RSS Mesoscale Discussions from Storm Prediction Center
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1052 AM CDT Mon Apr 20 2026
Valid 201630Z - 211200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe storms are not expected today.
...Synopsis...
An upper impulse will continue to pose a risk of scattered
thunderstorms over parts of NM and south/west TX through the
afternoon, with activity spreading into north-central TX late
tonight.
Other thunderstorms are possible this afternoon and evening over
south FL in a moist and marginally unstable air mass, along the
coast of southern New England, and over portions of OR/WA. In all
areas, weak instability will preclude the risk of organized severe
storms.
..Hart/Flournoy.. 04/20/2026
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SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1224 PM CDT Mon Apr 20 2026
Valid 211200Z - 221200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Thunderstorms will be possible across the West, portions of the
southern Plains, and the southern Great Lakes on Tuesday. Potential
for severe weather appears low.
...Synopsis...
Upper-level ridging is expected to build into the Plains on Tuesday.
Moderate northwesterly flow aloft will remain across the Upper
Midwest/Great Lakes. In the West, an upper trough will move into
California and the western Great Basin. At the surface, a high
pressure system will persist in the Southeast. Initial moisture
return around the western flank of this anticyclone will occur
through the day. This moisture will interact with a weak boundary
within the Midwest/Lower Great Lakes.
...Midwest/Lower Great Lakes...
Ahead of the weak surface boundary, some increase in low-level
moisture can be expected. Moisture should generally be greater along
the Iowa/Missouri border with diminishing dewpoints towards the
Lower Great Lakes/Ohio Valley. Within moderate northwesterly flow
aloft, a subtle shortwave trough is expected to move towards
southern Lake Michigan during the afternoon. Temperatures at 500 mb
of around -18C should promote some convection along the boundary by
late afternoon. Farther west, forcing for ascent will be weaker and
capping will be stronger. The main question in this scenario
continues to be the quantity of moisture return ahead of the
boundary. Guidance does suggest low 50s F are possible, but given
how dry the current airmass across the region is and how late this
initial moisture return will be, confidence in that forecast is low.
The current expectation is that isolated to widely scattered storms
are possible by late afternoon/early evening, particularly near
southern Lake Michigan. These storms may briefly strengthen and be
capable of gusty winds/small hail. Thereafter, nocturnal cooling
should lead to a weakening trend. Development near the Iowa/Missouri
is far more conditional.
...Trans-Pecos/Big Bend into Central Texas...
Convection will be ongoing Tuesday morning in central Texas.
Isolated small hail and gusty winds are possible, but deep-layer
shear will be weakening as the ridge builds into the Plains through
the day. Farther west, a weak dryline is possible into the Big Bend
region. An isolated storm or two could develop. Weak vertical shear
and marginal buoyancy should limit severe potential.
...California Central Valley...
After an initial period of precipitation in the morning, pockets of
surface heating in the afternoon may lead to MLCAPE of 250-500 J/kg.
While a stronger storm or two is possible, the severe threat will be
limited by weak deep-layer shear.
..Wendt.. 04/20/2026
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