Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 212030
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
430 PM EDT Fri Jul 21 2017

.NEAR TERM /TONIGHT AND SATURDAY/...
Convection will very slowly build on both seabreezes as they
press inland this afternoon, more so on the gulf breeze. Activity
will become enhanced around the time of sunset as the seabreezes
and outflow boundaries all come together across the interior.
Coastal areas will remain mostly dry as the seabreeze stabilizes
the airmass.

Storms across the interior this evening will tend to have a slow
and erratic storm movement but most of the activity should tend to
slowly drift back off towards our western zones this evening due
to the easterly flow aloft. Instability not expected to be quite
as high as yesterday but still high enough to support an isolated
severe storm or two. The main threats with the strongest storms
will be localized damaging wind gusts and locally heavy rainfall.
Very localized potential for large hail as well given 500 mb temps
of -9C with mid level low directly overhead. Diurnal storms should
wrap up by late evening but additional late night showers will be
possible across our southern zones as deeper moisture lifts up
from the south.

Prevailing flow will become southwesterly on Saturday.
Showers/storms will get off to an earlier start across our western
zones as moist southwest flow pushes the gulf seabreeze in early.
Storms across northeast florida will build toward the Atlantic
coast Saturday afternoon with an increase in intensity and
coverage expected late in the day near the I-95 corridor as the
dominant Gulf seabreeze slams into a slow moving Atlantic
seabreeze. Scattered to numerous storms will be possible across
northeast Florida in the afternoon with the highest chances south
of a line from Gainesville to St Augustine. Drier air across
southeast Georgia will keep convection more isolated there on
Saturday with max temps several degrees above normal with heat
indices topping out around 105 degrees. Max temps will be near
normal across our southern zones due to increased cloud cover with
early start to showers/storms off the Gulf. Temps will also be
hotter at the beaches due to a much later start to the seabreeze.

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
Deep-layered Atlantic ridging will build westward across south
Florida, creating a deepening southwesterly flow pattern.
Convection will initiate during the morning hours along an active
Gulf coast sea breeze, and this convection will progress eastward
during the afternoon. Convection will likely pulse as it
encounters a pinned Atlantic sea breeze along or just east of
Interstate 95 during the mid to late afternoon hours, with strong
to isolated severe thunderstorms possible in coastal locations.
Wet microbursts and excessive lightning strikes will be the
primary threats from this activity along and east of I-95 during
the late afternoon hours on Sunday and Monday. Convection should
push into the Atlantic coastal waters by sunset each day, with the
evening hours remaining mostly dry inland from Saturday through
early next week. Highs will generally climb into the lower 90s,
with southwest winds delaying the development of the Atlantic sea
breeze until the early to mid afternoon hours, resulting in highs
at or above 90 at area beaches on Sunday and Monday. An earlier
start to convection should keep heat index values in check at
inland locations, with daily maxes generally around 100. Lows will
generally range from the mid 70s inland to near 80 at the
beaches.


.LONG TERM /TUESDAY THROUGH FRIDAY/...
Deep-layered Atlantic ridging will extend across the Florida
peninsula on Tuesday, keeping a similar weather pattern from the
weekend and Monday in place, featuring a dominant Gulf coast sea
breeze pattern with scattered to numerous thunderstorms
progressing eastward across our region, mainly during the
afternoon hours. Highs will again climb into the lower 90s for
most locations, including the coast, as a deep southwesterly flow
pattern remains in place which will delay the development of the
Atlantic sea breeze until early to mid afternoon. Ridging aloft
will then build over the southern Plains states, which will drive
a deepening trough into Alabama, Georgia, and the Florida
panhandle by late Wednesday. This weather pattern will promote
scattered to numerous showers and thunderstorms developing at any
time, with temperatures generally near late July climo. Long-term
models currently disagree on how far south this trough will move
before weakening by late next week, with model blends yielding
near climo rain chances and temperatures for next Friday at this
time. There are indications that ridging over the Plains will
begin to expand eastward into the southeastern states towards the
end of next week, which could advect some drier air aloft into
southeast Georgia by late Friday.

&&

.AVIATION...
Mainly VFR conditions to prevail through the next 24 hours. Storms
this afternoon are expected to concentrate late in the day across
the interior. GNV could see another round of very heavy rain with
this activity, depending on exactly where it comes together. Have
shown a 2 hour TEMPO group for thunderstorms at GNV around the
time of sunset today. More specific details (LIFR, gusty winds)
may need to be added as we go through the afternoon and the
situation begins to unfold.

&&

.MARINE...
Surface high pressure will be East Southeast of the region
through the early part of next week. A trough of low pressure
will sink Southeast across the region and dissipate toward the
middle of next week.

Rip Currents: Moderate risk through Saturday.

&&

.CLIMATE...
Fifty days into meteorological summer, a whopping 28.26 inches of
rainfall has been measured at the Gainesville Regional Airport.
14.08 of this has fallen in July, placing the monthly record of
16.65 (set in 2013) in jeopardy. The wettest meteorological summer
on record at Gainesville occurred in 1965, when 32.55 inches of
rainfall was measured. Rainfall records at Gainesville date back
to July of 1890.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  73  94  74  93 /  30  20  20  60
SSI  75  92  81  90 /  10  20  20  60
JAX  72  93  75  91 /  10  40  20  70
SGJ  75  91  77  91 /  10  40  20  50
GNV  71  91  73  89 /  40  50  20  60
OCF  72  90  74  88 /  30  60  30  50

&&

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

$$

Nelson/Shuler/McGinnis



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