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Area Forecast Discussion (AFD)

Issued by Jacksonville, FL (JAX)

                            
000
FXUS62 KJAX 150801
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
401 AM EDT Sun Sep 15 2019

...STRONG ONSHORE WINDS WITH HIGH/ROUGH SURF THROUGH THE
WEEKEND...

.NEAR TERM (Today-tonight)...
TC Humberto over the wrn Atlantic near 28N77.5W continues to
slowly push north-northwest while fairly deep northeast flow up to 
around 3-5 km affects our region. Best moisture is over the far 
south and eastern zones (PWATs 1.9-2 inches), with low level 
convergence and a couple of rain bands on the outer parts of 
Humberto rotating through the southeast parts of the forecast 
area. Latest radar shows isolated to scattered showers over the 
marine waters, and narrow bands of showers pushing into northeast 
FL, generally fading past Highway 301. Best chances of rain today 
will be for the southeast zones with a forecast of 40-60 percent 
coastal northeast FL and 20-40 percent for inland northeast FL and
only 20 percent for southeast where moisture is just enough to 
support a couple of lone showers by the aftn. Chance of t-storms 
is fairly low given relatively weak instability with SBCAPE under 
2000 J/kg. Max temps today near 90 inland, and mid 80s at the 
coast due to more cloudiness and shower activity. Winds today will
increase to 15-20 mph with a few gusts up to 30 mph, especially 
for northeast FL and coastal southeast GA. For the time being, 
appears winds stay just below wind advy criteria but will be 
monitored. For tonight...we continue to advertise a chance of 
showers for the coastal counties but as the low level wind field 
backs, some drier air will filter in and the prospects for showers
will diminish for the inland areas of northeast FL. Lows may dip 
to near 70 over inland southeast GA but rest of the area expected 
to have lows from 72 to 78 deg. 

.SHORT TERM...MON THROUGH WED...

Low level ridging will continue to sit over southeastern CONUS and 
Humberto will continue to move further out into the Atlantic, keeping
northeasterly winds in place across the area. At the upper levels,
a ridge of high pressure will remain off to our west, with a 
trough axis stretching across the northern Gulf waters, and 
another UL trough over the northeastern CONUS. Relatively light 
will prevail aloft, but with a northerly component to the winds 
throughout much of the atmospheric column, we'll see a drier air 
mass work its way south into the area. Model PW values below 1.5" 
dig into SE GA and NE FL Monday night. Expect mostly dry conditions
with 20-40% chances for showers and isolated thunderstorms along 
the coast. Temperatures will peak in the mid 90s Monday and Tuesday,
lower 90s on Wednesday. Lows will be mostly in the low 70s.

.LONG TERM...THU THROUGH SUN...

Deep layer ridging will slowly push eastward through the end of the
work week. By Thursday-Friday, this high pressure to our north may
set up a wedge pattern with an air mass from the Appalachian Mountains
moving down into S GA. PoPs will be low through the long term, 
with 20-40% chances for showers and isolated thunderstorms, again 
mostly along the coast. Temperatures will be cooler, with highs in
the mid-upper 80s and lows in the upper 60s to low 70s.

&&

.AVIATION...

Periods of MVFR cigs are expected for the TAFs through this
morning, with lowest chance of MVFR at GNV. A few showers are to 
be expected for SGJ...CRG...VQQ and JAX. Lower chances for 
JAX and SSI...and MVFR vsby possible. Breezy northeast winds
at SGJ early this morning...but winds will pick up again 
by mid morning from the northeast at about 15G25kt. Some improvement
in clouds expected after about 20z-21z today into this evening 
but still a threat of MVFR cigs for SGJ into Sunday night due to
north-northeast flow over the Atlantic waters.

&&

.MARINE...

Winds and seas remain very hazardous for small boaters with solid SCA
in place. Northeast winds 20-25 kt and some occasional gusts up 
to 35 kt expected through tonight and early Monday. Winds and seas
may decrease a bit on Tuesday-Tuesday night but we see winds 
increasing again late Wed through Thu as high pressure ridge 
builds north of the area and winds pick up again to near 20 kt and
seas upwards of 5-8 feet. Swells from Humberto should continue to
affect area waters at least through late this coming week.

Rip Currents: High Risk of rip currents expected in the rough surf
conditions and surf/breakers of 5-7 ft range along the northeast 
FL coast and high surf advisor in effect, with 4-6 ft surf 
expected along the southeast GA coast. Elevated water levels 
expected along the St Johns River Basin/Atlc Coast during time of 
high tide with departures around 1 ft above predicted tide levels 
but this will continue to remain just below minor flood levels.

&&

.FIRE WEATHER...

Borderline high dispersion indices are anticipated this afternoon across
inland portions of SE GA, with more widespread dispersion indices
in the 75-85 range expected tomorrow. Moderate north-
northeasterly transport winds are forecast both days, but winds 
will lower on Tuesday. RH values will remain above critical 
thresholds through Monday, then drier air will begin to move in on
Tuesday. The drier air and higher winds will not occur at the 
same time, so no red flag conditions are forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  91  72  93  70 /  10   0  10   0 
SSI  87  76  88  75 /  30  20  20  10 
JAX  88  75  90  73 /  40  20  10  10 
SGJ  86  76  88  74 /  60  30  30  10 
GNV  89  73  91  71 /  30  10  10   0 
OCF  90  73  92  72 /  40  10  10   0 

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Monday evening for Coastal Duval-
     Coastal Flagler-Coastal Nassau-Coastal St. Johns.

     High Surf Advisory until 4 AM EDT Monday for Coastal Duval-
     Coastal Flagler-Coastal Nassau-Coastal St. Johns.

GA...High Rip Current Risk through Monday evening for Coastal Camden-
     Coastal Glynn.

AM...Small Craft Advisory until 10 PM EDT Tuesday 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 9 PM EDT Monday 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.

&&

$$

Shashy/Nguyen