Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 201832

Area Forecast Discussion
National Weather Service Jacksonville FL
232 PM EDT Fri Apr 20 2018



.Near Term.../through Saturday/...

High pressure will build to the North this afternoon and evening,
with an inverted trough over the Western Atlantic. These features
will enhance the pressure gradient keeping winds elevated. As the
high builds more to the Northeast late Tonight into Saturday, the
trough will push ashore, bringing the potential for rain showers,
with winds remaining elevated. The best chance for showers will be
across coastal portions of NE FL.

The same onshore winds that have caused cool readings across Eastern
counties Today, will help hold readings up across the East Tonight.
Coolest readings Tonight will be over inland SE GA.

.SHORT TERM...Sat night through Monday...

Stormy and wet weather this period as a surface low pressure
system develops near the lower MS River Valley region Saturday
night then intensifies through Monday as it tracks east across the
Gulf Coast states. The parent 500 mb vortex dives pretty far
south with this system, and lingers across TN/AL/MS Sun night-Mon
night before lifting NNE. This pattern will bring and sustain a
deep plume of high, deep layer moisture across the local area with
precipitable water values (PWATS) rising to 1.5-1.8" Sun
afternoon through Mon evening when a dry slot of air is expected
to cut-off rainfall from the WSW.

Sat night cloudy skies will prevail with breezy onshore flow as a
warm front lifts northward up the FL peninsula, with increasing
rain chances from south to north. Will continue with isolated to
scattered showers, with the best chances of localized heavy
rainfall potential along the NE FL Atlantic coast due to moisture
convergence along the northern edge of the lifting warm front.
Passing showers will continue into Sun as the airmass moistens
ahead of the intensifying low pressure system, with a chance of
isolated thunderstorms by Sun afternoon as both dynamical forcing
and instability increase from the west. Sun night through Mon
afternoon is expected to be the wettest period with waves of
widespread stratiform rainfall with embedded tstorms rotating over
the local area from west to east as several trough axes rotate
around the slow moving, almost vertically stacked, low pressure
system as it drifts eastward from MS toward Al and the western FL
panhandle through Mon evening. Widespread storm total rainfall
accumulations were still hovering around 1-3 inches, with locally
higher amounts, especially along the local Atlantic coast and
inland SE GA where convergence and dynamical forcing will be
strongest. There is the potential for embedded storms Sun through
Mon evening, with a chance of a few strong rotating cells Monday
when shear, surface based instability and forcing will phase
especially across the Suwannee River Valley and inland SE GA. Mon
evening the mid level 500 mb vortex finally begins to lift and
translate NNE, with a dry slot of air infiltrating the Gulf Coast
states including the local forecast area with PWATs falling below
1 inch and very dry mid level air. This instruction of dry air
will cease widespread rainfall and limit deep convective growth
needed for thunderstorms. Expect lingering scattered to isolated
showers Mon night as the surface low drifts east across GA with
plenty of low level moisture in place.

Temperatures will trend below normal for highs given cloud cover
and precip with highs generally in the 70s, with above normal lows
generally in the 60s.

.LONG TERM...Tuesday through Friday...

Generally drier conditions but progressive pattern with mean
layer eastern CONUS trough swinging weakening surface front across
the region. The surface low pressure system tracks across GA Tue
and up the mid-Atlantic coast then New England through Thu. Higher
potential now for another wave of showers and tstorms Tue with
the new 12Z GFS40 trending slower with low tracking across GA, and
thus increased precip chances generally east of Highway 301
toward the Atlantic coast Tue afternoon/evening. After Tue
evening, there will be a couple more waves of showers passing over
the local area as trailing wake troughs slide across the region
behind the departing surface low. Drier weather late Thu into Fri
as high pressure builds quickly east across the FL peninsula, then
another approaching cold front late Fri with a low chance of
rainfall. Drier weather returns Sat as high pressure builds
eastward across the Gulf Coast states through early next week.

Temperatures will generally trend near to slightly below normal
for highs generally in the 70s and near to slightly above normal
for lows generally in the upper 50s to lower 60s.



Restrictions will continue this 18z TAF period in stratus clouds.
Winds will remain elevated this period.



Strong high pressure will be to the North Tonight, then to the
Northeast over the weekend. An area of low pressure will track
Eastward across area from the Northern Gulf coast early next week.
This low will be to the North toward the middle of next week.
Elevated winds and seas will continue through this period.

Rip Currents: High risk through Saturday.


AMG  50  75  56  72 /   0  10  20  40
SSI  60  69  62  69 /   0  10  20  50
JAX  59  73  62  74 /   0  30  30  50
SGJ  65  72  63  74 /  40  50  30  50
GNV  59  76  62  77 /  10  50  30  60
OCF  61  78  62  80 /  40  50  30  60


FL...High Rip Current Risk through Saturday evening for Coastal Duval-
     Coastal Nassau-Flagler-St. Johns.

     Wind Advisory until 10 PM EDT this evening for Coastal Duval-
     Coastal Nassau-Flagler-Inland Duval-Inland Nassau-St. Johns.

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

     Wind Advisory until 10 PM EDT this evening for Coastal Camden-
     Coastal Glynn.

AM...Small Craft Advisory until 5 AM 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 4 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.



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