404
ACUS48 KWNS 030901
SWOD48
SPC AC 030900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Fri May 03 2024

Valid 061200Z - 111200Z

...SEVERE WEATHER OUTBREAK POSSIBLE ON D4/MON...

...DISCUSSION...
A multi-day period of organized severe thunderstorm potential
appears likely across parts of the central to eastern CONUS next
week, beginning on Day 4/Monday across the Plains, and continuing
through at least Day 6/Wednesday.

...Day 4/Monday...
A negatively tilted upper trough will eject northeastward over the
northern/central Plains on Monday. Pronounced low-level mass
response will encourage rich low-level moisture to advect northward
over the southern/central Plains, as a surface low rapidly deepens
over the northern High Plains. Strong deep-layer shear and at least
moderate instability are expected to be in place ahead of a surface
dryline extending across the southern/central Plains.

Thunderstorms will likely erupt along the length of the dryline by
late Monday afternoon from southern NE into central KS and
north-central OK. Supercells are likely to be the dominant mode
initially given the strength of the deep-layer shear. Both very
large hail and tornadoes will be possible with these supercells as
they spread eastward across the southern/central Plains through
Monday evening. With a southerly low-level jet forecast to
strengthen to at least 50-60 kt Saturday evening, a corresponding
rapid increase in low-level shear will likely support a continued
threat for tornadoes with any discrete convection. Some of these
tornadoes could be strong. The severe threat will likely continue
Monday night with eastward extent across the Plains, before
convection possibly weakens some towards early Tuesday morning.
Given increased confidence in high-end severe potential, a 30%
severe area has been introduced from parts of southern NE into
central KS and north-central OK.

...Day 5/Tuesday...
The large-scale upper trough/low is forecast to gradually occlude
over the northern Plains on Tuesday. But, an enhanced mid-level jet
and embedded vorticity maximum will likely overspread parts of the
Upper Midwest, mid MS Valley, and OH Valley through Tuesday evening.
An expansive warm sector will likely be in place across these
regions ahead of a surface cold front/dryline. Robust convection
should develop along/ahead of these boundaries through the day.
Sufficient instability and deep-layer shear will likely exist to
support organized severe thunderstorms, including supercells posing
a threat for all severe hazards. The northeastward extent of the
warm sector remains somewhat uncertain into the OH Valley. Still,
some severe risk will probably persist into Tuesday evening/night
with eastward extent across the mid MS Valley and lower OH
Valley/Midwest. Expansion of the 15% severe area may be needed in
later outlooks, pending better model agreement and increased
confidence in the eastward extent of rich low-level moisture and
related instability.

...Day 6/Wednesday...
The upper trough/low should gradually evolve eastward across the
northern Plains on Wednesday. While there are still some differences
in model guidance regarding the evolution of an embedded shortwave
trough, there appears to be enough agreement in the synoptic pattern
to include a 15% severe delineation for Wednesday for parts of the
southern Plains into the ArkLaTex/Ozarks and towards the mid MS
Valley. Across these areas, strong instability is forecast to
develop east of a front/dryline. With enhanced mid-level flow
persisting with a westerly mid/upper-level jet, organized severe
thunderstorms should once again develop Wednesday afternoon.
Supercells posing a threat for all severe hazards may occur. The
northern/eastern extent of the severe threat is unclear, as the
convection from Tuesday may tend to limit better low-level moisture
return into the OH/TN Valleys. Depending on model trends over the
next few days, the 15% severe area may need to be expanded to
include these regions.

...Day 7/Thursday and Day 8/Friday...
Some severe threat may continue on Thursday from parts of TX into
the lower MS Valley/Southeast, generally along/south of a front and
any convection that develops Wednesday. Too much uncertainty
currently exists to include a 15% severe area at this time, but
trends will be monitored. A severe risk also appears possible next
Friday across the same general regions, but confidence in the
placement of the front and convection is even lower than Thursday.

..Gleason.. 05/03/2024