Rather long, but a good write up from JAX ...
Area Forecast Discussion
National Weather Service Jacksonville FL
226 PM EDT Wed Apr 22 2020
...WARM AND BREEZY THU BEFORE WET WEATHER RETURNS WITH SEVERE
STORM POTENTIAL LATE THU AFTERNOON THROUGH FRI...
.NEAR TERM [Through Thu Tonight]...
Continued dry and
stable conditions this afternoon into the
evening with stacked high pressure over the region as surface high
pressure builds offshore of the SE Atlantic coast. Surface winds
will veer farther to the ESE into the evening with gusts near 15
mph trailing the east coast
sea breeze is it advanced inland. High
temperatures were topping our closer toward
climo values ranging
from the mid 70s along the Atlantic coast to the lower 80s inland
toward the I-75 corridor under
mostly clear skies with only
increasing high
cirrus clouds from the west. Tonight, mild low
temperature will trend above
climo with warmer SSE
flow developing
as a warm
front lifts north of the Altamaha River
basin after
midnight. A low chance of some spotty showers across SE GA zones
after midnight through sunrise Thu morning, but overall still dry
conditions with
boundary layer winds increasing through the night
and increasing mid and
high clouds to prevent significant
fog
formation.
Thu & Thu Night...Warm and breezy with warm air
advection ahead of
approaching storm system with SSW winds increasing to 15-20 mph by
midday and gusts up to 35 mph at times especially near bodies of
water. Although a stray shower may skirt near our NW GA zones
through 18z (2 pm Thu), most models have come into agreement with
dry low level air across the local area preventing rain chances
until later in the afternoon and evening focused across SE GA and
the Suwannee River Valley of inland NE FL where a pre-frontal line
of storms is expected into the early evening hours. The momentum
of this first round of severe weather potential is expected to
wane into the early evening as stronger forcing lifts NE with a
mid level short wave
trough, with a brief lull in severe weather
potential possible Thu night between 03-09z until yet another
short wave
trough deepens across the eastern GOMEX along the
actual surface cold
front. This second wave of severe storm
potential will
likely reignite storms lingering across SE GA
through sunrise Fri with intensification of storms ahead of yet a
newer pre-frontal line of storms moving across the FL panhandle
and toward the Suwannee River Valley of NE FL through 09z Fri
spreading eastward across the I-10 corridor of NE FL through 12z.
There remains a
tornado threat and
hail potential with this system
as it approaches SE GA late Thu afternoon into the evening where
higher
helicity (200 s2/m2+) will coincide with SSW 850
mb winds
increasing to 45-60
kts under bulk 0-6 km
shear of near 70
kts. In
addition, mid level lapse rates will cool to -8 to -10 deg/
c per
the
GFS, with this elevated
instability spreading southward across
NE FL through Fri morning. Stronger
wind GUST potential will edge
inland across NE FL and our SE GA zones Thu evening and overnight
through Friday as low level SW winds increase out of the GOMEX
nosing higher
dew pts inland across the Suwannee River Valley and
allowing better potential for stronger wind gusts to mix down
toward the surface along and ahead of the surface
front.
In addition to severe storm potential, there is a localized
flood
threat with the slow moving frontal zone edging southward across
our SE GA zones during the pre-
dawn hours Fri and gradually
beginning to stall over the FL peninsula. Unseasonably high
PWAT
of 1.6-2 inches under phased
upper level jet streams providing
deep layer
divergence will under uni-directional
flow will
certainly favor training cells and locally heavy
rainfall.
.SHORT TERM [Friday through Saturday Night]...
A secondary line of
convection with the pre- frontal
trof will
move south of U.S. 82 by the daylight hours Friday morning and
then south of I-10 by late morning into the early afternoon. There
is still some difference between the models but this solution is
starting to slowly converge to this solution. Friday morning into
the early afternoon there is plenty of unidirectional
southwesterly speed
shear and
CAPE of 2500-3000
J/kg. During
daylight morning hours into the afternoon believe the main mode
with be gusty thunderstorms winds associated with bowing segments
but other modes will present such as
isolated tornadoes,
hail and
pockets of heavy rain. By mid afternoon, the best
convection
should be confined to south of FL SR16. The remnants of the
frontal boundary is
likely to stall over SE GA or near the FL/GA
border on Friday afternoon, potentially leading to an another
round of showers and storms with a possibility of severe storm
conditions on Saturday as a secondary
front moves through the
region. Upper
trof axis swings
trough the region Saturday night
with
isolated chances of residual showers south of I-10.
Temperatures for the end of the week will be above the seasonal
average, with high temperatures reaching up into the upper 80s for
areas under the influence of a warm
front. Overnight low
temperatures will range withing the 60s.
.LONG TERM [Sunday Through Wednesday]...
The last remaining elements of
convection will disperse on Sunday
as high pressure and cool air builds in behind the frontal passage,
leading to lower temps, dry air, and clear skies for the
beginning of next week. Temperatures during this period are
expected to be just slightly below the seasonal average before
warming into the lower to mid 80s by Tuesday.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation is requested Thursday afternoon through Friday.
Spotters should safely
report significant weather conditions and/or
damage by calling the office or tweeting us @NWSJacksonville.