822 
FXUS62 KJAX 071558
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
1058 AM EST Thu Jan 7 2021

...SHOWERS ARRIVE LATE THIS AFTERNOON IN THE SUWANNEE VALLEY AND
INLAND SOUTHEAST GA...
...BREEZY WESTERLY WINDS AND SEASONABLY COOL WEATHER ON FRIDAY...

.UPDATE...

Late morning surface analysis depicts a weak coastal trough 
situated over the near shore Atlantic waters that is in the
process of lifting northward as high pressure (1024 millibars)
shifts eastward towards the Mid-Atlantic coast. Meanwhile, low 
pressure (1007 millibars) was moving eastward across the lower 
Mississippi River Valley, with a cold front extending southward
through central portions of the Gulf of Mexico and a warm front 
lifting northward towards the FL panhandle coast. Showers have
overspread the FL panhandle as isentropic lift strengthens along
and north of the warm front. Otherwise, our local pressure
gradient continues to tighten downstream of this approaching storm
system, with breezy easterly winds now observed at most inland
locations and northeast winds persisting along the immediate coast
as of 16Z. Temperatures were rising through the upper 50s across 
southeast GA and into the mid 60s for most of northeast and north
central FL as mid and especially high cloud cover are thickening 
from west to east.

Winds will continue to slowly increase and will veer to
southeasterly early this afternoon as low pressure pivots 
eastward into the Deep South. Highs will climb into the lower 70s 
for locations along and south of Interstate 10, where cloud cover 
will not thicken nor lower until the late afternoon hours, while 
highs elsewhere generally climb to the mid and upper 60s, except 
for lower 60s near the Ocmulgee/Altamaha Rivers and along the 
immediate southeast GA coast.

Latest short-term, high resolution guidance shifts shower 
activity eastward from the FL panhandle into the Suwannee Valley 
and inland southeast GA during the 3-4 PM hour, with activity then
migrating eastward towards U.S. Highway 301 towards sunset and 
then the I-95 corridor during the early to mid-evening hours. 
Although a 40-45 knot low level south-southwesterly jet at 850 
millibars (5,000 feet) will enter our region late this afternoon 
and early this evening, instability will only be elevated in 
nature, and thunderstorm activity is not anticipated as low
pressure exits the southeast GA coast during the predawn hours 
and this storm system's cold front sweeps offshore of the
northeast FL coast before sunrise. Shower activity should exit the
northeast FL coast shortly after midnight, with a period of
thicker stratus or stratocumulus continuing ahead of the front
through the overnight hours. Winds will shift to west-
southwesterly during and after the frontal passage, with cold air
advection dropping lows into the upper 40s for inland southeast GA
and the western Suwannee Valley, with low and mid 50s expected
elsewhere. Breezy westerly winds will quickly develop after
sunrise on Friday, with wrap-around moisture likely resulting in
mostly cloudy skies for much of the day across southeast GA as low
pressure strengthens as it accelerates northeastward off the U.S.
eastern seaboard.

&&

.AVIATION...
[Through 12Z Friday]

VFR conditions will prevail at the regional terminals through at
least 23Z. Showers will approach the GNV and VQQ terminals from
the west towards 23Z, bringing brief periods of MVFR conditions
at these terminals through around 04Z. Showers will then reach the
rest of the terminals after 01Z, brining brief periods of MVFR
conditions through around 05Z. MVFR ceilings of 2,000-3,000 feet
will then be possible through around 12Z at the regional 
terminals as surface winds shift to westerly at 5-10 knots. VFR 
conditions should then prevail after 12Z as ceilings rise to
3,000-4,000 feet and westerly surface winds increase to 10-15
knots. 

&&

.MARINE...

A coastal trough situated over our near shore waters this morning
will lift northward this afternoon as low pressure over the lower
Mississippi Valley pivots eastward across the Deep South, emerging
off the South Carolina coast towards sunrise on Friday.
Southeasterly winds will strengthen this afternoon, with Small 
Craft Advisory conditions developing over the offshore waters 
adjacent to northeast FL shortly after noon and then over the 
offshore Georgia waters towards sunset. Seas will build to 5-7
feet by late afternoon for the offshore FL waters and 4-6 feet for
the southeast GA waters, where Small Craft should exercise Caution
this afternoon. 

This storm system's cold front will push eastward through our 
region late this evening and overnight, accompanied by showers.
Seas offshore will build to 6-9 feet tonight, while seas of 3-5
feet expected near shore. Low pressure will strengthen as it 
accelerates northeastward off the U.S. eastern seaboard on Friday,
keeping strong offshore winds and elevated seas in place through 
Saturday. Winds and seas will briefly diminish late this weekend 
as high pressure builds into the southeastern states, followed by 
the next storm system quickly developing along the central Gulf 
coast region Sunday night and then moving over our region by 
Monday night and Tuesday.

Rip Currents: A high risk of rip currents continues today at the
northeast FL beaches due to a long period northeasterly ocean
swell combining with strengthening onshore winds. A moderate risk
is expected at the southeast GA beaches. The lingering long period
swell will keep a moderate rip current risk at all beaches on
Friday, with a low risk likely on Saturday as breezy offshore
persist.

&&

.FIRE WEATHER...

