SPC AC 211727
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1227 PM CDT Wed Apr 21 2021
Valid 221200Z - 231200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorms are not expected across the United States on
Thursday.
...Discussion...
As an upper low over the eastern U.S. shifts eastward/northeastward
into the western Atlantic/Canadian Maritime provinces, a trough
consisting of phased northern- and southern-stream components is
progged to advance across the West/Intermountain Region.
As the upper system advances, cool air aloft/steepening lapse rates
will support scattered showers, as well as some embedded lightning
-- particularly during the diurnal peak heating period. Lightning
may occur over portions of the Northwest/Continental Divide area,
and also across portions of the Four Corners states.
Overnight, warm advection is expected to increase across the
central/south-central states, as a low-level jet strengthens ahead
of the advancing upper trough. However, dry mid-level air atop
moistening low levels would generally imply that convective
development will remain unlikely through the end of the period
across the area. Near the very end of the period, convective
potential may increase in the vicinity of the Arklatex, and so a
conditional thunder area is being maintained there. Otherwise,
storm development is not expected through the end of the period.
Elsewhere, showers and a thunderstorm or two may occur over south
Florida and the Keys, mainly from afternoon onward.
..Goss.. 04/21/2021
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