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000
ACUS02 KWNS 131734
SWODY2
SPC AC 131732

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1232 PM CDT Sat Apr 13 2024

Valid 141200Z - 151200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS CENTERED OVER
PARTS OF PENNSYLVANIA...

...SUMMARY...
Scattered severe thunderstorms are possible from late afternoon into
the evening on Sunday, from southwestern Ohio east-northeastward to
southwestern New England. Damaging winds should be the primary
hazard, but a tornado or two and large hail are also possible.

...Synopsis...
A mid-level closed low initially centered over California will move
eastward across the Great Basin Sunday, with downstream ridging to
remain over the Plains/central U.S. through the period.  Farther
east, west-northwesterly flow aloft will prevail, with a belt of
enhanced/70 to 80 kt speeds across the Great Lakes and Northeast
states.  A subtle short-wave trough/vort max associated with the
mid-level jet is forecast to shift across the Upper Ohio
Valley/central Appalachians through the late afternoon/evening
hours.

At the surface, a weak frontal low initially over the Lower Michigan
vicinity should move quickly eastward to western New England by the
evening.  Meanwhile a trailing, east-west cold front will advance
southward across the southern Great Lakes region and into the
central Appalachians and Midwest States through the afternoon and
evening, and reaching the Mid-Atlantic region and Ohio Valley
overnight.

In the West, a cold front associated with the advancing upper low
will cross the Great Basin and Desert Southwest with time, reaching
the High Plains by Monday morning.

...Upper Ohio Valley area to far southwestern New England...
Steep mid-level lapse rates aloft are forecast to overspread the
northeastern quarter of the country Sunday, as a cold front drops
southward across the Northeast states.  Beneath this
eastward-advecting mid-level lapse rate plume, modest
east-northeastward advection of low-level moisture will occur, with
50s dewpoints expected ahead of the front, from southwestern New
England westward, by late afternoon in a narrow east-to-west
corridor.  This -- combined with diurnal heating across the warm
sector, should yield mixed-layer CAPE values to reach 500 J/kg over
southern New York/eastern Pennsylvania, to 1500 J/kg into western
Pennsylvania and Ohio.

As the front sags southward and destabilization maximizes through
the afternoon, storm initiation along and just ahead of the front is
expected.  Storms may initially include cellular mode, especially
from central Pennsylvania westward, but flow roughly parallel to the
front should favor quick upscale/linear evolution.  Still, weak
veering and rapid strengthening of the flow with height will support
organized storms -- including rotating updrafts within the line, and
particularly with any storms which can remain at least transiently
cellular.  While the expected linear storm mode should help to limit
tornado potential, a couple of tornadoes are anticipated,
particularly across western and central Pennsylvania, where large
hail may also occur.  Otherwise, the primary severe risk across the
region should be damaging wind gusts, aided by 40 to 50 kt
westerlies extending as low as 900mb per model point-forecast
soundings.

Storms will spread southward into the evening, but should eventually
weaken diurnally as the boundary layer begins to stabilize.

..Goss.. 04/13/2024

$$