328 
FXUS62 KJAX 171046
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
546 AM EST Tue Nov 17 2020

.AVIATION...
[Through 12Z Wednesday]

Northerly winds around 5-12 knots expected at all regional airfields 
today, winds are expected to increase to 10-15 knots at airfields
along the coast (KSGJ/KSSI) late this evening as onshore winds
strengthen. Clear skies expected throughout the period.

&&

.PREV DISCUSSION [327 AM EST]...

.NEAR TERM [Through Tonight]...

A cool, dry continental airmass in place has delivered clear skies 
and a Fall chill across northeast Florida and southeast Georgia 
this morning. Strong surface high will build southeastward to the
Tennessee Valley today leading a tightened pressure gradient and 
strengthening winds along the coast tonight. Temperatures will be
on the cool side this afternoon with highs peaking in the low 
70s. A reinforcing shot of cold air will push across southeastern
GA and northeast FL overnight lowering temps to the low 40s over 
interior southeastern Georgia and mid 40s across interior areas of
northeast Florida. Increasing onshore flow tonight will limit 
coastal cooling to the mid and upper 50s.


.SHORT TERM [Wednesday Through Thursday]...

Reinforcing high pressure will settle over the Ohio Valley and
the southern Appalachians early on Wednesday morning and will
continue to wedge down the southeastern seaboard, tightening
our local pressure gradient even further and creating windy
conditions all along the Atlantic coast. A wind advisory may
be required for portions of the northeast FL coast, especially
for St. Johns and Flagler Cos, where the gradient will be the
tightest and northeasterly winds will be sustained near 25 mph
with frequent gusts of 35-40 mph throughout the day on Wednesday. 
A cool and dry air mass will continue to advect into our region, 
and highs will only reach the 60-65 degree range, except upper 
60s in north central FL. These highs are about 8-11 degrees 
below mid-November climatology for our area.   

Meanwhile,troughing aloft will depart the U.S. eastern seaboard by
Wednesday evening, with heights aloft expected to gradually rise
over our region through the end of the work week. A coastal trough
will begin to take shape over our Atlantic waters on Wednesday night
as strong high pressure settles over the Mid-Atlantic region and 
the Carolinas. Convergent onshore flow will begin to drive 
stratocumulus onshore along the northeast FL coast, with showers 
developing over the Atlantic waters adjacent to northeast FL during
the late evening hours. Isolated to widely scattered showers will
move onshore during the predawn and early morning hours on Thursday,
initially along the northeast FL coastal counties and then expanding
northward over the southeast GA coastal counties by the mid to late
morning hours on Thursday. 

This onshore flow pattern will set up a large temperature gradient 
over our region as winds at inland locations decouple overnight and 
cloud cover does not expand into inland southeast GA until the 
predawn hours on Thursday. Lows Wednesday night will range from the 
upper 30s near the Altamaha/Ocmulgee River basins to the 40s 
elsewhere at inland locations, except lower 50s for inland north 
central FL. Lows at coastal locations will generally fall to the 50s 
as northeasterly winds remain sustained in the 15-20 mph range on
Wednesday night and Thursday. Highs on Thursday will again remain
in the mid 60s for southeast GA, ranging to the lower 70s in north
central FL as stratocumulus cloudiness continues to expand and thicken
from southeast to northwest. Lows on Thursday night will continue to
trend warmer as ridging aloft begins to take shape and coastal 
troughing prevails at the surface. Lows will range from the upper 40s 
near the Altamaha/Ocmulgee Rivers to the low and mid 60s along the 
northeast FL coast.


.LONG TERM [Friday Through Tuesday]...

Ridging aloft will prevail over our area on Friday and Saturday, and
our local pressure gradient will gradually loosen as high pressure 
slowly weakens over the southeastern states and then shifts offshore
towards the end of the weekend. Coastal troughing will continue to 
generate isolated to widely scattered showers, mainly for locations
along and east of I-95 in northeast FL. Temperatures and humidity
levels will continue to recover, with highs generally reaching the
mid to upper 70s both days, while lows range from 55-60 inland and 
the upper 60s at coastal locations on Friday night and warming 
further by a few degrees on Saturday night. 

