Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 180830
Area Forecast Discussion
National Weather Service Tallahassee FL
330 AM EST Wed Jan 18 2017
.NEAR TERM [Through Today]...
Dense fog has spread across portions of the CWA this morning and
thus have issued a dense fog advisory for much of the CWA. Went
further east with the advisory than current obs are showing dense
fog based on trends showing the dense fog spreading
eastward. Visibilities are expected to improve by mid morning.
Upper level ridging will continue to dominate the southeast today.
At the surface, southerly winds will continue to pump Gulf moisture
into the CWA. This combined with isentropic lift will allow for a
few showers today. There are already isolated showers noted on radar
over the marine area and these will continue to spread northward and
onshore throughout the day. Most areas have around a 20% chance of
showers today with a slightly higher chance (30%) between Panama
City and Tallahassee where the showers are expected to move onshore.
High temperatures today will continue to remain above normal with
highs in the 70s.
.SHORT TERM [Tonight Through Friday]...
The deep layer ridging that has been in place the past several days
will move east allowing an upper level trough and surface cold front
to approach on Thursday. By late Thursday, this upper trough is
forecast to become negatively tilted as the axis lifts northeastward
across the southeast states. Ample moisture and large-scale ascent
with this system will help to generate widespread rain along with
thunderstorms that will gradually spread across the local region
Thursday through Friday with the highest probabilities Thursday
night. SPC has highlighted a portion of the Lower Mississippi Valley
for a marginal risk of severe thunderstorms on Thursday. While
decent deep layer shear will be present, instability may be the
limiting severe factor due to extensive cloud cover. The severe
threat is expected to diminish as the ongoing convection moves into
our CWA late Thursday and Thursday night. Highs will be in the
upper 70s to around 80 both days with lows in the upper 50s to
.LONG TERM [Friday Night Through Wednesday]...
Friday into Saturday, the surface front is forecast to stall
across our area. This along with an mid/upper level disturbance
passing overhead Friday night/Saturday will bring another round
of rain with thunderstorms. While the severe threat currently
appears low, a few strong to severe storms cannot be ruled out.
The main severe weather threat will be on Sunday, as a vigorous
deep low pressure system develops and ejects eastward from the
Southern Plains into the Lower Mississippi Valley. At the
surface, the stalled front will lift north as a warm front with a
strong cold front moving into our western zones Sunday afternoon
and east of our CWA Sunday night/early Monday. The GFS shows a low
level jet of 40-50kts across portions of our FA Sunday
afternoon/evening as the surface low deepens. This along with
sufficient instability and shear will bring a threat of severe
thunderstorms including the threat for some tornadoes. Another
threat with these rain events over the weekend will be the
potential for very heavy rainfall that could result in minor
flooding. See more details on this in the hydrology section below.
Although the front will clear east of our CWA, wrap around
moisture will keep skies cloudy with lingering chances for rain on
Monday. A drying trend will begin Tuesday and continue at least
through mid-week. Temperatures will remain well above average
until the main system moves through on Sunday, then a cooler, more
seasonal airmass is expected to start next week.
.AVIATION [Through 06Z Thursday]...
Conditions at TAF sites will deteriorate this morning with VLIFR to
LIFR conditions expected due to fog and low cigs. There are
differences in guidance today on how much conditions will improve,
but TAFs are on the optimistic side with reaching VFR conditions by
late morning. A few showers are possible today, but chances are
too low to mention in the TAFs.
Winds will be light from the southeast today with winds and seas
increasing on Thursday as a front approaches. Rain and thunderstorm
chances will continue to increase through the weekend with
multiple disturbances affecting the marine area. A strong cold
front is expected to move through the marine area Sunday into
Monday with gusts to gale force expected and seas in excess of 10
feet. Some thunderstorms could also be strong to severe,
especially on Sunday.
Low dispersion values are possible today along the immediate Florida
coast. With RH values above critical thresholds there are no fire
weather concerns in terms of meeting Red Flag Warning conditions.
Chance of wetting rain will increase late in the week into the
weekend. There is dense fog across the area this morning and
dense fog is expected again Thursday morning.
Multiple rounds of rain are expected over the next several days.
The heaviest rounds of rain are likely to arrive on Saturday and
Sunday. Total widespread amounts through Monday are expected to be
in the 2-5 inch range, but there will likely be localized areas
that see higher amounts. Ultimately, the greatest threat for any
flooding will come at the end of the event on Sunday and will
depend on how much rain has fallen from the previous rounds. The
flooding potential will need to be monitored closely over the next
several days, but the magnitude of the flood threat remains pretty
uncertain at this point. There may also be a minor coastal flood
threat along Apalachee Bay depending on the timing of the
strongest winds with the tide cycle. The 12z ESTOFS is showing the
potential for around 3 feet of storm surge in Apalachee Bay given
the strong wind field associated with the low pressure system.
This could conceivably cause some minor coastal flooding if it
lines up with a high tide cycle.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 77 59 79 60 76 / 20 10 30 70 50
Panama City 72 62 77 63 73 / 20 10 40 80 40
Dothan 77 59 75 59 75 / 20 10 40 80 40
Albany 77 58 77 60 76 / 20 10 30 80 50
Valdosta 77 57 80 60 76 / 10 10 20 60 40
Cross City 78 56 80 60 75 / 10 10 10 30 40
Apalachicola 72 63 77 63 73 / 30 10 30 60 50
FL...Dense Fog Advisory until 9 AM EST /8 AM CST/ this morning for
Calhoun-Central Walton-Coastal Bay-Coastal Franklin-Coastal
Gulf-Coastal Jefferson-Coastal Taylor-Coastal Wakulla-
Gadsden-Holmes-Inland Bay-Inland Franklin-Inland Gulf-
Inland Jefferson-Inland Taylor-Inland Wakulla-Jackson-Leon-
Liberty-North Walton-South Walton-Washington.
GA...Dense Fog Advisory until 9 AM EST this morning for Baker-Calhoun-
AL...Dense Fog Advisory until 8 AM CST this morning for Coffee-Dale-