577
ACUS01 KWNS 021630
SWODY1
SPC AC 021628

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Tue Jul 02 2024

Valid 021630Z - 031200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHERN/CENTRAL IOWA...NORTHERN MISSOURI...NORTHEAST KANSAS...AND
SOUTHEAST NEBRASKA...

...SUMMARY...
Scattered to numerous damaging thunderstorm winds, a few tornadoes,
and occasional large hail appear most likely this afternoon and
early evening over parts of southern/central Iowa, northern
Missouri, and northeastern Kansas.

...Iowa/Missouri into Northeast Kansas and Vicinity...
Elevated thunderstorms with a marginal/isolated hail threat are
ongoing late this morning across eastern NE and southern IA in a
low-level warm advection regime. This activity is also being aided
by modest large-scale ascent associated with a subtle mid-level
vorticity maximum moving eastward over the central Plains. The
primary upper cyclone and related surface low will remain over
central Canada today, with a cold front extending southward over the
northern Plains/Upper Midwest and continuing southwestward into the
central Plains. An effective warm front extends northeastward from a
secondary surface low in north-central KS across northern MO into
southern IA. This boundary will likely serve as a focus for severe
thunderstorms this afternoon and evening as it attempts to lift
further northward into IA.

The 12Z sounding from TOP showed a very moist boundary layer, with
precipitable water values through the column greater than 2 inches
and somewhat steepened mid-level lapse rates. Robust daytime heating
of this airmass along/south of the front will likely aid the
development of moderate to strong instability by mid afternoon, even
though mid-level temperature remain somewhat warm. A belt of
stronger (40-55 kt) southwesterly mid-level flow associated with the
subtle central Plains shortwave trough will likely overspread the
frontal zone across IA and northern MO in the same time frame. With
sufficient veering/strengthening of the wind field with height
through mid-levels, around 35-50 kt of deep-layer shear is expected
to promote organized convection, including the potential for both
supercells and a bowing cluster.

Thunderstorms should intensify by early to mid afternoon near the
front across southeast NE/northeast KS into southern/central IA and
perhaps northern MO. If this initial development can remain at least
semi-discrete for a few hours, then sufficient low-level shear near
the warm front would support a threat for a few tornadoes. Isolated
severe hail may also occur with any sustained supercell. Otherwise,
upscale growth into an MCS by mid to late afternoon appears likely
given the mainly linear/frontal forcing and mid-level flow aligned
mostly parallel to the surface front. Scattered to numerous damaging
winds generally ranging 60-70 mph should become the primary severe
hazard by late afternoon and early evening across IA and northern
MO, but embedded QLCS circulations will also be possible. Convection
should tend to weaken later this evening as it approaches the MS
River and encounters a less unstable airmass.

...Southern/Central Plains...
Additional convection should develop along the front with
southwestward extent into KS and the southern/central High Plains.
Given a well-mixed boundary layer and steepened low-level lapse
rates with daytime heating, isolated to scattered severe/damaging
winds should be the main threat with this activity. Modest low-level
upslope flow in the post-frontal regime may encourage the
development of isolated supercells across parts of southeast CO and
vicinity. Occasional large hail and severe wind gusts may occur with
any intense convection that can persist, but confidence in a small
bowing cluster developing from this activity this evening remains
low. Other occasionally strong to severe convection may develop
southeastward from eastern WY into western NE this afternoon and
evening. Weaker instability across this region should keep the
overall severe threat rather isolated.

..Gleason/Thornton.. 07/02/2024

$$