521
FXUS63 KOAX 021115
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
615 AM CDT Tue Jul 2 2024

.KEY MESSAGES...

- Scattered strong to severe thunderstorms are expected this
  afternoon and evening across portions of southeast Nebraska
  and southwest Iowa. The primary hazard will be damaging winds,
  though a tornado or two cannot be ruled out.

- Additional rounds of thunderstorms will be possible Wednesday
  night and Thursday afternoon/evening. The storms on Thursday
  may also be on the stronger side.

- A third system will bring another potential round of rain and
  thunderstorms to the region this weekend. These storms are not
  expected to be severe at this time.

&&

.DISCUSSION...
Issued at 339 AM CDT Tue Jul 2 2024

     Today and Tonight...

Scattered showers along and south of the I-80 corridor are
expected to linger through mid-morning, particularly across
portions of southwest Iowa. By noon today, the primary upper
level disturbance will be centered over the northern High
Plains, with an embedded low-amplitude short wave ejecting out
into the central Plains at the same time. At the surface, a
low-pressure is expected to be somewhere in southeast Nebraska,
likely near US-80 south of I-80. South out of the low a cold
front will extend down into Kansas, with a warm front draped
across east-central Nebraska and into central Iowa. Sometime
between noon and 2 PM this afternoon, thunderstorms are expected
to initiate along these boundaries. While there may be a brief
period of time (within an hour or so of initiated) storms may
remain semi discrete, quick upscale growth into a line or bowing
segments is expected with shear vectors parallel the cold front.
A modestly unstable warm sector with SBCAPE ranging from 1500 to
2500 J/kg in addition to bulk shear magnitudes approaching 60
knots will help these storms become strong to severe within a
couple hours of initiating. By this time, storms will likely
extend along a line from Fairbury to Missouri Valley. Due to the
weak capping in version project across the warm sector this
afternoon, additional isolated strong to severe thunderstorms
will be possible ahead of this line. Over the course of the
afternoon and evening, these storms are expected to push east-
southeast across southeast Nebraska and southwest Iowa. The
primary hazard will be winds up to 70 mph, though hail up to
golf balls (particularly earlier in the afternoon) and a brief
tornado or two cannot be ruled out. The severe potential should
push out of our area by 8 PM, thought synoptic forcing for
ascent associated with PVA from the primary upper-level
disturbance may help showers and non-severe thunderstorms linger
across eastern Nebraska and western Iowa into the early
overnight hours.

     Tomorrow and Thursday...

A high pressure system is expected to traverse the central
Plains tomorrow during the day. As such, mostly sunny skies and
highs in the 80s will be on tap for much of the area. Wednesday
evening, thunderstorms are expected to develop off the high
terrain in portions of the central and northern High Plains.
These storms are expected to move into our area after midnight
tomorrow night in the form of a decaying MCS. These storms are
not expected to be severe at this time, though gusty winds and
small hail will be possible. Scattered showers and thunderstorms
may linger through the morning hours on Thursday.

On Thursday, another potent shortwave trough is expected to
eject out into the central Plains. A cold front will move
through eastern Nebraska and western Iowa sometime during the
afternoon/early evening hours. By mid-afternoon, scattered
thunderstorms are expected to develop along this front and push
to the east. With CAPE on the order of 1000 to 2000 J/kg and
bulk shear between 50 and 60 knots, strong to severe
thunderstorms will be possible again. Recent model runs do trend
this system a little more progressive than prior solutions. As
such, we may continue to see the primary risk for strong to
severe thunderstorms push east and south over the next couple
forecast cycles. But for now, the main region that may see these
stronger storms will be along and east of US-77. The primary
hazards with these storms will be hail up to quarters and wind
gusts up to 60 mph. The bulk of convection should push east into
Iowa and Missouri by 7 PM. However, with still some changes to
timing from model run to model run the last few forecast cycles,
the exact timing of these storms may be adjusted over the next
day or so.

     Friday through Tuesday...

Friday another high pressure is expected to build into the
region bringing mild weather and highs in the 70s. By the
weekend however, another trough is expected to traverse the
central and northern Plains bringing more unsettled weather. At
this time, there is enough difference in models runs to make it
difficult to pin down exact timing. Nonetheless, there will be
some chance for isolated to scattered thunderstorms across
portions of eastern Nebraska and western Iowa both days this
weekend. These storms do not appear to be severe at this time.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 607 AM CDT Tue Jul 2 2024

A frontal zone currently transects the forecast area, roughly
along a line from Albion to Sioux City. This front will slowly
move to the southeast over the course of the day. Ahead of this
front, winds will be southerly from 5 to 15 knots. Behind the
front, winds will become north/northwesterly at 10 to 20 knots.
This change in surface winds will take on the order of 1 to 2
hours as the surface front passes through. Scattered light
showers will persist this morning through 16Z along the I-80
corridor (KLNK and KOMA). Scattered thunderstorms are expected
to develop along and ahead of the front by 19Z (KLNK and KOMA).
A few storms may be severe with quarter sized hail and wind
gusts up to 65 knots.

&&

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

&&

$$

DISCUSSION...Darrah
AVIATION...Darrah