SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1205 AM CDT Sun Sep 25 2022
Valid 251200Z - 261200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN
APPALACHIANS INTO PARTS OF THE MID ATLANTIC AND SOUTHERN NEW
ENGLAND...
...SUMMARY...
Scattered severe storms producing large hail and damaging winds are
expected from mid to late afternoon across the northern Appalachians
and parts of the Mid Atlantic and southern New England through
evening.
...Portions of the Appalachians, Mid Atlantic and southern New
England...
Within a larger-scale upper trough, a lead wave will move from the
OH Valley to the Mid Atlantic during the day, providing cooling
aloft and midlevel winds of 60-70 kt, enhancing shear. At the
surface, low pressure will slowly deepen from Lake Huron into NY,
with a front trailing southwestward across PA, WV, eastern KY and
Middle TN by late afternoon. Meanwhile, a warm front will develop
over southern New England, resulting in destabilization toward
evening. Dewpoints will rise into the lower 60s F there, with upper
50s to lower 60s F southwestward along the front where heating and
mixing will be stronger.
The warm sector will become uncapped by around 18Z from PA southward
across WV, VA, KY and TN, with further destabilization 21-00Z from
NJ into southern New England. MLCAPE of 1000 J/kg will be common,
with locally higher values. Deep-layer shear will be strong beneath
the upper jet, with values around 60 kt common from eastern TN to
the DelMarVa.
Precipitation may be ongoing from OH into PA and western NY early in
the day, north of the midlevel jet where temperatures aloft will be
cold, and as warm advection around 850 mb translates east. Given
cold temperatures aloft, some of this activity could produce small
hail. As the air mass destabilizes beneath the cold air aloft, some
of these storms may expand and become severe across PA and NJ during
the afternoon, producing hail and wind. Later in the evening,
additional storms may interact with the warm front where low-level
shear will be stronger, and a brief/weak tornado could occur,
depending on whether surface temperatures are warm enough for
surface-based parcels.
Farther south, southwest winds will maintain a moist air mass along
the Appalachian Front, and heating will aid development after 18Z.
Long, straight hodographs should favor fast-moving storms producing
hail and wind. Additional isolated activity may occur into northern
GA and AL along the front, primarily late afternoon and evening.
..Jewell/Wendt.. 09/25/2022
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