089
FXUS63 KOAX 012315
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
615 PM CDT Mon Jul 1 2024

.KEY MESSAGES...

- Severe thunderstorms and flash flooding will be possible this
  evening and overnight tonight. The primary severe hazard looks
  to be damaging winds,but there is potential for tornadoes and
  some hail. The most likely area to experience wind gusts
  greater than 75 mph or a tornado will be south and west of a
  line from Ord to Norfolk to Fremont to Lincoln to Beatrice,
  and the most likely time will be between 7 PM and midnight.

- Another round of strong to severe thunderstorms will be
  possible tomorrow afternoon, primarily across southeast
  Nebraska and southwest Iowa. All severe hazards will again be
  possible with the primary risk being damaging straight-line
  winds.

- Unsettled weather continues through the week and into the
  weekend, with almost daily chances for thunderstorms. The 4th
  of July features a good chance for thunderstorms, mainly
  focused between 10 PM Wednesday and 9 PM Thursday.

&&

.DISCUSSION...
Issued at 319 PM CDT Mon Jul 1 2024

There is a lot going on around the region at 3 PM. Much of the
local forecast area is chilly, locked in to low cloud cover with
temperatures in the upper 60s to mid 70s with a stiff southeast
breeze. However, we don`t have to look very far south to find a
zone of warm moist air lifting in this direction...and just a
bit farther south to find an area of very hot and muggy
conditions also lifting north. A very impressive warm front
extended from just north of Goodland to north of Hill City to
just south of Concordia to near Emporia KS. To the south,
temperatures in the upper 90s to lower 100s with dewpoints in
the upper 60s to middle 70s. In the 50 mile zone north of this
front, cloud cover clears and temperatures quickly climb into
the middle to upper 80s with dewpoints in the low 70s. And north
of that zone, the cool but increasingly moist boundary layer
airmass remains. Over the next 6 hours, this front will continue
to lift north, along with the substantial instability that
exists within the frontal zone. While there is a very strong cap
in place north of the front, it is likely to erode somewhat
into the evening. The question is just how much that cap will
erode, and if the intensity of boundary layer destabilization
will overcome any remaining semblance of the cap aloft. The
near-frontal zone...that 40-50 miles north of the true surface
front, will feature very large cyclonically curved hodographs in
the lowest 1km, with favorable deep layer shear for supercell
storm mode. Even if linear convection interacts with this
frontal zone as it moves in from the west, the high-end low
level and deep layer shear would seem to favor some development
of isolated intense wind gusts and tornadoes. Additionally, as
the night progresses, additional moisture will be advected over
the top of any stable layer in eastern NE and western IA,
developing increasing MUCAPE. Do expect the near-surface layer
to remain stable well to the north of that frontal zone, but the
thermal profiles may still allow for some momentum transfer to
the surface from storms with elevated inflow sectors.
Furthermore, as expected, the moisture content locally will
become quite impressive with PWAT of 2-2.5 inches across much
of the forecast area and substantial warm cloud depth. The LLJ
will continue to focus moisture influx into the local area with
at least some instability recharge over the top of any outflow
and frontal boundaries suggesting multiple rounds of
thunderstorms possible.

So what will happen. Well, there is high confidence in the
storms that have developed over extreme northwest KS this
afternoon continuing to cluster and build to the east northeast.
Additional near-frontal convection immediately in advance of
this cluster should favor at least some growth on the southern
fringes amidst the very unstable and strongly sheared near-
frontal zone. Believe that this cluster of storms will approach
the Albion and Columbus areas between 7 and 8 PM, and may
extend southward toward I-80 with eastward progression toward
places like Lincoln and Fremont by closer to 10 PM. This cluster
of storms appears to have damaging winds as the primary hazard,
although with some hail potential as well. The possibility of
significant (75+ mph) damaging winds is also there along with a
chance for some QLCS tornado development...and that chance seems
to be highest with southward extent of the line, closer to the
very unstable and highly sheared frontal zone. Some model
guidance has maintained a more northerly track to the abundance
of convection, but given the nature of the lifting frontal
zone, believe that this cluster will at least try to favor some
periods of eastward or even east southeastward propagation into
the instability axis...until it outruns the instability which
should happen with eastward progression across our forecast
area.

