SPC Jun 28, 2020 0100 UTC Day 1 Convective Outlook

SPC 0100Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0759 PM CDT Sat Jun 27 2020

Valid 280100Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL HIGH PLAINS...

...SUMMARY...
Severe thunderstorms with large hail and wind damage will be
possible this evening across parts of the central and northern High
Plains. A marginal severe threat will exist from parts of the
central Plains eastward to the Mid-Atlantic and in the Southeast.

...Central High Plains...
The latest water vapor imagery shows a subtle shortwave trough over
the central Rockies. Scattered thunderstorms are located just ahead
of the trough from eastern Colorado into southwest Nebraska. This
convection is located on the western edge of a pocket of moderate to
strong instability. The RAP shows MLCAPE in the 1500 to 2500 J/kg
range across far eastern Colorado and western Kansas. Due to the
instability, the ongoing cluster of storms is expected to be
sustained for much of the evening. RAP forecast soundings across
much of the central Plains show moderate deep-layer shear and steep
mid-level lapse rates. This should be enough for supercell
development. Although supercells will be possible in areas where
parameters are locally most favorable, multicell will be the more
common storm type. For this reason, wind damage will be the primary
threat but hail could occur with the stronger updrafts.

...Central Plains/Mid Mississippi Valley/Ohio Valley/Mid-Atlantic...

The latest water vapor imagery shows a west-to-east flow pattern
across much of the central and eastern U.S. A subtle shortwave
trough is evident over eastern Missouri. Ahead of this feature, a
couple clusters of strong to severe thunderstorms are ongoing. The
first is in eastern Missouri and the second is from southern Indiana
into northern Kentucky. The airmass in these two areas is moderately
unstable according the RAP, with MLCAPE in the 1500 to 2500 J/kg
range. Regional WSR-88D VWPs generally have 0-6 km shear in the 20
to 30 kt range suggesting storm type will remain multicell. As
low-level lapse rates remain steep over the next hour or two, a few
damaging wind gusts will be possible. A marginal severe threat will
also exist further east into the Ohio Valley and Mid-Atlantic but
cell coverage should remain very isolated.

...Northeast Alabama/Georgia/South Carolina...
The latest surface analysis shows an area of high pressure to the
east of Florida with southerly flow to the west of the high across
much of the Gulf Coast region. A moist airmass is located across the
Southeast with dewpoints mostly from the upper 60s to the mid 70s F.
This is resulting in moderate to strong instability across much of
the region. Although deep-layer shear is relatively weak, low to
mid-level lapse rates are steep. This suggests that a marginal wind
damage threat will exist with the stronger multicells or pulse
storms.

...Northern Rockies/Northern High Plains...
The latest water vapor imagery shows an upper-level trough over the
Pacific Northwest with west-southwesterly mid-level flow over the
northern Rockies and northern High Plains. Ahead of the trough, a
moist airmass is in place across the northern Rockies and northern
High Plains the RAP is analyzing SBCAPE in the 1000 to 2000 J/kg
range. Scattered thunderstorms are ongoing on the northern edge of
the stronger instability from southwest Montana into north-central
Montana. Regional WSR-88D VWPs across this area show 0-6 km shear
generally from 45 to 55 kt suggesting the environment will support
supercells and organized multicells this evening. The greatest
severe threat should exist in central and northern Montana where the
combination of parameters is maximized. Isolated large hail and wind
damage will be the primary threats.

..Broyles.. 06/28/2020

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from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_0100.html