RSS Mesoscale Discussions from Storm Prediction Center
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Wed Mar 18 2026
Valid 181200Z - 191200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Isolated thunderstorms will be possible today across far south
Florida.
...DISCUSSION...
An upper-level trough will move across the eastern U.S. today, as
northwest mid-level flow remains over much of the rest of the
nation. At the surface, high pressure will move eastward to the
Eastern Seaboard, as a dry airmass stays in place over most of the
continental U.S. The only chance for thunderstorms today will be
over far south Florida, where enough instability will be in place
for isolated thunderstorm development. No severe threat is forecast
over the U.S. today and tonight.
..Broyles/Chalmers.. 03/18/2026
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SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1229 AM CDT Wed Mar 18 2026
Valid 191200Z - 201200Z
...NO THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Thunderstorms are unlikely on Thursday.
...Synopsis...
An upper high will be centered over Arizona on Thursday, with a
large-scale upper ridge from CA into the southern High Plains. East
of there, northwest flow aloft will be maintained over the central
states, as elongated upper troughing persists along the East Coast.
At the surface, high pressure will be prevalent over much of the
CONUS, with centers over the Great Basin and from the Mid Atlantic
into the northern Gulf of America. Given this dry and stable
pattern, thunderstorms are not expected.
..Jewell.. 03/18/2026
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SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
1229 AM CDT Wed Mar 18 2026
Valid 201200Z - 211200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
A low chance of a few thunderstorms may develop near the Upper Ohio
Valley and vicinity on Friday.
...Synopsis and Discussion...
An upper ridge will hold over the Southwest on Friday, with strong
northwest flow aloft along the Canadian border. A low-amplitude
upper wave will intensify into northern MN and toward the upper
Great Lakes late in the day and overnight, with a weak surface low
also traversing the Great Lakes. A cold front will extend from
southwest Ontario into IL and MO by 00Z, and southerly winds ahead
of it will bring a plume of low to mid 50s F dewpoints northward
across TN/KY/IN/OH during the afternoon.
Despite the low-level moistening, instability will likely be
minimal. However, weak elevated instability may develop within the
warm advection zone roughly from OH into PA, with a low chance of
isolated thunder.
..Jewell.. 03/18/2026
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0217 AM CDT Wed Mar 18 2026
Valid 211200Z - 261200Z
...DISCUSSION...
An upper ridge is forecast to break down across the Southwest late
Saturday/D4 into Sunday/D5, with a weak wave embedded in the
northwesterly flow regime aloft. During the same time, a stronger
but low-amplitude feature will move rapidly east/southeast along the
Canadian border, across the Great Lakes and into the Northeast.
In association with the northern/Great Lakes disturbance, a cold
front is forecast to push south into the Plains on Sunday/D5,
extending into the OH Valley by late in the day. This front will
interact with marginal moisture return across the Mid MS/OH Valleys,
and continue into the Southeast on Monday/D6. This front is forecast
to be roughly parallel to the upper flow, and would likely undercut
thunderstorms that develop along it. MUCAPE on the order of 500-1000
J/kg seems reasonable, which will support marginal severe at best.
For the latter days of the period, the forecast becomes less
predictable, however, models on a run to run basis appear to be
trending toward higher heights/possible ridging over the Southwest,
with little to no threat of severe storms.
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