Gale Warning 3, NWS Jacksonville, FL

Area Forecast Discussion
National Weather Service Jacksonville FL
1224 AM EST Thu Feb 6 2020

.AVIATION...
[Through 06Z Friday]

A strong low level jet will precede this evenings strong frontal
passage. Therefore, LLWS is a possibility until around mid morning,
when the lower levels will have a better chance to mix. Once the
mixing occurs gusty winds will persist through the afternoon. A
squall line is expected to race just ahead of the cold front across
the region late this afternoon into this evening. Current timing of
this line puts the line across area TAF sites between around 01z
and 05z. Strong to severe storms with potentially damaging winds
are expected with the line, with restrictions anticipated.

&&

.PREV DISCUSSION [910 PM EST]...

.NEAR TERM [Through Tonight]...

Gradually increasing rain chances from the SW through tonight as a
warm front axis lifts NNE out over the Gulf of Mexico placing the
entire forecast area within the warm sector of approaching, potent
storm system. Low level lift along and north of the warm front
combined with weak mid level PVA will bring a chance of showers
and isolated tstorms late this afternoon through tonight focused
across our western zones roughly from Jesup to Waycross southward
to Live Oak and Trenton where deeper moisture profile will reside.
Farther east and southeast, mid levels will remain a bit too dry
to support rain chances through tonight although some light,
fading sprinkles are possible. Deep layer, increasing SW flow will
keep winds elevated tonight, increasing to 10-15 mph after
midnight with gusts near daybreak up to 25 mph near coastal
locations. Mild, unseasonably warm low temperatures tonight will
range in the mid to upper 60s under cloudy skies. Too much wind
for fog potential, despite influx of moisture trailing warm front
axis.

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

An upper trough amplifies over the Plains on Thursday as it
progresses eastward. At the surface, a cold front moves eastward
across the southeastern US and pushes past the area Friday
morning. Ahead of the cold front, windy conditions are expected
with sustained south-southwesterly winds increasing Thursday
afternoon into the evening hours at about 20-25 mph with gusts of
30-40 mph possible. A wind advisory may be needed for portions of
the area. Near record high temperatures are expected tomorrow
with highs ranging from the mid 70s to mid 80s. A squall line
develops ahead of the front and moves into our western zones late
Thursday afternoon and pushes past our area by early Friday
morning. A strong low to mid level jet strengthens over the area
causing very strong deep layer shear of 60-70 kt over the warm
sector. This will support scattered to numerous strong to severe
thunderstorms along the squall line. The main impacts will be
damaging wind gusts with isolated tornadoes. Cold air advection
and windy conditions develop behind the frontal passage on Friday
keeping highs in the mid 50s to mid 60s. On Friday night, high
pressure builds in overhead leading to clearing skies and lighter
winds. Lows Friday night dip into the mid 30s inland to low 40s
along the Atlantic coast.

.LONG TERM [Saturday Through Tuesday]...

Mainly dry conditions prevail with a warming trend through mid-
week. High pressure over the area on Saturday moves to the
northeast and off the Mid-Atlantic coast as a weak frontal
boundary moves southward pass the area Saturday night. No rain is
expected with this front due to weak forcing and lack of moisture.
Warm return flow from the high pressure system over the Atlantic
develops across the region increasing low-level moisture and
temperatures. Temperatures rise above normal with highs starting
in the 60s on Saturday and increasing into the upper 70s to low
80s by Tuesday. The next system approaches the region mid-week.

.MARINE...

Winds and seas increase tonight in advance of a strong cold front
tracking east across the Gulf Coast states. Evening observations
indicate winds southerly winds 10-15 kts with combined seas
building to 2-4 ft. After midnight, winds will increase further
with Small Craft Exercise Caution (15-20 kts) headlined for
near shore waters and Advisory conditions as winds near 20 kts for
the outer waters. A few spotty showers will be possible. Gale
Watch remains in effect for the outer waters Thu & Thu night as
potent storm system approaches and crosses the local waters with a
strong pre- frontal squall line moving over the waters Thu night.
No changes to current headlines in effect.

.FIRE WEATHER...

High dispersion values are expected area-wide on Thursday ahead of a
strong cold front. South-southwesterly surface and transport winds
will become breezy tonight and will strengthen further on Thursday,
with sustained speeds up to 25 mph gusting to 40 mph possible in the
afternoon. Chances for showers and thunderstorms will increase on
Thursday, with a squall line of strong to severe thunderstorms
traversing our region from west to east from late Thursday afternoon
through Thursday evening. Damaging wind gusts, heavy rainfall, frequent
lightning and isolated tornadoes will be possible along and ahead of
this squall line. Drier air moves into the area Friday and Saturday
with RH values dropping into the 30s to lower 40 percent range over
most portions of the area. High dispersions and breezy westerly winds
also expected Friday.

.HYDROLOGY...

Highest rainfall amounts of around 1 to 2 inches forecast
Thursday- Thursday night northwest of a line from Jesup GA to
Live Oak FL due to the strong cold front moving through the area.
The rapid progress of the front/squall line will keep these
rainfall amounts in check. Due to expected significant rainfall
from this frontal passage upstream, the Altamaha River at Baxley
may reach minor flooding in the next five days.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  77  48  55  37  63 /  90 100  10   0  10
SSI  73  53  59  42  61 /  20 100  10   0   0
JAX  83  52  62  40  65 /  20 100  10   0   0
SGJ  83  55  63  42  64 /  20 100  10   0   0
GNV  82  52  62  38  66 /  20 100  10   0   0
OCF  83  54  64  39  68 /  20 100  10   0  10

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...Gale Watch from noon EST today through Friday morning 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 noon EST today 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 from 10 AM to 4 PM EST Friday 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 from 10 AM this morning to 10 AM EST Friday
     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.

&&