AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE 
TALLAHASSEE FL 1017 PM EST Mon Jan 23 2012


.UPDATE...The thin band of RAIN and thunderstorms has been pushing
gradually into our forecast area this evening from west to east,
reaching a EZM-ABY-MAI-ECP line by around 0230z. This activity has
advanced ahead of the main cold FRONT, which extended from just NW
of Atlanta to far southern Mississippi. A much drier AIR mass was
noted behind the front, with dewpoints 35-45F on most surface OBS.
HIGH-resolution model guidance, including all flavors of the 4km
WRF AS well as the HRRR, dminishes this activity to just ISOLATED
showers around 06z. This seems to match recent RADAR and LIGHTNING
trends, and makes sense with a lack of strong LOW-level forcing.
We used a 3-HR POP trend with hourly weather GRIDS to time the
PRECIPITATION trends in the very near term (0-6hr).

The other concern tonight is FOG potential. One area of fog was
already developing in the WAKE of the precipitation across SE
Alabama and the far western Florida Panhandle. KTOI and KCEW (both
just outside our forecast area) have reported visibilities as low
as 1/4SM in the past hour or so. Therefore, as the rain moves out
of our northwestern areas we will probably see some fog develop.
This may be abbreviated somewhat by the arrival of the main front
later tonight and therefore some drier air. As such, confidence
was not high enough in true dense fog (1/4SM or less) developing
to issue any ADVISORY in our AL zones and adjacent FL/GA zones.
Meanwhile, some of the high-resolution guidance and VSREF
probabilities indicate some potential for dense fog over Apalachee
Bay and into our eastern Big Bend counties as well, particularly
after 06z. There is uncertainty in those locations related to the
dense MID level CLOUD cover BLOWING off the CONVECTION to the
west. Also, no observations in that area have any restricted
VISIBILITY at this time. It isn`t inconceivable that a Dense Fog
Advisory may be needed later tonight, but confidence is not high
enough at this juncture to accurately place one.

Some minor tweaks were made to the weather and POPS into tomorrow
afternoon as well. Our 18z local 4km WRF-ARW, and to a lesser
extent the 12z SPC WRF-NMM, indicate some more focused afternoon
THUNDERSTORM activity around the rim of Apalachee Bay, from near
Apalachicola up towards Tallahassee and Madison. This seems to be
related to some enhanced onshore FLOW off the cooler waters as the
land areas heat up. PoPs were nudged up 5-10% in aforementioned
corridor. WRF forecast soundings show about 1000 j/kg of MLCAPE in
the afternoon, so THUNDER seems like a good bet south of wherever
the stalled cold front sets up.


&&

.AVIATION [through 00z Wednesday]...Tricky TAF package for the
overnight hours into Tuesday. Approaching cold front is forecast
to stall along the I-10 corridor all day Tuesday, creating impacts
for KTLH, KECP, and KVLD. SCATTERED showers and will impact KDHN,
KABY, and KECP for the next several hours before the activity
weakens. MVFR conditions expected at these sites through the
NIGHT. Conditions will improve through the day for the northern
terminals, which will be well north of the front. Farther south,
after patchy fog and low cigs overnight, conditions will LIKELY
only improve to near Alt. Arpt. thresholds during the day.
Isolated thunderstorms are possible during the afternoon.


&&

.MARINE...Considered a Marine Dense Fog Advisory for nearshore
waters from Apalachicola to the mouth of the Suwannee River.
However, despite a 63 degree dewpoint, Keaton Beach was holding
steady with a 2F dewpoint DEPRESSION, and there was no evidence of
any fog having developed yet at any coastal observations. This
will need to be monitored closely during the overnight. Subdued
SEAS and winds will continue through Wednesday when there should
be a gradual increase in southeasterly winds as a low develops
along the Texas Gulf coast. A front still looks to arrive late
Thursday Night, and advisory level winds and seas will be possible
just before and after the front. The front also looks to be
accompanied by some thunderstorms.