Severe Thunderstorm Warning 46, NWS Jacksonville, FL

Area Forecast Discussion
National Weather Service Jacksonville FL
744 AM EDT Mon Apr 13 2020

...TORNADO WATCH IN EFFECT FOR SOUTHEAST GA AND ALONG THE I-10
CORRIDOR OF NORTHEAST FL THROUGH 11 AM TODAY...

.AVIATION...
[Through 12Z Tuesday]

SSW winds of about 12-22 kt expected through the early morning
hours with a few gusts of 27-30 knots. Winds expected to shift to
the southwest by around 14Z-15Z at near 14-24 kt and gusty, with
winds becoming 5-10 kt after 23Z tonight. Early this morning,
mostly MVFR-VFR cigs for terminals until about 13-16Z. Squall
line is from roughly Jesup, GA to about Moody AFB at 1130z. This
line move to the southeast this morning. Quickly deteriorating
conditions as the squall line is likely to reach KSSI between 13Z-
15Z and then weaken slightly as it reaches the Duval County TAF
sites between 15Z-16Z. A threat of showers and storms moving into
the GNV and SGJ TAF sites by 20Z-22Z as well. More improved cigs
by and after 20z and through the evening with VFR conditions
outside of the any scattered aftn convection. Looks as though
a slight lull in convective activity from about 20z through the
early evening but will carry at least vicinity shower/storms
through the end of the period. CIGS deteriorate again after 03z-
06z time-frame as same cold front becomes stationary with MVFR
cigs and then IFR conditions developing south of this feature
from 06z-12z.

&&

.PREV DISCUSSION [403 AM EDT]...

.NEAR TERM [Through Tonight]...

Early radar analysis shows a complex line of of numerous to widespread
showers and storms located from the srn Appalachians swd to the
wrn central FL panhandle. Model guidance shows strong kinematics
occurring in tandem with the approaching squall line with 850 mb
winds of 50-60 kt over southeast GA and the Suwannee Valley and a
strong 250 mb jet of 145 kt over s central AL and GA. Effective
helicity values of a solid 400 m2/s2 are progged by the RAP by 09z
this morning over nrn parts of our area.

Before sunrise, we expect the squall line to move into northwest
zones accompanied by a risk of damaging winds and isolated
embedded tornadoes and a tornado watch is now in effect. This
line should stay intact for several hours, producing scattered to
numerous severe weather reports as it moves fairly quickly to the
east. Timing from guidance has the line moving into coastal
southeast GA and Suwannee Valley by about 9-10 AM and then
possibly becoming a less defined by noon-early afternoon as main
dynamics associated with a shortwave trough at 500 mb shifts
north-northeast of the area. In fact, the front is shown to stall
near the state line, with storms running out ahead of it toward
Orange Springs and St Augustine but possibly weakened as low level
convergence becomes more muted. Nonetheless, a corridor of
instability, characterized by SBCAPEs 1500-2500 J/kg is expected
generally around I-10 and to the south, with a chance of storms
expected this aftn, so some severe threat is still anticipated,
even if the squall line looses is punch. If a few storms are able
to get going in the aftn again, steep lapse rates aloft and about
45-50 kt of shear will be capable of producing severe hail and
damaging wind gusts.

Tonight...the stalled frontal boundary is expected to be located
in the vicinity of the FL/GA state line southwest to over the
Apalachee Bay and into the GOMEX. A good chance for showers and
thunderstorms will continue along this feature through tonight;
however, the main forcing for convection won't be realized until
after midnight and into the predawn hours. Given increased
convergence along the front, we have likely chances 60-70 percent
toward the early morning from JAX metro area to Gainesville and
Trenton. With high moisture content and weak to moderate
instability, there is a threat of locally moderate to heavy
rainfall, which could lead to localized areas of flooding in low
lying and urban areas. We can't rule out an isolated strong to
severe storm tonight as well given adequate shear and mid level
disturbances moving northeastward over the area after midnight.

.SHORT TERM [Tuesday Through Wednesday]...

