Area Forecast Discussion
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FXUS62 KTAE 221116
AFDTAE

Area Forecast Discussion
National Weather Service Tallahassee FL
616 AM EST Wed Nov 22 2017

.AVIATION [Through 12Z Thursday]...

LIFR conditions are currently being observed at TLH and VLD, with
low end IFR conditions at ECP at this hour. Vsby and CIGS will
gradually improve over the next several hours at these sites.
Expect MVFR CIGS to linger at nearly all sites through the period.
RA will spread across the region Wednesday evening, affecting
most terminals Wednesday night into Thursday.

&&

.PREV DISCUSSION [316 AM EST]...

.NEAR TERM [Through Today]...

Given wet soil from rain yesterday afternoon, patchy fog is
currently affecting portions of the tri-state region this morning.
Conditions will be slow to improve after sunrise, therefore anyone
who is planning to travel this morning should plan more time to
get to their destination and use low beam headlights.

Mostly cloudy conditions will linger through the day, as the
second in a series of shortwave troughs and associated Gulf lows
approaches the region today. Given the current trajectory and
speed of the aforementioned low, shower activity will likely
remain offshore through much of the period, with the likely onset
of activity over land occuring this evening. Modest PWAT values
will keep precipitation efficacy limited, thus keeping the threat
for any heavy rainfall and flooding with this activity low.
Widespread cloud cover will keep daytime heating limited, as highs
will remain limited to the upper 60s to low 70s region wide.


.SHORT TERM [Tonight Through Friday]...

The shortwave dropping into the western Gulf this morning will
spread eastward across the entire GOMEX before lifting northeast
into the western Atlantic on Friday evening. Convection ongoing
in the western Gulf initiated as the shortwave moved across a
surface temperature gradient where anomalously high SST`s exist.
Models agree that further deepening of a surface low should be
expected through Thursday as the shortwave passes over the even
warmer loop current. As the surface low deepens, low-level winds
will strengthen, resulting in a large area of strong isentropic
ascent across the northeast Gulf tonight, spreading into the Big
Bend, north-central Florida, and southeast Georgia early Thursday
morning. In the presence of a pre-existing coastal front and a
southward advancing wedge front, surface frontogenesis will be
maximized as the southerly winds ramp up tonight through Thursday
morning. Additionally, a plume of anomalously high PWATs will
spread into the aforementioned areas. Considering the ingredients,
there exists the potential for heavy rainfall primarily late
tonight through early Thursday afternoon and WPC has placed the
above mentioned region under a marginal risk for excessive
rainfall. See the hydrology discussion below for more detailed
rainfall forecasts and expected impacts.

While the surface low and shortwave wont be completely out of the
Gulf until Friday evening, as the surface low moves east and the
wedge moves through the region, isentropic ascent will be cut off
with deep layer subsidence increasing through Friday. Thus,
expect a drying trend starting late Thursday afternoon and a
mostly dry day on Friday with only scattered light to moderate
rain expected in the southeast Big Bend of Florida. While much
less rain is expected on Friday, expect cloud cover to remain
until the frontal system departs Friday night. Highs will
generally be in the middle 60s, with overnight lows in the 40s and
50s through the period.


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

No rain is expected through the extended range as the eastern
CONUS trough will progress eastward and eventually deep layer
ridging will take over. Expect seasonable highs and lows through
the period.


.MARINE...

Winds will start ramping up to just below advisory levels across
the northeast Gulf today. Expect Cautionary conditions to prevail
through Friday, falling below headline levels by Friday evening
through the remainder of the weekend. Rain should be expected
through Friday evening, with the heaviest rain expected tonight
through Thursday afternoon.


.FIRE WEATHER...

Hazardous fire weather conditions are not expected through the
next several days, as RH`s will remain well above critical levels
with high chances for wetting rains. Drier conditions are expected
for the weekend.


.HYDROLOGY...

There`ll likely be a sharp QPF gradient over the next day or so
that will depend upon where exactly the strongest winds and
surface convergence align. In general, the heaviest rain should be
expected in the eastern Big Bend and south-central/southeast
Georgia tonight through Thursday morning. In these areas expect
average rainfall totals on the order of 1-2", however, isolated
higher amounts could range from 3-6" (especially closer to the Big
Bend coast). Luckily we`re in need of rain and flash flood
guidance suggest these amounts won`t be too concerning. As far as
the river systems are concerned, many rivers in the aforementioned
region are in low stage, or at least near it. Ensemble guidance
suggests that even reasonable worst case scenario rainfall amounts
will be unable to force the Suwannee into even action stage. Thus,
the potential for flash or river flooding appears low with
Thursday and Friday`s frontal system.


.SPOTTER INFORMATION STATEMENT...

Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.

&&

.PRELIMINARY POINT TEMPS/POPS...

Tallahassee   72  57  65  51  66 /  10  50  50  20  20
Panama City   71  55  67  53  66 /  20  20  20  10  10
Dothan        70  49  65  46  65 /   0  10  10  10  10
Albany        71  53  62  47  64 /   0  20  20  10  20
Valdosta      72  56  63  51  62 /  10  40  50  30  30
Cross City    74  59  67  54  66 /  20  60  90  60  60
Apalachicola  72  58  67  55  66 /  30  60  40  30  20

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&

$$

NEAR TERM...Pullin
SHORT TERM...Harrigan
LONG TERM...Harrigan
AVIATION...Pullin
MARINE...Harrigan
FIRE WEATHER...Pullin
HYDROLOGY...Harrigan


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