Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 221517

Area Forecast Discussion
National Weather Service Jacksonville FL
1117 AM EDT Sat Jul 22 2017

...Strong to Isolated Severe Thunderstorms Possible Along I-95
corridor in Northeast Florida this Afternoon...

Late morning surface analysis depicts a weak surface trough along
the northern Gulf coast and Florida panhandle. Meanwhile, the axis
of Atlantic ridging (1023 millibars) extends across south Florida.
Aloft...ridging is centered over the Ozarks and the southwestern
Atlantic, with upper level lows spinning along the Louisiana coast
and just east of the Bahamas. The surface trough along the Gulf
coast aided in the development of scattered to numerous showers
and embedded thunderstorms along the Big Bend and Nature coasts
during the predawn and early morning hours, and an outflow
boundary from this morning convection has pushed northeastward
into the Suwannee Valley and southward along the Interstate 75
corridor in Alachua and Marion Counties. Convection is beginning
to develop along this boundary, and this activity is moving
northeastward. Short-term, hi-res guidance indicates that
convection will increase in coverage along this outflow boundary
as it crosses I-75 and moves towards U.S. Highway 301 corridor
during the early afternoon hours.

We have updated the forecast grids to indicate likely POPS for
most of northeast and north central Florida this afternoon, with
these higher rain chances extending into the Okefenokee Swamp. A
drier airmass will prevail over southeast Georgia today, with
convective coverage expected to decrease during the mid to late
afternoon as outflow boundaries progress into this area.
Convection in northeast Florida will intersect a pinned Atlantic
coast sea breeze along the Interstate 95 corridor during the mid
to late afternoon hours, with a few thunderstorms pulsing into the
strong to marginally severe range, with wet microbursts and
frequent lightning strikes being the primary threats. Light
southwesterly surface winds will slightly delay the development of
the Atlantic sea breeze, allowing coastal highs to soar into the
low to mid 90s. Highs will also climb into the low to mid 90s over
much of southeast Georgia, with upper 80s to near 90 expected in
the Suwannee Valley, where convection is already developing.
Isolated to widely scattered showers and thunderstorms may linger
into the evening hours over southeast Georgia, with activity over
northeast Florida pushing into the coastal waters towards sunset.
Lows tonight will range from the low/mid 70s inland to the upper
70s at area beaches.


A brief period of MVFR ceilings around 2500 feet is possible
through 16Z. Showers and thunderstorms have developed near the GNV
terminal, and we have placed tempo groups in through 18Z for brief
periods of sub-VFR conditions, mainly during heavy downpours.
Thunderstorms will likely be stronger in nature as they move
northeastward towards the Duval County terminals and SGJ after
18Z, with wind gusts in excess of 30 knots possible through around
22Z at these terminals. Thunderstorms should arrive after 21Z at
SSI, with activity possibly lingering until 01Z-02Z, while VFR
conditions develop elsewhere in the wake of afternoon activity.


The axis of Atlantic surface ridging will remain positioned over
the Florida peninsula during the next several days, keeping an
offshore wind regime in place through at least midweek. The
Atlantic sea breeze will develop over the near shore waters early
this afternoon, and will be slow to push westward across the
Intracoastal Waterway during the mid-afternoon. Thunderstorm
activity will push into the coastal waters during the late
afternoon and early evening hours late this afternoon and evening
and again on Sunday afternoon and evening, with activity possibly
lingering in the offshore waters overnight. A surface trough will
begin to push towards the Georgia coastal waters early next week,
and our local pressure gradient will tighten slightly, with
periods of SCEC conditions (southwest winds of 15-20 knots)
possible on Sunday evening and each evening through midweek,
mainly in the offshore waters.

Rip Currents: A persistent long period easterly ocean swell will
keep a low-end moderate risk in place at area beaches today.


AMG  93  75  93  75 /  40  30  60  20
SSI  91  79  91  78 /  30  30  60  20
JAX  92  75  91  76 /  60  20  60  10
SGJ  90  77  92  75 /  50  20  50  10
GNV  88  74  89  73 /  60  30  50  20
OCF  88  74  88  74 /  60  40  50  30




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