Area Forecast Discussion
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FXUS62 KTAE 150526
AFDTAE

Area Forecast Discussion
National Weather Service Tallahassee FL
1226 AM EST Fri Dec 15 2017

.AVIATION [Through 06Z Saturday]...

Mid/high clouds will continue to stream across the aerodromes
over this TAF period. MVFR vsbys are possible at TLH/VLD ahead of
a cold front expected to pass through the area overnight and into
the morning hours. Best timing for the vsbys will be around dawn.
Light and variable winds will become northwesterly behind the
front.

&&

.PREV DISCUSSION [734 PM EST]...

.NEAR TERM [Through Tonight]...

A large, positively-tilted upper level trough lies across most of
the eastern and central CONUS, with the axis of the trough
stretching from the Great Lakes down to northwest Mexico. A +PV
anomaly at the base of the trough well to our west is helping
amplify the feature this evening. Locally, however, the flow is
mostly zonal with the southern stream upper level jet stretching
along the northern Gulf coast, keeping us under a thick ribbon of
upper level cloud cover. At the low levels, our area has a vaguely
defined pressure pattern in place with weak low pressure
(~1016mb) along a dry cold front to our northwest (across northern
AL and central MS) and weak high pressure (~1020mb) well to our
east over Bermuda. Surface winds are calm to light and variable.
Overall, the forecast remains on track for mild conditions
tonight, with cloudy skies, calm winds, and low temperatures in
the 40s.


.SHORT TERM [Tonight Through Saturday]...

Zonal flow aloft will prevail through much of the period as the
eastern CONUS trough lifts north and an east/west subtropical ridge
lifts northward across the FL Peninsula. An area of +PV that will
mostly cutoff across northern Mexico and southern TX tomorrow, will
move northeast through the Southern Plains and Middle Mississippi
Valley Saturday through Saturday night. In advance of this wave, the
ridge will amplify a bit over the Southeast on Saturday. At the
surface, a dry cold front associated with a shortwave moving off the
Northeast coast today will gradually move through the Southeast
through Friday afternoon on the nose of a building surface ridge. No
rain is expected over land with this front, though there may be some
across the northeast Gulf as a weak southern stream wave passes over
the front. Highs will generally be in the lower to middle 60s, with
overnight lows ranging from the upper 30s to the middle 40s. These
forecast highs and lows remain very close to seasonal norms.


.LONG TERM [Saturday Night Through Thursday]...

The extended range forecast becomes a bit more complicated due to
the lack of agreement on some details between the global models. In
general, a transition to a wetter pattern is expected. The 00/12z
GFS` differs from the 00z ECMWF in that they fail to cutoff the
southern half of the northern stream longwave trough as it moves
through the Pacific Northwest. This essentially results in
differences as to how progressive the system is and just how dynamic
it is locally once it arrives. As of the 12z model cycle, the
Canadian has come into better agreement with the GFS on the more
progressive side. Regardless of the exact details, expect shower and
possibly thunderstorm chances to begin ramping up Sunday night. The
big question will be whether this system clears out of the Southeast
by Wednesday morning, or if it lingers through the end of the week
when another front will approach from the northwest. Expect both
highs and lows to be above average until the frontal system clears
the region.


.MARINE...

Winds and seas are forecast to remain below Cautionary conditions
through the weekend. A brief uptick in winds to around 15 knots is
expected behind a cold front tomorrow through tomorrow night.
Winds will likely be around 15 knots on Sunday as well; otherwise
relatively light winds are forecast.


.FIRE WEATHER...

No concerns.


.HYDROLOGY...

No meaningful rain is expected through much of the weekend. Late
Sunday through early next week, there`s the potential for average
rainfall amounts of 1-3" with isolated higher amounts. The QPF early
next week remains uncertain as models differ significantly regarding
the details of the evolution of the frontal system. These rainfall
estimates are subject to change in either direction. Based on the
current amounts forecast, flooding is not expected to be a concern.


.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   65  41  60  46  70 /   0   0   0   0  20
Panama City   61  43  60  52  70 /   0   0  10   0  40
Dothan        54  34  56  43  69 /   0   0   0   0  40
Albany        58  35  57  42  69 /   0   0   0   0  20
Valdosta      64  40  59  44  71 /   0   0   0   0  20
Cross City    71  45  65  48  74 /   0   0   0   0  10
Apalachicola  67  46  61  54  69 /  10   0   0   0  30

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk until 1 AM EST /midnight CST/ early this
     morning for Coastal Gulf.

GA...None.
AL...None.
GM...None.
&&

$$

NEAR TERM...Nguyen
SHORT TERM...Harrigan
LONG TERM...Harrigan
AVIATION...Scholl
MARINE...Harrigan
FIRE WEATHER...McD
HYDROLOGY...Harrigan


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