High Surf Advisory 7, NWS Tallahassee, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
252 PM EST Mon Nov 25 2013

...SEVERE STORMS POSSIBLE TUESDAY...

.NEAR TERM [Through Tonight]...
Clouds and rain chances will be on the increase tonight as a fairly
potent upper level low pressure system dives south-southeastward
from a position over extreme northern TX early this afternoon to
the SE TX Gulf coast by early Tuesday afternoon. This upper low
is already initiating Sfc cyclogenesis in the western Gulf of
Mexico, and as this new Sfc circulation gradually deepens and
heads NE towards our Coastal Waters tonight, increasing rain
chances should gradually begin to spread from SW to NE across the
region. This development should be aided by isentropic lift as
this new low creates a warm frontal boundary and encounters the
gradually weakening early season Arctic high pressure system,
which is still trying to hold in over the Carolinas for the time
being. As for temperatures, lows may actually occur during the
evening hours and then begin to slowly climb after midnight as
dewpoints will be on the rise as well. While rain or showers will
be the predominant weather group tonight, did begin sct
thunderstorms over the western FL Panhandle and adjacent Coastal
Waters at 09 UTC.

&&

.SHORT TERM [Tuesday Through Wednesday Night]...
Short summary...while we cannot rule out severe weather anywhere
in the forecast area on Tuesday, we think the greatest threat is
close to the coast, especially from near Panama City to near
Apalachicola anytime after sunrise through the mid-afternoon hours
and then spreading eastward from there for the remainder of the
day. Damaging straight line wind and isolated tornadoes are the
main threats with this event. Much colder air will move into the
area behind the front on Wednesday into Wednesday night with a
freeze looking likely over portions of the area Wednesday night.

Details...We are watching closely the buoy obs in the Gulf for
airmass recovery ahead of the approaching low pressure area.
Although it currently remains very dry across our forecast area
with dewpoints in the 30s to lower 40s inland, the gradient is
very tight with 65-70 dewpoints not far off the Louisiana coast.
This moisture has begun to move northward, and models are coming
into better agreement on the track of the surface low and the
quality of moisture return ahead of it. Confidence is a little
higher than yesterday that a sufficiently unstable airmass will
make it inland to give a threat for severe storms given stronger
model agreement and the obs over the Gulf showing decent recovery
so far. The highest chance of severe weather is still likely to
remain to near the coast, especially from Panama City to
Apalachicola. From a dynamics perspective, one important thing to
keep an eye on for this event will be whether or not a strong 850
mb jet develops offshore south of the western Florida panhandle
Tuesday morning. The 12z NAM is particularly aggressive with this
low level jet and brings 65 knot 850 mb winds across Panama City
during the day Tuesday. If this feature develops like the NAM is
advertising, then we will probably see severe weather along the
coast with damaging winds and isolated tornadoes. The 4 km NAM
nest forecast soundings around Panama City exhibit strongly curved
hodographs and 45-50 knot winds as low as 1000 ft. SBCAPE values
rise to over 1000 j/kg with this profile at 17z on the 4 km NAM
sounding. The 12z GFS has a similar feature, although it is a few
hours faster and just a tad to the west. The overlap between the
instability and shear is also not as prevalent on the GFS,
although it does manage to bring instability as high as 750 j/kg
as far north as southeast Alabama by 18z.

The threat farther to the north in southeast Alabama and southwest
Georgia has lower confidence due to lingering questions about how
far north the instability will get. Although both the NAM and GFS
show a low CAPE/high shear environment reaching into these areas
too, if a lot of rain develops ahead of the warm front, then that
could act to limit the northward progress of the instability. This
will have to be monitored closely.

&&

.LONG TERM [Thursday through Monday]...
Most of the long term is expected to remain dry with surface high
pressure north of the area. Temperatures will start out well below
average at the beginning of the period with a gradual warming trend
going forward. Another system may approach late in the period with
a chance of rain around Monday.

&&

.AVIATION...
[Through 18 UTC Tuesday] MVFR cigs will roll into the region this
evening. During the overnight hours widespread IFR conditions will
dominate with low ceilings being the main threat. Rain showers
will roll into the region after sunset, becoming more intense as
the night progresses. Rain will be moderate and possibly heavy at
times particularly during the morning hours. Thunder is a
possibility in the morning mainly at KECP.

&&

.MARINE...
The extended period of hazardous boating conditions will continue
at least through the middle of the week. Winds will start to veer
to the southeast tonight as a strong area of low pressure develops
along the Gulf coast. Winds will turn southerly and increase
across the entire area on Tuesday as the low moves through the
region. Behind this low, strong west to northwest winds are
expected on Wednesday with gale force gusts possible. Seas are
expected to reach 11 feet offshore on Wednesday.

&&

.FIRE WEATHER...
With the approaching low pressure system from the west, a
widespread rainfall is expected across the region on Tuesday, so
Wet Flags will be up across the region. Also, although much drier
air will return behind this next low pressure system and
associated cold front, afternoon temperatures are expected to be
too cool for any Red Flag concerns over the next several days.

&&

.HYDROLOGY...
Not much change in the hydrology outlook with the next period of
significant rain late tonight through Wednesday morning. Still
think that several areas will see 1 to 2 inch rainfall totals.
Since we will see embedded convection isolated heavier amounts
are likely which could result in increases on smaller streams and
creeks.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   54  75  47  55  31 / 60 100  70  10   0
Panama City   57  75  46  55  34 / 80 100  50  10   0
Dothan        47  68  42  49  29 / 80 100  70  10   0
Albany        46  69  45  52  29 / 60 100  80  20   0
Valdosta      52  74  48  56  31 / 60 100  80  10   0
Cross City    61  76  54  60  31 / 50  90  80  10   0
Apalachicola  62  76  49  59  35 / 70 100  60  10   0

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...SMALL CRAFT ADVISORY until 7 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.
&&

Near Term/Fire Weather...Gould
Short Term/Long Term/Marine...DVD
Aviation...McDermott/Gould
Hydrology...McDermott