Severe Thunderstorm Warning 51, NWS Jacksonville, FL

Area Forecast Discussion
National Weather Service Jacksonville FL
1117 AM EST Wed Feb 15 2017

...Strong to Severe Thunderstorms Possible this Afternoon...
...Wind Advisory Expanded to Include Southeast Georgia...

.Update...
Late morning surface analysis depicts low pressure (1000
millibars) centered over the southern Appalachians, with a
trailing cold front extending southwestward across southwest
Georgia, the Florida panhandle and into the central Gulf of
Mexico. Aloft...the mid/upper low that was moving across the
Tennessee Valley overnight has been sheared apart by longwave
troughing that is quickly digging southeastward from the Great
Lakes states. The morning sounding at Jacksonville displayed a
strong veering wind profile in place over our region ahead of a
cold front and associated broken line of showers and embedded
thunderstorms that is advancing rapidly east-northeastward at
nearly 50 mph. Isolated showers were developing ahead of
the broken line over our region. Breaks in the low cloud field
earlier this morning have allowed stronger winds aloft (around 40
knots at 2000 feet) to mix down to the surface, with gusts in
excess of 40 mph being recently reported throughout inland
southeast Georgia. We have thus extended the wind advisory to
cover all of southeast Georgia in addition to northeast and north
central Florida. Temperatures as of 16Z were climbing into the
mid/upper 70s, with dewpoints generally in the 60-65 range.

Deep-layered moisture appears to be a limiting factor to a more
widespread severe weather event this afternoon given the
impressive dynamics in place over our region. The greatest
instability and helicity values reside over southeast Georgia per
recent LAPS analysis, where the Storm Prediction Center has placed
a slight risk for severe thunderstorm development this afternoon.
Damaging wind gusts and isolated tornadoes will be the primary
threats in southeast Georgia through mid-afternoon as the cold
front and associated broken convective line progress rapidly
eastward. Short term high resolution guidance such as the HRRR
suggests that few discrete supercells may develop ahead of the
front, mainly from Interstate 10 northward, with activity
progressing rapidly east- northeastward at 45-55 mph. Fewer breaks
in the stratocumulus over northeast and north central Florida are
resulting in more limited instability, and the Storm Prediction
Center indicates a marginal risk for severe thunderstorm
development in these areas through late afternoon. Highs region-
wide will climb to 75-80 before showers and thunderstorms arrive.
Strong southwest to westerly wind gusts up to 45 mph will
continue ahead of the cold front, which should progress offshore
of southeast Georgia towards sunset and the northeast FL coast
during the early evening hours.

&&

.Aviation...
Periods of MVFR ceilings of 2000-3000 feet will be possible
through around 18Z, mainly at the northeast Florida terminals.
Southwesterly to westerly surface winds will remain sustained in
the 20-25 knot range, with occasional gusts to 35-40 knots
possible through 22Z. Scattered to numerous showers and embedded
thunderstorms will impact the terminals this afternoon, mainly
from 17Z through 22Z. Brief periods of IFR visibilities and MVFR
ceilings will be possible as this activity impacts the terminals,
as heavier showers and thunderstorms will likely be moving
east-northeastward at 40-50 mph. Isolated severe thunderstorms
will be possible, with strong wind gusts being the primary threat.
VFR conditions will prevail after 22Z, with surface winds becoming
northwesterly at 10-20 knots during the early evening hours.

&&

.Marine...
Small Craft Advisory conditions are developing over our coastal
waters this morning, with occasional southwesterly wind gusts to
gale force expected offshore during the afternoon and early
evening hours. Seas offshore will build to 5-7 feet this
afternoon, with near shore seas of 3-5 feet expected. Showers and
thunderstorms will increase in coverage over the waters towards
mid-afternoon, and should depart to the east by the early evening
hours as a cold front quickly crosses eastward across the waters.
Winds will shift to a northwesterly direction early this evening,
with speeds falling back to caution levels in the near shore
waters towards midnight, and during the predawn hours in the
offshore waters. Seas offshore will remain in the caution range of
4-6 feet through Thursday night. High pressure will continue to
build into our region from the west on Thursday, settling directly
over our coastal waters on Friday.

