150
FXUS63 KOAX 181914
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
214 PM CDT Sat Jul 18 2026

.KEY MESSAGES...

- Isolated showers and non-severe thunderstorms are possible
  this afternoon. Probability of occurrence 10-20%

- Sunday and Monday will be two of hottest days of the year.
  Heat index values on Sunday will reach 100 to 108 degrees.
  Monday will be even more oppressive in most locations with
  heat index values 100-110 degrees.


- Nighttime heat index values  73-77 degrees will not provide
  much relief. A Heat Advisory is in effect on Sunday across
  northeast Nebraska and this will be expanded on Monday.

- Cooler weather returns by midweek, with high temperatures
  falling back into the 80s. Along with more seasonable
  temperatures. there will be increasing chances for showers
  and thunderstorms Wednesday night into early Friday.

&&

.DISCUSSION...
Issued at 213 PM CDT Sat Jul 18 2026

Rest of today and tonight...

Satellite imagery continues to show an increase in cumulus
across the area due to diurnal mixing of hot and humid air. Most
dense coverage is along and north of a frontal boundary that is
pushing into the area due to modest isentropic ascent along the
310K surface. CAMS continue to show isolated showers, and
perhaps a thunderstorm or two, developing this afternoon along
the boundary, which essentially will park itself essentially
from Verdel, NE to Clarinda, IA later this afternoon. Very modest
forcing for ascent is possible this afternooon and early evening from
a jet streak moving across the Great Lakes region. H7
temperatures will be warm, 10-12C, and H5 temperatures -4 to 0C,
which will lead to warm rain process, with perhaps a little
glaciation in the upper mid- levels to permit charge separation
and lightning. Localized heavy rainfall and wind gusts up 45 mph
as storms collapse are the primary threats. Any convection that
develops will dissipate with the setting sun, especially since
the jet streak will be too far removed to assist with diabatic
forcing.

Sunday and Monday...

The two most impactful days in the short term. Hot temperatures
are expected, especially on Monday. The Extreme Forecast Index
continues to highlight a 90+% temperature event for Monday, and
a shift of tails of 1-2. The EFI has shown this extreme event
occurring for the last 3 model cycles. Continued and expanded
the heat advisory for northeast Nebraska for Sunday, where
actual temperatures tomorrow will be around 100, and apparent
temperatures 100-108. Conditions do not improve much overnight,
with apparent temperatures 75 to 80. For Monday, actual
temperatures from 100-107 are expected with heat indices
100-110 areawide. Dewpoints in the 70s will lead to wet-bulb
temperatures in the 80s and 90s. Given there will be several
outdoor sporting events/championships where children are
participating, I decided to hoist a heat advisory for most of
east central and southeast Nebraska along with western Iowa.
The fly in ointment will be whether convection late in the day
on Monday impact temperatures. Models have been advertising a
disorganized MCS developing Sunday night and moving across
mainly South Dakota. This will allow a stationary front to move
slightly northward into northern Nebraska on Monday. The hot and
humid airmass will lead to a lower tropospheric instability. I
expect afternoon cumulus and towering cumulus to develop during
the afternoon, with frontal and diabatic effects to develop
isolated showers/tstorms. Dynamic forcing increases late in the
day as a jet streak moves across the northern plains into the
upper midwest. This jet streak digs further south than the one
affecting the area today, thus coverage of convection may
increase.

Tuesday through Saturday...

The passage of the jet streak and low level cool advection will
push the front into Kansas. The most anticipated effect will be
the decrease in temperatures. Temperatures on Saturday only will
decrease about 10 degrees into the 90s, but as upper level
heights decrease even further, temperatures the rest of the
period will be in the 80s. Also something to look forward, are
periodic chances of showers and storms, as a series of
disturbances traverse the upper ridge axis over Texas, while
simultaneously the polar jet remains active and will further
increase opportunities for atmospheric ascent.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1248 PM CDT Sat Jul 18 2026

The latest satellite imagery is detecting increasing cumulus
cloud development across the area. Coverage is in the FEW-SCT
category at FL040-FL060. A weak front is moving into the
forecast domain. Afternoon heating, moisture pooling along the
front and instability will lead to a few showers and isolated
thunderstorms. Coverage of this activity <20%, and do not have
enough confidence adding to the TAF sites. Any activity will
dissipate between 19/02-03Z. The rest of the TAF period will be
quiet, with little or no clouds blo FL120 and light and variable
winds.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory from 10 AM to 10 PM CDT Monday for NEZ015-018-
     030>034-042>045-050>053-067-068-091-093.
     Heat Advisory from noon Sunday to 10 PM CDT Monday for NEZ011-
     012-016-017.
IA...Heat Advisory from 10 AM to 10 PM CDT Monday for IAZ043-055-
     056-069-079-080-090-091.

&&

$$

DISCUSSION...Fortin
AVIATION...Fortin