Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 171836
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
236 PM EDT Thu Aug 17 2017


.NEAR TERM...This afternoon through Friday...

An unsettled and wet pattern will bring waves of locally heavy
rainfall across NE Florida today and again on Friday as a weak
surface trough axis lingers across the area and interacts with
high moisture content (PWATs over 2.2 inches), daytime
instability, and the sea breezes. Mid/upper level high pressure
across the Gulf of Mexico extended a ridge axis across SE GA today
which was suppressing deep convective growth, but daytime heating
and high moisture content still sparked small but widespread
showers. Convection was drifting SSE 5 mph, and this weak storm
motion will enable both the Gulf and East coast sea breezes to be
drawn inland through the afternoon and evening hours,
rendezvousing somewhere between the Interstate 75 and St. Johns
River basin across NE FL. The main convective threats today will
remain locally heavy rainfall as well as the potential for wet
downburst winds of 30-60 mph.

Precipitation will slowly decrease in coverage and intensity
after sunset tonight, but will continue to advertise a low 20-30%
chance of rainfall through the night for coastal SE GA and across
NE FL on the southern side of the weak and meandering surface
trough axis. Before sunrise Fri, light WSW steering flow will
enhance rainfall potential along this trough axis across Apalachee
Bay, with convection expected to increase across the Suwanee
River Valley from the Gulf during the morning hours, potentially
reaching the JAX metro area by noon Fri.

Additional convection will pop along the Atlantic sea breeze and
across SE GA near the trough axis under daytime heating Fri, with
once again high moisture and several low level forcing boundaries
combining to bring a chance of a few strong storms capable of
strong wind gusts as well as locally heavy rainfall mainly Fri
afternoon.

The heat and high heat index values will continue with daytime
high temperatures in the mid 90s inland. These values combined
with high dew pts in the mid/upper 70s yield heat index values
105-108 deg. Muggy conditions will continue overnight with low
temps in the 70s inland to near 80 along the river basin and
coast.

&&

.SHORT TERM.../FRIDAY NIGHT THROUGH SUNDAY NIGHT/...

Ridge of high pressure will extend across the Western Atlantic and
to the South of the region into Saturday. The ridge axis will lift
North across forecast area Sunday. As a result the general flow will
change from South/Southwest to South/Southeast this period. With
this change the East coast sea breeze will become more dominant,
leading to greater chances for convection inland. Convection will
primarily be diurnal.

Temperatures will trend a little above seasonal averages.

&&

.LONG TERM.../MONDAY THROUGH THURSDAY/...

High pressure ridge will sink from near the FL/GA line into NE FL
this period. A surface trough will extend down the Southeast
US coast this period as well, with the base of this trough dipping
into Southeast Georgia. The flow will change this period from
South/Southeast to South/Southwest. With this change the West
coast sea breeze will become more dominant, with convection
developing across the region. Convection will continue to be
primarily diurnally driven.

Temperatures will continue to trend above normal this period.

&&


.AVIATION...

Restrictions to MVFR and IFR expected this afternoon and into the
early evening due to convection across the area. Light winds will
be variable through the afternoon with shower/tstorm activity,
with an east coast sea breeze expected to push inland of coastal
sites (SSI, CRG, SGJ) through 21Z. Winds will relax and become SSW
overnight once again. Elevated chances of morning convection Fri
with VCSH advertised at SSI and GNV by 10Z, and other terminals by
15Z with elevated chances of MVFR cigs.

&&

.MARINE...

Offshore flow will prevail between low pressure north of the
waters and high pressure across south Florida. Winds will become
onshore in the afternoon with the east coast sea breeze. High
pressure will build northward and extend over the local waters
early next week. Winds speeds will be 15 kts or less with combined
seas generally 4 ft or less with no headlines expected. Seas build
next week up to 5 feet over outer waters as swells increase from
storms over the Atlantic tropical waters.

Rip Currents: Low risk today and Friday.

&&


.PRELIMINARY POINT TEMPS/POPS...
AMG  75  94  77  93 /  20  40  20  40
SSI  80  91  78  90 /  30  50  30  40
JAX  76  92  76  92 /  40  60  20  50
SGJ  79  91  76  91 /  50  50  20  20
GNV  75  92  74  93 /  50  70  20  30
OCF  75  91  75  93 /  50  60  20  20

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&

$$

Struble/Enyedi


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