Rip Currents: Low risk expected through Friday due to offshore
winds.

&&

.Fire Weather...
Strong southwest to westerly surface and transport winds will
create high dispersion values region-wide through this afternoon.
A much drier and cooler airmass will filter in late tonight into
Thursday behind the front as winds decrease and shift to the NW
with RH values diving below critical levels Thursday and Friday
afternoons. Red Flag conditions are not expected at this time as
winds are not expected to reach above 10 mph on Thurs or Fri.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  76  40  63  37 /  60   0   0   0
SSI  75  47  63  43 /  60   0   0   0
JAX  80  46  65  42 /  60  10   0   0
SGJ  79  49  65  46 /  60  20   0   0
GNV  77  46  66  40 /  60  10   0   0
OCF  78  49  67  41 /  50   0   0   0

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Wind Advisory until 6 PM EST this evening for Alachua-Baker-
     Bradford-Clay-Coastal Duval-Coastal Nassau-Columbia-Flagler-
     Gilchrist-Hamilton-Inland Duval-Inland Nassau-Marion-Putnam-
     St. Johns-Suwannee-Union.

GA...Wind Advisory until 6 PM EST this evening for Appling-Atkinson-
     Bacon-Brantley-Charlton-Clinch-Coastal Camden-Coastal Glynn-
     Coffee-Echols-Inland Camden-Inland Glynn-Jeff Davis-Pierce-
     Ware-Wayne.

AM...Small Craft Advisory until 4 AM EST Thursday 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 11 PM EST this evening 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.

&&

Nelson/Elsenheimer/Enyedi/Cordero/Shuler

Hazardous Weather Outlook...UPDATED
National Weather Service Jacksonville FL
1151 AM EST Wed Feb 15 2017

AMZ450-452-454-470-472-474-FLZ020>025-030>033-035>038-040-124-125-
GAZ132>136-149>154-162>166-161700-
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-
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-
Hamilton-Suwannee-Columbia-Baker-Inland Nassau-Inland Duval-Union-
Bradford-Clay-St. Johns-Gilchrist-Alachua-Putnam-Flagler-Marion-
Coastal Nassau-Coastal Duval-Coffee-Jeff Davis-Bacon-Appling-
Wayne-Atkinson-Ware-Pierce-Brantley-Inland Glynn-Coastal Glynn-
Echols-Clinch-Charlton-Inland Camden-Coastal Camden-
1151 AM EST Wed Feb 15 2017

...Slight Risk of Severe Thunderstorms this Afternoon in Southeast
Georgia...
...Wind Advisory through Late this Afternoon...
...Small Craft Advisory through Tonight...

This Hazardous Weather Outlook is for Northeast Florida,
Southeast Georgia and the Adjacent Coastal Waters.

.DAY ONE...This Afternoon and Tonight...

A strong cold front will move quickly eastward across our region
from late this afternoon through this evening. Scattered to
numerous showers and embedded thunderstorms will develop ahead of
the front, with strong to isolated severe thunderstorms possible.
The Storm Prediction Center has placed southeast Georgia within a
slight risk of severe thunderstorm development this afternoon,
with a marginal risk for northeast and north central Florida.
Damaging wind gusts will be the primary threat within any strong
to severe thunderstorms that develop, with this activity moving
rapidly east-northeastward at 45 to 55 mph. Isolated tornadoes
will also be possible within any severe thunderstorms that
develop. Activity will diminish late this afternoon as the cold
front pushes quickly eastward and offshore by the early evening
hours.

Strong southwest to westerly winds sustained at 20 to 30 mph will
continue through around sunset, with occasional gusts up to 45 mph
possible outside of stronger thunderstorm activity. A wind
advisory is in effect for all of southeast Georgia and northeast
Florida through 6 PM this evening.

A small craft advisory continues until late this evening for the
near shore waters and through the overnight hours offshore. Winds
will occasionally gust to near gale force in the offshore waters
through the early evening hours.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday...

Isolated thunderstorms are possible over northeast Florida on
Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotters are asked to self-activate this afternoon if severe
weather warnings are issued.

For additional information, visit the National Weather Service in
Jacksonville website on the internet at weather.gov/jax.

Nelson

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