Strengthening easterly surface and transport winds late this
morning will shift to southeasterly this afternoon, creating good
dispersion values area-wide that will border on marginally high
values by the mid afternoon hours. Showers will impact our region
late this afternoon and especially this evening, followed by
strong westerly surface and transport winds on Friday. Increasing
cloudiness will keep dispersion values and humidity levels higher
on Friday afternoon in southeast GA, while a drier air mass and
good dispersion values are forecast for northeast and north
central FL. 

&&

.PREV DISCUSSION [526 AM EST]...

.NEAR TERM [through Tonight]...

High pressure will be centered to the north this morning, as a 
trough develops along the FL coast. This trough will lift north 
northeast through the morning and afternoon, and is expected to 
remain just off shore, along with much, if not all of its associated
showers. The precipitation associated with the approaching low 
pressure system will reach far western counties around 18z, then 
spread east through the afternoon, reaching the east coast around 
sunset. The low center will move to the northeast around midnight, 
with the cold front pushing to the east of forecast area during the
overnight. Shower activity will decrease from west to east during 
the overnight. Instability is expected to be limited, so have not
included Thunderstorms in the forecast. Can not completely rule 
one out, but chance too low for mention at this time. 

Temperatures will trend a little above normal over SE GA Today, but 
warm advection on southerly flow will push readings above normal 
into the 70s over NE FL, except for the Suwannee valley. The FL 
beaches will hold below 70 though due to the onshore flow across the
relatively cooler coastal waters.


.SHORT TERM [Friday Through Saturday Night]...

Friday...Low pressure continues to intensify as it tracks to the 
Carolina Coast and West Winds will increase to 15-25 mph with gusts 
up to 35 mph by the afternoon. Cooler airmass will hold Max Temps
at below normal levels with Highs in the 50s across SE GA and 
near 60 across NE FL under Mostly Cloudy skies. Lagging mid-level 
trof axis will likely not have enough moisture to trigger much in 
the way of shower activity, but a few sprinkles will be possible 
in the lower clouds through the day, mainly across SE GA, but 
overall measurable rainfall chances remain around 10% or less.

Friday Night...Partial cloud cover lingering on the back side of 
the low pressure system and elevated Northwest winds at 5-10 mph 
combined with cool temps falling into the upper 30s over inland 
areas and lower 40s along the coast will push Wind Chill readings 
down into the lower to middle 30s by sunrise.

Saturday...Chilly airmass settles into the region on Northwest 
winds at 10-15 mph and clearing skies by the afternoon hours as 
High Pressure builds in from the West. Below normal temps continue 
with Highs only in the 50s area-wide.

Saturday Night...High pressure ridge extends into the region from 
the Northwest and under mostly clear skies and light NW/near calm
winds expect a frosty night with lows in the lower 30s across 
inland SE GA/Suwannee Valley with a light freeze now possible, and
mid to upper 30s closer to the Atlc coast with plenty of frost 
expected and Frost/Freeze headlines may be required around 
sunrise.


.LONG TERM [Sunday Through Wednesday]...

Sunday...Mostly sunny and still cool as High Pressure moves north 
of the region and expect light and variable winds but still below
normal temps with Highs still mostly in the 50s/near 60 degrees. 
Cloud cover starts to increase ahead of the next system Sunday 
Night and while inland temps may still fall into the mid/upper 
30s, less frost formation is expected.

Monday...The GFS/ECMWF 00z runs have come into better agreement 
with low pressure system tracking out of the Gulf of Mexico and 
into South GA by Monday Evening and expect to have another of 
gusty showers by the afternoon/evening hours with an isolated 
thunderstorm possible, a very similar scenario to today's (1/7) 
system. Max temps rebound into the 60s, but overall fast speed of 
the system prevents deep moisture return on the latest model 
runs.

Tuesday...Depending on speed of exiting low pressure system, a few 
morning showers are possible otherwise clearing skies and 
seasonable temps with highs in the 60s and breezy West winds 
again.

Wednesday...Cool High pressure builds into the region from the 
Northwest and temps return to below normal levels with Highs 
around 60 and lows in the 30s inland/near 40 Atlc Coast, and some 
frost will be possible Tue and Wed nights.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  62  47  55  37  52 /  70  90  10  10   0 
SSI  63  53  59  40  52 /  40  60  10  10   0 
JAX  71  51  59  39  56 /  30  60  10  10   0 
SGJ  71  56  64  42  56 /  10  70  10  10   0 
GNV  71  52  61  39  57 /  50  70  10  10   0 
OCF  74  53  63  39  58 /  40  50  10  10   0 

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk until 7 PM EST this evening for Coastal 
     Duval-Coastal Flagler-Coastal Nassau-Coastal St. Johns.

GA...None.
AM...Small Craft Advisory from 1 PM this afternoon to 4 PM EST 
     Saturday for Waters from Fernandina Beach to St. Augustine 
     FL from 20 to 60 NM-Waters from St. Augustine to Flagler 
     Beach FL from 20 to 60 NM.

     Small Craft Advisory from 10 PM this evening to 10 AM EST 
     Saturday for Waters from Altamaha Sound GA to Fernandina 
     Beach FL from 20 to 60 NM.

&&