An unsettled weather pattern will continue to bring rain showers and
storms through Tuesday and Wednesday. The cold front will be nearly
stationary over NE FL on Tuesday and oriented west southwest to east
north east from the Suwannee Valley into coastal Southeast Georgia.
Some disturbances will be traversing the area in the west southwest
flow helping to generate likely showers and thunderstorms. The storm
prediction center has SE GA and NE FL in a Marginal risk for severe
weather and some isolated severe storms could form as the environment
over our region will have 1,500-2000 J/kg of MLCAPE and 40-50
knots of 0-6Km Bulk Shear. These conditions could support some
strong to severe wind gusts 40-60 mph and hail up to 1 inch in
diameter.

A second cold front will approach the southeast states Tuesday night
into Wednesday while a new wave of low pressure helps lift the old
frontal boundary northward into SE GA. With well above normal moisture
levels in place, the wave of low pressure will help to generate
additional rounds of rainfall and a chance of thunderstorms. An
isolated strong storm is possible over NE FL where more
instability will reside coupled with 0-6Km Bulk shear values near
50 knots. Potentially heavy rainfall is possible as showers and
storms could repeat over the same locations as the low and
midlevel flow remains unidirectional from the west southwest as
the front moves pushes back through the area.

High pressure behind the second cold front will push it southeast
into our area and should help kick the wave of low pressure
northeast and offshore into the Atlantic waters Wednesday night
with drier conditions behind the second front's passage overnight
into early Thursday.

Temperatures will be above normal values Tuesday with highs in
the 80s and lows in the mid to upper 60s. Temperatures will be
near normal Wednesday with highs in the upper 70s to low 80s and
lows in the mid to upper 80s over north central Florida.

.LONG TERM [Thursday Through Monday]...

On Thursday, surface high pressure to the north of the area will
push the cold front into central Florida by morning. The the high
will move to our northeast allowing the cold front to possibly
stall over central Florida. at the same time, high pressure moving
off the Atlantic coast will allow northerly winds behind the
front to quickly veer to the northeast and east. This will create
a long fetch onshore flow and allow a weak inverted trough to form
over the NE FL waters keeping a chance of rain showers in the
forecast along the coastal counties and locations east of Highway
301.

Friday and Saturday, the frontal boundary to the south of the
area will attempt to move back northward as a surface low develops
to the west of the region near the Mississippi Valley with a cold
front on its heels moving towards the southeast. As the boundary
lifts northward, additional rain chance are possible with greater
shortwave energy moving into the region on Saturday as the cold
front moves in from the northwest. Currently, the model
differences depict the enhanced lift and greater rain shower
chances beginning late Friday and again into the day Saturday with
the ECMWF delivering rain chances a bit later towards midday
Saturday. However, both models show greater chances and coverage
of showers over Central Florida.

High pressure will push the cold front into Central Florida late
Saturday into early Sunday with a lull in shower chances early in
the day before the high moves quickly northeast while a new low
pressure system develops along the Gulf coast and aids in lifting
the frontal boundary northward again as it approaches the region
from the west allowing rain chances to increase towards the
afternoon and evening hours.

Temperatures will be below normal Thursday and near normal
Friday through Sunday as unsettled weather continues over the
region.

.MARINE...

Strong southerly winds continue early this morning with SCA and
Gale warnings in effect for area waters. After sunrise,
anticipate a squall line pushing in from the west with showers
and thunderstorms moving across the area waters later this
morning. A tornado watch in effect for portions of area waters
until 11 AM. Winds relax a bit for this afternoon-evening but
elevated seas and gusty southwesterly winds are still expected.
The front will stall over the area waters on Tuesday with
additional rain and thunderstorms possible. A wave of low pressure
will develop and ride northeast along the frontal boundary
Tuesday- Wednesday bringing another round of showers and a chance
of thunderstorms. A coastal trof will set up Thursday and Friday
for isolated to widely scattered showers and breezy east-northeast
flow.

Rip currents: Rough surf and a moderate risk of rip currents and
today.

