-- Discussion containing changed information from previous version are highlighted. --
793
FXUS63 KOAX 251051
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
551 AM CDT Sat May 25 2024

.KEY MESSAGES...

- Another round of thunderstorms is expected tonight with some
  severe weather possible, especially along and south of I-80.
  Large hail, damaging winds, and localized flooding are the
  primary hazards.

- A strong storm or two is possible in southeast NE and
  southwest IA Sunday afternoon/evening with hail and/or gusty
  winds possible.

- Additional showers and storms are possible Wednesday night
  through Friday.

&&

.DISCUSSION...
Issued at 358 AM CDT Sat May 25 2024

.Today and Tonight:

A shortwave trough currently over the Great Basin into southern
CA will shear east-northeast into the central Plains this
afternoon and evening, ahead of a secondary midlevel disturbance
which will reach the central High Plains late tonight. In the
low levels, midnight surface analysis indicates a front
extending from the upper Midwest through the Ozarks into western
TX. That boundary will lift north today as a warm front as a
surface low deepens over eastern CO. By this evening, the
surface low is forecast to develop into central KS with the
surface boundary nearing the KS-NE border.

Strengthening warm advection in the 850-700-mb layer has
fostered the development of a midlevel cloud deck over portions
of western NE and northwest KS as of 3 AM with those clouds
expected to spread into northeast NE later this morning. The
CAMs indicate some potential for light rain or sprinkles within
that regime; however, considerable dry air in the sub-cloud
layer will likely limit measurable precipitation chances. As
such, this forecast update will indicate slight chance PoPs
(20%) near the SD border during the mid/late morning hours.

High temperatures this afternoon will be in the mid 70s to
around 80 with greatest boundary-layer moisture content and
resultant air mass destabilization remaining to the south of our
area, along and to the south of the retreating warm front. By
this evening, a strengthening low-level jet will enhance
moisture transport into the region with a moderately unstable
environment developing across the southern half of the area.

Consensus of latest CAM output suggests that thunderstorm
initiation will occur over western NE this afternoon with
activity growing upscale into clusters while progressing east
this evening. Other storms may form ahead of the surface low in
KS with either or both of these regimes spreading east into our
area after 9 or 10 pm. Proximity model soundings suggest these
storms may become slightly elevated by the time they reach our
area. Nonetheless, the presence of a vertically veering wind
profile with ample vertical shear will support organized storm
modes capable of large hail and damaging wind gusts, especially
along and south of I-80 where the strongest instability is
forecast to reside. The greatest severe weather threat will
exist from 9 PM until 3 AM Sunday.

Thunderstorms could linger into the overnight hours with an
increasing risk for localized flooding.


.Sunday and Sunday Night:

The above-mentioned, trailing shortwave trough is forecast to
track through the central Plains Sunday while the associated
surface low accelerates from eastern KS into the upper Midwest.
Forcing for ascent attendant to the midlevel wave will support
continued shower and thunderstorm chances (30-50%) across the
area Sunday. Steep low/midlevel lapse rates may yield sufficient
buoyancy for a few strong storms across portions of southeast
NE and southwest IA during the afternoon and evening hours with
a risk for some hail and/or gusty winds.

Precipitation chances will decrease Sunday night as the midlevel
system shifts to the east of the area.

Highs on Sunday will be in the 70s.

.Memorial Day:

The models indicate a fairly strong shortwave trough progressing
from the northern Plains into the upper Midwest with a few
showers or thunderstorms possible (20-30% chance) across
portions of northeast NE and southwest IA. Otherwise, skies are
expected to be partly to mostly sunny with highs in the mid to
upper 70s. Northwest winds will strengthen through the day with
gusts of 15-30 mph possible by afternoon.

.Tuesday through Friday:

The 25/00z global ensembles indicate midlevel ridging initially
over the Rockies Tuesday morning will shift into the Great
Plains by Wednesday. That feature is forecast to shift east of
the MS Valley by Friday in advance of a midlevel trough moving
through the western CONUS. The forecast will indicate highs
mainly in the 70s with shower and thunderstorm chances from
Wednesday night through Friday.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
-- Changed Discussion --
Issued at 547 AM CDT Sat May 25 2024

Winds will prevail out of the south this morning through the
evening hours across the entire forecast area. Between 14Z and
01Z will be the most likely time to see prevailing winds greater
than 12 knots, with local nuances in times reflected in the
TAFs. Rain and thunderstorm chances will move into the region
from the west and south after 02Z. Though thunderstorms are
likely, uncertainties with regards to timing preclude inclusion
in TAFs. As the time of arrival for these storms gets closer,
TEMPO or addition FM groups will likely be added to convey
increased confidence in coverage and timing. -RA has been
included for now to delineate the general times each TAF site
could see showers and/or thunderstorms tonight.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...Mead
AVIATION...Darrah