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419
FXUS63 KOAX 240437
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1137 PM CDT Sun Jun 23 2024

.KEY MESSAGES...

- Moderate to near Major flood stages are expected along the
  Missouri River from Blair to Rulo this week, rivaling stages
  that were last experienced in 2019.

- Flooding is ongoing along the Platte, Ponca Creek and Clear
  Creek. with flooding abating along the Ponca and Clear Creek
  in the next 24 hours

- Isolated to widely scattered thunderstorms possible late
  tonight and again Monday and Tuesday evenings. There is a
  Marginal risk for severe weather Monday and Slight Risk for
  Tuesday.

- The hottest temperatures of the year so far are forecast
  Monday, with heat indicies from 100 to 110. The heat may
  extend into Tuesday afternoon across southeast Nebraska.

- More widespread chances for rain and thunderstorms return
  Wednesday night through Friday night.

&&

.DISCUSSION...
Issued at 410 PM CDT Sun Jun 23 2024

A relatively uneventful day weatherwise, as high pressure
gradually moves southeast of the area. There are low (10-20%)
chances of of isolated thunderstorms late evening into the
overnight hours, with 40-45kt LLJ enhancing convergence and a
diffuse mid-level disturbance enhancing lift 310-315K. Moisture
looks a little scant, thus only anticipated isolated development
at best.

Monday and Tuesday:

Monday looks to be the hottest day of the year so far, with NBM
25-50% temperatures in the lower 90s to near 100s. NAEFS and
ECENS both noting 850 temperatures in the 99.5 percentile, which
if realized at the surface would push temperatures into the
100s areawide. The axis of warmest H8 temperatures generally is
north and west of the forecast area, thus decided just to trend
toward NBM 75 percentile which project max temps on Monday in
the upper 90s to lower 100s. Combined with dewpoints in the
lower 70s, maximum heat indicies during the afternoon hours
will range from 100-110. Tuesday also looks to be a hot day, but
confidence is not as great as whether heat index values of
100-105 will be met. Thunderstorms tomorrow afternoon along a
surface trough that will be in place across the area. The better
dynamic forcing will be further north in proximity to a vortex
moving across the central Canadian plains. Proximity soundings
note SB/MUCAPE 2000-2500 and bulk shear values 25-35kt. There is
some capping, but if that can be exceeded there is a potential
for some organized storms. The threat of storms diminishes
through the evening, with the attendant trough and any mesoscale
boundaries lingering across southeast sections of the forecast
area. Any storms that develop tomorrow leave a footprint and
minimize heating potential on Tuesday. Also, expecting
redevelopment of isolated to scattered storms on Tuesday. There
appears better potential for severe storms on Tuesday, as a
compact short wave dives southeast into the upper Midwest.
Kinematics will be a little stronger which should allow storms
to be better organized, with CSU Machine Learning providing some
indication, though better severe potential looks to be north
and east of the forecast area.

Wednesday through Sunday:

Wednesday is the one day of the forecast period in which no
precipitation is anticipated. Mid-level ridging and weak low
level cold advection will make for a more seasonable summer day.
But the quiet is short-lived as an upper level trough moves
eastward from the west coast, sending a series of upper
disturbances across the area Thursday into early Friday, before
the main shortwave trough moves across the northern plains
Friday into Saturday. Forecast precipitable water values of
1.6-2.0 inches are in the 75-90 percentile of normal for late
June, thus storms have potential to produce heavy rain though
ensembles are limiting the probability of widespread 1" plus
rainfall to 10-20%. All modes of severe weather look possible,
with Friday looking to have the greatest potential for severe
weather. Temperatures will remain slightly above normal through
Friday, with temperatures trending toward normal during the
upcoming weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
-- Changed Discussion --
Issued at 1125 PM CDT Sun Jun 23 2024

Winds have shifted southeasterly and decreased in speed this
evening, with winds just above the surface at FL020 already or
expected to soon increase to 35 to 40 kts out of the southwest,
increasing low-level wind shear. Aside from those conditions,
winds will once again increase tomorrow morning with gusts of
20-25 kts expected before dying down once again around 00z
tomorrow evening. A line of deeper clouds is beginning to
develop northeast of KOMA, and may result in an isolated storm
or two and some lightning just outside of KOMA`s territory.
-- End Changed Discussion --

&&

.HYDROLOGY...
Issued at 105 PM CDT Sun Jun 23 2024

A number of forecast changes occurred for the Missouri, Platte
and Little Sioux Rivers during the morning round of updates.
Water flow from Missouri River tributaries down stream of Gavins
Point dam remain in major flood, with minor impacts beginning
along the Missouri River between Sioux City and Decatur. Minor
to moderate flooding is expected to occur along the Missouri
between today and next weekend, with a 5-25% chance of flood
levels reaching major stages downstream of Plattsmouth due to
additional water flow from the Platte River. The Platte
currently is flooding between Leshara and Ashland, with minor
flooding expected from Louisville to the confluence with the
Missouri tonight into early Monday. Minor to moderate flooding
is anticipated along the Little Sioux River Monday and Tuesday,
with historic crest levels being reached in northwest Iowa. Flooding
is abating along Ponca Creek to its confluence with the
Missouri in Knox County.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
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NE...Heat Advisory from 1 PM to 8 PM CDT Monday for NEZ011-012-
     015>018-030>034-042>045-050>053-065>068-078-088>093.
IA...Heat Advisory from 1 PM to 8 PM CDT Monday for IAZ043-055-056-
     069-079-080-090-091.
-- End Changed Discussion --

&&

$$

DISCUSSION...Fortin
AVIATION...Petersen
HYDROLOGY...Fortin