SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 PM CDT Mon Jun 20 2022
Valid 202000Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SD...SOUTHEAST ND...AND NORTHWEST/WEST-CENTRAL MN...
...SUMMARY...
Scattered to numerous severe thunderstorms are likely across the
northern Great Plains through this evening. Destructive wind gusts,
very large hail, and a couple tornadoes are possible.
...20z Update...
The ongoing outlook remains on track and no changes have been made
with the 20z update. A cluster of severe thunderstorms within Severe
Thunderstorm Watch 393 is currently moving into the Nebraska
Panhandle. This activity is showing some characteristics toward
upscale development recently. With time, this activity may develop
into a bow capable of producing a swath of intense, damaging gusts
as it tracks northeast into central SD. Additional thunderstorm
development is expected over the next few hours across parts of the
eastern Dakotas/northwest MN within the baroclinic zone and ahead of
a stalled front. This activity also will pose a threat for intense
gusts and large hail. For additional information on short term
severe potential, reference MCD 1233. More forecast details can be
found in the previous outlook discussion below.
..Leitman.. 06/20/2022
.PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Jun 20 2022/
...Northern Great Plains...
A vigorous shortwave trough near the UT/ID/WY border area will eject
northeast into ND tonight, around the northwest periphery of a
closed high over the Mid-South. Attendant mid-level jet will
strengthen as it spreads from the central Rockies towards the Red
River Valley. A wavy surface front extending southwest from a
primary cyclone over northwest Ontario will move little today, and
then begin to accelerate eastward tonight in response to the
ejecting mid-level trough and convective outflows. A plume of upper
60s to lower 70s boundary-layer dewpoints will be maintained along
the front from north-central/northeast SD and ahead of it across MN.
The dryline should effectively mix into south-central SD through
central NE where mid to upper 90s surface temperatures become
common. Beneath steep mid-level lapse rates, the largest MLCAPE of
2500-4000 J/kg should become established across MN into the eastern
Dakotas, with a bent-back plume of moderate buoyancy extending
southwest along and to the cool side of the surface front into the
NE Panhandle.
Scattered thunderstorms are expected to develop by mid afternoon in
advance of the ejecting mid-level trough, within the post-frontal
environment from eastern WY into the NE Panhandle. Convection will
subsequently spread northeast across the Dakotas, as well as likely
develop separately along the baroclinic zone over the Red River
Valley through early evening. Vertical shear will be strongest along
and west of the stalled front, especially within the strengthening
500-mb southwesterly jet. Thus, the best chance for long-track
supercells with significant severe hail amid highly elongated and
nearly straight-line hodographs should be across northwest NE to
central SD. As this activity approaches larger buoyancy during the
evening, and likely impinges on downshear convection along the
front, multiple MCSs with sustained bowing segments will probably
develop, increasing the threat for severe wind gusts, some of which
may reach 80-90 mph. Greater tornado potential is more nebulous, but
a focused corridor for a couple tornadoes is apparent across
north-central SD and southeast ND into northwest MN with any
supercells/bows along this portion of the initially stalled front.
Overall severe potential should diminish overnight through a
combination of extensive convective overturning and increasing
warm-sector MLCIN.
...Central/south FL...
Scattered pulse thunderstorms will again develop along sea breezes
this afternoon within a large buoyancy environment characterized by
near 3000 J/kg of MLCAPE. Weak vertical shear will limit potential
for more organized convection, but localized damaging downbursts
will be possible in the strongest cells.
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