Mesoscale Discussion 0550
NWS Storm Prediction Center Norman OK
1102 AM CDT Sun Apr 23 2017
Areas affected...Portions of western/central GA...far southeastern
AL...and a small part of the FL Panhandle
Concerning...Severe potential...Watch possible
Valid 231602Z - 231800Z
Probability of Watch Issuance...40 percent
SUMMARY...Thunderstorms should strengthen along a cold front by
early afternoon, posing mainly a strong to locally damaging wind
threat. Watch issuance is possible.
DISCUSSION...As of 16Z, a surface low was located over far
northeastern AL/northwestern GA. A cold front extends southward from
this low generally along the AL/GA border into far southeastern AL
and the western FL Panhandle, moving eastward with time. Visible
satellite imagery shows partly to mostly sunny skies ahead of the
front across parts of west-central GA into the central FL Panhandle.
A narrow corridor of greater low-level moisture was analyzed along a
line from Atlanta to Macon to Albany GA, continuing southward to
Tallahassee FL and vicinity. A residual pocket of somewhat lower
theta-e air was located across central GA into northern FL per
latest surface observations.
As large-scale ascent associated with a mid-level low over western
TN overtakes the surface cold front, an increase in convective
coverage is expected along the length of the front over the next
several hours. Mid-level lapse rates remain generally poor across
this region per various 12Z soundings and should remain so through
the afternoon per RAP forecast soundings. Even with some diurnal
heating ahead of the front coincident with the narrow corridor of
greater low-level moisture, these poor mid-level lapse rates will
likely act to limit the amount of instability that can develop ahead
of the front. Most short-term guidance suggests MLCAPE should range
between 250-750 J/kg. Mid-level winds are forecast to strengthen
slightly, although only modest veering with height will likely limit
effective bulk shear values to 30-35 kt.
Multicells and line segments along the front should pose an isolated
threat for strong to locally damaging winds through the afternoon,
with perhaps marginally severe hail in a transient supercell
structure also possible. The eastward extent of this isolated threat
will likely be limited by the previously mentioned pocket of
slightly drier low-level air across central GA/northern FL. Radar
trends will be monitored for an increase in convective
coverage/intensity that may necessitate watch issuance.
..Gleason/Weiss.. 04/23/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FFC...TAE...
LAT...LON 33258455 33428414 33398360 33098332 32768321 32058330
31178373 30708406 30438488 30568532 30928562 31778510
32258485 33258455
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