705 
FXUS62 KJAX 261053
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
553 AM EST Tue Jan 26 2021

.AVIATION...
[Through 12Z Wednesday]

Tricky forecast this morning with an upper level deck of clouds
over all of our TAF sites preventing those previously forecast
MVFR-IFR cigs and vsbys from developing...at the same time, nearby
sites where upper level deck is less dense have dropped as
expected. There's still a chance for those MVFR-IFR conditions
near GNV and SSI this morning, with the fog now most likely to
develop a little after sunrise and hang around only for an hour 
or two. After that, VFR conditions forecast through around 06Z and
then scattered MVFR cigs will begin to filter northeastward into 
the area, with fog development expected near GNV again around 08Z.
Winds from the southwest around 5-10 kts are anticipated through
the period.

&&

.PREV DISCUSSION [319 AM EST]...

.NEAR TERM [Through Tonight]...

At 1 AM, an area of surface low pressure was near the TN-WV border
has a cold front extending southwestward from it across central
TN, northern AL, central MS, and into southwestern LA. Out ahead
of this front lies a very slow-moving broken line of showers and 
thunderstorms that stretches from west of Atlanta, GA through 
Birmingham, AL, then running south toward Hattiesburg, MA and 
Baton Rouge, LA. Model guidance shows this front will flatten out 
(becoming more east-west oriented) through the morning hours today
then begin to stall across central GA and the northern Gulf coast
by the evening hours. Our area will remain in the warm, humid air
mass ahead of the system through the period. 

In the morning, this will mean fog and low ceilings across the
region that could hang in through around 8 AM near Gainesville, 
FL and Ocala, FL. After that, we'll warm up into the the upper 70s
to the low 80s. As storms ahead of the front run eastward through
the afternoon hours and overnight, we'll see showers and isolated
thunderstorms making their way into inland SE GA. These storms 
could linger in place near the Altamaha River through much of the 
night, similar to the current line near Birmingham this morning. 
With low level warmth, there will be some instability available to
sustain storms long enough to possibly produce some damaging wind
gusts of around 40-60 mph. Overnight, another round of low clouds
and fog will likely develop south of the stalled frontal boundary.


.SHORT TERM [Wednesday Through Thursday]...

Low stratus and potentially dense fog will advect northeastward
from the northeast Gulf of Mexico across a large portion of 
northeast and north central FL early during the predawn
hours on Wednesday, with coverage of fog possibly extending
into coastal southeast GA. Fog and stratus will lift by
the mid-morning hours at these locations as southwesterly
low level winds quickly strengthen before sunrise.

A potent shortwave trough positioned over the southern Plains
states early on Wednesday morning will move rapidly eastward, 
reaching the Ohio Valley by sunset and then moving offshore of
the Mid-Atlantic states early on Thursday morning. A 160-knot
jet streak at 250 millibars (35,000 feet) located south of this 
trough over the Ozarks and Tennessee Valley on Wednesday morning
will weaken slightly as it traverses the southern Appalachians 
and the Carolinas, moving off the Carolina coast on Wednesday 
night. These features will induce weak cyclogenesis near Mobile
Bay along a stalled frontal boundary during the predawn hours on
Wednesday that will move east-northeastward across inland portions
of southeast GA on Wednesday afternoon, emerging near the GA/SC
coast on Wednesday evening. Deep west-southwesterly flow will be
in place locally on Wednesday, with a ribbon of deep moisture
surging into our area just ahead of the wave of low pressure along
the front. A broken convective squall line is expected to take
shape near the Altamaha/Ocmulgee Rivers during the late morning
hours, and this line will surge southeastward across our area
through the afternoon and early evening hours. Impressive speed
shear will overspread our region, with bulk shear values of 60-70
knots forecast by model soundings. Lapse rates will be a limiting
factor for a more significant severe weather event, as morning 
stratus will be slow to lift and insolation will be limited at
most locations. However, model soundings depict ML CAPE values of 
250-500 j/kg across southeast GA and the Suwannee Valley by early 
afternoon, and a few strong thunderstorms will be possible within
the broken squall line, with strong wind gusts of 40-50 mph possible.
Highs on Wednesday will climb to the mid and upper 70s, with a few
lower 80s possible in north central FL.

Convection within the broken squall line is expected to weaken 
towards sunset as activity approaches the I-95 corridor and north 
central FL. Showers will move offshore towards midnight, and cold
air advection will then overspread our area on the heels of 
breezy northwesterly winds that will drive lows down into the 40s
region-wide as skies rapidly clear from northwest to southeast 
during the overnight hours. 

