SPC Nov 21, 2024 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0144 PM CST Thu Nov 21 2024

Valid 212000Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected through tonight.

...Synopsis...
A line of convective rain/show showers continues across the
Appalachians with occasional lightning flashes. This will persist
for a few more hours before weakening late this afternoon as the
boundary layer cools and low-level lapse rates weaken. 

Lightning is expected to remain offshore near the New England coast
and the Pacific Northwest coast and therefore, the thunder line has
been removed from both areas.

..Bentley.. 11/21/2024

.PREV DISCUSSION... /ISSUED 1029 AM CST Thu Nov 21 2024/

...Synopsis...
A deep midlevel low, characterized by 500-mb temperatures around
-32C, will move from the Great Lakes into the Mid-Atlantic through
the period. These cold midlevel temperatures and strong height falls
accompanying the midlevel low may promote isolated lightning flashes
embedded in showers across the central Appalachians this afternoon.
Over coastal southern New England, low-level warm advection north of
a related occluded surface low will also support isolated
thunderstorms, given weak elevated instability. Most of this
activity should remain offshore. Isolated thunderstorms are also
possible over immediate coastal areas of WA, where forcing for
ascent in the left exit region of a jet streak is overlapping deep
tropospheric moisture/weak instability.

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