There is also the question of weather the northward lifting
frontal zone itself will foster isolated intense supercell
convection. There is currently an increasing cumulus field along
the front, and it seems to be a good chance for one or two
storms to develop along this front. Now, whether they are able
to move into our local forecast area is another question...but
if any isolated storms are able to develop in north central KS
and move northeast within the frontal zone long enough to
mature, would expect to see some enhanced tornado potential
prior to around 9 PM or so. The biggest question is if the cap
and inhibition are enough to limit that sustained storm from
developing.

Finally, as the night progresses, that initial cluster of storms
will lay out some semblance of a "cold pool" which looks likely
to act as a focus for further convective development near and
north of the boundary. As previously mentioned, some convective
recharge should allow for additional rounds of storms to develop
and move over the same areas, probably leading to isolated 3-5
inch rainfall amounts. There is still some uncertainty in the
exact location of this favored band of training, but have issued
a flood watch to encompass the parts of the forecast area with
the greatest chance for repeat thunderstorms and flash flooding.

Tuesday morning will probably feature showers and a few
thunderstorms lingering in the frontal zone, and perhaps some
lingering flooding concerns in that same area. Things become
more interesting by early afternoon as there should be some
heating in the warm sector producing surface based convection as
early as noon. Will also see some decent instability lingering
north of the surface front for several hours, so could thus have
a couple rounds of storms. The main focus will be on fresh
development between noon and 2 PM, probably in southeast NE into
southwest IA. The deep shear will be conducive to supercell
development, likely transitioning into clusters or bowing
segments. The low level shear should not be as impressive as
today, but may still suffice for at least a low end tornado
threat. The main hazard though will probably be damaging winds,
with at least a few hours of some potential for hail. As we get
deeper into the afternoon, by 4-6 PM, most all of this activity
should push east of the forecast area.

Dry conditions are expected until Wednesday evening when the
next short wave trough enters the Plains states. This should
support another round of storms across the region during the
overnight hours and then one more as the main trough axis and
front cross the region during the day on Independence Day. The
day as a whole should not be a constant rain-out, but with
periods of storms possible. The current indications are also
that the front will clear through the entire forecast area by
approximately 9 PM. And while that is very tight timing for the
many outdoor evening activities planned, please know that this
forecast is still a few days out and the exact timing is rather
uncertain. Here`s hoping for a fast front to clear natures
fireworks out of the area before dusk.

The first few days of the forecast have provided more than
enough to look at in terms of impactful weather, and the longer
term forecast has remained largely the same for now.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 615 PM CDT Mon Jul 1 2024

Line of strong to severe storms still on track to impact all TAF
sites, though still a few questions on exact timing with some
potential they linger for several hours. Should see a break with
perhaps some spotty -SHRA Tuesday morning before additional
strong to severe storms develop by early to mid afternoon.
Highest chances will be at LNK and OMA, but confidence is low on
if they`ll impact the sites, with some guidance suggesting the
higher chances will be off to the southeast. Otherwise expect
IFR to MVFR ceilings this evening, especially as storms move
through. Winds outside of storms should be southeasterly with
gusts of 20 to 30 kts, with storms perhaps bringing some 30 to
isolated 50+ kt gusts, most likely out of the west. Winds will
weaken behind the storms and eventually become northwesterly
with VFR conditions expected for the afternoon (outside of
storms).

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flood Watch through Tuesday morning for NEZ012-015>018-030>034-
     042>045-050>053-065>067.
IA...Flood Watch through Tuesday morning for IAZ043-055-056-069-079.

&&

$$

DISCUSSION...Barjenbruch
AVIATION...CA