344
FXUS63 KOAX 142308
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
608 PM CDT Sun Jul 14 2024

.KEY MESSAGES...

- Dangerous heat continues into Monday, with heat index readings
  of 100 to 110+ degrees likely.

- Widespread storm chances (20-40%) arrive Monday night and
  linger through Wednesday. Some storms may be severe.

&&

.DISCUSSION...
Issued at 345 PM CDT Sun Jul 14 2024

An upper level ridge continues to bring scorching heat to the
Four Corners area as it deamplifies and stretches east. Under
that ridge, the heat continues to build into the mid-Missouri
River valley. NAEFS climatology indicates a 15-30 year return
rate for H85 temps of this magnitude in mid-July.

Almost all of the AWOS/ASOS sites in the forecast area have
temps above 90F with heat indices pushing above 100F. Heat
headlines are in place for the entire CWA through 8pm. The heat
advisory will fall away then, but the excessive heat warning
will remain in place for the southeastern half of the CWA
including Lincoln and Omaha. While heat indices may fall shy of
our 110 degree criteria for excessive heat warnings, the danger
hinges in part on the lack of significant relief overnight.
Most of southeast Nebraska and southwest Iowa will see temps
only briefly slip into the mid-70s. Homes without air
conditioning will tend to hold heat overnight, adding additional
stress to occupants.

PoPs will remain low overnight, but not zero as a few of the
convection allowing models are dragging an MCS from near the
Bakken Formation in western North Dakota through SD and clipping
northeast Nebraska tonight. Have added 20% PoPs over much of
northeast Nebraska after midnight and on Monday morning.

.MONDAY...

More showers and thunderstorms are possible on Monday afternoon
and evening with a "cool" front slipping through the area mid-
day. Parameterized models aren`t producing much for convection
here, keeping it generally northeast of Sioux City. Capping
looks to be the reason. It`s worth mentioning that the models
have been underforecasting dewpoints for the past few days (slow
to pick up on the corn sweat). The NAM, for instance, has
dewpoints near 73 on Monday afternoon when 75-79 is the more
reasonable range. This will mean convection will be easier to
develop than suggested by guidance.

Four-thousand to 5,000 J/kg of CAPE means that any storm that
does develop would have a lot to work with. Lapse rates from the
surface to H5 will be over 8C/km and suggestive of a damaging
wind threat. There are lots of question marks in eventual
placement with a dry afternoon quite possible. Still, the
"slight" convective category seems warranted over western Iowa.

Heat will be mitigated by moderate cold air advection over the
northern half of the CWA. Heat headlines remain in place over
the southern 2/3 of the forecast area where heat indices of
100-113 degrees are forecast. Monday`s heat index forecast is a
bit warmer than the one issued 24 hours ago due not to increased
temperatures but higher dewpoints now forecast to peak in the
mid-70s for many and upper 70s for western Iowa. Partly sunny
skies are forecast, but increased cloud cover from potential
convection would be a possible cooling mechanism.

.TUESDAY AND BEYOND...

The ridge retreats west allowing for an amplified pattern.
Strong northwesterly flow over the the central CONUS will help
keep temperatures cool and the pattern pointing any shortwaves
directly at Omaha and Des Moines. Right now the best energy
suggests timing of Wednesday and Saturday as best opportunities
for a wetting rain.

High temps will mostly be in the upper-70s to mid-80s for the
rest of the work week and lingering into next weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 602 PM CDT Sun Jul 14 2024

VFR conditions are expected to prevail throughout the forecast
period. The night will begin with light southerly winds. There
is a low chance of scattered light rain showers impacting KOFK
in the 06-10Z timeframe. Low confidence in this occurrence has
led to opting out of including the possibility in the TAFs at
this time.

A front moving through the area from north to south through the
day Monday will shift winds clockwise from southerly to
northeasterly. A chance of scattered showers and thunderstorms
moves into the KOMA and KLNK area in the final hours of the
forecast period. There is low confidence in the coverage of
these storms, therefore it will be left for future TAF
issuances.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory until 8 PM CDT this evening for NEZ011-012-
     015>018-030>034-042>045-050-065-078-088.
     Heat Advisory from noon to 8 PM CDT Monday for NEZ015-033-034-
     042>045-050-065-078-088.
     Excessive Heat Warning until 8 PM CDT Monday for NEZ051>053-
     066>068-089>093.
IA...Heat Advisory until 8 PM CDT this evening for IAZ043-055-056.
     Heat Advisory from noon to 8 PM CDT Monday for IAZ043-055-056.
     Excessive Heat Warning until 8 PM CDT Monday for IAZ069-079-
     080-090-091.

&&

$$

DISCUSSION...Nicolaisen
AVIATION...Wood