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SPC Convective Outlook

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 Forecast Discussion

  
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ACUS01 KWNS 181950
SWODY1
SPC AC 181949

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0149 PM CST Sat Nov 18 2017

Valid 182000Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE OHIO
AND TENNESSEE VALLEY REGIONS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
MISSISSIPPI AND ALABAMA INTO OHIO...

...SUMMARY...
Thunderstorms capable of severe wind gusts, marginal hail, or a
brief tornado remain possible this afternoon across parts of the
Ohio and Tennessee Valley regions, and into northern Mississippi and
Alabama.

...Ohio and Tennessee Valleys...
A line of storms currently extends from west central Ohio
southwestward into northeast Arkansas along a strong cold front.
Ahead of this line exists a narrow corridor of instability, with the
greatest theta-e air into the lower Mississippi Valley where
temperatures are approaching 80. Despite weak instability, very
strong mean wind fields may produce gusts at or above severe levels
anywhere along the line. For more information see Mesoscale
Discussion 1770.

..Jewell.. 11/18/2017

.PREV DISCUSSION... /ISSUED 1022 AM CST Sat Nov 18 2017/

...OH/TN Valley Region...
Water vapor imagery shows a vigorous upper trough moving rapidly
eastward across the Central Plains.  Large scale forcing ahead of
this feature is overspreading the mid MS and lower OH valleys, and
should result in scattered afternoon thunderstorms.  Storms will be
focused along a cold front - initially over central/southern IL and
southeast MO.  This activity will spread eastward through the
evening hours into parts of IN/KY/TN.  Wind fields are very strong,
and are supportive of organized storms with bowing and supercell
structures.  However, low-level moisture and CAPE are quite limited
today with dewpoints only in the 50s to lower 60s, and MUCAPE values
below 1000 J/kg.  Considerable cloud cover and slightly veered
low-level winds are also negatives for a more robust severe event. 
Nevertheless, the initial storms over IL/MO and western KY/TN may
produce large hail, with the risk of damaging winds increasing
through the event farther east.  A tornado or two is also possible
in early supercells, and along the QLCS later today.

$$