Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 292040
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
440 PM EDT THU SEP 29 2016

.Near Term.../through Friday/...
Scattered showers and thunderstorms will continue over region this
afternoon and evening, in a moist Southwesterly flow, ahead of an
approaching cold front. This front will move Southeast into
Southeast Georgia this evening, and into Northeast Florida
tonight. This boundary is expected to stall just Southeast of the
region. Most storms will dissipate with loss of daytime heating
this evening, but redevelopment will be expected Friday morning
over Northeast Florida with the front remaining a focus.

High temperatures will be slightly above normal this period, but
dewpoints will be noticeably lower across much of the region
Friday, especially over Southeast Georgia. With the boundary
stalling, these lower dewpoints may not make into coastal portions
of Northeast Florida Friday.

.Short Term.../Friday night through Sunday night/...
Stacked cyclone over the Ohio and Tennessee Valleys will drift
only slightly northward, which will maintain a deep southwest
flow pattern over our region. This will keep the surface frontal
boundary stalled over north central FL, and a weak pressure
pattern locally will allow for a weak sea breeze to develop on
Friday afternoon over northeast FL that will be the trigger for
widely scattered showers and isolated thunderstorms that will
linger into the evening hours over the I-95 corridor...especially
for locations south of St. Augustine. Otherwise, a very dry air
mass will prevail over inland southeast GA and the western
Suwannee Valley. Fair skies in these locations will allow lows to
drop into the upper 50s by Saturday morning, which is about 5
degrees below early Oct climo. Lows over the rest of inland
northeast FL will generally fall to the low to mid 60s, but
coastal locations will remain near 70.

As the upper level cyclone drifts slightly northward this weekend,
Atlantic ridging will attempt to build westward. This will likely
push the remnant frontal boundary back into northeast FL by
Saturday afternoon. A weak pressure pattern will continue to
prevail, and the Atlantic sea breeze will likely develop at least
widely scattered convection during the afternoon hours over
coastal northeast and much of north central FL. The dry air mass
will prevail over inland southeast GA and the western Suwannee
Valley. Highs Saturday will generally climb into the upper 80s
inland, with mid 80s expected at the coast.

The axis of Atlantic ridging will continue to lift slowly
northward on Saturday night and Sunday, introducing a southeast
low level flow regime over north central FL on Saturday night and
northeast FL on Sunday. Widely scattered convection is possible
over coastal northeast FL Saturday night as the remnant front
remains in place and Atlantic moisture advects into the area.
Otherwise, the dry and relatively cool air mass will hang on for
one more evening over inland southeast GA and the western Suwannee
Valley, where lows will fall to the lower 60s, ranging to the
lower 70s over coastal northeast FL. Scattered convection will
remain possible over coastal locations on Sunday morning, with
activity spreading inland by afternoon as the dry air mass departs
inland portions of our region. Highs again will generally climb to
the upper 80s inland and the mid 80s at the coast. A deepening
onshore flow pattern will keep scattered showers possible on
Sunday night in the coastal counties, with isolated activity
possible inland. Lows will range from the upper 60s inland to the
mid 70s at the coast.

.Long Term.../Monday through Thursday.../
The details of the long term forecast will be dictated by the
size and track of Hurricane Matthew. Of particular concern will be
a piece of the upper trough over the Ohio/Tennessee Valley regions
this weekend cutting off over the eastern Gulf of Mexico on
Monday as shown by the 12Z operational GFS model. The 12Z
operational ECMWF model does not develop such a feature and thus
has much weaker steering currents over Matthew, with the cyclone
not entering the southern Bahamas until Tuesday night. The 12Z
operational GFS model indicates that Matthew will continue on a
northward trajectory during the early and middle portions of next
week, with the closest approach to our coast being on Wednesday at
about 300 miles east of Mayport, which is similar to the NHC/WPC
coordinated positions at days 6 and 7. A deep onshore flow pattern
will prevail over our region early next week, with scattered to
numerous showers from Monday through Wednesday. Locally heavy
rains are possible in coastal northeast FL by Tuesday and
Wednesday as tropical moisture begins to push into the area. Breezy
to windy conditions are possible by late Tuesday and Wednesday as
the pressure gradient tightens, assuming that Matthew continues
northward as the GFS depicts. Highs will generally remain in the
80s during this period, with lower 80s expected by midweek at the
coast as onshore winds strengthens. Lows will generally remain in
the upper 60s well inland to the mid 70s at the coast. A much
drier air mass may funnel into our region by Thursday from the
northwest, depending on where Matthew is at that time.

&&

.Aviation...
A cold front will cross area TAF sites Tonight. Ahead of this
boundary this afternoon, scattered showers and thunderstorms with
possible restrictions are expected. Patchy fog will be possible
overnight, mainly affecting inland sites such as KGNV. This
boundary is expected to stall just Southeast of the region Friday,
so a few storms will be possible Friday morning as well.

&&

.Marine...
A cold front will move Southeast into area waters late Tonight and
stall Friday. As the front dissipates a weak inverted trough will
develop over waters Saturday. This trough will break down as high
pressure builds North of area waters into Sunday. This high will
lead to a period of onshore flow into early next week.

Rip Currents: Low risk expected through the weekend, with an
elevated threat developing early next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  59  85  57  87 /  10   0   0   0
SSI  68  85  70  84 /  10  10  20  10
JAX  66  86  65  87 /  10  10  20  30
SGJ  71  86  70  85 /  30  30  30  30
GNV  68  87  64  88 /  10  20  10  30
OCF  70  87  66  88 /  20  30  10  40

&&

.JAX Watches/Warnings/Advisories...
FL...None.
GA...None.
AM...None.
&&

$$

Struble/Nelson/Shashy



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