Low pressure will strengthen as it moves quickly northeastward
past the Gulf Stream waters on Thursday morning, with strong
high pressure building southeastward from the Upper Midwest into
the Ohio Valley by Thursday evening. Breezy north-northwesterly
winds will shift to northerly by late afternoon, with speeds 
decreasing towards sunset as our local pressure gradient gradually
relaxes. Despite full sunshine, cold air advection will keep highs
in the 50s, except around 60 in north central FL. Thin cirrus 
could invade our skies within the deep northwesterly flow pattern
on Thursday evening, but surface winds will decouple at inland
locations, setting up a light freeze for most inland locations and
patchy frost possibly extending into coastal locations. Lows will
fall to the lower 30s inland, ranging to the mid and upper 30s at
coastal locations.


.LONG TERM [Friday Through Tuesday]...

Deep northwesterly flow aloft will continue on Friday and Friday
night as high pressure gradually weakens over the southeastern
states. Fair skies and a dry air mass will allow highs to rebound
to just slightly below climatology, with highs ranging from the
upper 50s to lower 60s, except mid 60s in north central FL. Frost
will be possible at inland locations on Friday night, where lows
will fall into the 30s, while low level onshore flow keeps coastal
lows in the 40-45 degree range. 

Low pressure will emerge from the lee side of the Rockies into the
southern Plains States on Saturday afternoon as high pressure
builds over the Great Lakes region and the Mid-Atlantic states, 
wedging down the southeastern seaboard late in the day. Low level
winds will become southeasterly, and developing zonal flow aloft
will result in highs climbing into the 60s, except around 70 in
north central FL. Low pressure traversing the Ozarks and Missouri 
Valley on Saturday night and Sunday will drag a cold front into
the lower Mississippi Valley by Sunday afternoon, resulting in 
strengthening southwesterly flow for our area, with warm air 
advection boosting highs into the 70s, except upper 60s for 
locations north of Waycross, where scattered showers are forecast
to arrive late in the day. Secondary low pressure will develop
over the southeastern states by late Sunday, with the cold front
slated to cross our area during the overnight hours, accompanied
by scattered showers. Breezy northwesterly winds in the wake of
this front will cool highs back towards early February 
climatology early next week, with lows falling back to the 30s at 
inland locations by Monday night.


.MARINE...

A cold front will stall to the west of our local waters today. On
Wednesday morning, an area of low pressure will develop along the
front near the Florida panhandle, which will allow the system to 
accelerate northeastward in the afternoon across the Georgia 
coastal waters, dragging the cold front across our area during 
the evening hours. As the front moves in, showers and isolated
thunderstorms will move over our coastal waters Wednesday into 
Wednesday night. Along and behind the front, westerly and then
northwesterly winds will increase across the coastal waters, with 
occasional Gale Force wind gusts possible offshore and Small Craft
Advisory conditions developing near shore. Small Craft Advisory 
conditions will persist for the offshore waters through early 
Friday. Weakening high pressure will then build into our region on
Friday afternoon, resulting in decreasing winds and subsiding 
seas.

Rip Currents: Low risk of rip currents at NE FL and SE GA beaches
through Wednesday.


.FIRE WEATHER...

Strong south-southwesterly transport winds will develop shortly 
after sunrise across inland southeast GA, with breezy transport 
speeds elsewhere. Breezy southwesterly surface winds are expected 
area-wide early this afternoon. Scattered to numerous showers and 
a few embedded strong thunderstorms will then traverse our region 
from northwest to southeast on Wednesday, with activity moving off 
the Atlantic coast during the early evening hours. Strong 
southwesterly surface and transport winds are expected area-wide. 
A colder and drier air mass will then plunge over our region late 
Wednesday night and Thursday, with breezy north-northwesterly 
surface and transport winds expected through the early afternoon 
hours on Thursday before diminishing late in the afternoon.


.HYDROLOGY...

Storm total rainfall values over inland SE GA could be around 1-3"
through Wednesday night, with totals of 1" or less further south.
Most of our area rivers are currently at low levels and most of SE
GA and NE FL area have seen 30 day rainfall departures 1-3" below
normal, so this rainfall is expected to be beneficial and not to
cause any widespread flooding issues. That said, isolated areas
could see higher totals from storms which could lead to localized
flooding issues.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  77  63  75  42  54 /  30  40  90  30   0 
SSI  74  61  74  45  54 /  10  10  50  60   0 
JAX  80  62  79  45  56 /  10  10  40  50   0 
SGJ  77  61  79  48  55 /  10  10  30  30   0 
GNV  78  60  79  46  59 /  10  10  50  30   0 
OCF  79  60  79  47  61 /  10  10  50  30   0 

&&

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