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866
FXUS63 KOAX 132309
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
609 PM CDT Thu Jun 13 2024

.KEY MESSAGES...

- Hot today with heat index values of 100 to 108. We could get
  hot again on Sunday with heat indices around 100 to 105.

- This afternoon and evening brings another chance for
  thunderstorms, this time generally across far southeast
  Nebraska and southwest Iowa. 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 319 PM CDT Thu Jun 13 2024

This afternoon - Tonight:

A weak boundary is dropping south across the area this afternoon
leading to an uptick in northeasterly winds as the front passes
south across our area. South of the boundary we have a very warm
and humid air mass with temperatures in the low 90s and dew
points in the 70s while to the north temperatures are in the 80s
with dew points in the mid 50s to low 60s. Areas in far southeast
Nebraska won`t see the front move through until after
temperatures will have already reached into the upper 90s with
heat indices in the 100 to 108 range this afternoon, so we have
a heat advisory for these counties in place through 7 PM.

We`ll see storm chances again this afternoon for far southeast
Nebraska and southwest Iowa, though CAMs show the better
chances for storms staying to our south over Kansas and
Missouri. We will have a very ripe environment for strong storms
to develop south of the frontal boundary with ample moisture
and instability. Shear will be on the lower side, with only 30
to 35 kt of effective bulk shear, and very little low-level
shear. This indicates more of a pulse thunderstorm environment
if storms were to develop into our area, with a greater threat
for damaging winds and hail, and a very low threat for a
tornado. Storm potential should end by 11 PM this evening. as
the front moves completely south of our area.

Friday - Saturday:

Friday we see the transition in the upper-level flow pattern to
southwesterly flow with the approach of the trough that will
kick up the ridge to our east. Friday through Friday afternoon
will be dry but fairly toasty as temperatures climb into the
upper 80s. Dew points stay down in the mid 50s helping to keep
humidity manageable. Overall it won`t be a terrible day. We`ll
see a shortwave pass through central Nebraska during the
afternoon kicking off a few scattered showers that will spread
east through the afternoon. Model soundings show a significant
cap limiting the amount of surface-based instability and dry
layer near the surface that may limit the amount of rain from
these showers that actually make it to the surface.

Friday evening we`ll see an MCS develop out over western
Nebraska that will roll across central Nebraska overnight,
decaying as it progresses eastward into a more and more stable
environment. By the time it gets here, expect little more than
scattered showers and weak thunderstorms. The slow moving nature
of these showers as well as PWAT values in excess of 1.7 inches
could lead to localized flooding concerns in areas where showers
and storms start to train over the same areas. WPC has us under
a marginal risk for excessive rainfall.

Shower and storm chances of 30-40% chance continue through
Saturday afternoon as the upper-level trough moves through. This
will bring a better chance for strong to severe storms as we
see a much more unstable environment develop with surface dew
points in the 70s ahead of the front that will move through
during the evening. Bulk shear of 50 to 60 kt appears likely
with 0-1 km SRH values in excess of 200 m2/s2 evident in the
NAM and 0-3 km SRH values in the GFS suggesting the potential
for strong to severe storms including supercells. Right now the
only limiting factor may be the lack of any sort of Cap which
would lead to more clustering of storms which could cause
convective development to become more linear very quickly. SPC
seems a bit concerned by uncertainty in the convective evolution
which may be influenced by remnant mesoscale features from
convection Friday night. If this clears the area, expect SPC to
ramp up the convective outlook and messaging. These storms
should be clear of our area by around midnight, but a few
showers could linger as late as 7 AM.

Sunday - Wednesday:

The southwesterly flow regime continues through midweek next
week bringing additional chances for showers and thunderstorms
which could be severe at times. We keep boundaries draped across
our area with dew points staying in the 60s to low 70s for the
most part, which provides ample moisture and instability for
strong storms to develop as shortwaves ride up across our area
from the southwest. Biggest concerns each day will probably be
wind and large hail, but tornadoes will probably be possible at
times when we can get enough low-level shear to develop.

One more thing to watch is the potential for repeated rounds of
rain which could lead to the potential for increased flooding
potential as the pattern wears on well through the week towards
next weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
-- Changed Discussion --
Issued at 609 PM CDT Thu Jun 13 2024

VFR conditions expected through the period with passing mid
clouds on Friday. A few pieces of guidance suggest some spotty
showers and isolated storms could develop Friday afternoon, but
confidence in this happening, much less one moving over a TAF
site, is rather low. Higher chances will move in after the end
of the period. Otherwise, current northeast winds will become
light overnight and pick back up out of the east/southeast
Friday morning, with speeds on either side of 10 kts.
-- End Changed Discussion --


&&

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

&&

$$

DISCUSSION...McCoy
AVIATION...CA