Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 231918
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
318 PM EDT Wed May 23 2018

.NEAR TERM (Rest of Today-Thursday)...

Weak forcing so far with only shallow scattered showers and a few
storms over mainly north zones shifting northeast slowly. Outflow
from convection to our northwest may force convection in the next
few hours over northwest zones. So anticipate increasing coverage
and intensity of showers and storms through rest of aftn and the
evening with main focus over southeast GA. Isolated strong storm
possible due to some dry air aloft enhancing downburst potential
later this aftn/early evening. A vort lobe over central GA will be
the driver of scattered to possibly numerous showers and more
isolated convection over northeast FL. CAM models don`t seem as
impressive carrying convection overnight but plan to carry
convection through about 07z/08z (3-4am). Heavy rainfall is the
main hazard along with lightning and gusty winds. Have maintained
some low POPS still after 3-4am across Jeff Davis...
Atkinson...Appling counties close to the vort lobe. Lows dip into
the upper 60s to lower 70s tonight. For Thursday...models show mid
level low pressure/vort lobe sinking southward slowly with
abundant moisture over southeast GA with PWATs around 2 inches.
Enhanced rain chances are forecast for this area with categorical
POPS around 70-80 percent inland southeast GA with lowering POPs
further south and east as sea breezes forcing most convective
inland. Highs should be able to manage mid to upper 80s again.

.SHORT TERM...Fri & Sat...

Fri & Fri night...Morning rainfall expected across SE GA under a
meandering mid level vorticity lobe while a broad surface
inverted trough axis rotates up the FL peninsula and drifts inland
along the local coast, which will also bring a good chance of
morning convection to coastal areas. As the surface trough drifts
inland with the east coast sea breeze into Fri afternoon and the
mid level low begins lift northward, mainly diurnally driven
precipitation will focus inland Friday afternoon, generally west
of Highway 301 and north of the I-10 corridor into Fri evening.
Locally heavy rainfall will continue to be the main convective
hazard due to a very moist airmass with PWATs 1.8-2" and a light
southerly steering flow at 10 kts or less. Could also have some
wet downburst winds due to heavy precip loading, but generally
expect sub-severe storms due to fairly warm mid level
temperatures. Convection will fade inland Friday evening with loss
of diurnal instability, then another weak trough axis begins to
edge northward up the central FL coast which could bring a few
coastal to mainly the St. Johns and Flagler counties by sunrise
Sat.

Sat & Sat night...Rain chances increase from south to north by
Saturday afternoon, with a mostly dry morning expected for the
local area except for mainly a coastal shower under SSE low level
flow. Band of deep tropical moisture with PWATs over 2" is
expected to sweep over the entire forecast area Sat afternoon
through Sat night as low pressure drifts northward across the
central or the eastern Gulf of Mexico, with the local forecast
area on the wet, east side of the system. If the low center tracks
farther east across the eastern Gulf, like what the latest 12Z
GFS advertised, higher rain chances and precipitation totals are
expected locally, while if the center tracks farther west, expect
a drier forecast with the better rain chances focused across the
western counties as the ECMWF continued to suggest. Still too much
model discrepancy to pin-down where greatest rainfall and
potential flood threats will coincide with this system, but at
this time it certainly looks like above normal rainfall chances
with waves of rainfall and embedded tstorms Sat afternoon through
Sat night as moisture overspreads and lingers over the local area.
Again, main convective hazard will be potentially flooding
rainfall. There could also be gusty wind potential depending on
the surface lows track, intensity and structure, with the stronger
winds near the coast and in stronger tstorms.

Maximum temperatures will trend below normal Fri & Sat with values in
the low/mid 80s due to increasing cloud cover and precip
potential. High temperatures will trend above normal with values
in the upper 60s to lower 70s.

.LONG TERM...Sun through Wed...

Forecast is highly dependent on the evolution and track of the
Gulf Low, with the National Hurricane Center now advertising a
60% chance of it developing into a tropical system during the Day
3-5 time frame. Favored the Weather Prediction Center (WPC) and
National Hurricane Guidance (NHC) collaborative guidance track
which trended more toward the ECMWF tracking the low center toward
the central or east central Gulf Coast, with the latest GFS
operational run on the relatively far eastern periphery of the
guidance spread. This pattern would support the potential for
widespread stratiform rainfall lifting over the forecast area
early Sunday, with some clearing midday, then a resurgence of
showers and tstorms in the afternoon across a moisture rich
environment along the sea breezes under stronger southerly
steering flow. Flooding rainfall and strong winds in storms would
be possible. Mon-Wed, stacked low pressure is progged to meander
across the Gulf Coast region where flooding rainfall will likely
occur as moisture streams northward on the east side of the slowly
moving low, while locally, expect more of diurnally driven
convection, but with decent coverage of showers and storms given
high moisture content lingering over the area, especially for SE
GA and the Suwannee River Valley of NE FL where deeper moisture
and sea breeze forcing will coincide.

High temperatures will trend near to below climo Sun due to cloud cover
and rainfall with highs in the low/mid 80s. Warming trend
expected Mon-Wed with general SSW mean layer flow over the area
between stacked low pressure meandering west of the region and the
Bermuda ridge east of the area, with highs reaching the mid/upper
80s. Low temperatures will trend near to above normal values in
the upper 60s to lower 70s.

&&

.AVIATION...
VFR prevail with area cigs near 050 or above. As anticipated
convection...so far it not at the terminals but increased chances
for SSI and possibly JAX later this aftn. May see some convection
drift in from the west or develop overhead for all terminals
except SGJ in the late aftn/evening. Another round of scattered
to numerous showers and storms on Thursday is expected.

&&

.MARINE...

Atlantic high pressure will remain mostly stationary through the
end of the week across the northeast Florida waters. Wind speeds
and seas will remain below caution levels on all waters through
Thursday night. A broad low pressure center will take shape over
the southern Gulf of Mexico by Friday and Saturday and move
slowly northward through the rest of the weekend. Our local
pressure gradient will gradually tighten as this broad low moves
into the central Gulf of Mexico, resulting in southeasterly winds
increasing Friday afternoon through Saturday and continue to be
breezy into Sunday. Waves of heavy showers and embedded thunderstorms
will begin to overspread our local waters on Friday afternoon.

Rip Currents: Enhanced rip current risk to continue today and
gradually increasing the rest of the week with high risk possible
Friday through the Weekend as southeast winds stay breezy kicking
up local surf conditions.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  69  84  68  83 /  50  80  50  60
SSI  72  81  72  80 /  10  30  20  30
JAX  69  86  69  85 /  20  60  20  40
SGJ  71  83  70  82 /   0  10  20  30
GNV  68  87  69  83 /  30  70  30  60
OCF  69  88  69  85 /  30  50  30  60

&&

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

$$

Shashy/Enyedi/McGinnis



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