River Flood Warning 4, NWS Jacksonville, FL

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

...LINE OF SEVERE STORMS WITH DAMAGING WINDS AND ISOLATED
TORNADOES EXPECTED LATE THIS AFTERNOON AND EVENING...

.UPDATE...
Forecast remains on track for windy and warm conditions ahead of
approaching squall line with near record high temps into the lower
to middle 80s through early afternoon. South to southwest winds
already into the 15 to 25 mph range with gusts to 35 mph this
morning with further increase into the 20 to 30 mph range with
gusts of 40 to 45 mph expected ahead of the squall line through
the afternoon hours and Wind Advisory looks good for all areas.
Some widely scattered shower activity will break out ahead of the
squall line late this morning and early this afternoon and a few
rogue discrete isolated supercell storms possible across SE GA in
the 1-4 pm time frame, but main event for inland areas still on
track for the 4-7pm time frame and 7-10 pm for the coastal areas
and I-95 corridor/St Johns River Basin. SPC watch will likely be
posted for the region by late this morning or early this afternoon
at the latest and will continue through the evening hours. Main
Severe threat continues to be damaging winds along the leading
edge of the squall line with widespread 50-60 mph winds and
isolated winds to 70 mph near bowing line segments and isolated
tornadoes in portions of the squall line. Rainfall amounts still
on track for mainly 1.5 to 2.5 inch amounts across SE GA and the
Suwannee River Valley of inland North FL and around an inch or so
for the rest of the area. Latest Hi-Res models are slightly faster
and pushing leading edge of squall line off the coast late this
evening around 10pm, with widespread rainfall continuing to around
midnight or so before diminishing quickly during the afternoon
hours. Windy conditions will continue through the overnight hours
as west winds develop but at slightly lower values in the 15-25
mph range with gusts of 30-35 mph.

Record High Max Temps for climate sites on Thu Feb 6th...
JAX 85/2008...GNV 88/1957...AMG 82/2008...SSI 81/2008...CRG 85/2008

Record High Min Temps for climate sites on Thu Feb 6th...
JAX 67/2004...GNV 64/2004...AMG 63/2004...SSI 61/1974...CRG 67/2004

Record High Wind Gusts (in mph) for climate sites on Thu Feb 6th...
JAX 48/1896...GNV 39/2008...AMG 46/1983...SSI 46/1992...CRG 55/1986

&&

.PREV DISCUSSION [622 AM EST]...

.NEAR TERM [Through Tonight]...

Warm advection will continue across the region this morning into the
afternoon, on an increasing low level jet. A few showers will be
possible in the warm advection pattern, but much of the
precipitation will hold off till late in the day ahead of a cold
front. A wind advisory will be in effect Today due to gusty winds,
which will result from the low level jet mixing down in increasing
instability.

The northeast to southwest oriented cold front is expected to reach
western counties around 00z, central counties around 03z, then off
the coast by 06z. With this timing, the airmass will have the chance
to destabilize ahead of passage. In addition, shear will increase
through the day. A squall line is expected to develop an hour or so
out ahead of the front itself, which will race east southeast across
the forecast area. Damaging wind potential is significant with this
system supported both by the wind field, and momentum created by the
forward speed of the line. There is also sufficient shear and
instability to support the production of a few tornadoes along the
line.

High pressure will build from the west southwest after midnight,
with drier air advecting in.

Temperatures will be well above normal Today, with highs in the
middle to upper 70s West, and lower to middle 80s east. Temperatures
will fall during the night with lows ranging from the middle 40s
inland, to the middle 50s along the coast.

.SHORT TERM [Friday Through Saturday]...

Friday...moderate to strong cold advection expected in the wake
of the front with areas of broken low clouds and perhaps a few
light showers in the morning. Clearer skies expected in the aftn
with low level mixing. With wind west winds up to 15-20 mph and
cold advection will keep highs in the mid 50s to mid 60s. Friday
night, lighter winds expected as sfc high pressure builds into
the area with much colder temps with widespread mid 30s now
expected inland, and with some temps at the coast near
40 (as some light drainage offshore northwest-north flow is
likely). A couple of inland sites may reach the freezing mark.
Patches of frost appear likely for inland areas.

