Flash Flood Warning 17, NWS Jacksonville, FL

Area Forecast Discussion
National Weather Service Jacksonville FL
910 PM EDT Sun Sep 6 2020

...WET, UNSETTLED WEATHER PATTERN FOR COASTAL & NE FL THROUGH
TUE...

.UPDATE...

A surface front was meandering across central FL with a broad
surface low forming along the boundary east of Cape Canaveral and
a surface ridge axis nosing southward across SW GA from a center
over the mid-Atlantic region. Aloft, an upper level trough was
deepening across the SE region with a plume of high moisture
content (PWAT over 2+ inches) across NE FL and coastal SE GA, with
drier air north of a Homerville to Waycross to Jesup line where
PWAT was < 1.7 inches.

Tonight, best coverage of showers and tstorms will continue to focus
over the adjacent coastal waters and impact our coastal counties
at times as low level winds back a bit more NNE with the development
of the broad surface low east of the CAPE. Increasing upper level
lift with the approach of the upper level trough over a very moist
airmass and low level convergence under ENE winds up to about 730 mb
will continue to focus localized heavy rainfall potential where slow
moving/training bands of precip occur tonight, especially for
coastal areas. With winds backing a bit more NNE, expect mostly
dry conditions after midnight for areas west of Highway 301.
Cloudy skies will keep temps mild int the 70s.

&&

.MARINE...

A front will linger over the central Florida peninsula through
Tuesday as high pressure persists northeast of the region. Waves
of showers and thunderstorms will impact the coastal waters
through the next 48 hrs under persistent ENE winds 10-15 kts and
combined seas 2-4 ft.

Rip Currents: Moderate rip current risk.

&&

.PREV DISCUSSION [747 PM EDT]...

.NEAR TERM [Through Tonight]...

Coverage of showers and storms is forecast to increase through
the afternoon hours across the area as ridging aloft weakens and
northeasterly low level flow increases. Numerous showers and
embedded storms are expected to the south and southeast of
Waycross this afternoon and into the evening hours. Coastal
showers and embedded storms are forecast to continue through the
overnight hours. High temperatures will be much lower today behind
the frontal boundary and due to the onshore flow, with highs in
the mid to upper 80s across interior southeast Georgia and coastal
areas, and the lower 90s across interior northeast Florida.

.SHORT TERM [Monday Through Tuesday]...

The quasi-stationary frontal boundary will continue to meander
southward down the FL Peninsula Monday as low level ridging builds
to our north, then the front should dissipate through Tuesday.
Mostly east winds around 5-10 kts in the 1000-700 mb layer Monday
and Tuesday should lead to a dominant east coast seabreeze both
days. PWATs will remain around 1.8" or less across inland SE GA,
limiting convection in that portion of our area, but 1.8-2.3"
PWATs on tap along coastal GA and NE FL will help fuel storms the
next couple days, so isolated storms could produce locally heavy
rainfall. Axis of greatest instability will also be focused over
coastal GA and NE FL, and with 500 mb temperatures around -7C,
meaning we could see also see a few isolated stronger storms.
Temperatures will be near to slightly above normal.

.LONG TERM [Wednesday Through Sunday]...

The low level ridge to our north will shift northeastward
Wednesday and Thursday with low level easterly flow continuing to
bring an active Atlantic seabreeze through the rest of the work
week. Deep layer troughing will set up over the Rockies Thursday
and develop a cold front out over the Plains. This cold front is
forecast to move into the southeast this weekend, bringing
widespread showers and thunderstorms to the local area.
Temperatures will continue to be near to slightly above normal
through the period.

.AVIATION...
[Through 00Z Tuesday]

Unsettled, wet onshore flow will continue waves of showers and
thunderstorms through the next 24 hrs and periodic restrictions.
This evening continued TEMPO groups for TS all terminals less GNV
with prevailing -RA. After midnight, inland rainfall potential
will decrease but showers and isolated tstorms will skirt near
coastal terminals through Monday morning with potential MVFR/IFR
due to low stratus forming inland as winds weaken overnight near
VQQ and GNV. Increasing ENE Mon after sunrise will once again
shift coastal showers and isolated tstorms inland through early
afternoon, with an increase in TS potential inland toward VQQ and
GNV into the afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  70  88  71  87  71 /  20  40  10  70  20
SSI  76  85  77  85  76 /  60  60  60  70  50
JAX  75  87  75  87  74 /  60  70  50  90  40
SGJ  75  87  75  86  75 /  60  70  50  90  40
GNV  73  88  72  88  73 /  60  70  30  90  20
OCF  74  89  72  89  73 /  60  80  40  90  20

&&

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

Special Weather Statement
National Weather Service Jacksonville FL
846 PM EDT Sun Sep 6 2020

FLZ125-133-070145-
Coastal St. Johns FL-Coastal Duval FL-
846 PM EDT Sun Sep 6 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN ST. JOHNS AND EAST
CENTRAL DUVAL COUNTIES UNTIL 945 PM EDT...

* At 846 PM EDT, National Weather Service meteorologists were
  tracking a strong thunderstorm over Fort Caroline, or near Unf,
  moving southwest at 10 mph.

* Excessive cloud-to-ground lightning and minor flooding due to heavy
  rainfall is possible with this storm.

* Locations impacted include...
  Unf, Ponte Vedra Beach, Neptune Beach, Palm Valley, Sawgrass, Craig
  Field, San Pablo, Little Talbot Island and Fort Caroline.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is occurring with this storm, and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm. If
you can hear thunder, you are close enough to be struck! Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3017 8135 3028 8162 3050 8148 3047 8138
      3030 8136 3023 8134
TIME...MOT...LOC 0046Z 028DEG 8KT 3037 8146

HESS

Special Weather Statement
National Weather Service Jacksonville FL
904 PM EDT Sun Sep 6 2020

FLZ124-125-133-070200-
Coastal St. Johns FL-Coastal Nassau FL-Coastal Duval FL-
904 PM EDT Sun Sep 6 2020

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL NASSAU...NORTH
CENTRAL ST. JOHNS AND EASTERN DUVAL COUNTIES UNTIL 1000 PM EDT...

* At 904 PM EDT, National Weather Service meteorologists were
  tracking a strong thunderstorm 10 miles east of Little Talbot
  Island, or 17 miles southeast of Fernandina Beach, moving southwest
  at 10 mph.

* Wind gusts of 40 to 45 mph, excessive cloud-to-ground lightning,
  and minor flooding due to heavy rainfall is possible with this
  storm.

* Locations impacted include...
  Unf, Ponte Vedra Beach, Neptune Beach, Sawgrass, Nocatee, Durbin,
  Craig Field, San Pablo, Little Talbot Island and Fort Caroline.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

These winds can down small tree limbs and branches, and blow around
unsecured small objects. Seek shelter in a safe building until the
storm passes.

Torrential rainfall is occurring with this storm, and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm. If
you can hear thunder, you are close enough to be struck! Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3006 8149 3007 8150 3010 8150 3012 8152
      3034 8157 3061 8156 3062 8140 3025 8135
      3009 8129
TIME...MOT...LOC 0104Z 037DEG 10KT 3048 8125

HESS

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