Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 021334
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
834 AM EST Tue Mar 2 2021

.UPDATE...
Light rain moving across the area this morning will increase this
afternoon and tonight. A mid level low will approach from the
Arklatex region...bringing a surface low across the area tonight.
Elevated instability will increase enough for embedded isolated
thunderstorms to develop tonight. Vertical speed shear will be
strong but potential for surface based storms needed for a severe
threat looks low. Areas of heavy rainfall expected to occur
across se Ga as models show a QPF ribbon of 2 to 3 inches across
our northern counties by morning. With clouds and a ne flow,
temperatures will be cooler today. High temperatures will be in
the upper 50s over se Ga and the 60s across ne Fl.

&&

.PREV DISCUSSION [543 AM EST]...

.NEAR TERM [Through Tonight]...

A 06Z regional surface analysis showed the cold front had pushed
south into Central Florida, stretching from near Daytona Beach to
near Homosassa, FL. Model guidance shows the front to push a
little further south by sunrise, then stall for a bit before
lifting north again as a warm front in the afternoon/evening when
a deepening low pressure system sweeps in from the west.
Overnight, the cold front trailing the approaching low will begin
to push through our area.

Today will be cool and rainy with rounds of light rain in the
morning, turning into heavier showers in the afternoon through
tonight. Rainfall totals of 2-3" possible across SE GA, 1-2" in NE
FL from near the I-10 corridor to the FL-GA line, and about 0.5"
or less for most areas of north-central and NE FL south of I-10.
In Georgia, especially where higher totals fall over short periods
of time, this rainfall may lead to localized flooding. This
rainfall will also likely prolong flooding along the Altamaha,
Satilla, and Alapaha Rivers.


.SHORT TERM [Wednesday Through Thursday]...

Potent shortwave troughing pivoting eastward across AL and GA on
Tuesday night will de-amplify as it approaches coastal SC and GA
on Wednesday morning. This system will help to strengthen surface
low pressure that will be moving off the southeast GA coast around
sunrise, with a trailing cold front pushing eastward across our
region during the early morning hours and offshore by late
morning. An accompanying 40-50 knot low level jet at 850 millibars
(5,000 feet) will be traversing areas along and south of
Interstate 10 at sunrise. However, instability will remain
elevated within the narrow warm sector ahead of the cold front,
and convection will likely not become surface based on Wednesday
morning, limiting chances for stronger thunderstorm activity.
Convection will move offshore by the mid-morning hours, with skies
gradually clearing across northeast and north central FL from west
to east during the afternoon hours, while wrap-around cloud cover
lingers across southeast GA through around sunset on the western
periphery of departing low pressure. Temperatures across southeast
GA will likely remain steady or slowly fall through the 50s during
the afternoon hours as cold air advection sets in, while afternoon
sunshine allows temperatures to recover to the low and mid 60s
along the I-10 corridor. Temperatures will likely fall into the
60s on Wednesday afternoon in north central FL following morning
temperatures in the 70s ahead of the cold front.

Troughing aloft will deepen over New England beginning on Wednesday
night, which will create a dry northwesterly flow pattern across
our region. High pressure building along the northern Gulf coast
in the wake of the departing storm system will weaken by late
Thursday and Thursday night as stronger high pressure builds over
the Great Lakes states and drives a reinforcing cold front into
the southeastern states.

Clearing skies and diminishing winds at inland locations will allow
lows to fall to the 40-45 degree range on both Thursday and Friday
mornings. A light northwesterly breeze will continue at coastal
locations on Wednesday night, with light northerly winds expected
on Thursday night and lows both nights mostly in the mid to upper
40s. These low temperatures are about 5 degrees below early March
climatology. Sunny skies and dry air mass will result in highs
climbing to around 70 at inland locations on Thursday, with lower
70s expected in north central FL. Winds will shift from northerly
to northeasterly at coastal locations on Thursday afternoon,
keeping highs mostly in the mid 60s.


.LONG TERM [Friday Through Tuesday]...

A closed trough aloft will move onshore along the southern
California coast on Wednesday, migrating eastward across the
Desert Southwest and southern Rockies on Thursday and then
pivoting southeastward from the lee side of the Rockies across the
southern Plains and the Ozarks on Friday. Flow aloft will become
zonal downstream of this approaching trough on Friday, with high
cloud cover increasing from west to east during the afternoon
hours. Our local pressure gradient will tighten as the day
progresses due to strengthening high pressure over the Great Lakes
region, with breezy northeasterly winds keeping highs in the 60s
across southeast GA and for all coastal locations, while highs
climb into the low and mid 70s for inland locations south of I-10.

