902
FXUS63 KOAX 181708
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1208 PM CDT Sat May 18 2024

.KEY MESSAGES...

- A weak cold front moving through this morning will bring
  slightly cooler temperatures to the region.

- Several rounds of strong to severe thunderstorms will be
  possible Sunday afternoon through Tuesday afternoon. All modes
  of severe weather will be possible including flash flooding.

- There will be additional chances for storms (40%) Thursday
  into next weekend.

&&

.DISCUSSION...
Issued at 235 AM CDT Sat May 18 2024

Mostly clear skies across the area early this morning, but we
do have a cold front approaching the area from the northwest. On
satellite we see the cold front stretching from the surface low
over eastern South Dakota down to southwestern Nebraska. This
front will start to move into northeast Nebraska around 7 AM
this morning and continue southeastward across our area through
the morning bringing in cooler air for the afternoon. High
temperatures today will mostly be in the upper 70s to low 80s,
apart from far southeast Nebraska and southwest Iowa, areas
which may see high temperatures reached in the mid-to-upper 80s
before the cold front arrives.

Sunday starts a pattern shift to much more active weather
through early next week. We see a series of shortwaves bring
chances for showers and storms, as well as the potential for
flash flooding and severe weather.

The trough train I guess actually started with the trough
tonight, but with dry air in place, we don`t see any
precipitation with this system. The next shortwave arrives
late tonight which kicks the surface High off to the east. We
see the development of a strong surface low over western Kansas
which sets up a strong low-level jet across the Central Plains,
advecting moisture into our region from the Gulf of Mexico.
Models differ on the placement of the warm front from the
surface low across western Kansas, with the GFS placing it
farther south in northern Kansas while the NAM brings it north
into southeastern Nebraska. Expect shower and storm activity to
develop overnight late Saturday night north of the warm front
through the morning hours Sunday morning associated with the
passage of the shortwave.

The Sunday afternoon/evening activity has become more
conditional due to the morning storm activity. SPC has honed in
on this by downgrading the severe potential across our area to
Marginal. The concern is that lingering showers and cloud cover
will struggle to clear in time to allow for the environment to
recharge for a stronger second round during the evening as
suggested in the models just yesterday. The NAM still shows this
potential across southeast Nebraska south of the warm front,
but the GFS with the warm front well south of our area keeps the
severe weather potential to a narrow window right around 00Z
and fairly low. Will continue to message that there is a
conditional threat if we see clouds clear early enough for the
environment to recover with a more northerly track of the
surface low on Sunday.

The next shortwave will bring another round of storms through
Monday night into early Tuesday. We could potentially see
another chance for severe weather again dependent on the track
of the surface low, with a more northerly track bringing a
greater potential for severe storms, while a more southerly
track brings a greater potential for heavy rainfall with
isolated large hail.

Tuesday afternoon another trough will move through bringing more
showers and storms and again, potential for a few strong to
severe storms. This time, the greater potential will be for far
southeast Nebraska and southwest Iowa, though models have been
trending slower which would could potentially add in far eastern
Nebraska to the potential for severe storms if this trend
continues. Still the better chance for severe storms on Tuesday
will probably be east of our area as storms may develop in our
southwest Iowa counties but quickly move off to the east.


Good news is it does look like at least right now we see a break
in storm chances on Wednesday. Haven`t completely removed PoPs
as ensembles have kept low PoPs in through the day. Right now
though it does look like Wednesday should be mostly dry with
highs in the upper 60s to low 70s.

Toward the end of the week we see another system that will bring
more storms on Thursday or Friday. We do see temperatures climb
back up into the upper 70s toward the weekend though chances for
showers and storms linger.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1157 AM CDT Sat May 18 2024

Gusty northwesterly winds will weaken throughout this afternoon.
Gusts up to 35 mph will be possible through 20Z at all TAF
sites, but particularly at KOFK. There is a very low chance (5
to 10%) of a stray thunderstorm or two in far southeast
Nebraska/southwest Iowa. If any storms develop they should
remain well southeast of TAF sites. A round of thunderstorms is
expected to develop tonight and move into the region from the
southwest by 12Z tomorrow morning. All TAF sites could see
rain/thunderstorms at some point, thought low probabilities and
uncertainty with regards to timing preclude any inclusion of
precip in LNK and OMA TAFs.

&&

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

&&

$$

DISCUSSION...McCoy
AVIATION...Darrah