SPC AC 171703
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1103 AM CST Fri Nov 17 2017
Valid 181200Z - 191200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE MID
MISSISSIPPI INTO THE OHIO VALLEY...
A few strong to severe storms capable of marginal hail or damaging
wind gusts will be possible Saturday mainly over the Ohio Valley
A strong shortwave trough will move from the Plains to the MS Valley
during the day, with a deepening surface low moving from St. Louis
to Lake Erie. A rapid increase of winds aloft will occur with a 100
kt midlevel jet into the OH Valley by 00Z. A strong cold front will
sweep eastward with southwesterly surface winds bringing a narrow
plume of mid 50s to lower 60s dewpoints northward into IL and IN.
Warm air advection in the low-levels will further be augmented by a
50-60 kt low-level jet. Despite the favorable synoptic scale setup,
instability will be minimal, with only a few marginally severe
storms expected during the day.
...Mid MS into the OH Valleys...
An area of mainly elevated thunderstorms is expected to occur early
in the day, perhaps across eastern MO, and then developing eastward
across IL and IN, with lift aided by warm air advection. Forecast
soundings show sufficient instability for marginally severe hail.
Other activity, perhaps surface based, will occur near the low, and
southward along the cold front. The main detriment to a more
substantial severe wind event appears to be the lack of heating,
with weak low-level lapse rates. This should keep warm sector
activity immediately along the front. Strong wind gusts will occur
with the frontal passage, and some of this could be convectively
Farther south into TN, MS, and AL, instability will be even less,
with a capping inversion preceding the front. Here too, some
convectively augmented wind gusts will be possible during the
afternoon and early evening.
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0700Z