.HYDROLOGY...

Locally heavy rainfall will accompany the line of showers and
storms today, with additional rainfall expected late tonight and
into Tuesday and Wednesday. A marginal risk of excessive rainfall
anticipated from Tuesday into Wednesday, with possible localized
flooding concerns developing by midweek. Estimated rainfall
amounts through Wednesday night are in the 2-4 inch range...with
the highest totals generally north of a line from Gainesville to
St Augustine. No river flooding issues expected at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  85  60  84  62  73 /  80  20  40  50  60
SSI  82  66  79  66  75 /  80  30  70  50  70
JAX  87  67  83  68  80 /  80  60  90  40  80
SGJ  89  68  82  68  83 /  40  70  80  20  70
GNV  86  67  85  67  82 /  60  70  90  30  80
OCF  89  69  88  68  85 /  40  30  30  10  50

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through this evening for Coastal Duval-
     Coastal Flagler-Coastal Nassau-Coastal St. Johns.

GA...High Rip Current Risk through this evening for Coastal Camden-
     Coastal Glynn.

AM...Small Craft Advisory from 11 AM this morning to 5 PM EDT this
     afternoon 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.

     Gale Warning until 11 AM EDT this morning 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 AM EDT this morning 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.

&&

PRELIMINARY LOCAL STORM REPORT
National Weather Service Jacksonville FL
651 AM EDT MON APR 13 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0640 AM     TSTM WND GST     DOUGLAS                 31.51N 82.85W
04/13/2020  M55 MPH          COFFEE             GA   ASOS

            DOUGLASS MUNICIPAL AIRPORT REPORTED A THUNDERSTORM WIND
            GUST OF 55 MPH AT 640 AM ET.

&&

SCORDERO

PRELIMINARY LOCAL STORM REPORT
National Weather Service Jacksonville FL
702 AM EDT MON APR 13 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0654 AM     TSTM WND GST     ALMA                    31.54N 82.48W
04/13/2020  M49 MPH          BACON              GA   ASOS

            ALMA ASOS MEASURED A PEAK GUST TO 49 MPH.

&&

PRELIMINARY LOCAL STORM REPORT
National Weather Service Jacksonville FL
704 AM EDT MON APR 13 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0632 AM     TSTM WND DMG     2 E DOUGLAS             31.51N 82.82W
04/13/2020                   Coffee             GA   EMERGENCY MNGR

            TREES AND POWER LINES DOWN ACROSS COFFEE COUNTY. ROOF ON
            HOME COLLAPSED ON SLEEPY HALLOW FARM ROAD.

&&

SCORDERO

PRELIMINARY LOCAL STORM REPORT
National Weather Service Jacksonville FL
725 AM EDT MON APR 13 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0624 AM     TSTM WND DMG     5 WNW DOUGLAS           31.54N 82.93W
04/13/2020                   Coffee             GA   EMERGENCY MNGR

            EMERGENCY MANAGER REPORTS WIND DAMAGE TO A VACATE MOBILE
            HOME NEAR CHANEY ROAD AND HIGHWAY 32. TIME ESTIMATED
            BASED ON RADAR.

&&

RBRICKER

PRELIMINARY LOCAL STORM REPORT
National Weather Service Jacksonville FL
745 AM EDT MON APR 13 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0725 AM     TSTM WND DMG     ODUM                    31.67N 82.03W
04/13/2020                   WAYNE              GA   LAW ENFORCEMENT

            WAYNE COUNTY SHERIFFS OFFICE REPORTS MULTIPLE HOUSES
            DAMAGED IN THE VICINITY OF ODUM.

&&

NELSON

PRELIMINARY LOCAL STORM REPORT
National Weather Service Jacksonville FL
754 AM EDT MON APR 13 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0738 AM     TSTM WND GST     JESUP                   31.60N 81.89W
04/13/2020  M41.00 MPH       Wayne              GA   AWOS

            JESUP GEORGIA AWOS STATION KJES MEASURED A GUST TO 41
            MPH.

&&