Severe Storm Outlook Narrative (AC)
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000
ACUS02 KWNS 231714
SWODY2
SPC AC 231713

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1213 PM CDT Tue May 23 2017

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR MUCH OF
FLORIDA...SOUTHERN AND EASTERN GEORGIA...AND SOUTHERN INTO CENTRAL
SOUTH CAROLINA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE FLORIDA
PANHANDLE NORTHWARD INTO PARTS OF THE OHIO VALLEY AND INTO PARTS OF
THE MID-ATLANTIC STATES...

...SUMMARY...
Severe storms will be possible Wednesday and Wednesday night across
much of Florida, central and eastern Georgia, and southern South
Carolina. More isolated severe storms will be possible from portions
of eastern Alabama northeast into southeast Virginia and possibly in
the parts of the Ohio Valley.

...Synopsis...
A mid-level low is forecast to move from MO into the southern
Appalachians.  A shortwave trough located over the central Rockies
midday Tuesday is forecast to move through the base of the
larger-scale trough along the central Gulf Coast during the day and
subsequently shear northeastward into the Carolinas after dark.  A
surface low over the OH Valley will occlude during the period as a
front draped from the OH Valley south to the central Gulf Coast
moves eastward reaching the VA Piedmont southward to the east of the
SC coast and into the central FL Peninsula by Thursday morning.

...Southeast/Mid-Atlantic States...
Moist southerly low-level flow will maintain mid 60s to lower 70s
degrees F dewpoints over much of this region.  Likely ongoing
clusters of showers/thunderstorms will continue into peak heating
across parts of FL/GA.  Isolated to scattered damaging winds are
possible but the potential for low-level storm rotation may
accompany the stronger storms from FL northeast into SC during the
day as weak to moderate surface-based buoyancy develops within a
weak lapse rate/moist profile.  Strengthening southwesterly 850-700
mb flow to 50+ kt across the FL peninsula late in the day will at
least be conditionally supportive of storm intensification in areas
not previously convectively overturned.  A risk for severe may
linger after dark and progressively shift farther south across the
FL Peninsula.

Farther north, a warm front will advance north across NC into VA.
The 23/12Z MHX raob sampled a very moist airmass (PW approaching 2
inches) and weak lapse rates.  This airmass will likely infiltrate
parts of southern VA within the northern periphery of a marginal
warm sector.  Hodographs are forecast to enlarge as a LLJ
strengthens over the Carolina Gulf Stream after dark and potentially
overlap with the development of weak surface-based buoyancy (250-750
J/kg SBCAPE).  Have included this area in low-severe probabilities
for the possibility of a late-night risk for strong/locally severe
thunderstorms.

...eastern KY/southern OH...
A conditional risk for a couple of stronger thunderstorms appears
possible beginning late Wednesday morning through peak heating with
the low risk spreading north from eastern KY into portions of
southern OH during the afternoon.  Widespread clouds will inhibit
strong heating but a relatively moist boundary layer in the left
exit region of an upper jet over GA/southern Appalachians will
promote diurnal shower/thunderstorm development.  Despite poor
low-level lapse rates, weak buoyancy and a shear profile supportive
of some storm organization may yield a low risk for damaging winds
or possibly a brief/weak tornado.  The storm activity will weaken
during the evening.

..Smith.. 05/23/2017

$$


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