Tropical Storm Warning 1003, NWS Tallahassee, FL

Area Forecast Discussion
National Weather Service Tallahassee FL
110 PM EDT Mon Jun 19 2017

.AVIATION [Through 18Z Tuesday]...

Scattered SHRA continues to spread across the region and will
intermittently affect terminals across the region. Temporary
reductions in vsbys and CIGS will occur under any SHRA. ISO
thunder will be possible, but not prevalent with this activity. RA
will increase in coverage late this evening/tonight, potentially
lowering CIGS to at least MVFR and lowering vsbys.

&&

.PREV DISCUSSION [1039 AM EDT]...

.NEAR TERM [Through Today]...

At 2 am EDT tropical disturbance "93L" had a minimum pressure of
about 1006 mb along the northeast Yucatan Peninsula. There were no
west winds in the region based on surface observations and ASCAT
data, indicating that the system lacked a well-defined circulation.
While deep moist convection had recently increased (with the
approach of the most favorable time of the tropical convection
diurnal cycle), it was poorly organized. This disturbance could
impact our local weather, either directly or indirectly, over the
next few days, but not today. Read more about the future of this
system in the "SHORT TERM" and "LONG TERM" sections that follow.

Sunday evening's 925 mb analysis showed a cold front extending along
the Red river to western NY. Upper air data showed a long wave
trough across the Upper Midwest, and a TUTT from the FL Panhandle to
Mexico. Vapor imagery showed deep layer moisture rapidly increasing
from south to north across our forecast area, which, when combined
with at least some Q-G forcing associated with a low-layer trough
over the eastern Gulf of Mexico, will mean a good chance of rain for
much of the forecast area today. We expect the bulk of the rain to
develop along a weak sea breeze front late this morning or early
afternoon in FL, then across south GA and AL this afternoon. Poor
mid-layer lapse rates and the lack of deep-layer shear should limit
the severe storm potential. High temperatures will range form the
mid 80s at the FL coast to lower 90s around Albany.

.SHORT TERM [Tonight Through Wednesday]...

The main focus for this period will be potential development of
the tropical/subtropical system in the Gulf and resulting impacts
to our area. Models suggest that it will gradually become better
organized as it moves northwestward into the central Gulf over
the next couple of days and an upper ridge builds westward,
replacing an upper trough currently in this area. While there is
still significant disagreement regarding the track of this feature
(the GFS still has one of the farthest east solutions with a
track toward southeast LA, while the ECMWF and other models favor
a track much farther west into southern TX or northeast Mexico),
at this point no solutions take the system near our area.

Due to a lack of consistency in recent models, confidence remains
low regarding the eventual track of this feature, but periods of
heavy rainfall appear to be the main threat for our area at this
time. Given the latest set of model output, the heaviest rainfall
(potentially around a foot looks likely to be west of our area.
However, if eastern solutions such as the GFS verify, some
locations could receive several inches of rain by Wednesday as a
plume of deep layer moisture to the east of the system (PWAT
values possibly around 2.5") pushes northward into our area. Also,
this may not be a purely tropical system, and as a result a
baroclinic zone could extend well northeast of the low itself and
enhance showers and thunderstorms across our area. Therefore, even
if the western solutions such as the ECMWF verify, periods of
showers and thunderstorms look likely across our area on Tuesday
and Wednesday.

With widespread cloud cover and periods of showers and
thunderstorms each day, diurnal temperature differences should be
small. Highs in the lower 80s are expected to prevail across our
area along with lows in the lower to mid 70s.

.LONG TERM [Wednesday Night Through Monday]...

As the aforementioned tropical/subtropical system moves farther
west/northwest of our area, more typical summer conditions for our
area are expected to develop later in the week through the
weekend. However, from Wednesday night through Thursday lingering
deep layer moisture should lead to good chances of showers and
thunderstorms (generally 50-60 percent across our area). Deep
layer ridging is expected to build across our area from Friday
into the weekend, although ample moisture and sea breeze forcing
should lead to chances of showers and thunderstorms each day, with
highest chances during peak heating times in the afternoon and
early evening. After highs remain suppressed in the lower-mid 80s
on Thursday with ample cloud cover, decreasing clouds will help
temperatures rise to the upper 80s and lower 90s from Friday
through the weekend. Low temperatures will remain in the low-mid
70s throughout this period.

.MARINE...

Winds and seas will increase today through tonight as a broad
area of low pressure develops in the southern Gulf and pressure
gradient tightens across our area. As a result, small craft
operators should exercise caution. A small craft advisory may be
needed across our area starting tonight or Tuesday morning as the
low moves northwestward into the Gulf and may develop into a
tropical system. However, there is still quite a bit of
uncertainty regarding the forecast track of this low. Regardless
of the exact track and intensity, be aware that choppy seas and
gusty winds will be possible through the next few days along with
periods of showers and thunderstorms.

.FIRE WEATHER...

No concerns.

.HYDROLOGY...

Periods of heavy rainfall are possible across our area during the
next few days as a result of the potential tropical system
projected to move northwestward into the Gulf of Mexico. Rainfall
amounts will depend on the track of this system; if it tracks
into the western Gulf as suggested by some models, widespread
flooding should not be an issue. However, if a more eastern
solution verifies, portions of our area would likely see several
inches of rain which could lead to river flooding and possibly
isolated flash flooding. We will continue to monitor this system
closely for flood potential.

&&

.PRELIMINARY POINT TEMPS/POPS...

Tallahassee   74  81  74  83  74 /  60  70  60  70  50
Panama City   75  81  75  83  77 /  70  80  60  70  50
Dothan        73  79  71  83  73 /  40  70  60  70  50
Albany        74  81  72  83  73 /  40  70  60  60  50
Valdosta      74  83  73  83  73 /  40  60  50  60  40
Cross City    74  85  74  84  74 /  50  70  50  50  50
Apalachicola  76  82  77  83  77 /  70  70  60  70  50

&&

.TAE WATCHES/WARNINGS/ADVISORIES...

FL...None.
GA...None.
AL...None.
GM...None.

&&

NEAR TERM...Pullin
SHORT TERM...Fournier
LONG TERM...Lahr
AVIATION...Pullin
MARINE...Fournier
FIRE WEATHER...Lahr
HYDROLOGY...Fournier