RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0246 PM CDT Mon Apr 20 2026
Valid 202000Z - 211200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe storms are not expected today.
...20Z Update...
The TSTM area over the coast of southern New England and the
Mid-Atlantic was removed, as large-scale forcing for ascent and
related thunderstorm activity has shifted offshore. Elsewhere, the
previous forecast remains on track.
..Weinman.. 04/20/2026
.PREV DISCUSSION... /ISSUED 1052 AM CDT Mon Apr 20 2026/
...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.
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 PM CDT Mon Apr 20 2026
Valid 221200Z - 231200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
HIGH PLAINS...
...SUMMARY...
Severe thunderstorms capable of hail and gusty winds may develop
during the late afternoon and evening across portions of the High
Plains.
...Synopsis...
A broad trough will begin to move into the Rockies and adjacent High
Plains. A shortwave trough will eject into the northern Plains in
association with the broader trough. At the surface, a deep surface
low will develop in eastern Montana with a lee trough/dryline
extending into the southern High Plains.
...High Plains...
As the upper-trough approaches the Rockies, the lee trough and
dryline are expected to sharpen. Forcing for ascent will be
strongest in the Nebraska Panhandle/western South Dakota vicinity.
This area is also has the largest variability in terms of moisture
return (the NAM being much more bullish than the ECMWF). Farther
south, moisture will generally be greater. Guidance is in agreement
that 60s F dewpoints are probable in the Texas South Plains and
perhaps parts of the Panhandle. The issue farther south will be the
lack of synoptic ascent. Temperatures behind the dryline will be in
the upper 80s F to perhaps low 90s F. The depth of the circulation
may be enough to initiate an isolated storm or two, but confidence
is still not overly high. Environmentally, deep-layer shear will be
oriented roughly perpendicular to the dryline, especially from
western Kansas southward. Supercells would be favored if storms
develop. MLCAPE of 1000 J/kg in South Dakota to 1500-2500 J/kg
farther south is expected by the afternoon. Large hail and severe
wind gusts would be possible.
...Central/Easter Montana...
With the surface low deepening through the day, at least modest
moisture return northwestward is anticipated into central/eastern
Montana. However, moisture will still be quite scant across the
region. Dewpoints may not reach the 40s F. Given the forcing for
ascent, high-based convection is possible. The very dry sub-cloud
layers could lead to gusty outflow winds. At present, confidence in
severe gusts is too low to warrant wind probabilities.
..Wendt.. 04/20/2026
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