SPC 1300Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0650 AM CST Tue Jan 05 2021

Valid 051300Z - 061200Z


Isolated thunderstorms may affect portions of the Carolinas today.

In mid/upper levels, a progressive and fairly amplified pattern will
continue, atop a generally dry and/or stable boundary layer.  This
pattern will keep rich theta-e shunted to lower latitudes and well
out over the Atlantic, precluding deep moist convection over the
bulk of the CONUS, with one possible exception noted below.  A
well-defined trough, arcing from ID south-southeastward across
northern AZ to northern Baja -- will shift eastward to the Great
Plains and southern Rockies by the end of the period, with a basal
shortwave/vorticity max digging across NM around 12Z tomorrow.  In
response, low-level pressure/height falls and related warm/moist
advection, will increase over the southern Plains through tonight,
but with insufficient moisture and lift for thunder until after the

Isolated thunder may accompany convection mainly across parts of
northern SC this afternoon.  A long, negatively tilted, mid/upper
trough is apparent in moisture-channel imagery from Lakes Superior/
Michigan across eastern portions of KY/TN to southeastern GA.  The
primary vorticity lobe now near CHA will shift east-southeastward
across SC today, beneath the left-exit region of a cyclonically
curved, 250-300-mb jet streak.  Associated large-scale ascent/
cooling in midlevels will steepen lapse rates enough to support
showers and isolated thunderstorms, with surface-based effective-
inflow parcels and minimal MLCINH possible by early/mid afternoon. 
Forecast soundings suggest equilibrium levels (EL) under the 500-mb
level but aloft of the -20 deg C isotherm, with surface-EL lapse
rates 6.5-7 deg C/km, and marginal but sufficient near-surface
moisture for around 50-200 J/kg MLCAPE.  Thunderstorm depth and
coverage should be greater offshore when the colder air aloft moves
over the Gulf Stream this afternoon and evening.

..Edwards.. 01/05/2021

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