Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 200717

Area Forecast Discussion
National Weather Service Jacksonville FL
317 AM EDT Mon Aug 20 2018

.NEAR TERM...Today and Tonight...Deep layer ridge will persist to
the south of the area today with a pocket of dry air aloft shifting
north across se Georgia. This dry air will limit convection to
isolated coverage over se Ga this aftenoon/evening. Higher moisuture
values with PWATs near 2 inches will exist ne Fl and result in
scattered storms with the east coast seabreeze reaching locations
near the Highway 301 corridor by late afternoon and early evening.
Wet microbursts will be possible mainly near the seabreeze front and
outflow boundaries. Hot and humid conditions will continue with
afternoon heat indices 100-105.

.SHORT TERM...Tue & Wed...

Increasing rain chances as an early season cold front approaches
from the WNW Tuesday, preceded by a few broken lines of pre-frontal
showers and tstorms that will develop over the local area as waves
of mid level PVA sweep overhead with deepening mid level trough
axis. Both the NAM and GFS advertised a chance of morning showers
and tstorms along a convergent band (likely remnant outflow
boundaries from todays convection) across NE FL, extending offshore
of the local Atlantic coast Tue morning. SW steering flow will
increase over the local area through the day ahead the mid level
trough deepens, which will likely pin the east coast sea breeze near
the SE GA Atlantic coast, with some inland progression of the east
coast sea breeze across coastal NE FL counties due to lighter
steering flow. The highest rain chances for NE FL will focus near
the St. Johns River basin eastward toward the Atlantic coast where
sea breeze and boundary mergers will converge during the late
afternoon and early evening. Rainfall chances will increase across
SE GA Tue afternoon through Tue night as a broken line of pre-
frontal showers/tstorms presses across eastward. Upper level
dynamical support and mid level lapse rates not overly impressive
with this first mid level short wave trough, thus the usual
diurnally enhanced pulse strong to severe storms capable of gusty
wet downbursts will be possible. A chance of tstorms will continue
Tue night as the surface front edges southward across southern GA,
then by Wed the highest rain chances will focus across NE FL as the
surface front stalls across the area. More stable NW flow and drier
air will filter over SE GA Wed afternoon, limiting rainfall and
tstorm development, while more unstable and unsettled SW flow will
persist over NE FL which will support stronger tstorm potential
during the afternoon and early evening. Resultant convection will
press offshore during the early evening hours.

Above normal temperatures expected with highs in the lower 90s with
muggy overnight conditions as lows range in the 70s.

.LONG TERM...Thu through Sun...

Surface frontal zone lingers across northern FL Thu as surface high
pressure bridges the boundary building eastward offshore of New
England through Sat. Drier and stable NW mid/upper level flow favors
lower than normal rain chances across the area for much of Thu. Late
Thu the lingering surface trough amplifies into an inverted coastal
trough with a broad surface low progged to develop along the
boundary across northern FL. Onshore flow on the northern side of
the boundary will focus elevated rain chances along the SE GA coast
Fri into Sat, with rainfall translating inland across inland SE GA
during the afternoon, enhanced by dirunal heating. In addition to
the low level forcing on the northern edge of the surface trough,
mid/upper level forcing and instability will increase Fri into Sat
as an upper trough deepens south over the SE Atlantic coast. These
phased ingredients will bring an increased chances for strong to
severe storms over the local area Fri into the weekend. Cool
temperatures aloft (500 mb -7 to -9 deg C) will continue into Sun as
the surface axis retrogrades inland with the surface ridge axis
settles farther southward down the Atlantic coast.

Temperatures will trend back toward climo values with highs near 90
and lows remaining in the 70s.


.AVIATION...VFR conditions will prevail today. Periods of MVFR
visibilities will be possible 08Z-12Z due to patchy early morning
fog. Scattered thunderstorms will be possible after 17Z with the
chance continuing inland at VQQ and GNV til around 01z this


.MARINE...Surface ridge to the south will maintain a south to
southwest flow becoming southeast near the coast during the
afternoon hours. A cold front will approach from the northwest on
Wednesday as it weakens and slows down. The front will stall near
the Georgia/Florida border Thursday and Friday bringing an
increase in showers and thunderstorms over the waters.

Rip Currents: Low risk.



Light transport winds will create low daytime dispersion today and
Tue across the St. Johns River basin.


AMG  93  72  92  73 /  20  10  30  20
SSI  91  75  90  76 /  20  30  20  10
JAX  94  74  93  74 /  30  30  40  10
SGJ  91  73  89  74 /  30  30  40  10
GNV  93  73  91  74 /  40  10  50  10
OCF  94  72  91  73 /  40  20  60  10




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