297
ACUS01 KWNS 011957
SWODY1
SPC AC 011956

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0256 PM CDT Mon Jul 01 2024

Valid 012000Z - 021200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE
NORTHERN PLAINS...

...SUMMARY...
Severe thunderstorms should occur this afternoon and tonight across
parts of the northern/central Plains, especially portions of
Nebraska and the Dakotas. Scattered severe/damaging winds, large
hail, and a few tornadoes all appear possible.

...20Z Updated...
A small general thunderstorm area was added to account for ongoing
convection over southern New England. This area is beneath the upper
trough, with steep lapse rates, and little inhibition. Continued
heating will support a few hours of shallow non-severe convection
through late afternoon.

The Marginal Risk area was reduced over parts of the southeast, as
much of the area is subsident. Any change of locally strong gusts
should be relegated to areas where upper 70s F dewpoints can
counteract the relatively warm temperatures aloft.

...Northern/Central Plains...
The severe risk area remains on track, with storms now developing
along the front over the northern High Plains as the upper trough
continues east. For more information see MCD 1503.

To the south, an impressive temperature gradient exists along the
warm front near the KS/NE border, with convection beginning to
develop over northwest KS and eastern CO where temperatures are hot.
Warming should spread north with the warm front later today into NE,
with increasing storm coverage over time. Any cell within the narrow
frontal zone may become supercellular, potentially thriving upon
both enhanced low-level shear and surface based warmth.

For more information, see forthcoming MCD 1504.

..Jewell.. 07/01/2024

.PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Jul 01 2024/

...Northern/Central Plains...
A notable upper trough across the northern Rockies will advance
eastward today over the northern/central Plains. Related low-level
mass response will encourage multiple surface lows to slowly deepen
across the northern/central High Plains. An occluded/cold front will
move eastward across the western/central Dakotas through this
evening, while a warm front attempts to lift northward across
northern KS into NE. Current expectations are for robust convection
to develop along both the front in the western Dakotas, and the
higher terrain of WY/CO as large-scale ascent associated with the
upper trough overspreads the warm sector. Low-level moisture will
remain more limited with northward extent into the Dakotas. But,
sufficient instability in a narrow corridor, along with strong
deep-layer shear, is still anticipated. Initial supercells over
western ND/SD should pose a threat for large hail, before convection
quickly grows upscale into a bowing cluster towards central ND/SD
with a greater threat for severe/damaging winds. With sufficient
ambient near-surface vorticity along the front, a brief tornado or
two also appears possible with initially more cellular development.
This activity should weaken with eastward extent tonight as it
encounters much weaker instability towards the MN border.

Initially high-based convection over central CO may pose an isolated
threat for severe wind gusts as it moves into eastern CO/western KS
and encounters a very well mixed boundary layer. The Marginal Risk
has been expanded westward and southward a bit in CO to account for
this potential. Otherwise, thunderstorms should eventually develop
and strengthen by late this afternoon along/east of a surface low
centered over northeast CO. Deep-layer shear will be strong enough
to support supercells, but convective mode may quickly become messy
as activity moves eastward along/near the northward-advancing warm
front in NE. Large hail may occur with any sustained supercell, and
sufficient low-level shear will be present along/near the warm front
to support a threat for a few tornadoes. Even so, a more
clustery/linear mode may become dominant fairly soon after initial
development. This would support a greater threat for severe/damaging
winds, and perhaps isolated gusts up to about 75 mph. Regardless of
continued uncertainty over what the dominant convective mode will
be, the severe threat will likely persist into eastern NE/western IA
this evening and tonight before thunderstorms eventually weaken.

...Southeast...
Scattered to numerous thunderstorms should develop this afternoon
along and south of a cold front draped east to west across parts of
the Southeast. Although mid-level flow and related deep-layer shear
will remain modest, steepened low-level lapse rates though daytime
heating and plentiful low-level moisture will easily support
moderate to strong instability. Occasional strong to damaging winds
may occur with the more robust cores and loosely organized clusters
as they move generally southward through the early evening before
eventually weakening.

$$