Flooding and Heavy Rain in Florida, December 14, 2018

Area Forecast Discussion
National Weather Service Jacksonville FL
857 PM EST Thu Dec 13 2018

...FLOOD WATCH THROUGH FRIDAY...

...RISK OF SEVERE STORMS FRIDAY AFTERNOON...

...RIVER FLOODING CONTINUES, EXPECTED TO WORSEN THIS WEEKEND...

.UPDATE...

Rain chances increase from the west, especially after midnight
tonight, with a warming and moistening trend under southerly flow
in the wake of this evening's warm front lifting northward over
the area. Coastal convergence and low level isentropic lift will
on the northern side of the lifting warm front will bring a low
chance of passing showers across SE GA through midnight, with
mostly dry conditions across NE FL east of Highway 301. West of
Highway 301, including over the Suwannee River Valley and inland
SE GA, rainfall will invade from the Gulf of Mexico through the
remainder of the night, with isolated embedded thunderstorms
bringing localized heavy rainfall. Saturated grounds and swollen
rivers combined with this localized heavy rainfall could cause
additional flooding tonight, which will make driving during the
pre-dawn hours Friday morning hazardous in these flood prone
areas. A flood watch remains in effect through Friday evening.

Temperatures are expected to fall slightly this evening, then
begin to warm after midnight. Lows will generally range from the
mid/upper 50s near the Altamaha River basin this evening to the
mid 60s across our southern FL zones. After midnight, temperatures
will warm into the 60s across SE GA, and continue in the 60s
overnight for much of NE FL.

Soaking rainfall still on track to overspread the local area
Friday and into Friday evening with embedded thunderstorm
activity. Strong dynamics and deep layer moisture will be in
place, with the limiting factor for severe thunderstorms low level
instability. Best potential for more surface heating will be
across portions of NE FL, roughly along and south of a JAX to GNV
line toward Ocala and eastward toward St. Augustine and Flagler
Beach, mid afternoon through early evening. Severe thunderstorm
hazards include damaging wind gusts and isolated tornadoes.

Rainfall will gradually tapper off from west to east Friday night,
but this system will be slow to shift rainfall across the area
with lingering showers into Saturday morning.

&&

.AVIATION...

MVFR restrictions most probable at SSI this evening, then MVFR
restrictions increase from the Gulf Coast region later tonight
through Friday morning. Widespread rainfall will overspread the
terminals by midday Friday, with thunderstorms potential elevated
Friday afternoon and Friday evening with VCTS include in all
terminals at this time. Further restrictions to IFR or lower are
likely in localized heavy rainfall Friday, with lingering low
clouds and rainfall expected into Friday night causing
restrictions. ESE winds generally 5-8 kts tonight will veer
further SSE into Friday with some gusts near 15-20 kts possible by
mid-morning.

&&

.MARINE...

ESE winds increase tonight with building seas into the 5-7 ft range
over the outer waters after midnight. Small craft advisory remains
in effect, with increasing winds near 20 knots for the outer
waters Friday. Widespread rainfall with embedded thunderstorms
will impact all the waters through Friday and Friday night.

Rip Currents: Moderate risk of rip currents.

&&

.HYDROLOGY...

No major changes in evening river forecast update.

Previous discussion...
Flood Watch remains in effect for all of SE GA and interior
portions of NE FL for a widespread 2-4 inches of rainfall, with
locally higher amounts, while amounts closer to 1-2 inches
expected for points SE of GNV/JAX across the rest of NE FL. A
localized 4-6 inch rainfall band possible in the Flood Watch area,
but too early to speculate exactly where this will fall.
Widespread minor to moderate river flooding expected for most
basins in the Flood Watch area, along with potential Major
FLooding for the Alapaha River Basin in Echols/Hamilton counties.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  58  68  58  68 /  80 100  90  20
SSI  60  67  58  67 /  50 100  90  30
JAX  61  73  61  72 /  30 100  90  30
SGJ  63  73  62  72 /  20  90  90  40
GNV  63  74  61  72 /  30 100  90  30
OCF  64  75  62  73 /  30  90  90  40

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch from 4 AM EST Friday through late Friday night for
     Alachua-Baker-Bradford-Clay-Coastal Duval-Coastal Nassau-
     Columbia-Gilchrist-Hamilton-Inland Duval-Inland Nassau-
     Suwannee-Union.

GA...Flood Watch from 4 AM EST Friday through late Friday night for
     Appling-Atkinson-Bacon-Brantley-Charlton-Clinch-Coastal
     Camden-Coastal Glynn-Coffee-Echols-Inland Camden-Inland
     Glynn-Jeff Davis-Pierce-Ware-Wayne.

AM...Small Craft Advisory until 3 PM EST Saturday for Waters from
     Altamaha Sound GA to Fernandina Beach FL from 20 to 60 NM-
     Waters from Fernandina Beach to St. Augustine FL from 20 to
     60 NM-Waters from St. Augustine to Flagler Beach FL from 20
     to 60 NM.

&&

Enyedi/Bricker