Tornadoes and Damaging Winds in Florida, November 26, 2013

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TALLAHASSEE FL
437 AM EST Tue Nov 26 2013

...SEVERE STORMS POSSIBLE TODAY AND TONIGHT...

.UPDATE...
Added a paragraph to the near term section to discuss high surf
and coastal flood potential.

&&

.NEAR TERM [Today]...
A split flow regime continues across the central and eastern U.S.
with a positively tilted trough over TX and another digging
southeastward across the Upper Great Lakes. Surface analysis shows
deepening low pressure over the northwestern Gulf of Mexico with a
warm front extending northeastward from it to Southeast LA and then
southeast across the eastern Gulf. A shield of rain is advancing
across the FL Panhandle north of the boundary. There has been little
change in our thinking concerning the evolution of today's primary
weather features and their impact our our weather locally. The two
upper level troughs will phase by the time the axis approaches our
western zones by around midnight. The surface low will move
northeast and come ashore near Pensacola by around 18 UTC and then
move north of the region by 00 UTC. The warm front will eventually
pull northward into our Southern GA zones, but will take most of
the day to do so. This will limit how far inland the greatest
instability can advance. Upper 60s dew points will primarily be
limited to FL. Shear profiles will certainly support severe weather
in the warm sector as a 60-kt 850-mb jet traverses the area. 0-6 km
bulk shear values will range from 40-50 kt over the warm sector, but
much of that will be concentrated in the lowest levels (0-1 km shear
values around 30-35 kt). There will therefore be a non-zero chance
for tornadoes. SPC has most of the area south of U.S. 84 in a slight
risk for severe storms with 2% tornado probabilities and 15% severe
wind gust probs. While this is certainly reasonable, we still think
the best chances for severe will occur south of the FL/GA line.
There may be multiple convective modes as the event unfolds with
discrete supercells and bowing segments eventually transitioning to
a squall line as the front approaches peninsular FL. PoPs will be
categorical today with max temps ranging from the mid to upper 70s
south of I-10 to the upper 60s north of an ABY-DHN line.

The high surf advisory was left as is, although the latest grids do
show marginal criteria (6 ft) continuing a bit later into the
night than 03 UTC, so this may need to be extended. Of course, the
associated rip current risk is high. Looking at the coastal flood
threat, we continue to show departures up to 2.5 above normal
astronomical tide levels in the Apalachee Bay. However, this surge
is out of phase with the tide cycle (will occur during low tide),
so it does not appear that our advisory criteria will be met. Note
that since this criteria has been newly established, we will be
monitoring how things go during this event to see if in fact the
impact levels are satisfactory.

&&

.SHORT TERM [Tonight Through Thursday]...
The surface low is forecast to be in SW Georgia with the southward
extending cold front near Apalachicola around 00z Wed. Thus, we
believe there will still be a lingering severe weather threat for
most of the Florida Big Bend and adjacent waters until the frontal
passage around or just before 06z. By daybreak Wednesday, much
colder and drier air will move into the area in the wake of the
front. On Wednesday, clouds may be slow to clear especially for our
northern zones due to the wrap around moisture and upper level vort
passing through. By afternoon most areas will see abundant sunshine
but with the strong cold air advection max temps should not reach 50
degrees for our northwest zones and only the lower to mid 50s for
most of the remaining CWA. The breezy northwest winds will make it
feel even colder. For Wednesday night, we will likely see our first
widespread freeze of this fall season as the center of the cold
airmass slides east along the Gulf coast. Some of our numerical
temperature guidance even supports a hard freeze for portions of our
CWA. Not quite ready to accept that as we should see light northerly
winds continuing through the night with the surface high centered
just to our west. Max temps on Thanksgiving Day will be similar to
Wednesday's but with much lighter winds.

&&

.LONG TERM [Thursday Night 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 06 UTC Wednesday] VFR cigs will lower to MVFR during the
predawn hours with IFR a distinct possibility at all terminals.
Rain will also overspread the region this morning with
thunderstorms preceding a cold front. Some of the storms could
produce strong winds. Even outside of thunderstorms, prevailing
winds will be gusty, out of the SSE today and then out of the WNW
after FROPA which will occur from late this afternoon through the
evening hours. Any periods of VFR conditions during the daylight
hours are expected to be brief.

&&

.MARINE...
Hazardous boating conditions will continue at least through
Wednesday night. Winds will become southerly today as a warm front
lifts across the waters and gradually veer to become west to
northwest with the passage of a strong area of low pressure and
associated cold front later today and tonight. Ahead of the low
pressure system, gale force gusts are possible for all but Apalachee
Bay and a gale warning is in effect until this afternoon. Seas are
already up to 11 feet in the offshore waters this morning and could
reach as high as 13 feet before winds and seas begin to subside
Wednesday night. Winds and seas should drop below headline criteria
late Thursday but increase once again over the upcoming weekend.

&&

.FIRE WEATHER...
A wetting rain is expected across the entire forecast area today
ahead of a cold front. Drier air will arrive behind the front for
the middle to latter part of the week. The driest day will be
Thursday and RH may briefly dip below 28% in FL. However, winds will
have dropped off by then so red flag criteria are still not
anticipated.

&&

.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   76  47  53  28  55 /100  80  10   0   0
Panama City   75  44  53  31  54 /100  70  10   0   0
Dothan        70  40  47  26  52 /100  70  10   0   0
Albany        71  44  50  26  54 /100  80  10   0   0
Valdosta      73  48  53  28  55 /100  90  10   0   0
Cross City    76  53  58  28  58 / 90  90  10   0   0
Apalachicola  76  48  56  31  53 /100  70  10   0   0

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...HIGH SURF ADVISORY until 10 PM EST /9 PM CST/ this evening for
     Coastal Bay-Coastal Franklin-Coastal Gulf-South Walton.
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 Suwannee River to
     Keaton Beach out 20 NM.
     SMALL CRAFT ADVISORY from 5 PM this afternoon to 7 AM EST
     Thursday 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.
     GALE WARNING until 5 PM EST this afternoon 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.
&&

Near Term/Aviation/Fire Weather...Wool
Long Term...DVD
Rest of Discussion...Barry
Hydrology...McDermott

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TALLAHASSEE FL
845 AM EST TUE NOV 26 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0837 AM     TSTM WND GST     APALACHICOLA AIRPORT    29.72N 85.03W
11/26/2013  M43.00 MPH       FRANKLIN           FL   ASOS

&&

GOULD