937
FXUS63 KOAX 212336
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
636 PM CDT Fri Jun 21 2024

.KEY MESSAGES...

- Main focus will be centered around severe thunderstorms
  tonight and the potential for continued heavy rain across our
  north.

- Flood Watch for northeast Nebraska and along the entire
  Missouri River.

- At least small storm chances nearly every day through the middle
  of next week. Severe weather will be possible at times.

- Gradually warming temperatures through the weekend into early
  next week. Heat indices approaching 100 to 110 on Monday and
  possibly Tuesday.

&&

.DISCUSSION...
Issued at 346 PM CDT Fri Jun 21 2024

Tonight

A nearly stationary surface boundary remains draped just to the
north of the Nebraska/South Dakota border and extends into northwest
Iowa. This will serve as the primary focus for late
afternoon/evening thunderstorm development where instability has
increased through the heating of the day. In addition, a
remnant MCV from overnight convection remains across southeast
SD. The boundary is forecast to slowly sag southward through the
evening across northeast Nebraska. Latest CAM output continues
to show thunderstorm development near this boundary as large-
scale forcing for ascent increases ahead of an approaching weak
shortwave. This activity will slowly sag south tonight across
northeast Nebraska. There remains a potential for supercells
with a few tornadoes along the boundary and a low-end wind/hail
threat. These will also be very efficient rain makers. In fact,
OAX just had a pop-up brief downpour with a rainfall rate of
1.34"/hr.

Heavy rainfall is expected across southeast SD and northeast Neb
with some model output on the order of +2.00" as we move into the
overnight hours. Storms should sink south and diminish by Saturday
morning.

As a result of the heavy rainfall upstream last night and the
forecast for additional heavy rain, we have hoisted a Flood Watch
for a large section of northeast Nebraska and then all areas along
the Missouri River.  The runoff from recent rain could potentially
bring the Missouri River, below Gavins Point Dam, well into flood
stage. With more rain expected today and again tonight, the
situation looks to worsen. Due to the large amount of water coming
down the river, the river will not crest until mid to late next week
with some locations reaching moderate flood stage.

Saturday into Sunday

The above mentioned front will continue to slide south Saturday and
is forecast to be south of our entire forecast area by 00z Sunday.
The severe weather threat pushes to our east/southeast while surface
high pressure builds south into the area Saturday night.

By Sunday, strong southerly return flow brings the heat and we
will warm up into Monday with upper level ridging overhead. By
Monday, temps will peak in the mid to upper 90s with maximum
heat indices near 105. HeatRisk will move into the Red/Major
category on both days suggesting a need for effective cooling
and hydration for anyone spending time in the afternoon sun.
Heat headlines will likely need to be explored.

Next week

A continued active pattern will carry us to the end of June.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 631 PM CDT Fri Jun 21 2024

Main concern of the forecast period continues to be shower and
storm chances near KOFK this evening into the overnight hours.
Storms to the west have been generally weakening as the move
east, and will continue to drift north and weaken as they
approach, limiting to an extent their eastward progression. The
best bet for storms in that area begins 05z when more widespread
activity occurs, but an amendment may be needed if a storm
holds together and arrives before then. Elsewhere, largely dry
conditions should persist. Low-level wind shear is expected
overnight despite the breezy conditions with winds at FL020
expected to be out of the southwest at 45 kts. Winds will shift
westerly over the course of the morning and then turn
northwesterly with wind speeds gradually tapering off by 00z
tomorrow.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flood Watch through Saturday morning for NEZ011-012-016>018.
IA...None.

&&

$$

DISCUSSION...Kern
AVIATION...Petersen