SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0255 PM CDT Mon May 30 2022
Valid 302000Z - 311200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING ACROSS PARTS OF EASTERN SOUTH DAKOTA AND
ADJACENT SOUTHWESTERN THROUGH NORTH CENTRAL MINNESOTA...
...SUMMARY...
Numerous severe thunderstorms are forecast across parts of the
Northern Plains and Upper Mississippi Valley, with more scattered to
isolated activity southward into the central Plains today into
tonight. Large to giant hail, 60-80 mph gusts, and a few
long-tracked, intense tornadoes are possible.
...20Z Update...
Adjustments to the 10 percent probability/categorical thunderstorm
line across the Rockies into northern intermountain west vicinity
have been made in an attempt to better account for where cloud
cover/ precipitation and areas of stronger insolation are impacting
boundary-layer destabilization.
East of the Rockies, categorical and probabilistic lines have been
adjusted to account for the progression of synoptic and subsynoptic
features, primarily across the northern Great Plains.
Farther south, across the central Great Plains into mid/lower
Missouri Valley vicinity, severe probabilities have been adjusted
westward a bit, closer to where the latest Rapid Refresh suggests
that a southeastward advancing cold front will overtake a retreating
dryline after 01-02Z. It appears that this forcing may account for
the better potential for more substantive/widespread thunderstorm
initiation (south of the northern Great Plains/upper Mississippi
Valley vicinity), with large hail probably the primary potential
severe hazard.
..Kerr.. 05/30/2022
.PREV DISCUSSION... /ISSUED 1125 AM CDT Mon May 30 2022/
...A substantial threat for severe storms with all hazards is
expected this afternoon/evening from eastern South Dakota into
Minnesota...
...Eastern SD into MN though late evening...
A midlevel shortwave trough and associated 70-90 kt midlevel jet
will progress quickly north-northeastward from western KS/NE toward
the upper MS Valley by tonight. An associated 992 mb surface low in
central NE as of late morning will develop quickly
north-northeastward across eastern SD to near the ND/MN border by
early tonight. Scattered elevated storms, some with large hail,
will likely persist through the day in the warm advection zone to
the north of the warm front across eastern SD into southwestern MN.
However, the warm sector with mid-upper 60s dewpoints now across
eastern NE/western IA will spread northward during the day, with
increasing potential for surface-based storm development near and
just ahead of the surface cyclone and ejecting midlevel trough by
midday/early afternoon.
It appears the convection will begin as clusters by midday across
east/southeast SD, and expand quickly northeastward into
central/northern MN by late afternoon/evening. All hazards can be
expected with the surface-based storms during the afternoon, in an
environment favorable for fast-moving supercells. However, there
are some concerns about mixed convective mode/bowing segments given
potential storm interactions and strong forcing for ascent.
Deep-layer vertical shear will be quite strong (effective shear in
excess of 65 kt), with long hodographs and low-level, clockwise
curvature (effective SRH of 300-400 m2/s2). These wind profiles, in
combination with midlevel lapse rates greater than 8 C/km and MLCAPE
of 2000-3000 J/kg, will support the threat for a few long-tracked,
intense tornadoes and very large hail with any semi-discrete
supercells. As previously mentioned, there will also be some
potential for storm interactions and upscale growth into line
segments capable of producing significant outflow gusts up to 80
mph, given the very strong environmental wind profiles.
...IA/NE to KS/northern OK later this afternoon into tonight...
The larger height falls and stronger forcing for ascent will spread
northward toward eastern SD/MN through the afternoon/evening, but
the warmest portion of the elevated mixed layer will be east of the
dryline by late afternoon. Forcing for ascent will be focused in
the low levels from the dryline/cold front intersection southward
along the dryline, and isolated storm development may occur by late
afternoon/evening. Lapse rates aloft will not be ideal, given
fairly warm temperatures near 500 mb on the anticyclonic side of the
jet. Still, the storm environment conditionally favors supercells
with all hazards, given sustained storm development. Otherwise,
despite height rises overnight, the threat for convection with
occasional large hail/damaging winds will persist (especially toward
northeast KS) as the cold front overtakes the remnant dryline, and
with warm advection on the nose of a 50+ kt low-level jet.
...FL/south GA this afternoon...
Scattered sea breeze storms are expected this afternoon, skewed to
the western half of the FL Peninsula given low-level easterly flow.
Strong surface heating and moderate buoyancy could support isolated
wind damage with downbursts, as well as some hail.
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SRL3v6
