205 
FXUS62 KJAX 170838
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
438 AM EDT Mon Jun 17 2019

...SCATTERED TO NUMEROUS AFTERNOON THUNDERSTORMS EACH DAY THIS
WEEK...

.Currently...

Early morning surface analysis depicts the axis of Atlantic
surface ridging extending westward along the FL/GA border. 
Meanwhile, weak low level troughing was pushing northward across 
south Florida. Aloft...southwesterly flow now prevails over our 
region as ridging aloft has shifted southward from the 
southwestern Atlantic over the Greater Antilles. Otherwise, a 
shortwave trough migrating across the Arklatex Region and 
approaching the Ozarks has spawned a Mesoscale Convective System 
(MCS) over the Texas Hill Country and the upper Texas coast. 
Latest GOES-East derived Total Precipitable Water imagery 
indicates that PWAT values have increased to 1.6 to 1.8 inches 
over southeast Georgia, while PWATs are now in the 1.8 to 2 inch 
range across most of northeast and north central Florida. A few 
sprinkles were already moving northward over our southeastern
counties. Showers and thunderstorms are also increasing over the 
offshore waters adjacent to east central Florida just north of the
low level trough that is moving northward, while a wave of 
convection is moving onshore onto the Treasure Coast counties 
south of Cape Canaveral. Mid and high altitude cloud cover is 
advancing northward over the northeast Florida coastal counties 
and the St. Johns River basin. Temperatures as of 08Z mostly 
ranged from the upper 60s to the lower 70s at inland locations, 
with mid and upper 70s prevailing at the coast. Dewpoints were 
generally in the upper 60s and lower 70s. 

.Near Term (this Morning through Tonight)...

The slow moving shortwave trough currently approaching the Ozarks
will progress eastward at a slightly faster rate of speed today, 
moving through the lower Mississippi, Tennessee and Ohio Valleys 
by late tonight. This feature will gradually deepen southwesterly
flow aloft over our region late today, which will lift the low
level trough axis and higher PWAT values over south Florida
northward. Latest short-term, high resolution guidance indicates
that convection associated with the low level trough will reach
Cape Canaveral after sunrise and will then advect northward over
Flagler County and the southern St. Johns basin by the late 
morning hours. Scattered to numerous showers and embedded 
thunderstorms will continue to progress quickly north-
northwestward, crossing the Interstate 10 corridor early this 
afternoon and then moving into inland southeast Georgia during the
mid to late afternoon hours. Convection should also develop this 
afternoon along an inland-moving Gulf coast sea breeze, with 
mesoscale boundaries from earlier convection along I-95 and U.S. 
Highway 301 interacting with this later developing convection to 
focus mid to late afternoon activity over the Suwannee Valley and 
along I-75 in north central Florida, where likely POPs were placed
in the forecast grids. Relatively mild mid-level temperatures and
weak lapse rates today should preclude severe thunderstorm 
development, with a few wet microbursts possible over inland 
locations late this afternoon as mesoscale boundaries collide, 
with the strongest activity possibly producing 40-50 mph wind 
gusts and locally heavy downpours. Plenty of cloud cover should 
keep highs in the upper 80s for locations east of U.S. Highway 301
in northeast and north central Florida, while convection 
developing late in the afternoon will allow highs to climb to the 
lower 90s across most of inland southeast Georgia.

The low level trough axis will begin to shift north-northeastward
over the Atlantic waters this evening, with a weak low pressure
center possibly developing overnight just offshore of Cape
Canaveral. Low level flow will become southwesterly by late
tonight over northeast and north central Florida as this trough 
axis/weak surface low pressure center move northeastward over the
coastal waters, where scattered to numerous showers and
thunderstorms will blossom overnight. Isolated convection may
impact coastal locations late tonight, and convection developing
over the northeast Gulf of Mexico may also be advected onshore
along the Florida Big Bend and Nature Coasts during the predawn
hours, possibly moving into southern portions of the Suwannee
Valley and west of I-75 in north central Florida towards sunrise.
Plenty of mid and high altitude cloud cover should prevail over
our region overnight, and lows will range from the lower 70s
inland to the mid and upper 70s at coastal locations. 

.Short Term (Tuesday through Wednesday Night)...

Tuesday...Mid level impulse/shortwave over the region will slowly
shift offshore through the day as flow pattern becomes more
southwesterly. Still expect diurnal heating to interact with deep
moisture as PWATs remain close to 2 inches and expect numerous
showers and storms with storm motion from the South-Southwest at
10-15 mph and will push storm activity closer to the I-95 corridor
during the afternoon and early evening hours. Deep Moisture and
cloud cover will hold Max Temps close to climo values in the upper
80s/near 90 degrees. Locally heavy rainfall will become a slightly
bigger issue as PWATs exceed 2 inches in some spots with storm
motion still less than 10 mph. Also, slightly cooler mid level
temps with 500mb in the -7C to -9C range will help enhance strong
thunderstorm potential, with isolated downdrafts pushing close to
50-60 mph in most intense activity. 

