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FXUS62 KJAX 240757
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
400 AM EDT Tue Oct 24 2017

...COOLER AND DRIER AIRMASS TO FILTER IN TONIGHT...

.NEAR TERM /TODAY-TONIGHT/...

Today...Initial Cold Frontal passage just crossing the FL/GA
border and steadily moving SE early this morning. Not much more
than a wind shift currently but Hi-Res models still show slight
chance of a few showers possible this morning as it moves through
NE FL and into the coastal waters. Otherwise partly to mostly
cloudy skies early this morning will show a clearing trend through
the day with skies becoming mostly sunny and will be cooler than
Monday but enough insolation to push Highs into the Upper 70s near
80 degrees in most locations with a W-NW wind around 10 mph.

Tonight...Secondary re-inforcing cold front to push through with
even cooler and drier airmass and this will keep NW surface winds
elevated around 10 mph and Temps will fall into the Mid/Upper 40s
inland and 50s along the coast and St Johns River Basin. A few
clouds possible with the secondary frontal passage otherwise
Mostly Clear skies are expected with the coolest temps since early
May.

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Upper troughing will continue to amplify over the eastern U.S. on
Wednesday as a reinforcing shortwave pivots through the Mid-Atlantic
states. Deep southwesterly flow aloft over our region early on
Wednesday will veer to northwesterly by the afternoon hours, which
will advect an even drier air mass into our region. A cool surface
ridge over Deep South Texas on Wednesday afternoon will quickly
build over our region by early Thursday morning. Despite full
sunshine, northwesterly winds of 10-15 mph and strengthening cold
air advection will keep highs in the upper 60s for locations north
of Waycross, ranging to the lower 70s in north central Florida.
These values are about 7-10 degrees below late Oct climo.

Clear skies and gradually diminishing winds on Wednesday night will
result in the coolest low temperatures since April 8-9, with a few
upper 30s possible in the Suwannee Valley as the surface ridge
settles over that area towards sunrise on Thursday. Lows elsewhere
will fall to the lower 40s, except upper 40s to lower 50s at area
beaches. Surface ridging will continue to slowly lift northeastward
on Thursday and will shift to a position just off the Carolina coast
by late in the day. A very loose pressure gradient will allow winds
to become onshore at the coast during the late afternoon hours on
Thursday. Full sunshine, light winds and rising heights aloft will
allow temperatures to rebound to the lower 70s for most locations,
except upper 60s to around 70 at the coast. Radiational cooling will
occur on Thursday evening area-wide, with low level winds becoming
onshore overnight. These light winds will keep coastal lows in the
low to mid 50s, with inland lows mostly in the 40s likely occurring
just after midnight before warm air advection potentially increases
temps a few degrees during the predawn hours on Friday.

.LONG TERM /FRIDAY THROUGH MONDAY/...
A potent shortwave trough over the Upper Midwest on Friday will
carve out the next deep upper trough that will impact our region
this weekend. This amplifying trough will drive a cold front into
the southeastern states on Saturday, with deepening southwesterly
flow aloft potentially tapping tropical moisture over the
northwestern Caribbean Sea ahead of the front by Saturday afternoon
and evening. Surface ridging just off the U.S. eastern seaboard on
Friday will strengthen as it slides northward, with low level flow
becoming southeasterly and deepening on Friday. A narrow ridge aloft
and an expected shallow cumulus/stratocumulus cloud field on Friday
afternoon will boost highs into the upper 70s for most inland
locations, with mid 70s at area beaches. Moisture off the Atlantic
will continue to slowly increase on Friday night, with a few coastal
showers possible after midnight. Lows will range from the mid 50s
inland to the mid 60s at the northeast Florida coast.

A veering wind profile will develop locally ahead of the approaching
cold front on Saturday as deep tropical moisture associated with a
potential tropical cyclone over the northwestern Caribbean Sea
advects northward into the Florida peninsula by late in the day.
Southeasterly surface winds will bring scattered showers onshore
from the Atlantic waters along the Interstate 95 corridor, with
increasing shower chances during the afternoon hours in north
central Florida as the deeper moisture arrives from the Florida
peninsula. Model blends currently depict scattered coverage of
showers for most locations in our region, with highs reaching the
mid to upper 70s despite increasing cloudiness. The cold front is
currently expected to sweep through our region on Saturday night,
with a wave of low pressure possibly developing over the near shore
Atlantic waters overnight. A few thunderstorms will be possible
along the front on Saturday evening as the energetic upper trough
approaches our area from the west, accompanied by a decent mid-level
jet per model soundings. Model blends currently yield high-end
chance POPs at this time, but these chances could increase depending
on how much of the deeper moisture to our south is able to advect
over our region. Surface winds will shift to westerly overnight,
with decreasing POPs during the predawn hours over inland southeast
Georgia and the western Suwannee Valley. Lows will range from near
50 over our far western counties to near 60 along the Atlantic coast.

A few showers could linger into early Sunday morning depending on
the timing of the frontal boundary and potential low pressure
development near our region. This low pressure center should
strengthen and will move quickly northeastward along the southeast
U.S. coast, with strengthening west-northwesterly winds expected
locally during the morning hours, with clearing skies from west to
east by the afternoon hours. Cold air advection will keep highs in
the 60s for southeast Georgia and the Suwannee Valley, with lower
70s elsewhere. A cool dome of high pressure will again quickly build
eastward along the northern Gulf coast states on Sunday night,
moving directly over our region by Monday. Northwesterly surface
winds will likely remain breezy on Sunday night in coastal
locations, with winds gradually decreasing after midnight inland.
Lows will fall into the low to mid 40s at inland locations by Monday
morning, ranging to the lower 50s at the northeast Florida coast.
Despite full sunshine and light northerly winds, a cool air mass
will likely keep highs in the mid to upper 60s for most locations on
Monday.

&&

.AVIATION...
Widespread IFR/MVFR CIGS from 800-2000 ft ahead of the front
across NE FL TAF sites this morning with improving conds to VFR
after 12z as front slowly clear the region.

&&

.MARINE...
Northwest flow behind the front today generally 10-15 knots with
seas 3-5 ft then surge of N-NW winds tonight increasing back
towards 15-20 knots/seas 4-6 ft and at least SCEC conds are
expected with possibly needing a brief SCA due to winds around 20
knots for a brief period of 4-6 hours. Will hold off with any SCA
issuance with this package for now. Moderate NW flow continues
through Wed then decreases for Thu/Fri as High pressure builds
over the waters. E to SE flow increases on Sat as High Pressure
builds into the Wrn Atlc and next frontal system approaches.

Rip Currents: Low Risk developing in the offshore flow behind the
front.

&&

.HYDROLOGY...
Will let Coastal Flood Advisory expire as last of St Johns River
Flooding ended across Putnam County yesterday and offshore flow
will continue to lower river levels the rest of the week.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG 77 45 68 42 / 0 0 0 0
SSI 77 54 68 49 / 0 0 0 0
JAX 80 52 71 43 / 0 0 0 0
SGJ 79 56 71 50 / 0 0 0 0
GNV 79 50 72 41 / 0 0 0 0
OCF 80 50 71 42 / 0 0 0 0

&&

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

&&

$$

Hess/Nelson
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