SPC Apr 7, 2020 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook
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Day 2 Convective Outlook NWS Storm Prediction Center Norman OK
Scattered strong to severe thunderstorms are possible over parts of
the Ohio and Tennessee Valleys on Wednesday evening and into the
overnight. Large hail, damaging gusts, and perhaps a couple of
tornadoes are the primary hazard. ...Synopsis...
A rather complex mid/upper-level pattern will prevail over the CONUS
on Wednesday into Thursday morning. An upper low off of the southern
CA coast Wednesday morning is forecast to drift northeastward into
portions of the Southwest by the end of the period. Meanwhile, a
northern stream shortwave trough will amplify and dig southeastward
into portions of the central/northern Plains and the upper Great
Lakes. Ahead of these features, multiple streams of enhanced
midlevel west-northwesterly flow are forecast from the Ohio Valley
into the Mid Atlantic, and also from the Arklatex region into the
Southeast. At the surface, a cold front will move quickly
southeastward from the northern Plains into portions of the
OH/TN/lower MS Valleys by Thursday morning, while a weaker front
will move southeastward from the Mid Atlantic into the Carolinas. ...Mid MS Valley into portions of the OH/TN Valleys...
The primary severe threat is expected to develop near or after 00Z
along the southeastward moving cold front as it advances into
portions of the OH/TN/Mid MS Valleys. Steep midlevel lapse rates
atop increasing low-level moisture will result in moderate
destabilization spreading as far northeast as the mid MS Valley,
with at least weak destabilization spreading into portions of the OH
Valley ahead of the front. Increasing deep-layer flow/shear into the
evening will support organized convection along the front. With
deep-layer shear vectors oriented at least somewhat orthogonal to
the frontal boundary, an initial discrete or semi-discrete mode is
possible, with a corresponding risk of large hail (potentially
significant) and damaging wind, and perhaps a couple of tornadoes in
areas where more substantial low-level moisture return can occur.
Some upscale growth is possible Wednesday night, at which point
damaging wind would likely become the primary threat. The magnitude and coverage of the severe threat, and also the
northeastern extent of the threat, will be highly dependent on the
amount of moistening and destabilization that can occur ahead of the
front by Wednesday evening, and considerable spread remains
regarding these details in the model guidance. A corridor of higher
severe probabilities may eventually be needed in future outlooks
once there is greater confidence in the magnitude of destabilization
across this region. ...Mid Atlantic into the Carolinas...
Lingering morning convection may pose some marginal wind risk across
portions of the Mid Atlantic, though this is highly uncertain. As
the weak front moves southeastward through the day, thunderstorm
redevelopment is possible across portions of VA/NC along the
boundary, and potentially into upstate SC coming off of the higher
terrain. There is considerable spread in model guidance regarding
the magnitude of destabilization and coverage of thunderstorms in
this area, but with sufficient deep-layer flow/shear across this
region, any substantial destabilization would result in a
conditional risk of severe thunderstorms capable of hail and
damaging wind. ...TX...
While large-scale ascent will likely be nebulous at best during the
day across portions of central into south TX, weak capping and the
influence of subtle features within the subtropical jet stream may
support at least isolated storm development, with a conditional risk
of severe wind/hail. There will also be a conditional risk of
development into portions of northeast TX late Wednesday night along
the cold front. ..Dean/Dial.. 04/07/2020 

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