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972
FXUS63 KOAX 230756
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
256 AM CDT Sun Jun 23 2024

.KEY MESSAGES...

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- 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.
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&&

.DISCUSSION...
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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.
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&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1203 AM CDT Sun Jun 23 2024

Latest runs of the short-term models suggest that fog chances
are decreasing at KOMA, but have elected to keep them in with
the expected slight winds, and potential for it to still by
patchy. Aside from the fog chances, winds have slackened and
will become calm to somewhat variable in not from the northwest,
and will return southwesterly tomorrow morning and turn
southeasterly while staying light.

&&

.HYDROLOGY...
Issued at 358 PM CDT Sat Jun 22 2024

Flood warnings have been posted along the Missouri River
downstream from Sioux City to Rulo. The successive river
forecasts during the past 24-36 hours have lagged the onset of
flooding and crests, forecasts are tracking with observations
more closely. This will be the first time since 2020 that the
Missouri has been in flood along its entire reach in the HSA.
Additionally flooding is occurring along Ponca Creak from its
headwaters to Verdel, with some indications that the river could
re-crest again based on the National Water Model. River levels
also are above action stage along the Platte between Schuyler
and North Bend, Loup upstream of Columbus and Clear Creek.
Fortunately there will be no precipitation in the short-term to
affect rivers in the next 24-48 hours, but precipitation Tuesday
and onward could impact the recession of the Missouri, and cause
other area rivers to rise from Wednesday onward.

&&

.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.
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&&

$$

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