Damaging Winds in Florida, September 12, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
354 AM EDT SAT SEP 12 2015

.Near Term [Through Today]...

A deep upper level long wave trough stretching from the Great Lakes
to the southeast states will progress eastward today. At the
surface, a fairly well defined cold front will move through the
region. This is the first real cold front to move through since last
spring, and it is a sign that the long, hot summer pattern is
starting to show signs of fading away.

In the meantime though, rain is likely today across the area. In
fact, deep moisture ahead of this front is above average for this
time of year with precipitable water values near 2" expected
across the area ahead of it. Given this, there is some potential
for heavy rain today, especially close to the coast. Since the
system will be progressive, we do not expect widespread flooding
to be a concern, but some localized flooding in poor drainage
areas could occur and heavy rain wording was inserted into the
forecast generally from near Panama City eastward to Cross City.
This is the area where the local ensemble of CAM guidance shows
the highest potential for heavy rainfall amounts today.
Tallahassee is likely to be on the northern extent of the heavy
rain area. Most areas from Panama City to Valdosta and southward
will likely see between one-half and one inch of rain today, but
areas across Taylor, Dixie, and Lafayette counties are expected to
see generally 1-2" with localized amounts over 3" possible.
Lighter amounts generally less than a half inch are expected
across the rest of the area.

In terms of rainfall timing through the day, there are still some
model differences of around 3-6 hours, which is to be expected. The
local ensemble of CAM guidance was again used heavily to derive 3-
hourly PoPs for today with rainfall chances peaking in the early
morning across the western areas and around noon farther to the
east. By the noon hour we expect the main area of rain and
thunderstorms to stretch from near Apalachicola to Perry with
Tallahassee on the northwestern edge of it. Behind this large area
of rain and storms, some redevelopment of scattered showers and
possibly a thunderstorm could occur through the remainder of the
afternoon hours, but this second batch of activity will not be as
widespread or heavy as the first round.

In terms of severe weather chances, with abundant cloud cover and
relatively unimpressive wind fields, the threat looks pretty low
over most of the land area. That being said, instability will be
higher over the water and some stronger storms are more likely
offshore. These storms will move towards the Taylor and Dixie county
coasts by the late morning and early afternoon hours with gusty
winds being the main threat.

.Short Term [Tonight Through Monday]...

The axis of the deep upper level trough will extend down from the
closed low over the Great Lakes to the eastern Gulf tonight. The
trough will quickly de-amplify with mid to upper flow becoming
nearly zonal by Monday as the low moves into New England. Low level
winds will start off northerly in the wake of Saturday's cold front
then gradually veer to become easterly on Monday as surface high
pressure centered over the Missouri Valley slides east to the mid-
Atlantic states. This period will be dry with below seasonal
temperatures. On Sunday, the max temp will only be around 80 to the
lower 80s under sunny skies with low humidity. It will be a little
warmer Monday with highs in the lower to mid 80s. Lows tonight will
range from the upper 50s northwest to upper 60s far southeast zones.
We will experience the coolest temperatures Sunday night will lows
in the mid to upper 50s most inland areas and lower to mid 60s along
the immediate coast.

.Long Term [Monday Night Through Saturday]...

The surface ridge will remain centered over or just east of the mid-
Atlantic coast through much of the week bringing increasing moisture
in from the Atlantic on easterly flow. Deeper moisture briefly
returns on Wednesday as the mid to upper flow becomes southerly with
a building upper ridge centered off the SE U.S. coast. Then, the
upper level pattern begins to de-amplify and flattens by early next
weekend. Rain chances and warmer temps return to the local region.

&&

.Aviation...

[Through 12z Sunday] A cold front will move through the region today
with widespread rain and some thunderstorms. Ceilings are also
expected to be in the MVFR to IFR category for much of the day. The
best chance of thunderstorms will be at ECP, TLH, and VLD. Activity
will gradually taper off from west to east during the afternoon.

&&

.Marine...

Winds will be southwest around 10 knots ahead of an approaching
cold front today. In the wake of the front, winds will shift to
the north and increase to near advisory levels tonight, then
diminish quickly during the day Sunday. Winds will swing around to
the east on Monday increasing to around 15 knots Monday night and
remain at these levels at least through the middle of the week.

&&

.Fire Weather...

After a wet day today, a drier airmass is expected to arrive on
Sunday behind a cold front, but RH will not be low enough for red
flag conditions.

&&

.Hydrology...

Widespread rain is expected through Saturday ahead of a cold front.
Rainfall totals around 1 inch or less expected through the weekend.
Rainfall not expected to cause any widespread flooding along area
rivers.

&&

.Preliminary Point Temps/PoPs...

Tallahassee   79  63  83  57  86 / 100  10   0   0   0
Panama City   80  65  80  63  83 / 100  10   0   0   0
Dothan        80  58  79  56  83 /  60  10   0   0   0
Albany        80  59  79  56  83 /  70  10   0   0   0
Valdosta      78  62  81  57  84 /  90  10   0   0   0
Cross City    79  68  83  60  86 / 100  30   0   0   0
Apalachicola  79  67  81  64  83 / 100  10   0   0   0

&&

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

&&

NEAR TERM...DVD
SHORT TERM...BARRY
LONG TERM...BARRY
AVIATION...DVD
MARINE...BARRY
FIRE WEATHER...DVD
HYDROLOGY...MCDERMOTT