Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 180511
Area Forecast Discussion
National Weather Service Tallahassee FL
1211 AM EST Wed Jan 18 2017
.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.
.PREV DISCUSSION [814 PM EST]...
.NEAR TERM [Through Tonight]...
Some light showers induced earlier by low level WAA have largely
dissipated. The remainder of the forecast looks on track. Look for
another unseasonably mild might for mid winter with lows ranging
from the lower 50s east to the upper 50s west. Conditions once
again look conducive for fog formation.
.SHORT TERM [Wednesday Through Thursday Night]...
We`ll enjoy one more relatively tranquil day on Wednesday before
changes to a stormier pattern start to take place on late Thursday
and beyond. Upper ridging across the southeast states will weaken
as an upper trough over the southwest states moves eastward over
the next couple of days. By late Thursday, this upper trough will
likely take on a negative tilt as the axis lifts northeastward
across the southeast states. Ample return flow and lift will allow
a large area of rain with some thunderstorms to develop west of
the area on Thursday morning and move into the western portions of
the area by late Thursday into Thursday night. Deep layer shear
values may increase to around 50 knots across the western portions
of the area on Thursday with SBCAPE values around 200 j/kg and 0-1
km shear values generally between 20 and 30 knots. If the low
level jet were to trend any stronger, then an isolated strong to
severe storm could conceivably occur on Thursday night across the
western portions of the area. This bears watching, although the
bigger threat is likely to come over the weekend.
.LONG TERM [Friday Through Tuesday]...
Rain and storms from Thursday night are expected to continue into
part of Friday before diminishing as the first upper trough lifts
northeastward away from the area.
On Saturday, the next shortwave is expected to affect the region
with another round of rain and thunderstorms. The 700-500 mb lapse
rates may steepen to around 7C/km on Saturday with increasing
instability. This may actually allow a hail threat to develop on
Saturday with some of the storms along the warm front as it lifts
northward with sufficient instability. Some severe weather cannot
be ruled out on Saturday.
On Sunday, the main system arrives, and on the synoptic scale it
continues to look impressive. Both the 12z GFS and ECMWF have a
strong, closed upper level low moving through the southeast states
with very strong upper level flow (greater than 100 knots at 500
mb) digging into the northern Gulf. The low level jet is forecast
to intensify during the day Sunday across the area with a
deepening surface low, although the mesoscale details of how this
evolves remain unclear with some differences noted. Regardless,
there appears to be sufficient instability and shear for a threat
of severe storms on Sunday. Given the overall strength of the
synoptic scale system, some significant severe storms, including
the threat of some tornadoes, cannot be ruled out.
After Sunday, the system pulls away from the area with a drying
trend for at least a few days. 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.
Winds will be southeasterly around 10 knots for the next couple of
days with winds and seas increasing late 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.
Marginally low (upper teens to near 20) dispersions are expected
along the Florida coast Wednesday afternoon. Otherwise, no
hazardous fire weather conditions are expected for the next
several days with increasing chances of wetting rains across the
region through the weekend.
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 2-4 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 75 61 76 / 20 10 30 70 50
Panama City 72 62 70 64 73 / 20 10 40 80 50
Dothan 76 59 75 60 75 / 10 10 40 80 40
Albany 77 58 76 61 76 / 10 10 30 80 50
Valdosta 76 57 76 60 76 / 20 10 20 60 50
Cross City 77 56 78 61 75 / 10 10 10 30 40
Apalachicola 72 62 71 63 73 / 20 10 40 60 50