FXUS62 KJAX 260730
Area Forecast Discussion
National Weather Service Jacksonville FL
330 AM EDT Mon Jun 26 2017
...LOCALLY HEAVY RAINFALL POTENTIAL CONTINUES TODAY...
.NEAR TERM...Broad surface low pressure will linger offshore of the
GA/SC Atlantic coast today and tonight as the parent upper level
tough deepens over the eastern CONUS. A surface cold front was just
NW of the Altamaha River Basin early this morning, noted by dew
pts in 50s & 60s behind the boundary and a wind shift to the NW.
This boundary will gradually settle south across the local
forecast area over the next 24 hrs as the broad low pressure
center lingers offshore. Waves of showers and isolated
thunderstorms will move across the area under moist SW steering
flow through today, with an increase in thunderstorm coverage and
intensity expected in the afternoon due to diurnal heating
interacting with the surface front, lingering outflows for
yesterdays storms, and coastal convergence as NE flow funnels
southward down the Atlantic coast as the surface front edges
farther south across N Florida.
The Weather Prediction Center (WPC) highlighted a 'marginal risk'
for excessive rainfall today along parts of the local Atlantic coast
and the St. Johns River basin. This means that there was a 2-5% chance
that rainfall accumulations could exceed flash flood guidance. Given
high moisture content with precipitable water values of 2 inches
or more generally along and south of a Jesup to Homerville line,
believe that localized heavy rainfall of 2-4 inches will be
possible as was the case yesterday across much of the forecast
area mainly midday through this evening...with a gradual decrease
in rainfall intensity and coverage after sunset with the loss of
The surface trough axis will meander across N Fl tonight and over
the adjacent Atlantic waters which will continue a low chance of a
nocturnal shower or lone tstorm across the area tonight. Patchy
fog and low stratus will also be possible after sunset.
Temperatures will be below climo today under cloudy skies with
highs in the 80s. Mild temps tonight will range in the 70s.
.SHORT TERM /Tuesday and Wednesday/...
Upper trough will become more established across the region on
Tuesday. Some drier air will begin to inch in from the north, but
most of our forecast area will remain entrenched within a rather
moist environment, with prevailing mostly cloudy to overcast
skies. This combined with light onshore flow at the surface will
lead to another day of reprieve from the heat, especially near the
coast where temps will be a good 4 to 5 degrees below normal.
Stalled surface trough across the area and potential for
differential heating boundary across southeast Georgia will lead
to scattered to numerous thunderstorms. The highest chances will
exist south of a line from Waycross to Brunswick. Locally heavy
rainfall and gusty winds will be possible with the strongest
storms on Tuesday.
Drier air will continue to filter southward Tuesday night, and
this will make for more comfortable overnight conditions,
especially across inland southeast Georgia into the Suwannee
valley of northeast Florida.
Heights will quickly rebound on Wednesday as shortwave ridging
moves overhead. Onshore flow will also increase as surface high
pressure north of the area builds down the coast. Temps will
rebound slightly but the increased onshore flow will keep temps
along the coast below normal for another day. Drier air over
southeast Georgia on Wednesday will keep it mostly dry there
through the day, with only a slight chance of a shower. Lingering
deep-layer moisture across northeast Florida will be supportive
of scattered storms with coverage and intensity building from east
to west during the day.
.LONG TERM /Thursday through Sunday/...
Upper troughing will begin to move in from the west on Thursday,
and deep-layer moisture will begin to shift back to the north
across southeast Georgia. Light onshore flow will prevail and
temps will be at or slightly below normal, with the lowest
readings once again along the Atlantic coast. Scattered to
numerous storms are expected on Thursday with the best chances
along the I-75 corridor.
Mid-level troughing will become even more established across the
region on Friday with an increase in mid-level shortwave energy
through the weekend. Low level flow will begin to veer to the
south on Friday with southerly flow expected over the weekend. We
will also see a rebound in temperatures and the moist/unstable
atmosphere with increased upper level support will bring a return
to above normal convective chances with numerous storms expected
across inland locations each afternoon and early evening. Locally
heavy rainfall, frequent lightning, and strong gusty winds will be
possible with the strongest storms each day.
.AVIATION...Tempo IFR restrictions due to low stratus expected at
JAX/CRG/VQQ early this morning. Elsewhere patchy ground fog and
low stratus possible, especially SGJ where heavy rainfall
occurred yesterday. Showers and tstorms will increase in coverage
through midday with activity focused near the terminals through
the afternoon and in the evening as a cold front presses southward
across the local area. Restrictions expected in convection.
.MARINE...Surface trough will press southward across the waters
today with winds shifting from WSW this morning to the NNE from
north to south through the day with the front stalling across the
local waters and north Florida tonight. Waves of showers and
thunderstorms are expected. Onshore flow will establish over the
waters Tue through Thu as high pressure builds over and east of
the Mid-Atlantic region.
Rip Currents: Low risk today. Low to moderate for SE GA Tuesday.
.HYDROLOGY...Pottsburg Creek in JAX running within Action Stage
due to heavy rainfall yesterday. Starting to crest early this
morning. The Sante Fe River at Worthington Springs was also steady
within Action Stage.
.PRELIMINARY POINT TEMPS/POPS...
AMG 87 70 88 67 / 30 20 40 20
SSI 84 74 85 72 / 70 30 40 10
JAX 87 72 85 70 / 70 50 60 10
SGJ 85 74 84 72 / 70 50 60 20
GNV 88 72 86 69 / 60 50 70 20
OCF 89 73 87 70 / 60 50 70 20
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