SPC 1730Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1132 AM CST Fri Nov 13 2020

Valid 141200Z - 151200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM FAR NORTHEAST
OK ACROSS NORTHWEST AR INTO SOUTHERN MO...

...SUMMARY...
Isolated severe thunderstorms may occur across eastern Oklahoma and
the Ozarks/Ark-La-Tex regions late Saturday afternoon and night.

...Synopsis...
A deep shortwave trough is forecast to move quickly across the
Plains and into the Upper/Middle MS Valley on Saturday. This
shortwave will be accompanied by a strong (i.e. 100 kt at 500 mb)
jet, which will likely extend from eastern KS through the middle MS
and southern OH Valleys, and into the Lower Great Lakes region early
Sunday morning. 

Surface cyclogenesis is anticipated ahead of this shortwave and
attendant jet streak. The resulting low is forecast to develop over
the mid MO Valley before then tracking quickly northeastward through
the Upper Midwest. An associated cold front will sweep
eastward/southeastward. By 00Z Sunday, this front will likely extend
from the low over central IA southwestward through western MO and
eastern OK. By 12Z Sunday, consensus of the guidance places the
front from Lower MI south-southwestward into western TN and then
back southwestward across the Lower MS Valley into the TX Hill
Country.

...Eastern Oklahoma/Ozarks/ArkLaTex...
Modest low-level moisture advection will be underway across the
southern Plains at the beginning of the period. Southwesterly
low-level flow will persist throughout the day from the southern
Plains into the Mid MS Valley, contributing to continued moisture
advection and the potential low 60s dewpoints into the Ozark Plateau
ahead of the front. Current observations place the low 60s dewpoints
in central TX, under north winds and weak cold advection. Early day
showers and cloudiness are also expected from northeast OK into
southern MO. As a result, there is some uncertainty whether low 60s
dewpoints will actually be able to advect as far north as the models
suggest.  

Whether or not this is enough low-level moisture to support severe
thunderstorms will also depend on the amount of heating the area
receives. Current consensus within the guidance is for overcast
conditions to hamper daytime heating, keeping temperatures in the
low 60s (perhaps even upper 50s across northwest AR and southern
MO). Given the resulting convective inhibition associated with those
surface temperatures, updrafts would likely struggle to maintain
depth and consistency, limiting the overall severe potential.

In contrast to the marginal thermodynamics, kinematic fields are
very supportive of organized storm structures with notable low-level
curvature and long hodographs. Any updrafts that are able to
maintain depth and consistency would likely pose a risk for damaging
wind gusts and tornadoes. The overall scenario is conditional on
destabilization but the strength of the wind fields merit upgrading
to a 5% tornado/15% wind Slight Risk.

..Mosier.. 11/13/2020

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