Severe Storm Outlook Narrative (AC)
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ACUS01 KWNS 191955
SPC AC 191954

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0254 PM CDT Fri Apr 19 2019

Valid 192000Z - 201200Z


Severe thunderstorms with considerable potential for producing
damaging wind gusts and a few tornadoes will continue the afternoon
and evening across portions of the southern mid-Atlantic Coast
region, particularly central and eastern North Carolina and

...Mid-Atlantic Vicinity southward to Florida...

The main updates this afternoon have been clearing/lowering severe
probabilities behind the main band of convection. A slight risk will
continue across parts of central and southern FL ahead of the
advancing squall line, where damaging wind gusts will be possible
into this evening. The bulk of the higher-end severe probabilities
(Moderate and Enhanced risk areas) have been confined to northern
portions of the SC coast northward through central/eastern VA ahead
of the surging QLCS. Widespread damaging winds will remain possible
with the QLCS into the evening hours. Isolated discrete cells are
also possible ahead of the line where strong heating beneath breaks
in clouds has resulted in 500-1000 J/kg MLCAPE. These cells could
continue to pose a tornado risk as backed low level flow enhances
0-1 km SRH in the presence 50+ kt effective shear and 12-14 g/kg
mean mixing ratios. These conditions also will continue to support
QLCS tornado threat as well.

With time and northward extent, the severe threat will gradually
diminish as storms approach the Philadelphia and New York City
vicinity later this evening.

..Leitman.. 04/19/2019

.PREV DISCUSSION... /ISSUED 1112 AM CDT Fri Apr 19 2019/

...Mid Atlantic southward to FL this afternoon/evening...
Forecast scenario appears largely on track for this afternoon.  A
deep midlevel trough over the lower MS Valley will pivot eastward
toward the southern Appalachians, with associated surface
cyclogenesis.  The deepening surface cyclone will maintain strong
moisture transport into the Carolinas/VA in the warm sector through
the afternoon, where pockets of surface heating will boost buoyancy
amid boundary-layer dewpoints of 65-70 F.  Isolated warm sector
supercells within a moist warm advection regime will continue to be
possible through the afternoon from VA into the Carolinas.  Farther
west, a pre-frontal squall line has consolidated from north FL to
near the Savannah River, and this convection will overspread the
Carolinas/VA through this evening.  Weak-moderate buoyancy (MLCAPE
of 500-1000 J/kg) and strong deep-layer vertical shear (effective
bulk shear in excess of 50 kt) will continue to favor embedded
supercell structures, while low-level moisture/shear will remain
sufficient for occasional tornadoes.  The tornado and damaging wind
threat will be maximized with the embedded supercells/bowing
segments through the afternoon/evening, with the most favorable
storm environment across the Carolinas into parts of VA.

The warm advection regime will spread northward across VA toward
southeastern PA, where some increase in low-level shear and weak
destabilization will favor a northward spread of the tornado and
damaging wind threat with the warm sector convection.  Farther
south, the convection should be concentrated in the primary squall
line that will cross north/central FL this afternoon, and
potentially maintain intensity into the northern parts of south FL.
Damaging winds will be the main threat with these storms, since the
primary synoptic wave (and associated low-level shear) will pass
farther to the north.

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