Severe Storm Outlook Narrative (AC)
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ACUS02 KWNS 190420
SWODY2
SPC AC 190420

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1120 PM CDT Wed Oct 18 2017

Valid 201200Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Some thunderstorm potential will exist across the south-central US
and over the upper Mississippi Valley and across parts of southern
Florida.

...Discussion...

Higher-PW air mass will begin to advance north across the western
Gulf basin into the Plains during the day2 period as broad troughing
establishes itself across the western parts of the US. One
low-latitude short-wave trough will eject across the southern High
Plains into OK/north TX during the afternoon and this should enhance
low-level warm advection such that isolated-scattered convection may
develop as air mass moistens. Forecast soundings do not exhibit
significant instability but adequate buoyancy should exist for
deeper updrafts to penetrate levels necessary for lightning. Weak
lapse rates and the lack of a strong focus suggest the probability
of severe is too low to warrant a severe risk this period.

Farther north, low-level warm advection will increase markedly
during the latter half of the period as strong LLJ develops from KS
into MN. Forecast instability is quite weak along this corridor but
likely adequate for a few elevated thunderstorms.

Upper ridge will dominate the southeastern US during the day2 period
and a dominant surface high should hold over the southern
Appalachians. As a result, deep easterly flow will persist across
the FL Peninsula. Deeper showers will congregate across the eastern
and southern Peninsula and isolated lightning could develop with
this activity.

..Darrow.. 10/19/2017

$$



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