SPC 1300Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0747 AM CDT Tue Oct 20 2020

Valid 201300Z - 211200Z


Severe storms are not expected through tonight.

In mid/upper levels, broadly cyclonic flow will continue to dominate
the northern 1/2-2/3 of the CONUS, interspersed with several mostly 
minor shortwaves.  The strongest shortwave trough -- apparent in
moisture-channel imagery initially over the northern High Plains of
eastern MT/WY -- will assume more-negative tilt today.  By 00Z, the
trough should extend from northern/eastern ND across southwestern
MN, before ejecting northeastward across the upper Mississippi
Valley, WI, and Upper MI late overnight.  Meanwhile, a slow-moving
mid/upper trough in the subtropics will continue to spread vorticity
lobes and maxima across much of FL and southern GA, combining with a
residual low-level baroclinic zone and a moist-weakly capped
low-level environment, to support general thunder potential from FL
to the eastern Carolinas.

At the surface, a wavy/quasistationary frontal zone was analyzed
from offshore of the Carolinas across northern FL and ear the
northern Gulf Coast, becoming diffuse across southeast TX.  This
boundary will move little through most of the period, except for
minor mesoscale oscillations.  A cold front was drawn from the
Adirondacks southwestward through a weak low between CVG-SDF, to
near MEM, becoming quasistationary to weakly warm frontal over
central AR to central/southwest TX.  The western segment of this
boundary should move northward as a warm front through the period,
across parts of west/north TX into southern/central OK.  

Isolated to widely scattered thunderstorms are expected mostly west
and north of the latter front, in a zone of largely elevated
buoyancy.  Convection will be supported by warm advection, moisture
transport, and isentropic ascent to LFC, amidst weak CINH.  With
modest low/middle-level lapse rates, and strongest flow aloft
displaced more poleward, the shear/buoyancy parameter space should
remain insufficient for an organized severe threat.

..Edwards/Leitman.. 10/20/2020

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