629
FXUS62 KJAX 092216
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
616 PM EDT Thu May 9 2024

...New UPDATE...

.UPDATE...
Issued at 615 PM EDT Thu May 9 2024

For the latest NE FL and SE GA Daily Key Messages please visit:
https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf

The Tornado Watch has ended for NE FL and SE GA. Isolated strong
to severe thunderstorms remain a threat through the evening, with
gusty winds likely ahead of the storms as well.

Timing for tomorrow`s storms has not changed much, expect SE GA
and the Suwannee valley area to see strong to severe thunderstorms
move in around sunrise. Storms will move east and southeastward
through the morning and afternoon, with potential for a second
round in the evening. The second round will rely heavily on how
storms progress Friday morning. Again, the main hazard for
tomorrow will be damaging winds, although isolated tornadoes and
hail cannot be ruled out as well.

&&

.SYNOPSIS...
Issued at 335 PM EDT Thu May 9 2024

Afternoon surface analysis depicts a wavy frontal boundary
extending from the Chesapeake Bay westward across the Ohio Valley
and then southwestward across the Tennessee Valley, the Ozarks
and northern Texas. Meanwhile, Atlantic high pressure centered to
the east of Bermuda continues to extend its axis westward across
the FL peninsula. Aloft...stout ridging centered over Mexico`s
Yucatan Peninsula continues to flatten in response to a longwave
that was digging southeastward from the Great Lakes and Upper
Midwest. Otherwise, cutoff troughing continues to slowly
retrograde westward across the Rockies. A strengthening jet streak
at 250 millibars (around 35,000 feet) positioned to the south of
the digging longwave trough was migrating from the Mid-
Mississippi Valley towards the Tennessee Valley, and this jet
streak and associated shortwave troughing was energizing a
Mesoscale Convective System (MCS) and associated strong to severe
thunderstorms that were progressing east southeastward across
inland portions of southeast GA. A drier and more subsident air
mass resides closer to the northern periphery of the ridge axis
across northeast and north central FL, where temperatures have
soared to record levels in the mid to upper 90s, while
thunderstorms have cooled temperatures back to the 70s for
locations north and west of Waycross. Dewpoints at 19Z ranged
from the mid 60s to lower 70s.

&&

.NEAR TERM...
(through Tonight)
Issued at 335 PM EDT Thu May 9 2024

Strong to severe thunderstorms associated with the southeastward
moving MCS will continue to impact southeast GA through late
afternoon, with activity expected to cross the FL/GA border in the
5 PM - 7 PM time frame. This MCS will continue racing
southeastward early evening hours, with weakening likely as the
line pushes across the Interstate 10 corridor towards sunset as
it encounters the drier and more stable air mass that remains in
place across north central FL. Damaging straight line wind gusts
of 50-70 mph will be the primary threat for locations north of
I-10, but a few isolated incidents of hail and tornadoes cannot be
ruled out across southeast GA through late afternoon. The Storm
Prediction Center has maintained an Enhanced Risk (level 3 out of
5) for severe thunderstorms across southeast GA, where a 10%
probability of downburst wind gusts in excess of 74 mph exists, in
addition to 5% probabilities for tornadoes along with enhanced
probabilities for large hail. A Slight Risk was maintained for
locations along and south of I-10 into the early evening hours.

The longwave trough will continue to dig southeastward across the
Tennessee and Ohio Valleys tonight, with strengthening westerly
flow to the south of this feature propelling another shortwave
trough and associated MCS across the Deep South during the
overnight and predawn hours. The prior weakening MCS will push
across north central and coastal northeast FL during the early to
mid evening hours, with a break in between MCSs expected through
the overnight hours. Short-term, high resolution guidance is in
relatively good agreement in positioning this next MCS and
associated strong to severe thunderstorm threat at the doorstep of
the Ocmulgee/Alapaha/Suwannee Rivers around sunrise on Friday,
with this activity then sweeping eastward across our area through
the morning hours. Breezy west- southwesterly boundary layer flow
in advance of this upstream MCS is expected to advect a stratus
layer across the Suwannee Valley and inland southeast GA
overnight, with these low clouds possibly crossing the I-95
corridor around sunrise. Cloud cover and warm air advection
downstream of the approaching cold front should keep lows in the
70-75 degree range overnight.

&&

.SHORT TERM...
(Friday through Saturday night)
Issued at 335 PM EDT Thu May 9 2024

Upper shortwave trough and associated MCS will move across the
region Friday morning bringing strong to severe thunderstorms to
the Ocmulgee/Alapaha/Suwannee River basins around sunrise on
Friday. This activity will then sweep eastward across our area
through the late-morning hours before shifting offshore. There
remains uncertainty with the next round of potentially severe
weather. If the morning MCS clears the area early enough, the
airmass may be able to recover ahead of the approaching cold front
from the northwest Friday afternoon into evening. Storms will
redevelop ahead of the front but the severity of them will be
determined by the airmass recovery. Regardless, damaging straight-
line winds will be the main threat along with the potential for
hail and isolated tornadoes. The cold front and associated
convection is expected to exit to the south Friday evening with a
drier airmass clearing the skies in its wake. Sunny skies and
around normal temperatures in the 80s are anticipated for Saturday
with lows dipping into the upper 50s and 60s.

