Area Forecast Discussion


881 
FXUS62 KTAE 130124
AFDTAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
924 PM EDT Mon Aug 12 2013
.NEAR TERM [Through Rest of Tonight]...
The large scale pattern remains highlighted in the Nrn stream by a 
blocking pattern with a trough in the extreme Ern Pacific, a ridge
from Canada's NW territories extending SEWD to Wrn TX, and a
trough over the NE quarter of U.S. extending into the Canadian
Maritimes. The Srn stream is dominated by the subtropical ridge
gradually weakening from E-W. By 9 pm EDT, an H5 impulse
responsible for igniting earlier convection along the Gulf
seabreeze across SE AL lifted into E/Cntrl GA taking convection
focus with it. This plus loss of diurnal heating rapidly reduced
thermodynamic support for showers and thunderstorms with
convection ending.
Although there is shower and thunderstorm activity just to the
east of our CWA, recent radar trends along with high resolution
model guidance affirm that the storms will dissipate before
reaching our CWA. After 06z, expect wdly sct marine convection
developing over Panhandle waters and lifting to adjacent coasts
thru 12z. Grid updates reflect this forecast thinking. Otherwise,
high debris clouds from dying convection should dissipate after
midnight with skies mostly clear late for good viewing of the
annual Perseid meteor shower. Only exception will be Panhandle
coastal counties towards morning and Ern most counties of Big Bend
and GA until around 2 AM EDT.
Glamp and SREF again imply patchy light fog towards sunrise. Given
high PWATS, calm winds, and residual moisture from earlier
precipitation, added patchy fog to the grids before sunrise tomorrow.
Another warm and muggy night is expected with lows in the lower to
mid 70s with highest low temperatures in areas where rain/clouds
persist well past sundown.
&&
.SHORT TERM [Tuesday Through Wednesday Night]...
A broad upper level trough will continue to deepen across the 
eastern CONUS with an axis from the lower Great Lakes to the central 
Gulf coast. This will push a weak front down to southern AL/GA and 
advect deep moisture currently just to our west into our area 
tonight into Tuesday. This points to increasing rain Tuesday focused 
in the northwest 1/2 of our area... SE AL and the FL panhandle, 
spreading across the entire region Wednesday and Wednesday night, 
except portions of the FL Big Bend. 
Localized heavy rainfall is likely due to the deep moisture and weak 
flow aloft resulting in very slow storm motion. High temperatures 
will moderate under cloudy skies from the recent hot readings, with 
a NW-SE gradient and the warmest temps over the FL Big Bend. Low 
temperatures will be warm due to increased overnight cloud cover. 
&&
.LONG TERM [Thursday through Monday]...
A long wave trough will remain in place from the Great Lakes to the 
central Gulf Coast early in the period as a reinforcing short wave 
in the northern plains drops into the trough, resulting in a closed 
low over the Lower Mississippi Valley by Saturday. This low 
gradually fills and weakens, leaving behind a weak trough for early 
next week with an axis still to our west.  
The end result is a prolonged period of rain for the southeast with 
periods of heavy rain likely. Total rainfall from the GFS indicates 
areas of rain up to 10 inches across the FL panhandle through 
Monday, due in part to its development of a tropical cyclone in the 
gulf which it brings into the FL panhandle Saturday. The Canadian 
also generates a tropical system similar to the GFS, however the 
ECMWF does not generate a tropical system and therefore depicts 
rainfall totals through Monday of about 5 inches. 
Confidence of a period of heavy rain is high, and if the 
GFS-advertised tropical system does develop then local rainfall 
amounts could be double or triple the current WPC 5.5" totals. 
&&
.Aviation...
VFR conditions are anticipated through much of the night with
scattered mid/upper clouds from afternoon/evening convection.
Towards dawn, showers along the Panhandle coast may impact KECP.
Whether it rains or not, MVFR ceilings will be likely here.
Elsewhere, expect VFR conditions to continue until thunderstorms
become more widespread later in the day. Thunderstorms will be
likely late in the TAF at all sites but KVLD.
&&
.MARINE...
A weak pressure pattern will persist keeping winds around 10 knots 
or less, with seas 2 feet or less. Thunderstorm activity over the 
waters will increase by Wednesday.
&&
.FIRE WEATHER...
No fire weather concerns.
&&
.HYDROLOGY...
Area river levels continue to slowly decrease or remain steady and 
this. A wet pattern will develop by mid-week, which will begin to 
increase flows on several rivers later into the week and over the 
weekend depending on which basins receive the heaviest amounts. As 
of now the highest model rainfall amounts for the period from 
Wednesday through the weekend are focused on the FL panhandle into 
southwest GA, but that is a preliminary outlook.  
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   74  95  75  92  73 / 20  40  20  60  30 
Panama City   78  90  78  89  76 / 20  40  20  50  30 
Dothan        75  91  75  89  73 / 30  70  30  70  40 
Albany        75  93  76  91  74 / 30  60  30  70  40 
Valdosta      72  96  75  94  73 / 20  30  20  60  40 
Cross City    73  94  75  94  73 / 20  20  10  30  30 
Apalachicola  78  90  79  89  77 / 20  20  20  50  30 
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&
$$
NEAR TERM/Marine...Block/Navarro
SHORT TERM...Barry 
LONG TERM...Hollingsworth 
AVIATION...Hollingsworth/Harrigan
FIRE WEATHER...Barry 
HYDROLOGY...Hollingsworth