Day 1 Severe Weather Outlook

Valid 311200Z – 011200Z

…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
PENNSYLVANIA TO NORTHERN NORTH CAROLINA…

…SUMMARY…
Severe thunderstorms capable of strong wind gusts are expected
across much of the eastern US today — particularly from areas along
and east of the central and southern Appalachians to the mid
Atlantic and Carolinas coastal areas.

…Discussion…

Strong mid-level short-wave trough is forecast to eject across the
MS Valley into the OH Valley by 01/00z as 130kt 500mb speed max
translates into OH. In response, intense 12hr 500mb height falls,
approaching 130m, will overspread areas immediately ahead of the
short wave. Very strong large-scale forcing for ascent is expected
to contribute to a band of frontal convection that will surge across
the Central/Southern Appalachians into the Middle
Atlantic/Carolinas.

Early this morning, moistening boundary layer was advancing north
across the Gulf States and Carolinas where 70F dew points are now
evident. This air mass is expected to move into portions of southern
VA prior to frontal passage. Additionally, LLJ is forecast to
strengthen across KY by sunrise then shift east of the higher
terrain by late afternoon in response to the progressive trough.
While pre-frontal boundary layer conditions will gradually moisten
through the period, forecast lapse rates will limit buoyancy within
a strongly sheared environment. Even so, forecast soundings ahead of
the wind shift suggest convection that develops along the front will
be at, or near-surface based as far north as the NY/PA border.
Earlier thoughts regarding the prospect for damaging winds with a
frontal squall line remain. Latest thinking is frontal convection
will begin to increase in coverage/intensity by 18z from eastern KY
into southwest PA, then an upward-evolving squall line with
potentially damaging winds should surge east toward the Delmarva,
extending south into southern VA, possibly into NC by early evening.
Linear storm mode certainly favors straight-line wind damage as
storm motions are forecast to be quite fast. A few embedded
tornadoes can not be ruled out due to the strength of the wind
fields.

..Darrow/Bentley.. 10/31/2019

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