Area Forecast Discussion
Issued by NWS Jacksonville, FL
FXUS62 KJAX 300855
Area Forecast Discussion
National Weather Service Jacksonville FL
455 AM EDT SAT JUL 30 2016
...Very Hot Temperatures Continue this Weekend...
Overnight surface analysis depicts high pressure (1018 millibars)
centered over the eastern Gulf of Mexico. Aloft...deep-layered
ridging remains centered over the Florida peninsula. Meanwhile, a
TUTT low was spinning westward through the southeastern Bahamas.
Upper troughing in place over the Upper Midwest was slowly digging
east-southeastward through the Great Lakes states. Fair skies
prevail over our region, with muggy conditions continuing as
temperatures at 08Z ranged from the mid 70s to the lower 80s, with
dewpoints in the 70s.
.Near Term (through Sunday)...
Deep-layered ridging in place over our region will begin a
gradual weakening trend today as troughing over the Great Lakes
states slowly digs southward, while the TUTT low slowly advances
westward through the Bahamas. A pocket of deeper moisture over
central FL will shift northeastward, igniting the Gulf coast sea
breeze over Marion County towards noon. Less subsidence and a
slightly weaker pressure gradient will allow the Atlantic sea
breeze to advance inland more quickly today, with isolated
convection developing along the I-95 corridor around noon. Higher
moisture values will also push southeastward into our interior
southeast GA counties late this afternoon, developing isolated to
widely scattered convection. Temperatures aloft will remain rather
warm (-4 to -5 Celsius at 500 millibars), which should keep
coverage scattered and likely brief in duration. Highs will again
soar into the mid to upper 90s. Less subsidence will result in
higher dewpoints than recent afternoons across northeast and north
central FL, where heat indices will approach or perhaps exceed 105
degrees. However, values should stay just below heat advisory
The Atlantic and Gulf coast sea breeze will collide near the U.S.
Highway 301 corridor around sunset, which may keep widely
scattered convection in place through the mid evening hours over
inland northeast and north central FL, with coverage decreasing to
isolated by early evening over inland southeast GA. Convection
will wane by midnight, but land breeze activity may flare over the
northeast Gulf by late evening, with isolated activity possible
over the western Suwannee Valley during the predawn hours on
Sunday. Debris clouds will thin overnight elsewhere, with lows in
the mid 70s along the I-75 corridor, ranging to the lower 80s at
Ridging aloft will retrograde well west of our area on Sunday as
the TUTT low moves into southeast FL and troughing aloft gradually
digs into the Ohio and Tennessee Valleys. Although mid level
temperatures will cool off (generally -6 to -7 Celsius at 500
millibars), subsidence on the western side of the TUTT will move
over north central and northeast FL during the afternoon hours.
Higher moisture and instability values will reside over southeast
GA, where scattered convection is expected during the afternoon
hours. Widely scattered convection may overcome an overall
subsident atmosphere during the late afternoon hours at inland
locations of northeast and north central FL as the Gulf and
Atlantic sea breezes collide. Inland highs will generally climb
into the mid 90s, with heat index values up near 105 in most
locations. An earlier developing sea breeze should keep highs in
the lower 90s at the beaches.
.Short Term (Sunday night through Tuesday)...
The region will be between high pressure to the East/Southeast and
a trough to the Northwest Sunday night into Monday. This pattern
will result in Southwesterly/Southerly flow. With this pattern
would expect convection to initiate over Western counties, with
this area moving East through the afternoon, then intersecting
with East coast sea breeze late.
The high pressure ridge will slide North Monday night into
Tuesday, stretching across Northern Florida. Expecting scattered
afternoon and evening convection.
Temperatures will remain above normal this period.
.Long Term (Tuesday night through Friday)...
Weak high pressure will be East/Northeast of the region this
period, leading to mainly Southerly/Southeasterly flow. This will
be a moist pattern with convection initiating on the sea breezes,
with East and West sea breezes meeting in the mid to late
afternoon. Have favored higher than normal precipitation chances
this period. With additional cloud cover expected, temperatures
will trend closer to normal.
VFR conditions will prevail at the regional terminals through at
least 16Z. Isolated to widely scattered thunderstorms may impact
the northeast Florida terminals after 16Z through 03Z. Timing and
intensity remain in question, so we used VCTS at the northeast
Florida terminals for now. The Atlantic sea breeze will move
inland this afternoon, crossing SGJ around 16Z, CRG and SSI around
18Z, JAX around 19Z, and VQQ around 20Z. Surface winds will
become southeasterly at 10-15 knots after the sea breeze passes
these terminals...and will then veer to a southerly direction with
slowly decreasing speeds towards 00Z.
Evening southerly wind surge is keeping caution level speeds over
the offshore waters. Winds will veer to a southwesterly
direction during the predawn hours, with speeds gradually
decreasing below 15 knots. Light west to northwesterly will
prevail this morning, with the sea breeze developing in the near
shore waters towards noon, shifting winds to a southeasterly
direction with speeds increasing to near 15 knots. Southerly winds
closer to 10 knots are expected offshore today. Another evening
wind surge will bring south to southwest winds up to caution
speeds offshore shortly after sunset, with speeds near caution
nearshore. Winds overnight will become southwesterly with
gradually decreasing speeds.
High pressure will build to the southeast of our waters on
Sunday, with southerly winds just below caution speeds expected,
except southeasterly on Sunday afternoon in the near shore waters.
Only isolated thunderstorms, mainly during the late afternoon
and evening hours, are expected through the weekend. Another
southwesterly wind surge will result in caution conditions in the
offshore waters on Sunday night. High pressure will then weaken
during the early to middle portions of next week as a weak trough
sinks southward towards our waters. Thunderstorm coverage will
gradually increase over the coastal waters next week. Evening wind
surges will continue, with seas building up to 3-5 feet offshore
Rip Currents: Low risk expected this weekend.
Record highs for today (7/30):
Jacksonville 102 (2010)
Gainesville 100 (1896)
St. Simons Island 99 (2010)
Alma 101 (1961)
.PRELIMINARY POINT TEMPS/POPS...
AMG 99 76 97 74 / 30 20 40 30
SSI 95 81 93 78 / 20 20 30 10
JAX 97 77 95 75 / 30 20 30 10
SGJ 94 79 92 78 / 20 20 20 10
GNV 96 75 95 74 / 30 30 40 20
OCF 94 75 95 74 / 40 30 30 20