913
FXUS63 KOAX 151713
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1213 PM CDT Mon Jul 15 2024

.KEY MESSAGES...

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

- Widespread storm chances (20-40%) this afternoon and linger
  through Wednesday. Best chances for severe storms will be
  across southwest Iowa 3 to 10 PM with wind being the primary
  threat.

- An extended stretch of cooler-than-average temperatures will
  carry us into the weekend, with chances for widespread rain
  increasing into next week.

&&

.DISCUSSION...
Issued at 355 AM CDT Mon Jul 15 2024

Today and Tomorrow:

Water vapor imagery this morning features broad ridging over the
western half of the CONUS with increasingly northwesterly flow in
the mid/upper levels locally and a pair of storm clusters
traveling across ND/MN and IL/IN/MI. A recent surface map
places a surface trough or warm front extending northeastward
from a surface low in north-central Kansas stretching into
western and central Iowa, with notably increased surface
moisture and temperatures along and just to the south of it.
Areas of fog also exist near this boundary where weak winds and
more efficient radiational cooling have been in full force.
Expect this front to dissolve by mid-morning with temperatures
quickly rebounding alongside increasing dewpoints to create
dangerous heat for much of eastern Nebraska and southwest Iowa
ahead of a front and cooler airmass moving in from the north.
Heat indices for southeastern Nebraska including Lincoln and
Omaha/CB are expected to reach the 105-110+ degree range, aided
by the soon-to- depart low-level thermal ridge, compressional
heating, and the increased evapotranspiration. Despite leaning
towards a more conservative temperature and moisture forecast,
cloud cover to the west of the area and a thin veil of smoke
could serve as potential failure mechanisms and could keep us
cooler than forecast.

In addition to the heat, 4500+ J/kg of surface-based CAPE will be in
place in western/central Iowa where they are joined by healthy lapse
rates to result in strong to severe storm chances in that area
decreasing to the west. Damaging wind will lead the way hazard-wise
driven by high DCAPE values, while damaging hail and a brief tornado
can`t be ruled out due to the high instability and ambient surface
vorticity from the leftover AM front. Chances go from the late
afternoon and generally wrap up by 10 PM as the remaining storm
clusters move east and south of the area. Activity from western
Nebraska will carry additional light rain chances into Tuesday
morning, before what could be another round of storms in northeast
Nebraska after 3 PM (by which we`ll be enjoying noticeably
cooler high temperatures in the mid 80s.

Wednesday and Beyond:

By Wednesday, we`ll find ourselves starting a cooler than average
stretch as the northwesterly mid/upper jet shifts directly overhead
with ridging staying bottled up out west. The name of the game
during this part of the forecast period will be monitoring subtle
shortwaves as they get lobbed towards the forecast area, with the
most potent of which seems to come late Friday into Saturday. Based
on the main deterministic models, the upper ridge over the western
CONUS only becomes more pronounced with time and we could see
ourselves seeing this cool period linger into next week with
increasing rain chances.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1213 PM CDT Mon Jul 15 2024

VFR conditions likely through the period with passing clouds of
6000 to 15000 ft. A front continues to slide through, bringing
a switch to northwesterly winds and possibly a few showers and
storms this afternoon into this evening, with the highest
chances being at OMA in the 21-00Z window. However, latest
guidance continues to suggest the highest chances will stay
east, so did not include mention at this time. Also can`t
completely rule out some spotty showers overnight. Otherwise,
winds should largely remain under 12 kts and then become more
northeasterly late this evening and overnight.

&&

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

&&

$$

DISCUSSION...Petersen
AVIATION...CA