. First, there remains a decent amount of spread on how
quickly the warm front advances northward and where exactly it
will be when storms develop. In addition, the low and strongest
forcing for ascent don`t really eject/directly impact our area
until the early Tuesday morning hours. Semi-related, the
strongest mid-level flow will be closer to the low, which will
limit deep layer shear, though latest guidance does suggest
30-40 kts of 0-6 km shear, which would be sufficient for
organized storms. Finally, while we will get surface dewpoints
in the 60s, overall depth of the moisture will be somewhat
lacking. With all that said, ingredients are certainly there for
severe weather, including supercells capable of all hazards.
The main threat does look to be large hail, as lapse rates look
to be fairly steep, but damaging winds and tornadoes will also
be possible, especially with any surface-based storms as low
level shear ramps up in the early evening hours. In addition,
some localized flooding will be possible in areas that see
repeated rounds of storms as we go through the overnight hours
and additional storm development occurs as moisture transport
continues pointing into the area.

By mid to late Tuesday morning the low is progged to be over
central NE with a dryline/punch pushing into southeast NE. While
convection will likely be ongoing to the east, guidance is in
good agreement of another plume of instability working into the
area and becoming largely uncapped in this timeframe. As a
result, expect additional storm development along said dryline,
and while hodographs look rather messy, enhanced vertical
vorticity in vicinity of the surface low will lend itself to
tornado potential late Tuesday morning into the afternoon, along
with a continued hail, damaging wind, and localized flooding
threat. Regarding rainfall amounts, guidance continues to
suggest a 30-50% chance of at least 2 inches by early Wednesday
within the primary band of rainfall. The question is just where
that ends up being. EPS guidance would suggest it would be near
and north of a line from Columbus to Omaha, while GEFS keeps
those higher chances more into west-central to northwest IA. So
all in all, Monday afternoon through Tuesday afternoon will be a
time to watch for severe weather, with large hail, damaging
winds, tornadoes, and flooding all possible at times.

Rain should exit by Wednesday morning as the low pushes toward
the Great Lakes. Northwest flow behind the system will start
bringing in cooler air through the end of the week. We`ll still
be near average for this time of year on Wednesday, with highs
mostly in the 60s. However, additional shortwave energy will
slide through Wednesday night into Thursday and again Friday,
while a reinforcing cold front will push south through the area.
This will result in more rain chances and high temperatures in
the 50s and perhaps 40s Thursday through Saturday. In addition,
lows look to dip into the 30s with some spots getting below
freezing. So if you put some plants outside with the recent warm
weather, you may want be ready to protect them for a couple
nights.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
-- Changed Discussion --
Issued at 1135 PM CDT Sun Apr 14 2024

VFR conditions will prevail through Monday afternoon. There is
an increased chance of ceiling and/or visibility restrictions
in the vicinity of any thunderstorm development Monday evening.
But, given the large spread in model solutions at that time,
neither TSRA nor ceiling/visibility restrictions will be
included in this forecast. LLWS still looks probable at KOFK and
KLNK overnight, prior to strengthening southeast surface winds
Monday morning. Sustained speeds of 20 kt with gusts of 30 kt
are likely from early afternoon into Monday evening.
-- End Changed Discussion --

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
NE...Fire Weather Watch from 11 AM CDT Monday through Monday
     evening for NEZ011-012-015-017-018-032>034.
IA...Fire Weather Watch from 11 AM CDT Monday through Monday
     evening for IAZ043.
-- End Changed Discussion --

&&

$$

DISCUSSION...CA
AVIATION...Mead