Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 040054
Area Forecast Discussion
National Weather Service Tallahassee FL
754 PM EST Sat Dec 3 2016
Upstream radars show an area of mostly light rain spreading
eastward into central and southern Alabama. Some of this activity
along with additional development due to isentropic ascent will
likely move into at least our western zones overnight. Current
forecast is on track and no updates to grids or zones are
.PREV DISCUSSION [646 PM EST]...
.NEAR TERM [Through Tonight]...
As low level flow veers across the eastern Gulf through tonight, the
temperature gradient near the coast will tighten and the warm front
that currently extends through the mouth of the Mississippi will
reach along the Florida panhandle coast. Isentropic ascent along the
developing front will spread from west to east across the Panhandle
through the night. Just how quickly and how far east he low-levels
saturate is not extremely well agreed upon, but will favor the more
aggressive solutions since models can be slow to generate isentropic
rain. This will essentially mean that by morning, locations along
and west of a line from Albany through Panama City should be getting
at least light rain, maybe even moderate across SE Alabama and the
far western Panhandle. With the saturating airmass and expected
cloud cover, lows tonight should bottom out in the low to mid 50s
.SHORT TERM [Sunday Through Monday Night]...
The cut off low will move eastward over NW Mexico Sunday and across
to SE Texas by Monday night before converging into the northern
stream mid-week. A warm front boundary associated with this upper
level disturbance runs westward along the northern Gulf coast from
AL to TX with an area of low pressure S of Corpus Christi, TX. As
the upper low swings eastward, the surface low will deepen as it
moves northeastward along the Gulf coast, lifting to central AL
Monday night. By Sunday afternoon, the warm front will lengthen its
eastward extent into our area and we will start to see an increase
in chances for rain over our western zones. Model PW values start to
sharply increase over our area Sunday night, rising into the 1.5-2"
territory Monday night. Mid level shear is roughly parallel to the
warm frontal boundary most of this Sunday night to Monday night
period, which, combined with the abundant moisture could be a recipe
for some heavy rainfall. Widespread totals are expected to be around
2-4" over our area, however isolated areas will see higher
accumulations, which could potentially lead to flash flooding.
Late Monday night, as the mid and upper level low get closer to the
region, the mid and low level winds over our area increase. This
will in turn increase our wind shear values- with 0-6 km shear
rising to 40-50 kts and 0-1 km shear rising to 20-30 kts. Although
instability will remain fairly low (MLCAPE of 600 J/kg or less), it
may be just enough to produce damaging wind gusts or spawn a few
isolated tornadoes. The Storm Prediction Center has portions of the
FL Panhandle under a slight risk for severe thunderstorms on Monday
.LONG TERM [Tuesday Through Saturday]...
The aforementioned low pressure system will move off to the NE. For
the start of the long term period our CWA will still be in the warm
sector with CAPE values around 900 to 1200 J/kg. Tuesday morning
into the afternoon, will be the main time period to watch for
isolated thunderstorms. Although the confidence in timing of the
cold front passage is relatively high, it is important to keep in
mind that this will be a governing factor for the intensity of the
associated storms. A frontal passage during the afternoon will call
for increased risk for isolated thunderstorms. With respect to
precipitation, models are showing PW values of up to 2 inches ahead
of the front which allow for the possibility of high QPF. Drying and
slight cooling will occur rapidly thereafter.
The next system to affect the CWA is expected Thursday night into
Friday. While both the GFS and ECMWF push a cold front into the
southeast, the GFS weakens it with no precipitation associated. On
the other hand, the ECMWF pushes a wet front through the CWA. Given
these major differences, the forecast reliability as of now is low.
Regardless of precipitation, significantly colder and drier air is
expected to move into the CWA after the frontal passage. Low temps
will be in the high 20s to mid 30s while high temps will struggle to
reach the mid 50s.
.AVIATION [Through 00Z Monday]...
VFR conditions becoming MVFR late in the period. Ceilings will begin
to lower from West to East overnight, becoming around 2-3 kft at
the Western terminals, TLH and VLD will linger a bit longer in
the 3-5 kft range. Increasing chances for rain West and North of
TLH along with the possibility of a slight reduction to
visibility. Winds will be breezy at times generally from the East,
transitioning to Southeasterly throughout the day Sunday.
A small craft advisory remains in effect for coastal waters from
Ochlockonee to Destin out to 60 NM for winds around 20 to 25 knots
and seas up to 6 feet through Sunday morning ahead of a developing
low pressure system. Although winds may fall below 20 knots Sunday,
they will approach it again Monday night and Tuesday when the front
finally crosses into our forecast area.
A transition to southerly flow will bring an increase in moisture to
the area, this will keep fire weather concerns to a minimum through
at least midweek. Rain chances will also be on the increase with
some gusty winds possible near stronger storms.
Rainfall totals of 2-4" are expected between Sunday night and
Tuesday, with isolated higher values. While our rivers are well
poised to handle these rainfall totals given the current drought,
if we see higher rainfall totals over shorter time periods, there
is the potential for flash flooding.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 54 74 65 76 69 / 10 20 50 70 80
Panama City 60 73 68 77 68 / 20 40 60 70 70
Dothan 53 71 61 74 63 / 30 60 70 80 80
Albany 53 70 60 72 64 / 20 40 60 70 80
Valdosta 52 76 63 76 68 / 10 10 50 60 80
Cross City 53 78 63 77 68 / 0 10 30 50 80
Apalachicola 63 73 68 76 69 / 20 20 50 70 70
GM...Small Craft Advisory until 2 PM EST Sunday for Coastal Waters
From Ochlockonee River to Apalachicola Fl out to 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.