Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jacksonville Florida
938 am EDT Wednesday Jul 29 2015
13z objective analysis (rap/laps) indicates a weak and subtle
surface trough near the western boundary of our forecast area...or
roughly in the Interstate-75 corridor. Coincident with this trough
is a pool of higher surface dewpoints and some light confluence of
the low-level flow. Therefore...this is expected to be a favored
zone for convective initiation in the 16-19z timeframe...and that
scenario is largely supported by the suite of available convection
allowing model guidance (hi-res wrfs and hrrr). Although the
majority of this convective development may occur to the west of
our area...some may bleed over into our south-central Georgia
counties and the I-75 corridor in our Florida counties. However,
the most active convective time period today may actually be after
21z and before 03z...as the Atlantic sea breeze progresses west
and some collisions with existing outflow boundaries may occur.
This scenario is also well depicted by the convection allowing
model guidance. Therefore...likely probability of precipitation (60%) were added west of a
line from Waycross to Macclenny to Juniper Springs generally
between 21z and 03z. Northeast low-level flow should keep the
coastal areas and near-coastal areas slightly cooler today (upper
80s to around 90)...with middle 90s highs possible over interior
sections of the forecast area. Some heat index readings in south
central Georgia may approach heat advisory criteria (109f) but
given the possibility of earlier convective initiation in those
areas...we will not issue an advisory at this time.
The 12z soundings from both Jacksonville and Tallahassee indicate
a very moist troposphere...with precipitable water around 2 inches
and freezing levels over 16000 feet above ground level. This is likely to support
some efficient rain processes today...so locally heavy rainfall
will be possible...particularly in the aforementioned interior
areas where storms are more likely. Frequent lightning and gusty
winds are also possible with the stronger storms.
VFR conditions will generally prevail today. Some scattered
showers may affect the coastal and near coastal terminals (jax,
ssi, crg, vqq, sgj) from late this morning into the afternoon and
vcsh were included in those tafs. Further inland...showers and
even thunderstorms may be more numerous in vicinity of gnv. Any of the
showers or storms today could briefly reduce visibilities to IFR
levels and produce gusty winds.
the surface low near the eastern boundary of the coastal waters
may produce some locally gusty winds or higher seas. Otherwise no
changes to the previous discussion at this time.
Weak surface low over the waters will result in light
winds and seas. Low and trough will shift to the north of the
waters the next few days with winds increasing from the south
through the weekend.
Rip currents: low risk today and Thursday.
Preliminary point temps/pops...
amg 95 73 95 74 / 60 60 30 20
ssi 88 74 87 75 / 20 20 30 20
jax 92 74 92 74 / 40 30 40 20
sgj 88 73 88 74 / 40 30 40 30
gnv 91 72 88 72 / 60 60 60 40
ocf 91 73 87 73 / 60 60 60 40