186
FXUS63 KOAX 231805
AFDOAX

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

.KEY MESSAGES...

- Flooding of the Missouri River tributaries in southeast South
  Dakota and northwest Iowa will lead to increased water flow
  into the Missouri River downstream of Sioux City. Flood
  warnings are in effect along the Missouri from Decatur to Rulo
  beginning early next week.

- The hottest temperatures so far this year are expected Monday
  and possibly Tuesday, with heat index readings of 100 to 110.

- There will be additional storm chances next week, with
  occasional severe weather and heavy rainfall possible,
  particularly on Tuesday and Friday.

&&

.DISCUSSION...
Issued at 251 AM CDT Sun Jun 23 2024

Short Term (Today and Tomorrow)

Upper level ridging is expected to build into the Central Plains as
a longwave trough pushes into the eastern CONUS. This pattern change
is expected to bring an increase in temperatures over the coming
days. Highs today are expected to reach into the upper 80s/low 90s.
Dewpoints in the mid 60s will bring heat index values in the 91 to
95 degree range. CAM guidance is developing isolated thunderstorms
late Sunday night/Monday morning ahead of a warm front pushing
through eastern Nebraska. MLCAPE values of 1000-1250 J/kg along with
30-40 kts of bulk shear will be available in areas that can break
through the cap. Severe potential remains low with these storms,
however an isolated small hail risk may be possible if an
updraft can sustain itself.

Monday is expected to be the warmest day of the week with high
temperatures peaking in the 96 to 102 range. Dewpoints are expected
to reach the lower 70s in some areas with heat index values of 105
to 1110 across the area. Mostly clear skies and prolonged heat
has led to the newly released HeatRisk product displaying a
Major Risk for heat-related impacts for much of the area. A Heat
Advisory has been issued for Monday afternoon. Isolated
thunderstorm development is possible late Monday
afternoon/evening as a weak cold front pushes into the area.
Sufficient MLCAPE values of 2500-4000 J/kg with bulk shear
values of 25-35 kts could support a severe wind and hail risk
for any sustained updrafts. SPC has placed much of the area in a
marginal risk (level 1 out of 5) for severe weather. QPF values
remain under 0.25", thus flood concerns remain low but will
need to be monitored given the current hydrologic environment.

Long Term (Tuesday through Saturday)

High temperatures on Tuesday will depend on the timing of the
aforementioned cold front pushing through. Southeast Nebraska could
see high temperatures pushing 100 while highs drop towards 90
degrees by the NE/SD border. Severe weather redevelopment is
possible along the front Tuesday afternoon/evening. The
location of severe weather potential will once again be
dependent on the front location. This will likely be constrained
to southeast NE/southwest IA, yet there is still some
disagreement among ensemble members that will need to be ironed
out as it approaches.

The upper level ridge will begin to break down on Wednesday,
bringing high temperatures in the mid 80s to low 90s. These
temperatures are much closer to the climatological average for late
June. Precipitation chances return on Thursday as a shortwave trough
pushes into the area. A prolonged period of 30 to 45 percent
PoPs begins on Thursday and continues into the weekend. WPC has
issued a slight risk for excessive rainfall on Thursday as a
swath of QPF values greater than 1.25" covers an already
sensitive area. PoPs increase to the 50 to 60 percent range on
Friday as a cold front pushes through the area. Severe weather
potential is also present on Friday depending on the timing of
the frontal passage. Additional precipitation chances continue
into Saturday with some disagreement among long range guidance
on the timing/location of clearing. Additional flooding concerns
remain elevated with the possibility of continued rainfall.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1227 PM CDT Sun Jun 23 2024

Low level wind shear conditions are expected to develop between
24/07-08z at KOFK and KLNK. Southerly low level flow will
increase this afternoon through the overnight hours due to
leeside cyclogenesis across the western high plains. South to
southwest winds of generally 10 kts or less are expected today.
The atmosphere will decouple early this evening, allowing winds
to back to southeast direction. Meanwhile a south-southwest low
level jet will develop, with winds of 35-45kts from 200-220. For
now, it appears KOFK and KLNK only will be impacted with the
main axis of the jet from northwest Kansas into northeast
Nebraska.

In terms of sky and visibility conditions, VFR will prevail at
all three TAF sites through the period.

&&

.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...
NE...Heat Advisory from 1 PM Monday to 7 AM CDT Tuesday for NEZ011-
     012-015>018-030>034-042>045-050>053-065>068-078-088>093.
IA...Heat Advisory from 1 PM Monday to 7 AM CDT Tuesday for IAZ043-
     055-056-069-079-080-090-091.

&&

$$

DISCUSSION...Wood
AVIATION...Fortin
HYDROLOGY...Fortin