995
FXUS63 KOAX 041122
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
622 AM CDT Thu Jul 4 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms are expected to develop
  across far eastern Nebraska and Iowa this afternoon. A storm
  or two may be strong to severe, though the bulk of this
  activity should be east and south of the region.

- Another system will bring the chance for scattered strong to
  potentially severe thunderstorms Saturday evening.

- Ridging out west will largely keep things drier next week,
  though occasional chances for isolated afternoon thunderstorms
  will be possible.

&&

.DISCUSSION...
Issued at 304 AM CDT Thu Jul 4 2024

     Today and Tomorrow...

A cold front currently extending from central South Dakota into
central Nebraska is expected to sweep across the region late
this morning into early this afternoon. By noon, this front
should roughly be in line with the Missouri River. By this time,
scattered showers and thunderstorms are expected to begin
developing along and head of the front. Modest instability on
the order of 1000-2000 J/kg and bulk shear ranging from 50 to 60
knots will help these storms organize fairly quick. With the
progressive movement of this front, activity should quickly push
east of the region by mid-afternoon. Nonetheless, there will be
a period this afternoon, likely between noon and 4 PM, where
scattered strong thunderstorms may develop (40 to 50 percent
chance of rain), primarily across southwest Iowa. The primary
hazards with these storms will be hail up to the size of
quarters and wind gusts up to 60 mph.

Behind this front, there will be some residual instability due
to steep lapse rates aloft. As such, there is a low chance (20
percent) of isolated showers developing across northeast
Nebraska between 3 PM and 10 PM this afternoon and evening. Any
convection that is able to develop will be diurnally driven and
should dissipate shortly after sundown.

Tomorrow, though the front should be well to the east and south
of our area, the upper-level disturbance will still linger over
the northern Plains and upper Midwest. This will maintain steep
lapse rates aloft via cold air advection. As such, there will be
enough instability to again result in diurnally driven showers
developing across northeast Nebraska and into west-central Iowa.
The coverage, if these develop, will be isolated (any given
location seeing a 15 to 25 percent chance of rain).

     Saturday and Sunday...

The upper level pattern beginning this weekend will favor
ridging over the western CONUS. As such, northwesterly flow
aloft will prevail over the Plains. To our northwest, a
shortwave trough from Alberta will dive southeast over the
central CONUS. At the surface, a cold front is expected to
stretch somewhere from central South Dakota into central
Nebraska by midday on Saturday. The airmass ahead of the front
is expected to destabilize by the afternoon, with CAPE ranging
from 1500 to 2500 J/kg. As such, scattered thunderstorms (40 to
50 percent chance of rain) are expected to develop across
eastern Nebraska by early afternoon. With bulk shear likely
exceeding 40 knots, convection that is able to develop and
mature will likely become organized to some degree, bringing the
threat for strong to severe thunderstorms for much of the area.
While there are still some questions with regards to when
storms will initiate and the mode of convection that will be
favored, confidence is growing in scattered strong thunderstorms
traversing the region Saturday afternoon and evening.

There are some slower model solutions that suggest the front
will stall across southeast Nebraska into south-central Iowa. As
such, a potential second day of thunderstorms would be possible
Sunday afternoon across portions of southeast Nebraska and
southwest Iowa. These storms, however, are not expected to be
severe at this time should they develop in our area.

     Monday through Wednesday...

The ridge that is forecast out west is expected to amplify next
week, pushing disturbances diving southeast out of Canada east
of our area for the most part. This will keep conditions
seasonal and dry, with highs in the mid to upper 80s.
Nonetheless, there is still a signal amongst medium-range
guidance that suggest embedded low-amplitude disturbances may
periodically traverse the northern Plains. Should PVA ahead of
these disturbances coincide with peak diurnal heating across our
area, isolated thunderstorms may develop. Uncertainty in timing
and magnitude of these disturbances precludes any further
discussion on specific days of concerns. The main takeaway for
this part of the discussion is that though next week will
likely be much drier than the last few weeks, there will still
be a day or two with low end precipitation chances.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 622 AM CDT Thu Jul 4 2024

A cluster of thunderstorms has recently developed over south-
central NE within a zone of locally stronger instability and
minimal capping, per objective analysis. There is a fair amount
of uncertainty in how that convection will evolve this morning
given the poor handling of it by the models, and that
instability decreases with eastward extent into eastern
Nebraska. For now, -TSRA will not be included in the forecast.
However, TEMPO groups for -SHRA will be maintained. The forecast
will indicate prevailing VFR conditions with winds increasing to
12+ kt by late morning at KOFK, and early to mid afternoon at
KOMA and KLNK. The winds are expected to diminish by around 8 PM
(05/01z).



&&

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

&&

$$

DISCUSSION...Darrah
AVIATION...Mead