National Weather Service Raw Text Product

Displaying AFOS PIL: AFDTAE Received: 2012-12-26 04:09 UTC


210 
FXUS62 KTAE 260409 AAA
AFDTAE

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TALLAHASSEE FL
1109 PM EST Tue Dec 25 2012

...Tornado Watch #698 is now in effect until 5 AM EST/ 4AM CST/
for all of Southeast Alabama, the Florida Panhandle and the
adjacent Coastal Waters, western portions of the Florida Big Bend,
and much of Southwest Georgia...

.MESOSCALE UPDATE...With the powerful pre-frontal squall line
continuing to hold together as it begins to enter our CWA from the
west, the latest Tornado Watch has been extended eastward to
include all but the eastern 1/3 of the CWA until 10Z. Furthermore,
in this strong and highly sheared environment, we still need to
keep a very close eye on any fore-running Supercells that have
been developing over the Panhandle Waters, as some of these storms may
produce brief Tornadoes.

&&

.NEAR TERM [Through Tonight]...
19 UTC regional mesoanalysis shows the surface low continues to
deepen over Western Louisiana now down to 998 mb. The warm front
has continued to slowly lift northward across Southern
Mississippi/Alabama and then dropping southeastward along the
Florida-Georgia border. Observational data from offshore buoys and
oil platforms are showing a large reservoir of 65+ degree dewpoints
over the North Central Gulf of Mexico. This very moist airmass
will continue to be advected inland and eventually even move into
the Florida Panhandle and Southeast Alabama later this evening.
Further east, observational data around Apalachee Bay show that
greater destabilization will be required this evening to further
the severe weather threat - but in this particular case, the
kinematics are so strong, that only marginal instability would be
needed. 

So, the set up looks to be coming together as a strong jet rounds
the base of a potent upper level low moving into Southern
Arkansas. 0-6km deep layer shear values will approach 75 to 80 kts
at times across the Southeast and into our region late tonight.
Low level shear will be as equally as impressive with 0-1 km shear
values of 30 to 40 kt. 

Within our area the best area of overlap of sufficient instability
/SBCAPES of 500-750 J/KG/ and strong wind shear is clearly across
the Florida Panhandle, into Southeast Alabama, and far
Southwestern Georgia. It is within this area that there is a likely
chance of significant severe weather activity tonight. While
discrete supercellular convection cannot be ruled out within this
zone (in fact - a couple of mini-supercells are in progress 40mi
south of Destin at 20z), the most likely threat appears to be
destructive straight line winds with the squall line. Wind gusts
with the line could easily exceed 60 to 70 kts.

Further to the east into South Central Georgia and the Florida Big
Bend, the stabilizing influence of Apalachee Bay will likely
diminish the intensity of the squall line somewhat - but the
current thinking is that even though the predicted SBCAPES drop
off to about 200-400 J/KG that the strong kinematics will overcome
the marginally unstable airmass and sustain severe level wind
gusts along the squall line through the predawn hours while
the squall line approaches Interstate 75.

&&

.SHORT TERM [Wednesday Through Thursday Night]...
As the upper level jet moves eastward, pushing the front through our 
area Wednesday, expect a rainy morning across the eastern portions 
of our area, with rain chances decreasing throughout the day. 
Wednesday will be cooler than we've been seeing lately, with high 
temperatures in the lower to mid 50s in southeast Alabama, 
increasing to the southeast to the mid 60s ahead of the front where 
cloud cover and precipitation will still be present throughout the 
day. After the front clears our forecast area, a much cooler, drier 
air mass will enter the region. Within this air mass, Wednesday lows 
are expected to dip into the lower to mid 30s across the region. 
Thursday will be dry with mostly clear skies in the wake of the 
front, but cooler with high temperatures in the upper 40s to lower 
50s across the area. Thursday night lows will be in the lower 30s.

&&

.LONG TERM [Friday through Tuesday]...
A progressive pattern will remain in place through the period
with the 25/00z GFS and 25/00z ECMWF agreeing that the next rain
maker will move into the area on Saturday. This system currently
does not look nearly as impressive in terms of convective
potential as the system we are dealing with now, and the official
forecast only carries a slight chance of thunder close to the
coast. For the most part, temperatures are expected to be within a
few degrees of the seasonal averages, except cooler than average
Thursday night as weak high pressure temporarily builds in from
the north.

&&

.AVIATION...[Through 00z Thursday]
Strong convection is expected to develop across the area, some of 
which could be very severe overnight. The main period of strongest 
activity is expected across the area tonight between 04Z to 12Z 
along a fast moving windy squall line ahead of a rapidly moving cold 
front. Winds will shift sharply from southerly to westerly behind 
this front. MVFR cigs/vsbys and gusty onshore winds will accompany 
these systems. IFR and even brief LIFR possible with any heavy rain. 
After cold exits, MVFR cigs and vsbys in fog persist into mid to late
morning from west to east. strong and very gusty west then nw west 
winds in wake of front until close to sunset.  

