SPC Jul 15, 2020 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0242 AM CDT Wed Jul 15 2020

Valid 171200Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE DAKOTAS INTO WESTERN MN...

...SUMMARY...
Severe thunderstorms are expected across portions of the northern
Plains on Friday afternoon and evening. At this time, damaging wind
gusts and hail appear to be the primary hazards associated with this
activity.

...Northern Plains vicinity...

An upper ridge centered over eastern portions of the northern Plains
will quickly shift eastward on Friday as a shortwave trough over the
northern Rockies ejects eastward across the Dakotas. A second
embedded shortwave may also eject across the central Plains toward
the mid-MO Valley, but this is less certain. Regardless, a band of
strong westerlies will overspread the Plains while strengthening
southerly low level flow transports rich boundary layer moisture
northward. A surface low is forecast to be located over SK, with a
trailing cold front extending southward near the MT/ND border
vicinity by midday. Thunderstorms are expected to develop along the
surface boundary in a strongly sheared, very unstable airmass.
Supercell wind profiles will support organized cells capable of
large hail and strong gusts. If cells remain discrete, a couple of
tornadoes also will be possible near any developing surface low
along the frontal wave across eastern ND/SD into western MN.
Forecast guidance indicates a strong southwesterly low level jet
developing during the evening, and upscale growth into a bowing MCS
will be possible as convection spreads eastward into MN. 

Additional severe storms could develop further south across parts of
NE, as some guidance depicts another shortwave impulse ejecting from
the central Rockies into the central Plains. However, capping will
likely increase with southward extent and forcing will be weaker.
Given this uncertainty, will keep the slight risk confined to the
northern Plains where the stronger upper trough and surface front
will provide strong forcing and a more focused threat.

...Mid-South to the Mid-Atlantic...

A surface cold front will push offshore the Northeast and
Mid-Atlantic coast by around midday Friday. The southwestern extent
of the surface boundary will become ill-defined across the
Mid-South. However, a very moist and moderately unstable airmass
will be in place. Ongoing convection and cloud cover my limit strong
destabilization, and weakening vertical shear is expected as an
upper trough lifts northeast early in the period. Nevertheless, a
few strong storms could produce locally damaging gusts. This
somewhat limited parameter space and the uncertainty related to
ongoing convection at the beginning of the period, will preclude
severe probabilities at this time.

..Leitman.. 07/15/2020

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from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day3otlk_0730.html