SPC MD 2010

SPC MD 2010


Mesoscale Discussion 2010
NWS Storm Prediction Center Norman OK
1004 PM CDT Thu Aug 17 2023

Areas affected…Parts of central/eastern PA and southern NY

Concerning…Severe potential…Watch possible

Valid 180304Z – 180600Z

Probability of Watch Issuance…40 percent

SUMMARY…The potential for damaging gusts and possibly a tornado or
two should gradually increase during the next few hours, as a line
of storms develops/spreads eastward.

DISCUSSION…Latest water vapor imagery indicates a substantial
midlevel trough moving eastward over the Great Lakes and Ohio River
vicinity. Related large-scale ascent/midlevel height falls preceding
this feature are gradually impinging on central PA/southern NY —
where a north/south-oriented quasi-stationary baroclinic zone is
evident. As the trough takes on a slight negative tilt and stronger
height falls overspread the frontal zone during the next few hours,
storms should gradually increase in coverage/intensity before
spreading eastward along an evolving cold front.

Around 40-50 kt of midlevel south-southwesterly flow (sampled by
regional VWP) generally parallel to the frontal zone and the
strengthening DCVA suggest an organized line of storms/QLCS should
be the favored mode. While nocturnally cooling surface temperatures
and lingering warm air aloft (per regional 00Z observed soundings)
cast uncertainty on storms rooting at the surface (especially in the
near-term), moist low-level southeasterlies beneath a developing
30-35 kt low-level jet (and related warm-air advection) could
eventually offset this given the strengthening midlevel height
falls. Damaging gusts, aided by convective momentum transfer and an
organizing cold pool, will be the main concern, though expanding
low-level hodographs could also support embedded rotating updrafts
and a non-zero risk for a brief tornado or two. While there is
lingering uncertainty regarding surface-based storms (and related
hazards), trends will be monitored for a possible watch issuance
during the next few hours.

..Weinman/Guyer.. 08/18/2023

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


LAT…LON 40837732 41237699 41727664 42047642 42277624 42547606
42887588 42967557 42817500 42607459 42187450 41647475
40247566 39927627 39827696 39997763 40197769 40477760

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