RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0247 PM CDT Wed Mar 18 2026
Valid 182000Z - 191200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Isolated thunderstorms will be possible today across far south
Florida.
...Synopsis...
The previous forecast remains on track with no adjustments required.
Latest GOES imagery shows shallow convection developing immediately
north of the current thunder line and south of Lake Okeechobee.
While a lightning flash or two is possible with this activity, the
lack of vertical development/limited cloud phase change (per Day
Cloud Phase imagery) limits confidence in lightning potential.
Latest guidance continues to suggest the greatest lightning threat
will remain along the southeast FL coast through evening.
..Moore.. 03/18/2026
.PREV DISCUSSION... /ISSUED 1044 AM CDT Wed Mar 18 2026/
...Synopsis...
A substantial upper high and attendant ridge is apparent in morning
water vapor imagery over the western U.S. Further east, a stalled
front is noted across the Bahamas and Florida Straits. Surface high
pressure in the wake of the frontal boundary across the Southeast
will maintain offshore trajectories and a dearth of boundary layer
moisture. This will preclude thunderstorm activity across most of
the CONUS.
Some lingering low-level moisture and weak elevated instability may
support a couple of thunderstorms over far south FL and portions of
the Keys today, though most activity will remain offshore.
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SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1215 PM CDT Wed Mar 18 2026
Valid 191200Z - 201200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorms are not expected on Thursday.
...Synopsis...
Little change to the large-scale pattern is expected on Thursday,
with an upper ridge remaining in place over the western CONUS, and a
deep upper trough over the East. A general dearth of moisture and
instability will continue to limit thunderstorm potential over most
of the CONUS.
Near and offshore of the southeast FL Peninsula, modest moisture and
instability may support weak convection as a midlevel shortwave
moves through the large-scale trough. This convection may pose a low
(around 10 percent) thunderstorm threat, mainly during the latter
half of the forecast period.
..Dean.. 03/18/2026
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0155 PM CDT Wed Mar 18 2026
Valid 201200Z - 211200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
A low chance of a few thunderstorms may develop on Friday near the
Upper Ohio Valley and vicinity, and also near the southeast Florida
coast.
...Synopsis...
An expansive upper ridge will remain in place over most of the
western CONUS on Friday. A downstream large-scale upper trough will
persist over the East. Within the large-scale trough, one shortwave
will move offshore of Florida early in the period, while an upstream
shortwave moves across the Great Lakes. A surface low will accompany
the Great Lakes shortwave trough as it moves southeastward, as a
trailing cold front moves through the Ohio Valley.
A low probability (around 10 percent) thunderstorm threat may
continue from late D2/Thursday into early D3/Friday near the
southeast FL coast. Farther north, modest low-level moistening (with
dewpoints increasing to near/above 50 F) may support isolated
thunderstorm development during the afternoon and evening near the
Upper Ohio Valley, in the vicinity of the advancing cold front. Weak
instability is currently expected to limit organized
severe-thunderstorm potential.
..Dean.. 03/18/2026
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