Saturday-Saturday night, after cold morning on Saturday, sfc high
pressure system will drift east-southeast while weak return flow
brings in a warming trend with highs in the lower to mid 60s to
around 70. Some increased clouds look possible over the northwest
zones as a weak shortwave moves in from the northwest with an
associated weak trough of low pressure moving in from the
northwest Saturday night. Not anticipating mentionable POPs with
this weak trough. Lows drop through the 40s Sat night.

.LONG TERM [Sunday Through Thursday]...

Sunday...weak trough/front washes out over the area sfc high pressure
located over the Appalachians pushes eastward setting up another
return flow pattern and a gradual warm-up. This will also result
in increasing moisture and some increased cloudiness going into
Sunday night and Monday. High temps a few degrees above normal on
Sunday.

The next frontal system will be moving through the northeast U.S.
and TN and lower MS valley early Monday. Warm return flow expected
over the area Monday with widespread highs in the 70s. With prevailing
zonal flow aloft, there is enough push to the east and more than
ample moisture to bring a low chance of showers to the northwest
zones late Monday with chances increasing a bit Mon night into
Tuesday but the frontal system is currently progged to stay just
north of the area, though not too confident with frontal position
given disagreement between GFS and ECMWF. By Wed and Thu,
mid/upper level trough over the southwest U.S. is forecast to
eject northeastward allowing for a building ridge to occur over FL
and the Bahamas. Thus, should see moisture lift back northward
over our area and decreased rain chances, and continue to see
above normal temps.

.AVIATION...
[Through 12Z 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 it across area TAF sites between around 01z
and 04z. Strong to severe storms with potentially damaging winds
are expected with the line, with restrictions anticipated.
Conditions will improve during the overnight.

.MARINE...

High pressure will move to the southeast this morning. A strong cold
front will cross the region late this afternoon into this evening.
Strong to severe winds are expected to accompany the front. High
pressure will build from the west southwest late Tonight into
Friday, then overhead Friday night. This high will move to the east
Saturday. A weak cold front will move southeast across region
Saturday night. High pressure will then build to the north Sunday,
and northeast Sunday night. The high will move to the east Monday.
A cold front will move southeast across area Tuesday.

Rip Currents...Moderate through Friday.

.FIRE WEATHER...

Areas with high dispersions are likely today with values well in
excess of 75 over parts of northeast FL. Windy conditions as well
but RH values will stay well above critical values. On Friday,
cooler and drier behind the front and winds will be westerly at
about 15 mph and gusty, elevated-high dispersions, and RH values
possibly down to around 28-32 percent so will be a fire sensitive
day but no red flags expected at this time.

.HYDROLOGY...

Still looking at rainfall mounts up to the 1-2 inches with this
upcoming weather event. May see parts of Altamaha River reach
minor flood stage within the next few days.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  79  48  55  35  62 /  90 100  10   0  10
SSI  73  52  58  40  59 /  20 100   0   0   0
JAX  84  53  62  37  65 /  20 100   0   0   0
SGJ  84  56  64  41  64 /  20 100   0   0   0
GNV  83  53  61  36  66 /  20 100   0   0   0
OCF  85  55  64  37  68 /  20 100   0   0   0

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Wind Advisory from noon today to 3 AM EST Friday for Baker-
     Bradford-Central Marion-Clay-Coastal Duval-Coastal Flagler-
     Coastal Nassau-Coastal St. Johns-Eastern Alachua-Eastern
     Marion-Gilchrist-Hamilton-Inland Duval-Inland Flagler-
     Inland Nassau-Inland St. Johns-Northern Columbia-Putnam-
     Southern Columbia-Suwannee-Union-Western Alachua-Western
     Marion.

GA...Wind Advisory from noon today to 3 AM EST Friday for Appling-
     Atkinson-Bacon-Brantley-Clinch-Coastal Camden-Coastal Glynn-
     Coffee-Echols-Inland Camden-Inland Glynn-Jeff Davis-
     Northeastern Charlton-Northern Ware-Pierce-Southern Ware-
     Wayne-Western Charlton.

AM...Small Craft Advisory until 9 AM EST this 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.

     Gale Warning until 3 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 until 3 PM 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.

&&