634 
FXUS62 KJAX 092137
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
437 PM EST Sat Jan 9 2021

...LIGHT INLAND FREEZE AND WIDESPREAD FROST TONIGHT...

.NEAR TERM [Through Tonight]...

Strong high pressure NW of the region over the MS Valley is providing 
cold air advection with NW flow over the area as wrap around moisture 
this afternoon continues to provide broken to overcast low ceilings
due to a slow moving mid level low over the Atlantic waters east of 
the Outer Banks of NC. Cold daytime high temperatures have resulted 
today due to the persistent low cloud cover as readings have 
barely managed to rise into the low 50s over north central Florida
while only reaching the mid to upper 40s over most of NE FL along
and north of a line from Gainesville ESE to Flagler Beach while 
SE GA has remained in the low to mid 40s this afternoon. Winds 
around 10-15 mph today from the NW have made temperatures feel 
even colder with winds chills in the upper 30s to near 40 degrees 
over the area. 

Tonight, guidance supports low clouds remaining over much of SE GA 
and along the I-10 corridor through midnight with some guidance 
suggesting clouds could linger south of I-10 well after midnight
over NE FL. For this forecast, have chosen to bring scattered cloud 
coverage towards I-10 by 10 PM based on visible satellite trends 
and leaning more towards the SREF guidance. Otherwise, widespread 
frost still appears likely as temperatures are expected to fall to
at or just below freezing west of I-95 over SE GA and west of the
St Johns river over NE FL and coincide with light winds around 
3-5 mph or less with relative humidity near saturation levels late
tonight. A Freeze Warning will go into effect after 3 AM for 
eastern portions of NE FL areas along and east of Highway 301 to 
the St Johns river through 9 AM including Gainesville, Ocala, and 
western parts of Jacksonville. A Frost Advisory will begin at 4 AM
for coastal NE FL counties through 9 AM where widespread to areas
of frost are expected as temperatures there fall as low as 33 
degrees. 

.SHORT TERM [Sunday Through Monday Night]...

High pressure will be north of the region to begin the period with
dry conditions and slightly warmer temps under mostly sunny 
skies. Winds will veer from the north to light onshore flow from 
the NE during the day allowing low clouds off the Atlantic to 
intrude along the coast. Clouds will increase late in the day as 
shortwave energy moves east from the Gulf well ahead of a 
shortwave trough moving into the ArklaTex region. The shortwave 
energy will help to form weak inverted troughing over the NE FL 
coastal waters with some light showers moving near the coastal 
counties towards dawn. Low temperatures will moderate some by for 
Monday morning into the upper 30s and low 40s over SE GA and the 
low to mid 40s over NE FL and the SE GA coast with upper 40s to 
near 50 degrees expected along the immediate NE FL coast. 

Monday, high pressure north of the area will move east to the 
Carolina coast as a low pressure system approaches our region 
from the west with increasing clouds through the day. A lifting 
inverted trough and warm front ahead of the low pressure system 
will present a slight chance of showers along the coast early in 
the day and near the Altamaha basin later in the afternoon with 
ENE winds becoming southeasterly and high temperatures further 
increasing towards above seasonal values in the upper 60s to low 
70s over NE FL while SE GA remain cooler and near seasonal with 
highs in the upper 50s to low 60s north of the warm front. Lows 
overnight Monday into Tuesday will begin above seasonal in the 
50s over NE FL and the upper 40s over SE GA. 

.LONG TERM [Tuesday Through Saturday]...

Tuesday, The low pressure system will exit off the SE GA coast 
into the Atlantic waters NE of the region taking its limited 
coverage of showers with it as it departs by midday with mostly 
cloudy skies becoming partly cloudy skies by the mid afternoon 
time frame. Winds behind the cold front and low pressure system 
will become northerly and temperatures will begin to cool down 
again from above seasonal high temperatures in the 60s to near 
70 degrees as high pressure builds in from the west. 

Wednesday into Thursday, drier conditions will prevail as high 
pressure builds NW of our region with light NW flow over the area.
A shortwave trough will swing over the region from the TN Valley,
but the atmosphere overhead appears to be too dry at this time to
support any chance of showers. Temperatures will be near seasonal
values in the 60s Wednesday into Thursday. Low temps will be near
seasonal Wednesday morning and below seasonal values Thursday 
morning.

Friday will begin dry with a few showers possible over western 
potions of the area as a cold front approaches from the NW and 
moves through the area late Friday night into Saturday morning. 
Light west to SW winds and near seasonal temperatures in the 60s 
are expected with colder temperatures arriving behind the cold
front for the weekend.

&&

.AVIATION...
[Through 18Z Sunday]

MVFR clouds expected to be slow to lift and dissipate this 
afternoon so continued to show MVFR cigs through about 06Z-08Z 
Sunday. Exceptions are GNV and SGJ possibly seeing SCT decks of 
2-3 kft in the evening, though may need to be amended to be more 
pessimistic. Guidance overall has been too quick to erode these 
clouds so general confidence in the forecast after 00Z is low, as 
it appears that some areas of low cigs at MVFR could redevelop 
into Sunday morning, and even lower to about 1500 ft. For now, 
went with generally SCT stratocu decks on Sunday, with more cig 
issues around 3000 ft possible for SGJ, CRG, and SSI due to low 
level flow turning northerly. Sfc winds will be west-northwest 
near 10 kt rest of the aftn, becoming light tonight, and then 
shifting to north to northeast Sunday 12Z-15Z.


&&

.MARINE...

Strong low pressure is exiting away from the region into the 
western Atlantic waters this afternoon as high pressure gradually
builds into the region from the northwest through tonight with 
northwest winds and elevated seas offshore through Sunday morning.
High pressure will move eastward Sunday and build north of the 
region Sunday night. Weak low pressure will develop along the 
Upper Texas coastline and move along the northern Gulf coast on 
Monday. This weak low pressure center will then move across north 
Florida Monday night and into the Atlantic waters on Tuesday.

Rip Currents: Low risk for NE FL and SE GA beaches through Sunday

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  30  56  38  60  47 /   0   0   0  10  20 
SSI  36  55  45  62  50 /   0   0  10  10  10 
JAX  32  57  44  67  52 /   0   0  10   0  10 
SGJ  36  58  48  68  54 /   0   0  20   0  10 
GNV  31  59  41  70  50 /   0   0   0   0  10 
OCF  31  61  42  72  53 /   0   0   0   0   0 

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Freeze Warning from 3 AM to 9 AM EST Sunday for Bradford-Central 
     Marion-Clay-Eastern Alachua-Eastern Marion-Inland Duval-
     Inland Nassau-Putnam-Western Alachua-Western Marion.

     Frost Advisory from 4 AM to 9 AM EST Sunday for Coastal Duval-
     Coastal Flagler-Coastal Nassau-Coastal St. Johns-Inland 
     Flagler-Inland St. Johns.

GA...None.
AM...None.
&&