River Flood Warning 92, NWS Tallahassee, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
348 AM EDT Tue Aug 20 2013

...More Flash Flooding Possible Again Today...

.NEAR TERM [Through Today]...
This morning's regional analysis shows much of the country in a
generally static pattern since this time yesterday. Two prominent
ridges are located over the Four Corners region and the western
Atlantic, with broad troughing across the northeastern half of the
country. The upper trough axis extends south from the Great Lakes
region through the Middle Mississippi Valley before getting lost in
a rather weak pressure pattern near the Gulf Coast. At the surface,
a messy ridge covers the eastern half of the country with a weak
front extending down the Mid-Atlantic coastline through central
Georgia, up into the Tennessee Valley. Further south, the continued
broad area of low pressure generally centered over the western Gulf
is affecting much of the central and eastern Gulf as well with a
broad trough extending northeast from the "center" to near the
Florida coastline where it is lost in several mesoscale troughs
generated by last night's convection.

Today, the mesoscale troughs will dampen out and and the broad area
of troughing will be pushed further west by the advancing western
Atlantic surface ridge. This will likely focus much of today's most
widespread convection across the western half of the Tri-State
region. However, scattered showers and storms will encroach on our
eastern counties later in the day associated with increasing
convergent easterly flow. Additionally, the plume of above average
precipitable water will be focused more over the west/northwestern
half of our region where the greatest threat for flash flooding will
exist. Have included this area in a new Flash Flood Watch beginning
this morning.

In general, the threat for severe weather remains low again today,
with unfavorable mid-level lapse rates in nearly moist adiabatic
profiles. However, with a substantial amount of water in the column,
an isolated strong to severe precip loaded downdraft cannot be
ruled out.

&&

.SHORT TERM [Tonight Through Thursday]...
An upper level low will track up the Ohio River Valley tonight and
Wednesday and to the Mid Atlantic States on Thursday. Since the
lower heights will remain farther north of the area than recent
days, the upper ridge off the Southeast U.S. coast should be able to
make some westward progress during this period along the Gulf Coast.
This will lower precipitable water and hopefully the flash flood
threat by Wednesday. PoPs will reflect a combination and statistical
and hi-res guidance along with climatology. There will be a general
downward trend toward the climatology through the period. Temps will
very close to normal and maybe even a degree or two above normal on
Thursday. Organized severe weather is not anticipated.

&&

.LONG TERM [Thursday Night through Monday]...
With precipitable water levels returning closer to normal values
for this time of year in the extended, and an overall lack of
strong forcing mechanisms, we should see more typical convection
that is forced predominately by the sea breeze. Temperatures and
PoPs for much of the extended forecast are expected to be close to
normal values: daytime highs around 90 with PoPs around 40%;
overnight lows in the lower 70s with PoPs around 15%.

&&

.AVIATION...
[Through 06 UTC Wednesday] Scattered, becoming more widespread,
MVFR to VFR ceilings are expected once again this morning. The
substantial amount of cloud debris from last nights convection may
limit the thickness of the low deck along and east of a line from
KABY to KTLH, thus allowing low clouds in this area to mix out to
VFR levels not long after sunrise. However, KDHN may need a few
more hours to scatter out. Showers and thunderstorms will be most
likely at KDHN and KECP today, with isolated to scattered storms
to possibly impact our remaining terminals later in the
day/evening.

&&

.MARINE...
Winds will remain light over the marine area for the next several
days, generally out of the east or southeast at 10 kt or less. Seas
will generally run 2 ft or less and much of that will be residual
swell today. The wind and wave forecast would not normally support a
high risk for rip currents. However, deep channels that have
developed within the surf zone have been resulting in strong rip
currents over the past couple of days that have necessitated
numerous rescues in from Franklin County west to Bay and Walton
Counties. Based on yesterday's reports, the high risk will be posted
for the latter two counties with moderate elsewhere.

&&

.FIRE WEATHER...
Red Flag conditions are not expected and dispersions will remain
within acceptable levels for the foreseeable future.

&&

.HYDROLOGY...
Once again areas of Heavy rain affected portions of the forecast
area today. Flooding is now occurring or forecast along portions
of the Ochlockonee, Choctawhatchee, Chipola, Apalachicola Rivers,
as well as the Kinchafoonee and Spring Creeks. Minor flooding is
forecast in most area. However, the Choctawhatchee at Bruce is in
moderate flood and the Ochlockonee at Concord and Havana are now
both forecast to reach that level. The Chipola at Altha has
dropped below moderate flood stage.

Based on reports from some of our counties - especially in the
western Florida Panhandle which received substantial amounts of
rain in July - there is already quite a bit of high water with
flooding affecting some roads and infrastructure. In some places
this may be due to streams and creeks, but in others it could just
be due to a high water table affecting low-lying spots, ditches,
and small ponds. Either way any additional rainfall would only
worsen flooding conditions in these areas. A few counties in the FL
Panhandle (Walton, Washington and Jackson) have declared local
states of emergency due to flooding.

The most up to date, specific river forecast information can be
found on the AHPS web page at:

http:/water.weather.gov/ahps2/index.php?wfo=tae.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   91  72  93  73  93 / 40  30  40  20  30
Panama City   87  75  90  75  91 / 60  30  40  20  40
Dothan        88  72  90  71  92 / 60  30  50  30  30
Albany        90  72  91  72  93 / 40  30  40  20  30
Valdosta      91  72  94  71  94 / 50  30  40  20  40
Cross City    92  71  92  71  93 / 40  30  50  30  40
Apalachicola  87  75  89  75  90 / 50  30  30  20  40

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...FLASH FLOOD WATCH from 8 AM EDT /7 AM CDT/ this morning
     through Wednesday morning for Calhoun-Central Walton-
     Coastal Bay-Coastal Franklin-Coastal Gulf-Gadsden-Holmes-
     Inland Bay-Inland Franklin-Inland Gulf-Inland Walton-
     Jackson-Liberty-South Walton-Washington.
     High Risk for Rip Currents for until 7 PM CDT this evening
     for Bay-Walton.
GA...FLASH FLOOD WATCH from 8 AM EDT this morning through Wednesday
     morning for Baker-Calhoun-Clay-Decatur-Early- Miller-Quitman-
     Randolph-Seminole.
AL...FLASH FLOOD WATCH from 7 AM CDT this morning through Wednesday
     morning for Coffee-Dale-Geneva-Henry-Houston.
GM...None.

&&

Near Term/Aviation/Fire Weather... Harrigan
Long Term...Lamers
Rest of Discussion...Wool