Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 210840

Area Forecast Discussion
National Weather Service Jacksonville FL
340 AM EST Sat Jan 21 2017

...Multiple Rounds of Severe Storms Expected This afternoon, Tonight
and Sunday...

.NEAR TERM...Today and tonight...Multiples waves of strong to severe
storms will move into the area starting today. Storms will affect
mainly the Suwannee Valley and se Ga this afternoon...and again late
tonight. Shear and instability will increase bringing the
possibility of damaging winds...large hail...and isolated tornadoes.
Capes will increase to around 1000 J/kg with 0-3km Helicity
exceeding 250 m2/s2 this afternoon and tonight. Locally heavy
rainfall will also occur. Warm and humid conditions will continue
with well above normal temperatures continuing.

.SHORT TERM...Sunday through Monday Night...

Sunday...Second round of severe storms mainly impacting SE GA is
expected to lift northward early in the morning, while next squall
line develops across the FL panhandle/GOMEX in response to strong
850mb LLJ of 50-60 knots below strong upper level jet exceeding 100
knots. This squall line will push from the NE GOMEX and across all
of NE FL/SE GA during the afternoon hours with numerous severe
storms as multiple bow echo line segments are expected with damaging
winds of 60 to 80 mph the main threat, although isolated tornadoes
and large hail will still be possible. Most models are in good
agreement with this timing except for the NAM solution which remains
slower with convection lingering into the evening hours with the
cold frontal passage. Still think much of the convection will race
offshore around sunset. Strong SW winds will develop ahead of the
squall line with gradient flow of 15-25G35 mph expected and may need
Wind Advisories to handle this, but will likely be overshadowed by
the squall line itself. Max Temps in the warm SW Flow should still
push well into the 70s/near 80 despite the abundant cloud cover.

Sunday Night...Evening convection will end after sunset leaving just
a few isolated showers with frontal passage as winds shift to the
West and remain windy through the night with pressure rises keeping
them in the 15-25G35 mph range at times. Partial clearing is
expected along with slowly falling temps into the 50s by morning.

Monday...Overall expect Windy conditions in the wraparound flow
behind departing low pressure system. While partly to mostly cloudy
skies are expected...not much moisture to trigger measurable
rainfall but a few sprinkles possible mainly across SE GA. Max Temps
only expected to bump back upwards in the 60s. West winds at 15-
25G35 mph will continue and may be close to wind advisory of 40 mph
gusts at times.

Monday Night...Skies becoming mostly clear as high pressure builds
in from the West and W/NW winds decrease to around 10 mph by morning
and will allow for min temps to fall into the 40s.

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

Tue/Wed...High pressure builds across the region from the west on
Tue and into the Atlc on Wed. This will provide mostly sunny and dry
conds with near climo temps on Tue, then pushing back to above
normal levels on Wed in the lower to middle 70s for Highs.

Thu...Long-range models in decent agreement for cold frontal
passage with scattered showers with highs near 70 degrees.

Friday...Much Colder and Drier airmass pushes into the region with
highs below normal from the mid 50s to lower 60s, then falling into
the 30s for Friday Night, but way too early to determine if any
frost/freeze headlines would be necessary for next weekend.


.AVIATION...Low clouds are advecting eastward from GNV into the
Jacksonville TAF sites. Expect low clouds to reach SSI and SGJ
around 09-11z. IFR/LIFR conditions expected to persist until 15z
with VFR conditions thereafter. VCTS at SSI after 18z and over ne
Fl after 20z.


.MARINE...South winds will increase today and tonight ahead of
approaching storm system. Advisory conditions expected to develop
offshore late tonight as sustained SSW winds reach 20 knots.
Strong to severe storms expected over the waters on Sunday
preceding the cold front. Advisory conditions should develop for
near shore zones by Sunday evening. Gale force gusts offshore will
be likely behind frontal passage Sunday night into Tuesday morning
as surface low deepens to the north and pressure gradient
tightens. Conditions will improve to below headline criteria
Tuesday night and Wednesday.

Rip Currents: Low risk today and Moderate risk Sunday as winds
and seas increase.


AMG  76  63  78  52 /  70  90  90  30
SSI  71  63  74  55 /  60  80  90  50
JAX  78  64  79  54 /  60  70  90  50
SGJ  79  64  79  56 /  40  50  80  70
GNV  80  64  78  53 /  50  70  90  50
OCF  82  64  80  56 /  30  50  90  50


AM...Small Craft Advisory from 4 AM Sunday to 10 AM EST 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.



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