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Mesoscale Discussion 1844
NWS Storm Prediction Center Norman OK
1206 PM CDT Tue Aug 06 2024

Areas affected...Portions of eastern Pennsylvania...New Jersey...far
eastern Maryland...northern Delaware

Concerning...Severe potential...Severe Thunderstorm Watch likely 

Valid 061706Z - 061830Z

Probability of Watch Issuance...80 percent

SUMMARY...The severe threat should increase through the afternoon,
with multiple rounds of strong to severe thunderstorms expected.
Damaging gusts are the main threat, though a couple instances of
large hail or a tornado are also possible. A Severe Thunderstorm
Watch issuance will eventually be needed.

DISCUSSION...Multiple semi-discrete, robust updrafts (including
supercells) have beco*e established over western PA and are poised
to track eastward through the afternoon. However, before these
storms cross the Appalachians, at least scattered thunderstorms are
expected to develop east of the Appalachians amid a destabilizing
airmass. Visible satellite shows a rapidly expanding CU field, with
MRMS mosaic radar data showing convective initiation potentially
already underway. To the lee of the Appalachians, surface
temperatures are already reaching 90 F amid 70+ F dewpoints,
supporting 8 C/km boundary-layer lapse rates (per 16Z mesoanalysis).
Though deep-layer shear should remain modest through at least early
to mid afternoon (i.e. around 30 kts effective bulk shear), the
steepening low-level lapse rates will support a damaging gust
threat.

Later this afternoon, as the stronger storms to the west approach
the region, an instance or two of large hail and maybe even a
tornado could occur as these storms traverse a baroclinic boundary,
where low-level shear may be locally maximized. A Severe
Thunderstorm Watch will be needed soon to address the impending
severe threat.

..Squitieri/Hart.. 08/06/2024

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...OKX...PHI...BGM...CTP...LWX...

LAT...LON   41547634 41337471 41107410 40487393 39777413 39157450
            39087501 39117540 39457603 40057578 40817586 41547634