Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 182020

Area Forecast Discussion
National Weather Service Jacksonville FL
320 PM EST Wed Jan 18 2017


A weak frontal boundary will slide Southeast across Southeast
Georgia Tonight, and become nearly stationary through Thursday.
Weak ridging will be South of this boundary. A Southwest flow from
the gulf is expected to result in low stratus and fog advecting
Northeast across the forecast area Tonight. Anticipate this fog
and stratus to eventually overspread the region, with low
visibilities developing. A dense fog advisory may need to be
issued Tonight for much, if not all, of the forecast area. With
winds along the coast becoming North/Northeast Thursday morning
the fog could linger through much of Thursday morning there. A
partly to mostly cloudy day is expected for Thursday, with
temperature remaining above normal.

.SHORT TERM /Thursday Night through Friday Night/...

The period begins with an upper ridge across the eastern conus,
and an upper low over the middle of the country. The upper low
over the middle of the country will lift northward as it gets
blocked, and will then shear out as it tries to go over the top of
the ridge. A shortwave is forecast to move across the region late
Thursday night, and scattered showers are possible after midnight
through daybreak Friday for the Suwannee Valley and southeast
Georgia. Another shortwave will dig across the intermountain west
and move into the southern Plains on Friday. Deep southwesterly
flow is forecast, and isolated to widely scattered showers are
possible across the Suwannee Valley and western portion of
southeast Georgia Friday afternoon. Well above normal temperatures
will continue, with highs in the upper 70s to lower 80s and lows
in the mid 50s to lower 60s.

.LONG TERM /Saturday through Tuesday/...

Overview: A very complicated setup is forecast for the extended
period as multiple areas of low pressure develop. The upper ridge
over the eastern seaboard will shift east on Saturday and several
upper lows will be across the middle of the country by Sunday
morning. The southern stream upper low will move across the
ArkLaTex region Sunday morning, with a shortwave out ahead of it
pushing through northern Georgia. Surface low pressure is forecast
to develop across the southern Appalachians, with the main low
over Arkansas, and a prefrontal trough is now forecast to push
into northeast Florida by Sunday morning. Severe weather is
possible Saturday night through Sunday evening. Locally heavy
rainfall is also possible. Another area of low pressure may
develop across central Georgia Sunday afternoon in the right front
quadrant of the upper level energy, with the three areas of low
pressure forming into a large gyre across the southeast by Sunday
night. The system will shift east of the system on Monday, and a
cold front will push through the region. Wrap around showers will
continue through the day on Monday. Cooler and drier conditions
are then forecast on Tuesday.

Saturday and Saturday night: A warm front will lift northward
into central Georgia on Saturday and stall. A wave will move
across the region on Saturday, and a prefrontal trough will move
into the region late in the day. Scattered showers and storms are
possible across southeast Georgia and western northeast Florida in
the afternoon, and then spread east through the evening and
overnight hours. Mid level lapse rates will increase to near 7.0
C/km as 500mb temperatures cool to near -14C by Saturday evening.
0-6km shear will increase to 40-50 knots by Saturday evening, and
then around 60 knots by Sunday morning. 0-1km SRH is forecast to
increase to over 300 m2/2. So, there will be a significant threat
of severe weather, including large hail and tornadoes Saturday

Sunday and Sunday night: Models are in good agreement with this
event, but they are now 18-30 hours faster than this time
yesterday. Significant severe weather may be ongoing Sunday
morning across the region, with significant tornadoes, very large
hail and extremely damaging winds possible. Another round of
severe weather is possible area-wide Sunday afternoon as an area
of low pressure develops across the panhandle of Florida or
southern Georgia along the cold front. Locally heavy rainfall is
also possible as storms train across the same region. The severe
threat is then forecast to end from northwest to southeast Sunday
evening as the cold front pushes through the region. Scattered
showers are expected after midnight.

Monday and Tuesday: Light showers are possible through the day on
Monday as moisture wraps around the system. Cooler temperatures
are forecast, with highs in the 60s Monday and Tuesday. Drier air
will move into the region Monday night and sunny skies are
forecast on Tuesday. Overnight lows will be cooler in the mid 40s
to lower 50s.


Low level moisture is expected to result in fog and low stratus
development Tonight. IFR and lower conditions are expected during
the Overnight into Thursday morning. The fog will then be fairly
slow to lift Thursday morning. Expecting the fog/stratus to linger
longest over Eastern terminals due to a North/Northeast flow
developing along the coast.


A cold front will slide South across area waters Tonight and
stall. Weak high pressure will build back in from the South
Thursday. A frontal boundary will be just North of area waters
then through Saturday. A strong cold front will sweep East across
the region Sunday.


AMG  57  75  59  80 /  10  10  40  40
SSI  59  72  59  74 /   0   0  20  20
JAX  57  76  58  79 /  10   0  20  10
SGJ  58  74  58  77 /   0   0  10  10
GNV  54  77  57  80 /   0  10  20  10
OCF  55  78  58  80 /   0   0  10  10




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