SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0240 PM CDT Thu Oct 22 2020

Valid 222000Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE UPPER MIDWEST...

...SUMMARY...
Strong to severe thunderstorms are possible this afternoon and early
evening over parts of eastern Iowa and small parts of adjoining
Illinois and Wisconsin.

...Discussion...
At this time, no appreciable changes appear necessary to the ongoing
outlook, as prior reasoning continues to reflect the latest
expectations regarding evolution of storms over the Iowa vicinity.  


Meanwhile, latest HRRR runs are less bullish with respect to any
isolated severe risk over the Texas South Plains vicinity.  However,
will maintain low-probability/MRGL risk across this area for the
time being.

..Goss.. 10/22/2020

.PREV DISCUSSION... /ISSUED 1114 AM CDT Thu Oct 22 2020/

...MO/IA/IL/WI...
Morning water vapor loop shows a deepening upper trough over the
central Rockies that will emerge into the Plains this afternoon and
tonight.  Meanwhile at the surface, a cold front will begin surging
southward across the Plains into IA/KS/OK by evening.  This front
will be the focus of lift and scattered precipitation later today.

12z CAM solutions are in strong agreement that thunderstorms will
develop late this afternoon in vicinity of the cold front from
central IA into central WI.  A combination of a weak capping
inversion and strong ana-frontal low-level winds are expected to
relegate convective development to elevated storms behind the front.
 Stable near-surface conditions will limit the amount of convective
augmentation of larger-scale wind gusts, suggesting that the risk of
severe thunderstorm winds is marginal.  Sufficient elevated CAPE,
cool mid-level temperatures, and strong deep-layer shear may result
in hail in the more robust updrafts through this evening.

...West TX...
A small cluster of thunderstorms continues to be forecast for parts
of west TX this afternoon and evening in vicinity of a diffuse
surface dryline.  Forecast soundings suggest some risk of hail and
gusty winds in these storms through the early evening before
nocturnal cooling decreases the threat.

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