Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 192304
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
704 PM EDT Sun May 19 2013
...SEVERE THUNDERSTORM WATCH HAS ENDED FOR SRN GA AND MADISON
.NEAR TERM [Tonight]...
The larger scale pattern is dominated by troughing over Wrn states
and ridging over Ern states. However, at a more regional level,
weak mid/upper shortwave moved over mid-Atlc states helping to
deepen a trough down SE coast. This generated vorticity and a Swd
moving impulse/cold pool and aided in lift and steepening mid-
level lapse rates. At the surface, weak ridge stretched W-E over
Nrn Gulf of Mex providing onshore moist and unstable flow along
with a weak pressure gradient. Looking north a several outflow
boundaries moved south across GA counties while the Gulf seabreeze
moved newd and the east coast sea breeze moved wwd.
During, the afternoon, the combination of impulse/upper cold pool
moving into a moderately unstable airmass and interacting with
outflow boundaries generated some strong storms propagating SSE
parallel to outflow boundary across mainly NE tier of our GA
counties. However, weak low/mid tropospheric flow was weak,
preventing significant storm organization and/or updraft rotation
and inhibiting storm clusters from organizing more. One report at
440 pm EDT noted several trees down in Fitzgerald, Ben Hill GA. By
7 PM EDT, most of the convection was located east of a line from
Brooks thru Berrien Counties in GA enhanced by SE moving outflow
boundary with strong winds and possibly small hail. However the
widespread severe weather threat and the severe thunderstorm watch
Although some strong storms remain possible into the evening
across mainly Thomas Ewd to Lowndes counties, most of the
strongest activity later this evening should be just east of our
forecast area and I-75 where seabreeze and outflow mergers can
generate strong to possibly severe storms. Father west,
thunderstorms will gradually diminish, followed by generally fair
weather later tonight. Once again there may be areas of low clouds
and fog, especially west of the Apalachicola River and in areas
that get rain. Expect lows generally 65 to 70.
.SHORT TERM [Monday through Tuesday Night]...
The consensus of numerical model guidance portrays an average mid-
upper level shortwave ridge over much of our area in the Monday
and Tuesday time frame, with a west-to-east gradient in PWAT. The
lowest values will be situated over the western part of our area,
with the highest values in the east - closer to the influence of
the Atlantic Ocean. The overall flow pattern through the depth of
the troposphere should be fairly weak, so there shouldn`t be a
larger-scale forcing mechanism for widespread convection. PoPs
were concentrated in our Georgia and Florida Big Bend zones where
deeper moisture will reside, with a diurnal trend to be maximized
in the late afternoon. Highs away from the coast will be around 90
degrees in general.
.LONG TERM [Wednesday through Sunday]...
Chances for showers and thunderstorms are expected to be a little
more widespread in our area on Wednesday and Thursday as a low
amplitude mid-upper level trough ejects east from the Plains. On
Wednesday, our area will be situated right underneath highly
divergent flow aloft, and by Thursday a weak surface front should
be developing into our area; both situations favor at least a bit
of a focus for larger scale vertical motion. Therefore, PoPs on
Wednesday and Thursday were increased into the 30-40% range. After
that, a strong surface high builds south into the eastern US, and
the weak surface front shifts south into the Florida Peninsula.
This should allow for some drier air to arrive and slightly lower
PoPs closer to climatological normals. The temperature forecast is
one of persistence, with highs maintaining close to 90.
.AVIATION [through 00 UTC Tuesday]...
Thunderstorms continue to diminish but will hold together across
mainly Ern GA counties and adjacent Nrn Big Bend. Tstms possible
until around 02z at KVLD. Wind gusts of 35 KT and IFR Vis are
possible with any storms as they translate southeastward. It`s
unlikely that these storms will affect the other terminals. Fog
and low CIGS are possible early Monday morning, especially at KECP
Winds and seas should remain relatively calm through the work
week. Winds will be generally 10 knots or less, and seas 2 feet or
less. There will be a chance for a few showers or storms, and
winds could be briefly higher near storms. Storms would be most
likely near the coast and in the late afternoon or evening hours.
Relative humidity values will remain above critical levels through
Tuesday with relatively light transport winds and deep mixing
heights especially over Florida. The airmass should remain
sufficiently moist to preclude red flag conditions into the upcoming
Any rain through Friday would likely arrive in the form of
scattered showers and thunderstorms, and average rainfall totals
should be low enough to prevent any widespread flooding concerns
or issues on mainstem rivers across the area.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 66 90 66 90 69 / 20 20 10 20 20
Panama City 70 85 69 85 71 / 10 10 10 10 10
Dothan 68 91 67 91 71 / 10 10 10 10 10
Albany 68 90 67 91 69 / 30 20 20 20 20
Valdosta 67 89 65 90 68 / 30 40 20 30 20
Cross City 66 88 64 89 67 / 20 30 20 30 20
Apalachicola 69 83 68 82 71 / 0 10 10 20 10