Shortwave troughing will de-amplify on Friday night and Saturday
as in encounters a confluent flow pattern aloft along the eastern
seaboard, compliments of a deepening trough over New England.
This system will progress eastward across the Deep South, with
only weak cyclogenesis progged over the Gulf of Mexico that will
cross south FL on Saturday. Isentropic lift will strengthen from
west to east on Friday night, with increasingly convergent low level
onshore winds likely developing showers towards midnight along the
northeast FL coast, with light showers then overspreading our area
during the predawn and early morning hours on Saturday. Thickening
cloud cover will keep lows in the upper 40s and lower 50s for most
locations on Friday night. A brief period of moderate rainfall will
be possible for locations along and south of I-10 on Saturday, with
lighter rainfall expected for southeast GA that should depart before
sunset. Cloud cover and rainfall will keep highs below early March
climatology on Saturday, with most locations reaching the 60-65
degree range, except upper 50s for locations from Waycross northward.
A few coastal showers may linger on Saturday evening in northeast FL,
while skies clear overnight from west to east. Lows will fall into
the 40s, except around 50 in coastal northeast FL.

Troughing aloft will then amplify along the eastern seaboard late this
weekend, creating another period of deep and dry northwesterly flow that
will keep temperatures below climatology, with highs on Sunday remaining
in the 60-65 degree range as breezy north-northeasterly winds continue
along the I-95 corridor. Our local pressure gradient will then loosen
on Sunday night and Monday as strong high pressure builds directly over
our region. Inland lows may fall into the 30s by Monday morning, although
model blends at this point are remaining in the 40s. Temperatures will be
slow to rebound early next week as this strong surface ridge remains in
place, but troughing aloft will gradually exit the east coast, allowing
highs at inland locations to rebound into the 70s by Tuesday.


.AVIATION...
[Through 12Z Wednesday]

On and off rain showers will continue through the early morning
hours. Showers will increase in coverage through the day today,
with the highest coverage forecast along the coast and in SE GA.
MVFR-IFR cigs and vsbys have already developed in spots this
morning, mainly associated with heavier showers. By mid-day,
scattered to broken IFR cigs are likely to be seen across most of
the area.


.MARINE...

Northeast winds of 20 to 25 knots with gusts to gale force and
seas of 5 to 9 feet anticipated for most of the day behind last
night`s cold front passage. Winds will become easterly around 15
to 20 knots this evening as the frontal boundary nudges northward
when an area of low pressure in the northern Gulf waters
approaches our region. This low pressure system will bring a
second cold front through our coastal waters Wednesday, with winds
becoming west-northwesterly around 20 to 25 knots with gusts to
gale force again. By Wednesday night, northwest winds should lower
to 15 to 20 knots. Thursday and Friday, winds will become
northerly and then northeasterly as a surface ridge of high
pressure moves off the mid-Atlantic coastline.

Rip Currents: High risk of rip currents at area beaches today and
a moderate risk on Wednesday.


.FIRE WEATHER...

Northeasterly surface and transport winds will strengthen this
morning, with windy conditions expected at coastal locations
through this evening . Heavy rainfall and a few embedded
thunderstorms will move across southeast Georgia beginning around
sunset and persisting through around sunrise on Wednesday, with
widespread 2-3 inch totals forecast. Showers and a few
thunderstorms will overspread the I-10 corridor overnight, with
activity exiting the northeast Florida coast before noon on
Wednesday. Surface and transport winds will shift to northwesterly
early on Wednesday, with breezy conditions expected throughout
the day at coastal locations. Surface and transport winds will
then shift to northerly with decreasing speeds on Thursday as a
drier air mass plunges into our region, resulting in minimum
relative humidity values falling to around 35 percent at inland
locations on Thursday afternoon.


.HYDROLOGY...

Heavy rainfall will overspread southeast GA early this evening and
will persist through around sunrise on Wednesday. Widespread 2-3
inch totals are forecast, creating the potential for localized
flooding in normally flood prone locations. Much of the heavier
rainfall will not occur over the main stem river basins in
southeast GA, but saturated ground conditions will create
significant runoff that will likely result in rivers rising
somewhat later this week, but mostly minor flooding is currently
forecast heading into the upcoming weekend. Moderate flooding will
continue along the lower Santa Fe River near the Three Rivers
Estates gauge through at least Saturday, mainly due to backwater
flooding from the flood wave traveling down the lower Suwannee
River.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  56  45  60  41  69 /  90 100  50   0   0
SSI  58  51  59  46  65 /  90 100  70   0   0
JAX  60  54  65  44  70 /  80  70  70   0   0
SGJ  64  59  66  49  66 /  80  60  70   0   0
GNV  65  57  70  45  72 /  40  60  50   0   0
OCF  71  61  73  47  73 /  20  50  50   0   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...High Rip Current Risk until 7 PM EST this evening for Coastal
     Camden-Coastal Glynn.

AM...Small Craft Advisory until 10 PM EST Wednesday for 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-Waters from St. Augustine to Flagler Beach FL from 20
     to 60 NM.

     Small Craft Advisory until 7 AM EST Wednesday 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-Coastal waters from St. Augustine to Flagler
     Beach FL out 20 NM.

&&


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