Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 250719
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
319 AM EDT Thu Sep 25 2014
.Near Term [Through Today]...
An upper level trough lies over the Appalachian mountains with
surface high pressure in place over the Ern CONUS. This surface high
pressure is lifting north, meaning the pressure gradient will be
weaker, so it won`t be as windy today as it was yesterday. It will
be another cool and cloudy day, however, and particularly so for
south-central GA once again. Highs today will be in the mid-upper
70s in south-central Georgia, low 80s elsewhere.
.Short Term [Tonight Through Saturday]...
Under the influence of middle and upper level ridging, essentially
no deep-layer synoptic forcing for ascent is expected through
Saturday. Instead, any showers or isolated storms that do develop
will be forced in the lower-levels. The primary mechanism for
showers and storms will be an inverted surface trough currently
bending down the Southeast coastline. Although the cutoff low that
initially forced this trough has moved away, its presence has been
maintained by the strong temperature gradient between the warm
Gulf Stream waters and the very cool adjacent land temperatures as
a result of the persistent low cloud deck yesterday that is
expected once again today. Through tonight, southerly steering
flow will force a low-level PV anomaly forced by ongoing
convection off of the southeast Florida coastline, northward
along the Florida east coast. This low-level support will further
enhance the already pronounced surface trough. By Friday, the
mid-level ridge axis will pivot to a more east-west orientation.
This will result in a more easterly steering regime over the
Peninsula, thereby forcing the coupled low/mid-level trough system
west into the northeast Gulf by Friday night. What this all means is
that rain chances will drastically increase beginning Friday
afternoon over the southeast Big Bend of Florida and south-central
Georgia. The highest threat for rain will shift westward through
the first part of the weekend with the best chance for rain
Saturday along and south of the southern tier of counties in
Georgia and Alabama. The environment will not be favorable for the
development of severe storms, though heavy rain will be a
possibility; see the hydrology discussion below.
.Long Term [Saturday Night Through Thursday]...
By late in the weekend a developing trough over the Southern
Plains will pull the aforementioned surface trough and moisture
further north, with enhanced rain chances across the remainder of
the area. With precipitable water values possibly exceeding 2
inches, the potential for locally heavy rainfall will continue.
Into Monday and Tuesday, the global guidance diverges with the
ECMWF cutting off an upper low over the Arklatex and pushing a
strong front into the Deep South. The GFS is much weaker and more
progressive with its evolution. At this time, have leaned more
towards the wetter ECMWF solution for Monday and Monday night.
With the approach of the inverted trough and it`s more tropical
airmass, temperatures will likely be a bit above normal for the
weekend into early next week (especially for min temps).
[Through 12Z Friday]
MVFR-IFR cigs will affect all local terminals this morning except
ECP (and possibly briefly there as well, although confidence is
lower). Skies are expected to start clearing out from west to east
starting in the late morning and into the afternoon, except at VLD
where they may hang in through the period.
On-and-off cautionary level easterly winds will continue through
the weekend. Thereafter, winds will lower below headline levels as
a broad area of weak low pressure moves across the Southeast.
Relative humidity values will remain above critical thresholds
through the period. Red flag conditions will not be met.
The above mentioned period of wet weather (Friday through at least
Sunday) could produce, on average, 1 to 3 inches of rain across
north Florida. Elsewhere, averages on the order of an inch or less
are more likely. These amounts are not expected to result in any
river flooding due to the widespread low flows. Depending on
whether the heavy rain persists through Tuesday, which is
uncertain, there may be some minor river flooding issues.
.Preliminary Point Temps/PoPs...
Tallahassee 82 64 85 73 84 / 0 10 40 40 60
Panama City 82 67 83 73 82 / 0 0 30 30 70
Dothan 80 63 82 69 81 / 0 0 10 20 40
Albany 78 64 81 69 82 / 0 10 10 20 40
Valdosta 79 66 83 71 85 / 10 10 50 40 60
Cross City 84 69 85 72 85 / 10 10 70 60 50
Apalachicola 82 70 83 75 82 / 0 10 40 40 70