076
FXUS63 KOAX 121741
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1241 PM CDT Fri Jul 12 2024

.KEY MESSAGES...

- Dangerous heat is expected for much of the area this weekend
  into Monday, with heat index readings of 100 to 110+ degrees
  likely. Sunday and Monday will be the hottest days.

- Spotty showers are possible today through this evening
  (10-30% chance, highest in northeast Nebraska). The strongest
  storm or two could produce a gusty downburst or quarter-sized
  hail.

- More widespread storm chances (20-40%) arrive Monday night
  and linger through Wednesday.

&&

.DISCUSSION...
Issued at 404 AM CDT Fri Jul 12 2024

Today and Tomorrow:

Water vapor imagery this morning features a broad ridge over the
western half of the CONUS, with departing troughing centered over
the Missouri/Iowa area helping influence the development of some
nocturnal showers. To across western Nebraska and south-central
South Dakota, an additional shortwave is dipping south-southeast to
help trigger more isolated storm activity that will likely expand to
clip parts of northeastern and eastern Nebraska later this morning
into the early afternoon hours. Plentiful instability thanks to
increasing surface moisture and warm temperatures joins steep mid-
level lapse rates to signal that we may see a storm or two result in
damaging hail or a downburst of wind despite the relatively weak
shear. CAMs have continued to be highly inconsistent both with each
other and from run to run, but the overall severe threat outlined by
the Day 1 Marginal risk from SPC highlights the extent of the
steeper lapse rates well, keeping most of the risk in eastern
Nebraska and points west into the evening hours.

For Saturday, temperatures begin to heat up as the trough to the
east flattens out and ridging broadens. Highs tomorrow are expected
to reach into the mid 90s to just over 100 degrees, with the
warmest temperatures expected in southeast to south-central
Nebraska (with another hot spot being in Knox County just under
100 degrees). Heat indices will flirt with Heat Advisory
criteria of 105 degrees, while the better bets to reach it
arrive later in the weekend. The general lack of surface
features will make afternoon/evening pulse storms harder to form
in the area, but CAMs have been showing some weak convective
activity to the north and west that may waft into the forecast
area late Saturday.

Sunday and Monday:

The main concern of the forecast period comes Sunday and Monday,
where the most oppressive heat is expected to settle into much of
southeastern Nebraska into southwest Iowa. 850 mb temperatures reach
their highest levels both days as an arm of thermal ridging extends
from eastern Colorado northeast into Iowa. At the same time,
increased evapotranspiration from corn and other agriculture will
continue to be in full swing, bringing additional moisture into the
equation. With that in mind, we`ve leaned towards higher dewpoints
this weekend which has in turn increased the heat danger. An
Excessive Heat Watch is in place for Sunday into Monday largely in
east-central Nebraska, where higher confidence the urban footprint
intersect. As we approach, expect to see expansion of some heat
watch or warning to be expanded to the full forecast area once
confidence is higher in just how hot and humid we`ll get.
Thankfully, an incoming front will help keep the heat from going on
for too long, and will bring rain chances back late Monday into the
overnight hours.

Tuesday and Beyond:

Early Tuesday the aforementioned front will continue its push east-
southeast continuing rain chances through much of the day as the
front slows down. Highs in the low-to-mid 80s will feel much cooler
than the days previous, with those numbers only being improved upon
comfortability-wise on Wednesday. Highs Wednesday are expected to be
in the upper 70s while another day of rain and storm chances follow
along and north of Tuesday`s stalling out front. Peering into the
late work work, we`ll find ourselves just barely on the cooler side
of almost northerly mid/upper flow that will likely bring with
it several shortwaves for nearly daily rain chances as highs
generally range in the 80s.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1238 PM CDT Fri Jul 12 2024

Some MVFR cigs around the Missouri River and western Iowa have
developed mid-day today but are expected to slide east over the
course of the afternoon. VFR conditions are forecast in its wake
with south-southeasterly winds forecast over the next 24 hours.
Some wind gusts up to 20 knots are possible, especially at KOFK
through the afternoon hours.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Excessive Heat Watch from Sunday afternoon through Monday
     evening for NEZ034-042>045-050>053-065>068.
IA...Excessive Heat Watch from Sunday afternoon through Monday
     evening for IAZ055-056-069-079-080-090-091.

&&

$$

DISCUSSION...Petersen
AVIATION...Nicolaisen