899
FXUS63 KOAX 301120
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
620 AM CDT Sun Jun 30 2024

.KEY MESSAGES...

- Flooding continues on the Missouri River below Decatur through
  the coming week.

- Tonight through Tuesday night will feature multiple rounds of
  thunderstorms. Severe thunderstorms are possible,
  particularly Monday evening through Tuesday evening, with very
  heavy rain possible during this time frame as well.

- Thunderstorms are possible on Independence Day, but overall
  confidence is low, and thunderstorm potential may change based
  on minor changes with speed of the storm system.

&&

.DISCUSSION...
Issued at 331 AM CDT Sun Jun 30 2024

.Today and Tonight:

A surface high located over central NE early this morning will
build east through the mid MO Valley today in response to a
deepening lee trough over the northern High Plains.
Strengthening warm advection on the backside of the departing
high will contribute to increasing clouds this morning with a
few showers possible this afternoon across portions of eastern
NE. Highs will be in the mid 70s.

Tonight, the movement of a weak shortwave trough into the
northern Plains will induce a 40-45 kt low-level jet across KS
and NE. Moisture and warm-air advection occurring along that
feature will contribute to the development of numerous showers
and thunderstorms late tonight into Monday morning across the
area.

.Monday and Monday Night:

Another shortwave trough will traverse the northern Plains and
mid MO Valley with an associated surface low developing from
southwestern into central NE by Monday evening. Meanwhile, a
warm front, reinforced by early-day showers and thunderstorms,
will concurrently lift through central into eastern NE, with
moderate to strong instability developing to the south and west
of the boundary.

Model soundings suggest that a cap may remain in place across
eastern NE through much of the day with the 30/00z CAMs almost
unanimously indicating thunderstorm development to our west, in
closer proximity to the surface low. By Monday evening into
Monday night, those storms are likely to spread into our area
with the parameterized-convection models indicating a pronounced
QPF signal across northeast NE and west-central IA, in closer
proximity to the stronger height falls attendant to the
shortwave trough. Vertical shear will be rather strong, so all
severe weather hazards appear possible, even with the event
occurring during the evening/nighttime hours. Furthermore, the
presence of an unseasonably moist inflow air mass will support
the potential for excessive rainfall, which could lead to flash
flooding and the exacerbation of ongoing river flooding.


.Tuesday and Tuesday Night:

A vigorous shortwave trough is forecast to progress through the
northern Plains and mid MO Valley with an associated cool front
moving through the area. It remains uncertain whether any of
Monday night`s storms will persist into Tuesday morning and slow
the destabilization process ahead of the front. However, the
models suggest that a strongly unstable air mass will
materialize by afternoon as temperatures warm into the upper
80s to low 90s. In fact, heat indices could approach 100-105
across portions of southeast NE and southwest IA by late
afternoon/early evening.

The combination of increasing height falls ahead of the
shortwave trough and sustained convergence along the front is
likely to yield scattered thunderstorm development during the
afternoon and evening hours as any residual capping is removed.
Vertical shear will remain seasonably strong and supportive of
organized storm modes capable of all severe weather hazards,
including heavy rain and potential flooding.


.Wednesday and Thursday:

The above-mentioned front is expected to temporarily stall
across KS and MO Wednesday before lifting back north into our
area Wednesday night and Thursday ahead of a shortwave trough
amplifying over the north-central U.S. Wednesday looks dry with
increasing shower and thunderstorm chances Wednesday night into
at least Thursday morning. Precipitation chances on Thursday
afternoon and evening will be dependent on the speed at which
the surface front moves through the area. Severe weather and
heavy rain potential remains uncertain owing to model
differences in the timing/movement of the surface front and the
associated mid-level system.


Friday and Saturday:

The global models indicate a fairly strong midlevel trough
centered over MN/WI Friday with some signal for shower activity
across eastern NE and western IA within the cooler, post-
frontal environment. Saturday currently looks drier.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 615 AM CDT Sun Jun 30 2024

A high pressure over eastern Nebraska is keeping winds generally
under 5 knots this morning. By 17Z as the high shifts east,
winds will strengthen to 5 to 10 knots and generally prevail out
of the southeast. After 08Z tonight, scattered showers and
thunderstorms are expected to develop across eastern Nebraska,
potentially impacting all TAF sites. While just outside of the
TAF period, MVFR and IFR ceilings will be possible tomorrow
morning. These will likely be included in a subsequent TAF
issuance.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.

&&

$$

DISCUSSION...Mead
AVIATION...Darrah