Wednesday...In the wake of trof pushing into the Carolinas,
surface High Pressure ridge will rebuild south of the region
across the Southern FL Peninsula and this will set up a faster
West-Southwest flow across NE FL/SE GA and with tropical moisture
with Precipitable Water Amounts (PWATs) still around 2 inches,
expect numerous showers and storms to break out along the I-75
corridor of inland NE FL by late morning and track across the rest
of the area through the afternoon hours reaching a
stationary/pinned East Coast Sea Breeze at the Atlc Coast by late
afternoon. Cool temps aloft of -9C at 500mb will help to enhance
storm strength and along with faster storm motion expect isolated
severe storms with downburst potential to 60 mph at times, and the
cooler air aloft will support some hail potential in the most
intense storms. Max Temps in the upper 80s where storms start up
first, while areas towards the Atlc Coast will push to around 90
degrees with West to Southwest winds at 10-15G20 mph at times.
Dewpoints in the mid 70s will support Heat Indices into the
100-105 range.

.Long Term (Thursday through Sunday)...

Thu/Fri...Faster West to Southwest flow still expected to continue
across the deep south and along the North Gulf Coast and push a
series of mid level impulses/shortwaves that will trigger daily
numerous showers and storms that will develop along the Gulf
Coast/Suwannee River Valley and push towards the E-NE while the
flow will be strong enough to keep the East Coast Sea Breeze
pinned along the Atlc Coast as Surface West to Southwest winds
will increase to 10-15G20 mph each day. This will push the Max
Temps into the 90-95 range each day with Heat Indices into the
100-105F range. While moisture levels will be slightly less with
PWATs just under 2 inches and storm coverage may be less than on
Mon/Tue, expect the faster storm movement to cover more territory
and still lead to PoPs in the 50-70% range. The cooler and more
unstable conds aloft will continue to support scattered strong to
isolated severe storms with the faster storm motion will allow for
better chances for wind gusts up to 60 mph in the most intense
storms during the afternoon and early evening hours. 

Sat/Sun...High pressure at the surface and aloft will begin to
build back into the region from the SW and push belt of faster
westerly flow just north of the area. This will lead to slightly
less storm coverage with PoPs in the 30-50% range. Max Temps into
the lower to middle 90s will be more widespread in the afternoon
due to less clouds and less storm coverage and will push Heat
Indices to around 105 degrees all the way to the coast as enough
lingering westerly flow will keep East Coast Sea Breeze close to
the beaches. Still expect cool/unstable conds aloft to continue to
support scattered strong to isolated severe storms at times.

&&

.Aviation...

Periods of MVFR visibilities will be possible at VQQ and GNV
through around 12Z. Otherwise, VFR conditions will prevail, with
light southerly surface winds developing shortly after 12Z.
Showers and thunderstorms will develop over east central Florida
and the St. Johns River basin during the mid to late morning hours
and will move northward, reaching SGJ towards 16Z and then the
Duval County terminals towards 17Z. Thunderstorms are likely to
develop near SSI towards 18Z, but activity may stay just inland 
from the terminal. Thunderstorms will then shift inland towards
GNV by 19Z. Due to uncertainties in timing and intensity, we opted
to use PROB30 groups at each terminal except for SSI, where
prevailing VCTS conditions are expected beginning around 18Z.
Briefly gusty southeasterly winds and MVFR to IFR visibilities are
expected with convection this afternoon. Activity may linger
through around 00Z at GNV. The Atlantic sea breeze will push
inland early this afternoon, with surface winds becoming 
southeasterly and sustained speeds increasing to 10-15 knots
towards 16Z at SGJ and then after 17Z at the Duval County
terminals and SSI.

&&

.Marine...

High pressure centered near Bermuda will drift slowly southward
this week, with its axis shifting south of the northeast Florida
waters by late Tuesday. Meanwhile, weak low pressure will 
develop near Cape Canaveral tonight and will move north-
northeastward across the offshore waters on Tuesday and will then
accelerate over the Gulf Stream waters off the Carolina coast
Tuesday night. Showers and thunderstorms will increase over the
waters south of St. Augustine this morning and will move northward,
with additional activity developing over mainly the offshore 
waters tonight. A southerly wind surge this evening will bring
sustained speeds up to near 15 knots. Seas of 2-4 feet will
prevail through Tuesday. Winds will shift to west-southwesterly 
by Tuesday evening, with rounds of showers and thunderstorms 
impacting the waters each afternoon and evening through Friday. 
Outside of thunderstorm activity, caution level wind speeds will 
develop offshore beginning on Tuesday evening. Caution level wind
speeds will then develop near shore during the evening wind surge
on Wednesday, with Small Craft Advisory level speeds near 20 knots
possible offshore during the Thursday evening wind surge. Caution
level seas of 4-6 feet are expected to develop offshore beginning
on Wednesday night. Prevailing Caution level winds are expected
near shore and offshore late this week.

Rip Currents: Winds will become onshore early this afternoon,
creating a low-end moderate risk through around the time of low
tide during the mid-afternoon hours. A low risk is expected at the
southeast Georgia beaches. A low risk is then expected to prevail
at all area beaches Tuesday through at least Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  92  71  91  72 /  50  30  70  30 
SSI  88  77  86  75 /  10  30  60  30 
JAX  89  72  91  73 /  50  10  70  30 
SGJ  87  75  88  73 /  40  20  70  30 
GNV  90  70  89  72 /  60  40  70  20 
OCF  88  72  88  72 /  60  40  70  30 

&&

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

$$

Nelson/Hess