Special Weather Statement, NWS Jacksonville, FL

Area Forecast Discussion
National Weather Service Jacksonville FL
308 PM EDT Thu Aug 6 2020

.NEAR TERM [Through Tonight]...

Afternoon convection continue over inland areas near both inland advancing
sea breezes and along a SW-NE oriented boundary across SE GA. This activity
will continue to expand in coverage northward across SE GA and between
both sea breezes across NE Fl through early evening. High moisture
content, slow SW storm motion near 10 kts, steeper mid level lapse
rates and cooler mid level temps (500 mb -6.7 degC) all continued
to support strong to pulse severe storm potential into the evening,
especially across NE FL where boundary collisions will focus between
Highway 301 and the St. Johns River basin. Storms will tend to drift
back toward the Atlantic coast through 9-11 pm under light SW steering
flow while fading in coverage and intensity as diurnal instability fades.
Convection will continue over the Atlantic waters tonight and resurrect
near the Gulf Coast region after 06z through sunrise possibly impacting
parts of our Suwannee River Valley zones. Partly to mostly clear skies
will develop after midnight with lingering debris clouds across the
area.

Muggy, mild lows will trend above normal in the mid 70s inland to
upper 70s coast with possibly some shallow ground fog where heavy
rainfall recently fell.

.SHORT TERM [Friday Through Sunday]...

Synopsis...Dog days of summer are here - hot, sticky with mainly
afternoon & early evening t'storms.

Deep tropical moisture with precipitable water (PWAT) above climo
(1.8"+) will linger across NE FL and eastern parts of SE GA
(generally east of Waycross) into the weekend as a mean layer
1000-500 mb ridge strengthens westward from the central Atlantic
with a ridge axis across south FL Friday pivoting northward across
central FL through Sunday. This will keep frontal systems well
north and west of the region and favors active diurnally enhanced
sea breezes over the FL peninsula and parts of SE GA, with lower
rain chances across our inland GA zones from roughly Jesup toward
Pearson Sat/Sun due to drier air (PWAT < 1.6"). SW steering flow
will be light (< 10 kts) with the ridge axis building northward
toward the local area. This regime favors morning convection near
the Gulf Coast drifting slowly inland through mid-morning but
generally remaining west of the I-75 corridor. By midday as
convective temps are achieved, more 'pop-corn' airmass showers
will begin to pop inland with tstorm potential increasing along
the slight strong west coast sea breeze as it begins to press
inland and along near the slowly inland progressing east coast sea
breeze. Sea breeze and outflow boundary mergers will focus across
the interior of the forecast area each afternoon and early
evening generally between I-75 and St. Johns River basin/Highway
301 for SE GA, with a slightly drift back toward the east coast
under mean layer SW flow. Convection will fade through 9-11p each
evening with just a rogue shower overnight mainly near the Gulf
Coast region due to such a saturated airmass.

Main tstorm hazard this period will be locally heavy, potentially
briefly flooding rainfall due to such high atmospheric moisture
content and slow, erratic storm motion along boundary mergers.
Does not appear to be as much hail potential into the weekend
compared to the past few days due to weaker mid/upper level winds
as the ridge builds northward over the FL peninsula and the
moisture profile deepens. However, cool near to just below normal
500 mb temps of -6 to -7 and hot low levels will create steeper
low level lapse rates so a few strong to pulse severe storms will
still be possible in the afternoon into the early evening where
boundary mergers occur, with wet downburst winds capable of
outflow gusts of 40-60 mph.

Above normal temperatures expected as mean layer ridging
strengthens over the FL peninsula. Highs will range in the low/mid
90s inland to near 90 coast before the east coast sea breeze
advances inland. Sticky dew pts in the mid/upper 70s combined with
the dry bulb temps will create heat index values of 105-110 degF.
Nighttime lows will trend above normal as well in the mid/upper
70s for most areas.

.LONG TERM [Monday Through Thursday]...

Light SSW steering flow continues as the the mean layer 1000-500
mb ridge axis lifts from central FL Monday to across north FL Wed
with high atmospheric moisture (PWATs over 2") edging northward,
blanketing SE GA and NE FL. This will bring elevated rain chances
across the entire CWA with convection mainly driven by sea breeze
and outflow boundary intersections. Thu through the end of the
week a pattern shift is advertised with a more dominant east coast
sea breeze regime as the mean layer ridge lifts across SE GA
where the higher PWAT plume will linger and favor elevated rain
chances, while lower rain chances are expected south of the ridge
axis across much of NE FL where PWATs are expected to fall below
normal and a dominant east coast sea breeze regime will be
favored. This set-up will bring morning coastal showers and
possibly a tstorm toward the Atlantic coast, then clearing from
the east into the afternoon with the focus for afternoon/evening
storms inland across the Suwannee River Valley and SE GA.

Temperatures expected to trend near to slightly above normal.

&&

.AVIATION...
[Through 18Z Friday]

Scattered showers and thunderstorms have developed over ne Fl and
se Ga and will be become numerous over the interior as seabreeze
and boundaries merge this afternoon and early evening. Have TEMPO
thunder in TAF forecasts til around 22Z with VCTS til around 00Z.
Expect VFR conditions to prevail overnight as convection dies off
this evening.

&&

.MARINE...

High pressure will extend across the Florida peninsula with
surface troughs remaining north of the local waters. This weather
pattern will produce prevailing south-southwesterly winds through
much of the forecast period until the east coast sea breeze
develops along the coast around midday each day which will back
winds onshore and increase speeds to near 10-15 kts. Combined seas
will will continue near 2-4 ft. Scattered showers and
thunderstorms possible each period.

Rip Currents: Low to moderate risk expected into the weekend.

&&

.FIRE WEATHER...

Low daytime dispersion today (< 20 units) and most of NE FL Fri
due to light transport winds.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  74  93  74  95  74 /  20  50  40  40  20
SSI  79  89  78  92  78 /  30  30  30  40  30
JAX  74  92  75  95  76 /  40  70  40  50  30
SGJ  76  90  76  92  75 /  30  40  30  50  20
GNV  74  92  74  93  74 /  50  70  40  60  20
OCF  74  92  74  93  74 /  40  60  30  60  20

&&

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

Special Weather Statement
National Weather Service Jacksonville FL
321 PM EDT Thu Aug 6 2020

FLZ024-GAZ165-264-062000-
Inland Nassau FL-Northeastern Charlton GA-Inland Camden GA-
321 PM EDT Thu Aug 6 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN NASSAU...
SOUTHWESTERN CAMDEN AND EAST CENTRAL CHARLTON COUNTIES UNTIL 400 PM
EDT...

* At 320 PM EDT, National Weather Service meteorologists were
  tracking a cluster of strong thunderstorms near Hilliard, moving
  northeast at 20 mph.

* Penny size hail, excessive cloud-to-ground lightning, wind gusts
  45 to 55 mph, and minor flooding due to heavy rainfall is possible
  with this storm.

* Locations impacted include...
  Hilliard, Woodbine, Kings Ferry, Tarboro and Colesburg.

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 3074 8169 3063 8176 3054 8189 3066 8201
      3076 8200 3078 8199 3078 8198 3080 8199
      3104 8188 3105 8174 3100 8165
TIME...MOT...LOC 1920Z 207DEG 16KT 3066 8196

SHASHY

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