-- Discussion containing changed information from previous version are highlighted. --
164
FXUS63 KOAX 131051
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
551 AM CDT Thu Jun 13 2024

.KEY MESSAGES...

- It will be hot south of Interstate 80 on Thursday, with heat
  index values of 100 to 107. Additional hot conditions are
  likely on Sunday and Monday, when the heat index may once
  again approach 105.

- This afternoon and evening brings another chance for
  thunderstorms, this time generally south of Interstate 80. If
  storms develop, they could quickly become severe with damaging
  wind, large hail, and an isolated tornado mainly in the 3 PM
  to 7 PM time frame.

- A cluster of storms will march east from western Nebraska
  Friday night, bringing gusty winds and flooding chances into
  the overnight hours.

- Details on specific timing and location are not yet clear, but
  there are daily storm chances Saturday into next week with
  several periods capable of producing strong to severe storms
  and flooding.

&&

.DISCUSSION...
Issued at 404 AM CDT Thu Jun 13 2024

Today:

Water vapor imagery this morning depicts zonal flow with the main
mid/upper jet located along the US/Canada border with a pair of
shortwaves in the western Nebraska/eastern Wyoming region. A
recent surface analysis places a frontal boundary along the
NE/SD border, with a local surface pressure minimum in far
northwestern Nebraska while a peak moisture/heat axis lies in
far eastern Nebraska into southwestern Iowa. Convergence at 700
mb on the northern fringe of the low-level jet extending from
north-central Nebraska into south-central SD will result in
showers and storms moving ESE through mid-morning that could
clip northeast Nebraska.

Through the rest of the morning, the aforementioned front along the
NE/SD border will sag to the south, finding itself extending through
southeast Nebraska and southwest Iowa by the afternoon hours. Recent
model runs have this front placed farther south by around 2-3
counties compared to yesterday`s runs, but nonetheless, convergence
along this boundary will help pool moisture and increase
temperatures for highs to reach 95 to 99 degrees and heat
indices 100 to 106 (thus leading to the continued Heat
Advisory). In addition to the heat, the convergence will also
result in plenty of instability and shear (2000-3500 ML CAPE and
30-35 kt 0-6 shear) to provide some form of convective
initiation in southeast Nebraska and southwest Iowa this
afternoon around 4 PM. Storms that do form in the vicinity of
the boundary will have the benefit of steep low-level lapse
rates and increased ambient vorticity, signaling that there is
a tornadic threat as storms pull themselves together. The ample
boundary parallel shear vector and steep mid-level lapse rates
point to hail and wind being the primary threats when storms
begin to grow upscale. All in all, the storm threat for the
forecast area largely lies between 3 PM and 7 PM, with any
convection that does form quickly scooting off to the south and
east by the later evening hours. one curiosity to watch for is
forecast hodographs in northeast Kansas showing left-split
storms being favored, and could make for interesting radar
imagery.

Friday through Sunday:

Friday and Saturday is expected to see the previous day`s front that
has sagged southward sap most of the instability from the area, with
an axis of CAPE setting up over the High Plains and western
Nebraska. We`ll see the active weather pattern for portions of the
forecast area take the form of an MCS that starts in western
Nebraska and moves east during the very late evening and overnight
hours. With instability in place for the forecast area, overall
strength of the MCS as it moves into the area remains in question
with the more likely hazard posed being heavy rain and a stray gust
of strong wind. This activity is expected to be invigorated during
the late morning and afternoon by a compact shortwave ejecting ENE
from northeast Colorado. The combination of the lingering MCS from
the early morning hours and this compact shortwave will provide the
forecast`s best chance at seeing area-wide rainfall, with severe
potential being left up to our ability to destabilize after the
morning MCS dissipates or pushes east. Flooding may end up being the
most likely outcome with the stronger forcing for ascent and
saturated soils from the morning. Highs for Friday will be slightly
cooler in the upper 80s while Saturday sees areas of southeast
Nebraska climb into the lower 90s.

Sunday and Beyond:

By Sunday and Monday, deterministic forecast evolution begin to
diverge, with the main uncertainty stemming front the orientation of
southwesterly flow that we`ll find ourselves in and as a result a
strung out boundary south of the upper jet. What does appear more
likely is the return of warmer temperatures, with the current
forecast for both days climbing back into the low-to-mid 90s.
Continued rain chances are forecast as healthy moisture
convergence sets up in a line from eastern Colorado to central
Wisconsin. If storm do end up being widespread through this
period, repeated rounds of rain could spell increased flooding
chances as the pattern wears on well through the week and
towards next weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
-- Changed Discussion --
Issued at 548 AM CDT Thu Jun 13 2024

VFR conditions are expected through the forecast period with a
few passing mid/high clouds. Surface winds will become
northeasterly early in the period with gusts this afternoon
around 20kts. There is a chance of thunderstorms across far
southeast Nebraska between 21-00z but confidence is high that
these will remain south of the terminals.
-- End Changed Discussion --

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory from noon today to 7 PM CDT this evening for
     NEZ068-088>093.
IA...Heat Advisory from noon today to 7 PM CDT this evening for
     IAZ090-091.

&&

$$

DISCUSSION...Petersen
AVIATION...Kern