Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 221537
SWOMCD
SPC MCD 221537
ALZ000-FLZ000-MSZ000-LAZ000-221800-

Mesoscale Discussion 0281
NWS Storm Prediction Center Norman OK
1037 AM CDT Sun Apr 22 2018

Areas affected...Southeast Louisiana...Southern
Mississippi...Southwest Alabama...Far Western Florida Panhandle

Concerning...Severe potential...Watch unlikely

Valid 221537Z - 221800Z

Probability of Watch Issuance...20 percent

SUMMARY...A marginal tornado and wind damage threat will persist
into the early afternoon across parts of southeast Louisiana,
southern Mississippi. The threats will likely affect southwest
Alabama and the far western Florida Panhandle later today. No
weather watch is expected due to the marginal setup.

DISCUSSION...The latest surface analysis shows a 1011 mb low over
southeast Louisiana with a warm front extending eastward across
south-central Mississippi. A moist airmass was located south of the
front with surface dewpoints in the mid to upper 60s F. Water vapor
imagery showed a shortwave trough over the lower Mississippi Valley.
Large-scale ascent associated with this feature will continue to
support thunderstorm development along the warm front into the
afternoon where a marginal wind damage threat will persist.

Further south across far southern Mississippi and southeast
Louisiana, surface dewpoints are near 70 F and instability is
considerably stronger. The RAP suggests that SBCAPE is estimated to
be near 1000 J/kg right along the Mississippi coast. The Mobile
WSR-88D VWP does show enough speed and directional shear in the
lowest 2 km AGL for a  marginal tornado threat. However, due to
widespread clouds and precipitation ahead of the activity, most of
the instability is offshore suggesting that any tornado threat will
remain marginal.

..Broyles/Hart.. 04/22/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...BMX...MOB...JAN...LIX...

LAT...LON   32228846 31898933 31658983 31339026 31009034 30769035
            30079004 29338980 29108918 29878854 30398728 32108749
            32228846




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