SPC Apr 5, 2017 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1224 PM CDT Wed Apr 05 2017

Valid 061200Z - 071200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR EASTERN NC
AND EASTERN VA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN NC
NORTHWARD TO SOUTHERN NJ...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE MID-ATLANTIC...

...SUMMARY...
Organized severe storms are expected across parts of the
Mid-Atlantic region Thursday, primarily during the morning and early
afternoon hours. The potential exists for tornadoes and a few swaths
of damaging winds during this time frame.

...Synopsis...
A powerful mid/upper trough will advance towards the East Coast
Thursday, as a vigorous impulse rotates around its periphery from
the southern Appalachians towards southern New England by Thursday
night. Concurrently, a closed low at the center of the trough will
continue to deepen as it pushes east across the lower Great Lakes
region. The surface response will feature one low translate from
northern Ohio east/northeastward to western New York, while another
develops/lifts from northern Virginia into eastern Pennsylvania. A
cold front trailing to its south will surge eastward towards the
Atlantic coast through the day.

...Mid-Atlantic...
To the east of the aforementioned low and attendant surface front,
strong southerly low-level flow will transport surface dew points in
the low/mid 60s northward across coastal NC and into southeastern
Virginia. With what remains of a remnant EML plume pushing over the
region, this uptick in low-level moisture (as well as northward
warm-air advection) should give rise to approximately 1000-2000 J/kg
of MLCAPE by morning. While considerable uncertainty exists with
ongoing convection expected across the region at the beginning of
the period, the crossover of ample effective shear and favorable
buoyancy over this area should contribute to an organized severe
threat within a mixture of storm modes. Ahead of the composite cold
front/outflow boundary, an initial opportunity exists for
semi-discrete convection organizing along confluent boundaries
within the warm sector. Strong low-level shear and a moist boundary
layer suggest tornadoes will be possible with any of these cells.
The ongoing enhanced risk was expanded southward to the NC coast to
account for this potential. Through the morning, however, increasing
forcing for ascent and a veer-back-veer wind profile with height may
force more linear modes, favorable for damaging wind gusts and
perhaps a few embedded circulations. Considering the strength of
surface-to-850mb flow, a few swaths of damaging wind gusts may be
possible with these developing linear segments.

No significant changes are made to the ongoing northern extent of
the severe risk categories. Some uncertainty remains with regards to
the depth of the stable layer (and resultant ability of stronger
downdrafts to reach the surface with sufficient momentum) along the
northern fringes of the slight/marginal risks across the Delmarva
and coastal New Jersey. However, considering the strong kinematic
fields and potential for sufficient warming of the near-surface
stable layer, the strong wind threat appears considerable enough to
maintain the ongoing categories.

..Picca.. 04/05/2017

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