Severe Storm Outlook Narrative (AC)
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000
ACUS02 KWNS 231655
SWODY2
SPC AC 231654

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1154 AM CDT Mon Oct 23 2017

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
THE NORTHEAST STATES...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE
ATLANTIC INTO A PORTION OF THE NORTHEAST STATES...

...SUMMARY...
A few severe thunderstorms are possible Tuesday across a part of the
Northeast, particularly near the northern Mid Atlantic coast
northward through the Hudson Valley.  These storms will be
accompanied by a modest risk for a few strong to damaging wind gusts
and possibly a couple of tornadoes.

...Synopsis...

Shortwave trough now over the Southeast States will deamplify as it
ejects northward into the Great Lakes in response to an upstream
impulse that will move southeast into base of the synoptic trough,
resulting in significant amplification of this feature over the
eastern half of the U.S. Tuesday. Surface low will occlude over the
Great Lakes with a trailing front extending from the low southward
through the Mid Atlantic, eastern Carolinas and northern FL by 12Z
Tuesday. The winds aloft will become nearly parallel to this
boundary as the upper trough amplifies, resulting in a slower
eastward progression. By the end of the period this front should
extend from New England southward through the western Atlantic and
into south FL.

...Northeast States...

Bands of low-topped convection and possibly a few thunderstorms will
be ongoing ahead of the front along the warm conveyor belt from
eastern North Carolina, the coastal Mid Atlantic into a portion of
the Northeast States. The thermodynamic environment will be
characterized by very weak instability (MLCAPE at or below 300 J/kg)
and near moist adiabatic profiles. However, convection will remain
embedded within strong deep layer winds and vertical shear nearly
parallel to the developing bands with 60+ kt within the first few
hundred meters of the surface. Despite the limiting factors imposed
by very marginal thermodynamic profiles, this environment will
support at least a modest risk for low-topped bowing segments and
embedded meso-vortices capable of producing a few instances of
damaging wind and a brief tornado or two as activity develops
eastward during the day.

..Dial.. 10/23/2017

$$


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