SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0158 PM CST Sat Nov 14 2020

Valid 142000Z - 151200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
MISSOURI AND ARKANSAS...

...SUMMARY...
Thunderstorms may produce damaging winds and the threat of a few
tornadoes this evening into tonight over parts of Missouri and
Arkansas.

...20Z Update...
The only appreciable change to the ongoing forecast has been to
expand the Marginal/Slight risk areas a little westward in
central/western MO based on latest observational and short-term
guidance trends. It still appears likely that surface-based
convective initiation along/ahead of a cold front across this area
will occur after 00Z this evening. Both damaging wind gusts and a
few tornadoes may occur with these initially semi-discrete storms,
before transitioning to more of an isolated strong/gusty wind threat
as storms congeal into one or more bowing line segments with
eastward extent later in the evening/overnight.

..Gleason.. 11/14/2020

.PREV DISCUSSION... /ISSUED 1017 AM CST Sat Nov 14 2020/

...MO/AR...
Latest water vapor loop shows an amplifying upper trough over the
central Rockies.  This system will intensify and move into the
Plains this evening - and into the mid MS Valley overnight.  At the
surface, a cold front will extend from central IA/MO into northeast
OK by evening.  This boundary will provide the focus for
thunderstorm development.

Present indications are that thunderstorms will begin to form -
mainly after dark - from southeast IA into central MO and northwest
AR.  Moisture/instability will be very limited in the northern parts
of the risk area, limiting a more robust severe event.  However from
central MO southward into northwest AR, forecast soundings suggest
dewpoints approaching 60F and moderately steep mid-level lapse
rates.  This should yield sufficient CAPE for a few vigorous
updrafts with supercells possible for a few hours.  Very strong
vertical shear would suggest a risk of all hazards in these
fast-moving storms, including a few tornadoes.  Storms will likely
organize into bowing segments tonight and move into a progressively
more stable air mass.  Nevertheless, the potential for locally
damaging wind gusts could be maintained as far east as southern IL
and western KY/TN.

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