Area Forecast Discussion
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FXUS62 KTAE 190034

Area Forecast Discussion
National Weather Service Tallahassee FL
834 PM EDT Sun Mar 18 2018



Initial round of convection has largely transitioned to stratiform
rain over the eastern 2/3 of the forecast area. This will
temporarily stabilize the atmosphere. However, our earlier thinking
outlined in the near-term section below has not changed. A second
round of convection should arrive after midnight and work its way
across the forecast area through the pre-dawn hours. PoPs through
06z were adjusted based on radar trends, but the late-night
forecast remains the same.



.NEAR TERM [Through Tonight]...

A few light showers originating from the seabreeze have developed
out ahead of the advancing convective complex to the west along the
Florida Gulf Coast at this hour. This activity is expected to remain
weak. With instability being limited by cloud cover this afternoon,
the severe weather threat this afternoon remains largely conditional
on any mesoscale interactions (differential heating zones, sea-
breeze/boundary interactions, cell mergers) as the aforementioned
convective complex moves into the region later this evening. Given
the available shear profile and relatively poor lapse-rates, the
main threat with this initial wave through this evening will be
damaging wind gusts, though this threat is on the low side through
this evening.

The latest hi-res model runs continues to show a second round of
intense convection developing overnight(generally around/after 06Z)
associated with a subtle shortwave interacting with the warm front
along the eastern Gulf Coast. In addition to increasing bulk shear
across the region, steeper lapse rates will finally work into the
region from the northwest. This combination of shear, moisture, and
increased instability will yield a threat for hail, damaging winds,
and even tornadoes, as forecast hodographs are favorable to support
rotating updrafts into Monday morning, as the warm front lifts
northward. The timing and coverage of this wave will directly affect
the evolution of the severe threat during the day Monday, as
discussed in the short term period.

.SHORT TERM [Monday Through Tuesday Night]...

A weak shortwave, south of the main +PV core moving through the
Tennessee Valley, will pass over the region on Monday. As it does
so it will aid convective development along the coastal front, as
well as along a warm front draped across southeast Alabama and
south Georgia. Should convection tonight not be too intense or
widespread, the confidence in severe weather on Monday will be
higher. The atmosphere will be much more supportive of severe
thunderstorm development on Monday than overnight tonight, with
rather steep lapse rates and plenty of deep/low layer shear and
instability. The presence of a warm front across south Georgia
also increases the potential for tornadoes, with damaging winds
and marginally severe hail also possible. As showers and
thunderstorms move northeast out of the region on Monday evening,
there should be a lull in activity before the approach of the cold
front late Monday night. Due to the activity in the afternoon, it
appears less likely that the front will produce much organized
severe weather overnight Monday. However, with the front still in
the southeast Big Bend on Tuesday morning and afternoon, there is
a small window of time where severe weather would be probable in
this region. The SPC has placed portions of Taylor, Lafayette, and
dixie counties in an Enhanced Risk for severe weather on Tuesday.
The main threats Tuesday would be damaging winds, tornadoes, and
severe hail. Seasonable lows and drier conditions are expected
beginning Tuesday night.

.LONG TERM [Wednesday Through Sunday]...

The eastern CONUS trough will remain in place through the end of
the week before transitioning to a more zonal regime over the
weekend. Seasonable temperatures are expected through the end of
the week, gradually rising above average by the weekend. No rain
is expected.

.AVIATION [Through 00Z Tuesday]...

MVFR conditions will develop overnight and then lower to IFR. An
initial round of showers and isolated thunderstorms will move
east and dissipate. A second round is expected to impact the
terminals after midnight through the pre-dawn hours. A third round
is then expected from midday into the late afternoon hours.
Strong to severe storms will be possible in the latter two rounds.


Cautionary conditions may begin as early as Monday, with showers
and thunderstorms from tonight through Tuesday morning. Behind the
cold front on Tuesday winds will quickly increase to solid
Advisory levels with gusts to Gale force possible. Advisory
conditions should taper off by Wednesday night, falling below
Cautionary levels by Thursday night.


Humid conditions are forecast into Tuesday. Deep mixing heights and
strong transport winds will produce very high dispersion indices on
Tuesday. Much drier air will arrive behind a cold front for
Wednesday through Friday. However, red flag conditions are not
anticipated at this time.


Widespread flooding is not expected as average rainfall amounts
are forecast to be around 1-2" through Tuesday. Isolated higher
amounts 2-4" are possible (mainly east of the Apalachicola and
Chattahoochee rivers). It`s not out of the question that some
minor localized flooding could occur in places getting those
higher amounts. No rain is expected beyond Tuesday through next


Spotter activation is requested through Tuesday. Spotters should
safely report significant weather conditions and/or damage by
calling the office or tweeting us @NWSTallahassee.



Tallahassee   64  78  67  78  49 / 100  70  60  30   0
Panama City   67  73  66  71  51 /  70  70  60  20   0
Dothan        63  77  62  75  43 /  90  60  50  20  10
Albany        62  78  65  76  44 / 100  70  60  30  10
Valdosta      64  77  66  80  48 / 100  70  60  50  10
Cross City    62  75  67  76  52 /  50  60  50  70  10
Apalachicola  67  73  67  73  52 /  60  70  60  40   0




NEAR TERM...Pullin
SHORT TERM...Harrigan
LONG TERM...Harrigan
HYDROLOGY...Harrigan is the U.S. government's official web portal to all federal, state and local government web resources and services.