Severe Storm Outlook Narrative (AC)
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ACUS11 KWNS 251725
SPC MCD 251724

Mesoscale Discussion 0211
NWS Storm Prediction Center Norman OK
1124 AM CST Sat Feb 25 2017

Areas affected...Maryland...central and eastern Virginia and
northern North Carolina

Concerning...Severe potential...Watch possible

Valid 251724Z - 251930Z

Probability of Watch Issuance...60 percent

SUMMARY...Thunderstorms are expected to increase in coverage and
intensity this afternoon ahead of a cold front. Locally damaging
winds are possible, along with hail in the strongest cells. A watch
may be needed if it is clear storms will become severe.

DISCUSSION...Rapid surface heating continues across the region ahead
of the cold front which extended from northwestern VA into western
NC as of 17Z. Dewpoints were holding in the mid to upper 50s
suggesting a well-mixed and unstable boundary layer with MUCAPE to
around 1000 J/kg.

Satellite and radar show a few weak thunderstorms already forming
over the higher terrain near the front, and a general upward trend
is expected through the afternoon as it progresses east. By 18-19Z,
some storms may be severe. Wind profiles will continue to
strengthen, especially in the mid to upper levels, with long
hodographs favoring long-lived storms. Damaging winds appear to be
the main threat with a broken line of cells or small bows. The cold
air in the mid to upper levels would support the formation of hail.
However, a relatively warm layer exists above 700 mb, and updrafts
may struggle. As a result of this warm layer, storms may be slow to
become severe, but with time, long-acting shear may overcome this,
especially over eastern VA into MD, and northeastern NC later this

The tornado threat is low, but not zero. Although storms could
remain cellular, and low-level shear is in the sufficient category
with 0-1 SRH near 100 m2/s2, strong boundary layer mixing will be a
detriment, as will be the warm layer aloft hampering vertical
updraft accelerations in the lower parts of the storm.

..Jewell/Hart.. 02/25/2017

...Please see for graphic product...


LAT...LON   37997518 37457556 37037585 36707636 36497718 36377824
            36457905 36887910 37257891 37657868 38207835 38657805
            39117772 39627728 39737666 39627590 39267550 38877524
            38427508 37997518 is the U.S. government's official web portal to all federal, state and local government web resources and services.