A shortwave trough that will traverse the Great Lakes region late in
the weekend will flatten the ridge aloft over our area and will drive
a cold front into the southeastern states by Monday. Low level onshore
flow will continue on Sunday, followed by the coastal trough finally
breaking down by Sunday evening as low level flow begins to veer ahead
of the approaching frontal boundary. Highs on Monday will approach 80
at inland locations, with an afternoon sea breeze keeping coastal
highs mostly in the upper 70s. Lows will continue to run above seasonal
averages on Sunday and Monday nights, with values around 60 inland and
the mid to upper 60s at coastal locations.


.MARINE...

Due to breezy winds and elevated seas, Exercise Caution 
conditions will continue across area waters through the early 
afternoon. As high pressure builds southeastward into the Tennessee 
Valley today, post-frontal winds will increase over the coastal and 
outer waters this afternoon leading to a prolonged period Small 
Craft Advisory conditions through at least Thursday. As pressure 
field weakens late in the week, Small Craft Advisory conditions are 
only likely offshore with Exercise Caution for the near-shore waters 
Friday and into the weekend.

Rip Currents: Breezy northerly winds will lead to a moderate risk
at all area beaches today. Onshore winds will strengthen 
Wednesday and continue through the end of the week leading to high
rip current risk for all northeast FL and southeast GA beaches.


.FIRE WEATHER...

Red Flag criteria will not be met during the next several days 
across our region. Breezy northerly transport winds will funnel 
a cool and dry air mass into our region today. Long durations
of critically low humidity values around 25 percent and 
marginally high dispersion values are expected this afternoon 
inland, while northerly surface winds become breezy at coastal 
locations. Strong northeasterly transport winds will then 
overspread our region early on Wednesday, with breezy surface 
winds expected throughout inland northeast and north central FL 
and windy conditions at all coastal locations throughout the day. 
Humidity values may approach critical thresholds on Wednesday 
afternoon across inland southeast GA, where sustained surface 
winds will remain below 15 mph. Transport winds will shift to 
easterly on Thursday, resulting in higher humidity values and 
widely scattered showers at coastal locations.


.HYDROLOGY...

Coastal Flood Advisory will continue for the Atlantic
coast and inland waterways through this afternoon before a lull 
in elevated tides tonight. Strengthening onshore flow will 
increase water levels again on Wednesday. Prolonged onshore flow
will elevate tides will through the rest of the week resulting in
periods of minor tidal flood impacts. Generally, water levels are
expected to reach 1-2 feet above normally dry ground at times of 
high tide.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  70  39  60  39  65 /   0   0   0   0   0 
SSI  72  50  60  51  65 /   0   0   0  10  30 
JAX  72  49  63  46  68 /   0   0   0  10  30 
SGJ  72  58  65  57  70 /   0   0   0  20  20 
GNV  72  46  66  48  71 /   0   0   0  10  10 
OCF  73  49  69  51  73 /   0   0   0  10  10 

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory until 7 PM EST this evening for Clay-
     Coastal Duval-Coastal Flagler-Coastal Nassau-Coastal St. 
     Johns-Inland Duval-Inland Flagler-Inland Nassau-Inland St. 
     Johns-Putnam.

GA...Coastal Flood Advisory until 7 PM EST this evening for Coastal 
     Camden-Coastal Glynn-Inland Camden.

AM...Small Craft Advisory from 4 PM this afternoon to 7 AM EST 
     Thursday for Coastal waters from St. Augustine to Flagler 
     Beach FL out 20 NM-Waters from St. Augustine to Flagler 
     Beach FL from 20 to 60 NM.

     Small Craft Advisory from 7 PM this evening to 7 AM EST Thursday 
     for Coastal waters from Altamaha Sound to Fernandina Beach 
     FL out 20 NM-Coastal waters from Fernandina Beach to St. 
     Augustine FL out 20 NM-Waters from Altamaha Sound GA to 
     Fernandina Beach FL from 20 to 60 NM-Waters from Fernandina 
     Beach to St. Augustine FL from 20 to 60 NM.

&&