Area Forecast Discussion
Issued by NWS Jacksonville, FL

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385
FXUS62 KJAX 201841
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
241 PM EDT Sun Aug 20 2017

.NEAR TERM /Through Monday/...

Another hot August day was observed across the region with
temperatures in the low to mid 90s. Only widely scattered showers
and storms have developed thus far this afternoon due to the
subsidence aloft and the slow progression of the east coast sea
breeze. Expect scattered to numerous showers and storms to develop
across the interior in the moisture tongue that exists from west
of St. Simons to the Suwannee Valley. A few strong storms with
gusty winds and small hail are possible. Scattered showers/storms
will remain along the Suwannee Valley towards I-75 in the evening,
dissipating a few hours after sunset. As a trough approaches the
region tonight, shower chances will increase along the coast
overnight. Overnight lows will be in the 70s.

Upper level low over the south central Gulf of Mexico will shift
to the western Gulf on Monday. An +PV anomaly associated with an
inverted trough/wave was located from south central Florida
northeastward into the western Atlantic. This feature shows up
well on satellite, with significant cloud across southern and
central Florida, and to the east of the region this afternoon. The
trough will slide north to northwestward tonight and Monday,
moving to the northeast Florida coastline by Monday morning. A
strong upper level ridge across the western Atlantic will build
across Georgia and the Southeast on Monday. A vort max associated
with the inverted trough over south central Florida this afternoon
will move over northeast Florida on Monday, and this will bring
deep moisture to the area, with precipitable water values above 2
inches. In addition, increasing cloud cover and rainfall chances
are expected along the coast late tonight into Monday morning.
Scattered showers and storms will then move inland through the day
as the wave axis shifts across the interior. Mostly cloudy skies
are expected across the southeastern half of the region Monday
morning, with clouds spreading inland as the trough moves to the
northwest. The best viewing locations for the eclipse on Monday
are northwest of Alma and possibly along the coast in northeast
Florida to the east of I-95 as the wave axis pushes across the
interior and a weak east coast sea breeze moves inland. Otherwise,
mostly cloudy skies will prevail through the day with scattered
showers and storms. Temperatures are forecast to be lower on
Monday due to cloud cover and scattered showers/storms, with highs
in the upper 80s to lower 90s.

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...

MONDAY NIGHT...There will some drier air with precipitable water
values 1.30 to 1.60 inches working its way into north central
Florida early Monday evening, in the wake of exiting trof axis
that moves into the Gulf of Mexico. However, moisture rich
atmosphere will exist between just south of I-10 corridor to just
north of Georgia Highway 82. Between this defined area and mainly
along and west of highway 301 some residual and ongoing convection
is most anticipated during the evening hours, then lifting
northward mainly north of the FL/GA border during the late evening
through a couple hours past midnight, before everything abating
during the pre-dawn hours.

TUESDAY AND TUESDAY NIGHT...Tuesday will  feature a drier day
particularly south of I-10. Upper level ridge centered across the
Southeast, and onshore flow continues as surface high pressure
moves further north across the mid Atlantic. 30-40% POPS are
across the region where there will be lingering shortwave energy
may remain with remnant weak surface trof just north of the
Altamaha River Basin. The thunderstorm chances should diminish
pretty rapidly Tuesday night with the loss of heating and upper
ridging extending from the offshore Atlantic through the region
into the NE Gulf of Mexico.

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A cold front will approach the  Altamaha River Basin Wednesday
morning and reside near the FL/GA midday with pre-frontal trof
near I-10 during the afternoon. Strong heating and convergence
into a prefrontal trough supports thunderstorms mainly in the
afternoon. Consensus models and Superblend have pops 30 to 50
percent. The thunderstorm chance will continue Wednesday night and
Thursday with the front in the area. It looks to be drier with
the front just off the coast Friday and Saturday, but confidence
is low with the front lingering not far to the east. Best chances
of rain will mainly be over NE Florida particularly over the
eastern sections. A more consolidated tropical low may eventually
form along the remnant boundary across the east-central FL coast
Friday morning and shift east then NE over the open Atlantic late
Friday through Saturday. Temperatures should remain above normal
ahead of the front through Wednesday. Expect maximum heat index
readings 100 to 105 Wednesday afternoon. The GFS and ECMWF MOS
support near normal temperatures Thursday through Saturday.

&&

.AVIATION...
An isolated shower moved over KCRG around 18Z, and an isolated
storm moved north of KJAX along the east coast sea breeze.
Showers/storms will develop and push inland this afternoon. Best
chance for shower/storms later this afternoon will be at KVQQ and
KGNV. East to southeast winds 5-10 knots will prevail this
afternoon. Mid/high clouds will increase overnight as a trough
moves towards the region, and showers are possible along the coast
late overnight into Monday morning. Have VCSH from late tonight
through the end of the TAF period with increasing cloud cover.

&&

.MARINE...
Surface ridge axis will continue to shift north of the area
resulting in an easterly flow. The surface ridge will remain
northeast of the region through Tuesday. A frontal boundary will
then shift into the southeast by the middle of the week and the
ridge will shift back to the south.

Rip Currents: Low risk today, and Low to Moderate risk of rip
currents on Monday.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  75  91  74  92 /  10  30  20  30
SSI  78  87  78  89 /  40  50  20  20
JAX  76  89  75  91 /  30  40  20  10
SGJ  75  88  77  89 /  30  40  10  10
GNV  73  90  74  93 /  20  40  10  20
OCF  74  91  74  93 /  10  30  10  20

&&

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

$$

Kennedy/Cordero/McGinnis



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