&&

.MARINE...
A very powerful squall line develops out ahead of the approaching 
Cold Front overnight. Gale Force winds (or frequent gusts) and seas 
will overtake the marine area, with even stronger winds in the 
vicinity of any thunderstorms. These gale conditions will linger for 
a while out of the west behind the Cold Front during the first half 
of Wednesday, before slightly diminishing back to Advisory levels 
out of the northwest into Wednesday night.

&&

.FIRE WEATHER...
There are no red flag concerns for the next several days with 
wetting rain on the way.

&&

.HYDROLOGY...
Much of the region is expected to receive an additional 1 to 2 
inches of rainfall during the next 12 hrs. This may cause some 
minor rises along area rivers, but due to low flows in area basins, 
no significant rises are expected at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   60  64  34  52  33 /100  30  10   0  10 
Panama City   56  62  38  52  43 /100  10  10   0  10 
Dothan        50  55  32  49  33 /100  10  10   0  10 
Albany        54  59  31  50  32 /100  30  10   0  10 
Valdosta      58  63  34  52  32 /100  90  10   0  10 
Cross City    58  67  36  56  32 /100 100  10   0  10 
Apalachicola  61  65  39  53  46 /100  20  10   0  10 

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...WIND ADVISORY from 7 AM EST /6 AM CST/ to 5 PM EST /4 PM CST/ 
     Wednesday for Calhoun-Central Walton-Coastal Bay-Coastal 
     Dixie-Coastal Franklin-Coastal Gulf-Coastal Jefferson-
     Coastal Taylor-Coastal Wakulla-Gadsden-Holmes-Inland Bay-
     Inland Dixie-Inland Franklin-Inland Gulf-Inland Jefferson-
     Inland Taylor-Inland Wakulla-Inland Walton-Jackson-
     Lafayette-Leon-Liberty-Madison-South Walton-Washington.
     HIGH SURF ADVISORY until 7 PM EST /6 PM CST/ Wednesday for 
     Coastal Bay-Coastal Gulf-South Walton.
GA...WIND ADVISORY from 7 AM to 5 PM EST Wednesday for Baker-Ben 
     Hill-Berrien-Brooks-Calhoun-Clay-Colquitt-Cook-Decatur-
     Dougherty-Early-Grady-Irwin-Lanier-Lee-Lowndes-Miller-
     Mitchell-Quitman-Randolph-Seminole-Terrell-Thomas-Tift-
     Turner-Worth.
AL...WIND ADVISORY from 6 AM to 4 PM CST Wednesday for Coffee-Dale-
     Geneva-Henry-Houston.
GM...SMALL CRAFT ADVISORY until 1 AM EST Wednesday for Apalachee 
     Bay or Coastal Waters From Keaton Beach to Ochlockonee 
     River Fl out to 20 Nm-Coastal Waters From Ochlockonee 
     River to Apalachicola Fl out to 20 Nm-Coastal waters from 
     Suwannee River to Keaton Beach out 20 NM-Waters from 
     Suwannee River to Apalachicola FL from 20 to 60 NM. 
     SMALL CRAFT ADVISORY from 1 PM Wednesday to 1 AM EST Thursday 
     for Apalachee Bay or Coastal Waters From Keaton Beach to 
     Ochlockonee River Fl out to 20 Nm-Coastal Waters From 
     Ochlockonee River to Apalachicola Fl out to 20 Nm-Coastal 
     waters from Suwannee River to Keaton Beach out 20 NM-
     Coastal waters from Apalachicola to Destin FL out 20 NM-
     Waters from Suwannee River to Apalachicola FL from 20 to 
     60 NM-Waters from Apalachicola to Destin FL from 20 to 60 
     NM. 
     GALE WARNING until 1 PM EST Wednesday for Apalachee Bay or 
     Coastal Waters From Keaton Beach to Ochlockonee River Fl 
     out to 20 Nm-Coastal Waters From Ochlockonee River to 
     Apalachicola Fl out to 20 Nm-Coastal waters from Suwannee 
     River to Keaton Beach out 20 NM-Waters from Suwannee 
     River to Apalachicola FL from 20 to 60 NM. 
     GALE WARNING until 1 PM EST Wednesday for Coastal waters from 
     Apalachicola to Destin FL out 20 NM-Waters from 
     Apalachicola to Destin FL from 20 to 60 NM.

&&

$$

MESOSCALE UPDATE...Gould
NEAR TERM...Block
SHORT TERM...Moore 
LONG TERM...Lanier
AVIATION...Block 
MARINE...Moore 
FIRE WEATHER...Lanier
HYDROLOGY...Godsey