Area Forecast Discussion
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FXUS62 KTAE 181813

Area Forecast Discussion
National Weather Service Tallahassee FL
113 PM EST Mon Dec 18 2017

.AVIATION [Through 18Z Tuesday]...

IFR/MVFR cigs continue at all TAF sites at 18z with only DHN
still experiencing MVFR vsbys. Patchy light to moderate rain will
continue to spread from west to east across the local region for
the remainder of this afternoon briefly impacting all TAF sites.
Then, look for rapidly deteriorating conditions this evening and
overnight as advection fog spreads inland from the coastal areas.
VLIFR cigs/vsbys are certainly possible everywhere with slow
improvement after daybreak Tuesday.



.NEAR TERM [Through Today]...

A dense fog advisory was issued for all but the Florida Panhandle
and Western Big Bend counties until 10 am est. Although the advisory
has expired, patchy fog will continue at several locations for a few
more hours. Otherwise, extensive low level clouds and intermittent
mostly light rain can be expected today with above seasonal temps in
the 70s to around 80 degrees.

.SHORT TERM [Tonight Through Wednesday]...

A relatively strong 500 mb ridge over the Southeast will weaken
Tuesday night and Wednesday as a short wave trough (currently over
the Baja Peninsula) moves eastward across the Southeast. Until
then rain chances for our forecast area will be slight and
confined mainly to the northern parts of our area, on the fringes
of weak Q-G forcing and increasing deep-layer moisture. Rain
chances will increase Wednesday, especially across the FL
Panhandle, southeast AL, and southwest GA, where the greatest
concentration of large scale ascent and moisture will be. (PoPs
will range from 60% at Dothan to 30% at Tallahassee, and less than
20% at Cross City).

Although most of the upper-level height falls will be to our
north, 0-6km bulk shear values of at least 50 knots over our
forecast area would suggest at least some possibility of storm
organization. However, MLCAPE values will struggle to reach 500
J/kg. Thus with limited buoyancy and large-scale ascent, the
threat of isolated severe storms on Wednesday is low, and would
consist primarily of damaging wind gusts (40-60 MPH) or perhaps
a brief tornado, mainly north and west of Tallahassee.

Temperatures are likely to be well above climatology, despite
significant cloud cover during the daytime. Lows will be in the
lower 60s (climatology is lower 40s). Highs will be in the mid
70s (climatology is lower 60s).

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

Rain chances will end quickly Wednesday night once the
aforementioned upper trough and associated surface baroclinic trough
move by, with only a slight drop in temperatures to close out the
work week. Considerable differences arise between the global models
by the weekend. The GFS brings a cold front slowly through our
forecast area and stalls it just to our south, with gradually
cooling temperatures and persistent rain chances through Christmas
Day. The ECMWF keeps the front well to our northwest, with
continued warm temperatures and fair weather. As usual this far
out, we have blended the solutions and get PoPs in the 20-30%
range, highs in the upper 60s (north) to mid 70s (south), and lows
in the 50s. Hopefully the models will trend toward the same
solution in subsequent forecast cycles.


Relatively light south to southwest winds and lowering seas will be
the rule through Tuesday under the influence of a weak high pressure
system. Southwest winds will briefly increase on Wednesday as a
low pressure trough moves through the region, with light winds and
low seas returning Wednesday night and Thursday.


Relatively humid conditions will preclude most fire weather concerns
over the next several days. Dispersion values will be on the low
side today and tomorrow, but not quite low enough to warrant a
headline. Patchy fog is possible this morning, but a widespread,
possibly dense fog, is expected tonight.


The latest NOAA ESRL analog QPF (through Saturday), based on
Sunday`s GEFS, shows QPF ranging from half an inch over portions of
southeast AL and south GA to a quarter of an inch or less elsewhere.
This is very close to WPC`s latest 7-day QPF totals. This is an area
average, and isolated higher amounts are possible in deep
convection. These values would have little impact on the local river
system, and are unlikely to cause flooding.


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.



Tallahassee   62  78  60  75  55 /  20  10  10  30  20
Panama City   64  74  63  73  57 /  10  10  10  30  10
Dothan        60  76  62  75  52 /  20  10  20  60  10
Albany        60  74  61  75  54 /  30  10  10  60  20
Valdosta      63  76  60  75  56 /  20  10  10  30  20
Cross City    60  78  57  76  57 /  10  10  10  10  20
Apalachicola  63  74  61  74  57 /  10  10  10  20  20




SHORT TERM...Fournier
LONG TERM...Fournier
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