National Weather Service Weather Forecast Office

Area Forecast Discussion

960
FXUS62 KTAE 180019
AFDTAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
819 PM EDT Fri May 17 2013

.Near Term [Through Rest of Tonight]...
The large scale longwave pattern is highlighted by a trough over the
Wrn states, building ridge over Cntrl states, a trough over the TN
River Valley and SWD, and a ridge of high pressure across the Wrn
Atlc. Locally, area remains on Wrn edge of this ridge. Upper low
over Nrn AL slowly weakening as it moves Ewd. Assocd H5 shortwave
rotating across N/Cntrl AL and moving WNW-ESE spreading ample
convection over Nrn AL/GA but only mid and high level cloud debris
across local area. At surface, subtropical ridge extends from Ern
Atlc to across NRN FL yielding generally SE flow.

During the rest of tonight, upper trough, low and shortwave continue
their slow Ewd trek allowing upstream ridge to move into MS Valley.
Assocd clouds at base of trough will also spread EWD impacting
mainly our Nrn most counties but increasingly diminishing with loss
of heat and as they move away from local area. The combination of
the departing clouds, the light onshore humid flow (Rap 12z Sat TAE
sounding of 1.26 inches) and mild temperatures will provide another
favorable setup for fog. While the most favored area appears to be
along the FL Panhandle and into SE AL, some potential for fog is
possible across Southwestern Georgia as well altho not enough to
include in wx grids. Based on current trends in temps, tweaked up
min temps a few degrees land and water. Also based on model guidance
and persistence, changed wx GRIDS 10z-13z from areas and patchy
light fog to areas/patchy dense fog. Temps overnight will be
in the low to mid 60s.

&&

.SHORT TERM [Saturday through Monday]...

The 500 mb trough axis (currently over western TN) will be over our
forecast area Saturday afternoon, then east of our area by Sunday
morning. Any vertical motion/deep layer moisture associated with
this feature appears rather limited, and the dynamical and
statistical NWP guidance aren`t very "bullish" on PoP or QPF. The
00 UTC Convection Allowing Model (CAM) runs also showed very
little in the way of deep moist convection for Saturday, so our
PoP over the weekend will be low (10-30%...with the highest PoP
during the afternoon hours in our northern zones). Temperatures
will be a few degrees above average- generally around 90 deg,
except for the beaches where the highs will be in the lower 80s
because of the cooler water.

&&

.LONG TERM [Monday night through Friday]...

The 500mb ridge over the Southeast U.S. early in the work week will
transition to a weak trough by late week. The height falls over our
forecast area will be modest so only a slight increase in PoP is
expected later in the week. Until then, the GFS forecasts more deep
layer moisture (hence QPF) than the ECMWF for our region.
Climatologically it`s still a bit early for widespread mesoscale-
induced convection, so an average of the two solutions will get us
close to our climatological PoP (around 20%), with a diurnal
cycle. High temperatures will be at or a few degrees above
average, with lows near average (in the 60s).

&&

.Aviation...
VFR conditions this evening will gradually give way to prevailing
MVFR visibilities at DHN, ABY and VLD after midnight as fog
develops. IFR/LIFR conditions are expected at the ECP and TLH TAF
sites. IFR/LIFR conditions can`t be ruled out at DHN, ABY, and
VLD, but the chance of fog is much lower at these terminals. Shortly
after daybreak, any remaining fog should dissipate and all terminals
will return to VFR conditions with southerly winds around 10 knots.

&&

.MARINE...

Winds and seas will remain low for the next several days, but for
brief increases (to 10 to 15 KT) in winds and chop near the coast
during the afternoon, due to the sea breeze circulation
enhancement.

&&

.Fire Weather...

Relative humidity levels will remain above critical thresholds for
the next several days. Therefore, Red Flag conditions are not
anticipated.

&&

.HYDROLOGY...

Area rivers and streams will likely remain well below flood stage
for the next several days.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   64  88  64  88  66 /  0  10  10  10  10
Panama City   68  83  69  83  70 /  0  10  10  10  10
Dothan        66  88  67  89  69 / 10  20  20  10  10
Albany        66  89  67  90  68 / 10  20  20  20  20
Valdosta      65  88  63  88  65 /  0  10  20  20  20
Cross City    64  88  62  88  65 /  0  10  10  20  10
Apalachicola  66  81  67  81  69 /  0  10   0  10  10

&&

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

&&

$$

NEAR TERM...Block
SHORT TERM...Fournier
LONG TERM...Fournier
AVIATION...Barry
MARINE...Block/Fournier
FIRE WEATHER...Godsey
HYDROLOGY...Fournier