&&

.LONG TERM...
(Sunday through next Thursday)
Issued at 335 PM EDT Thu May 9 2024

Warm and dry conditions on Sunday quickly give way to a wet and
unsettled pattern for next week as upper shortwaves parade across
the region. A wave of low pressure will move eastward across the
northern Gulf lifting a stationary front across southern FL up the
peninsula Monday into Tuesday as a warm front. As the warm front
lifts across the region, a moist and unstable airmass will become
established which will support an increasing thunderstorm
potential throughout next week. High temperatures will generally
be around normal in the 80s and then trend upward on Wednesday.

&&

.AVIATION...
(18Z TAFS)
Issued at 232 PM EDT Thu May 9 2024

VFR conditions will prevail at the regional terminals through at
least 20Z. A Mesoscale Convective System (MCS) is expected to race
southeastward towards the terminals late this afternoon through
around sunset, bringing the potential for strong to severe
thunderstorms to SSI and the Duval County terminals after 21Z. We
have included TEMPO groups for wind gusts of 30-45 knots, along
with IFR visibilities and MVFR ceilings as this squall line
potentially moves across these terminals through 01Z. The
MCS/broken squall line will then weaken after 01Z, with confidence
too low to indicate anything other than vicinity thunderstorm
coverage at GNV and SGJ at this time. MVFR to IFR ceilings will
then overspread the regional terminals after 04Z through the early
morning hours on Friday. Another MCS is then expected to impact
our region after 12Z Friday, with this convective complex expected
to move rapidly eastward during the morning hours. We included
PROB30 groups from 13Z-18Z at each terminal for the potential of
20-40 knot wind gusts, along with MVFR to IFR conditions during
heavier downpours. Gusty southwesterly surface winds sustained
around 15 knots, with surface winds shifting to southerly at 10-15
knots at SGJ after 19Z due to a pinned Atlantic sea breeze
boundary near the coast. A period of breezy northerly surface
winds can be expected in the 00Z-04Z time frame in the wake of the
squall line/MCS passage. Otherwise, southwesterly winds of 5-10
knots will resume around or after 06Z Friday. Outside of
thunderstorm activity on Friday morning, west- southwesterly
surface winds will increase to 15-20 knots and gusty before 15Z.

&&

.MARINE...
Issued at 335 PM EDT Thu May 9 2024

A squall line of strong to severe thunderstorms will traverse the
Georgia waters during the mid to late afternoon hours today, with
this line reaching the northeast Florida waters during the late
afternoon and early evening hours. This squall line is expected to
weaken after sunset as it approaches the waters from St. Augustine
southward. Strong to severe thunderstorms will be capable of
producing damaging wind gusts, hail, and frequent lightning
strikes. Outside of thunderstorm activity, seas of 3-5 feet will
prevail both near shore and offshore through tonight. Otherwise,
a cold front will enter the southeastern states tonight and will
progress southeastward across our local waters on Friday afternoon
and evening.

Additional rounds of strong to severe thunderstorms will be
possible after sunrise and again during the afternoon hours ahead
of this front. Winds will shift to northwesterly in the wake of
the frontal passage on Friday night and Saturday morning, with
weak high pressure the expected to build eastward from the Ozarks
on Saturday night, reaching the coastal Carolina region by Monday
afternoon. This weather pattern will result in onshore wind
development on Sunday afternoon, with onshore winds then
strengthening on Monday night ahead of an approaching warm front.
Showers and thunderstorms will overspread our local waters by late
Monday night as this warm front lifts northeastward across our
area.

Rip Currents: Gusty offshore winds should result in a low risk at
all area beaches on Friday and Saturday.

&&

.FIRE WEATHER...
Issued at 335 PM EDT Thu May 9 2024

Low cloud cover is expected to overspread our region late tonight
through early Friday morning. Strong west-southwesterly surface
and transport winds on Friday will result in high daytime
dispersion values for north central FL, with good values expected
elsewhere across northeast FL despite abundant cloud cover and
increasing rain chances, with fair values forecast across
southeast GA. Rounds of strong to severe thunderstorms are
expected from the Interstate 10 corridor northward through the
early evening hours today, and then area-wide on Friday morning
and again on Friday afternoon. Strong to severe thunderstorms will
be capable of producing damaging wind gusts, hail, and frequent
lightning strikes. An isolated tornado cannot be ruled out during
the severe weather potential through early evening. A cooler and
drier air mass will then filter into our region during the
weekend, with minimum relative humidity values falling to around
30 percent at most inland locations during the afternoon hours on
Saturday and Sunday. Breezy northwesterly transport winds and
elevated mixing heights on Saturday could result in elevated
daytime dispersion values.

&&

.CLIMATE...
Issued at 1232 PM EDT Wed May 8 2024

Daily record Maximum Temperatures at the local climate sites for...

Thursday, May 9th...JAX 96/1962...CRG 93/2008...GNV 95/2011...AMG 95/1962

Friday, May 10th...JAX 94/2017...CRG 95/2003...GNV 95/2011...AMG 95/2011

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  71  83  60  81 /  60  70  10   0
SSI  73  84  64  80 /  80  70  20   0
JAX  73  87  64  84 /  80  80  30   0
SGJ  74  91  67  83 /  20  60  30  10
GNV  73  88  64  87 /  20  60  30  10
OCF  72  89  68  89 /  20  50  30  10

&&

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

$$