Scientific Forecaster Discussion
fxus62 kjax 160907
Area forecast discussion
National Weather Service Jacksonville Florida
407 am EST Mon Jan 16 2017
..Spring-like warmth continues this week...
early morning surface analysis depicts a backdoor cold front
approaching the Georgia coastal waters from the north. High
pressure (1031 millibars) resides along the mid-Atlantic coast in
the wake of this front. A quasi-stationary frontal boundary
extends from eastern Texas east-northeastward through the lower
Mississippi Valley to the Appalachians. Aloft...deep-layered
ridging is positioned over the Florida Peninsula and Cuba.
Meanwhile, a potent shortwave trough over the Texas and OK Panhandle
region was moving slowly north-northeastward. A cirrus shield was
being advecting eastward across our region on the northern
periphery of strong ridging centered to our south. A few patches
of stratocumulus clouds were also moving through our area.
A patch of showers associated with a persistent coastal trough is
moving slowly northwestward through the offshore Atlantic waters
adjacent to southeast Georgia. Cloudiness has limited the extent
of fog formation thus far, despite dewpoints rising well into the
50s inland and now around 60 in coastal northeast Florida. Inland
temperatures were generally in the 50s, with lower to mid 60s in
coastal locations as of 09z.
Near term (today through tuesday)...
the main forecast challenge will be potential fog and low stratus
development around sunrise as the back edge of the cirrus shield
exits our area from west to east. These clouds may not exit
eastern sections until after sunrise, so adjustments to areas
expected to have reduced visibilities may be forthcoming along the
Interstate 95 corridor. Otherwise, deep-layered ridging will
remain in control of our weather pattern during the next few days.
High pressure to the north of the backdoor cold front along the
mid-Atlantic coast will shift southeastward while weakening. The
backdoor front will stall over coastal South Carolina today and
will lift northward as a warm front on Tuesday. This weather
pattern will result in low level winds veering during the next few
days, with light southeasterly winds expected today becoming
southerly by Tuesday. A relatively weak local pressure gradient
will allow a sea breeze to develop over coastal locations early
this afternoon, which will keep highs for locations east of
Interstate 95 in the 70-75 range, except upper 60s for the
southeast Georgia beaches due to chilly shelf waters. Inland highs
will climb to 75-80, which is around 15 degrees above mid-January
climo. Daily record highs are in the 80s today at all four of our
climate sites, so those will not be threatened.
Sea fog may become the main forecast challenge tonight in coastal
locations as dewpoints nudge up to near 60 degrees. Another area
of high cirrus is expected to advect into our region overnight,
which could temper fog formation at inland locations. Sref fog
probabilities are highest over southeast Georgia and coastal
northeast Florida, but confidence remains low enough and we will
continue to indicate gradually deteriorating visibilities
overnight through sunrise on Tuesday for all locations. Well above
normal temperatures will continue, with inland lows generally in
the mid 50s, ranging to near 60 in coastal locations. These values
are again nearly 15 degrees above mid-January climo.
Sea fog may linger throughout the morning hours in coastal
locations on Tuesday. Otherwise, we expect fog to dissipate by the
mid-morning hours inland, with a light southerly flow boosting
highs to near 80 for most inland locations. This will approach
the daily record for Jan. 17 at Alma (79 degrees, set in 1949).
Seasonably cool shelf waters and an afternoon sea breeze will keep
coastal highs generally in the low to mid 70s.
Short term (tuesday night through Thursday night)...
Tue night...ridging begins to break down and shift south-southeast of the
local area as a sheared out frontal system draped across the mid-
Atlantic region edges southward. High cirrus clouds will filter
across southeast GA Tue night while a low level west-southwest out of the Gulf of
Mexico favors an increase in low stratus clouds across NE Florida.
Mild temperatures will range in the 50s. Fog development likely
especially across NE Florida where low stratus is expected to
advect under low level subsidence.
Wed & Wed night...cloud cover invades from the north through the
day with a low chance (< 20%) of an afternoon or early evening
shower across southeast Georgia ahead of a weakening and diffuse low level
frontal zone. Mid and upper level ridge will restrengthen over the
area Wed night and combined with low level moisture pooling late
night fog will be possible once again. Mild above normal
temperatures will continue with highs in the 70s Wed and lows in
the 50s Wed night.
Thu & Thu night...diffuse low level trough axis slides south-southeast of the
region with a weak high pressure ridge across the Carolinas
dominating the local weather Thu under mid/upper level ridging.
Mostly dry conditions expected with above normal warmth under
southerly flow as highs warm into the 70s. Thu night the diffuse
front lifts back northward across the forecast area ahead of a
weakening short wave trough lifting northward across the MS/Ohio
River valleys. A low chance of showers in the 20-40% range was
advertised generally along and north of the I-10 corridor where
the warm front will lift and positive vorticity advection from a sheared out mid/upper
level trough will coincide. Mild overnight low temps in the 50s
Long term (friday through monday) ...
a progressive pattern as a long wave trough slowly carves out
across the central US through the weekend which will Orient a
moist and unsettled SW flow across the local area Fri-sun which
will continue above normal warm temperatures and waves of
rainfall. Extended models were in good agreement with the long
wave trough pushing east with a warm front lifting across the area
Sat then a pre-frontal squall line pushing across the area sun
through Sun night ahead of a strong surface cold front. Indicated
a chance of thunderstorms during this time frame. Based on GFS
dynamics and instability there will be a chance of rotating storms
Sat along and ahead of the warm front...then a chance of strong
wind gusts in storms sun into Sun night as low level 850 mb jet of
near 50 kts out of the Gulf advect higher low level instability
and moisture over the forecast area ahead of the cold front ahead
of a digging upper level trough axis. Precipitation expected to
push downstream of the area early Monday trailed by a cooler and
drier airmass early next week with temperatures returning to near
sub-IFR visibilities will be possible through 13z at gnv. We
expect fog and possibly low stratus ceilings to develop at the
remainder of the terminals in the 11z-13z time frame as high
cloudiness departs our region around sunrise. Confidence remains
low for the terminals other than gnv, so significant adjustments
to the 12z tafs are possible. VFR conditions will prevail after
14z at the regional terminals. Sub-IFR conditions are possible
region-wide tonight after 06z, but confidence remains low due to
high clouds that may temper dense fog formation.
an easterly ocean swell will keep seas offshore slightly elevated
in the 3-4 foot range today. Otherwise, high pressure along the
mid-Atlantic coast this morning will shift southeastward into the
Atlantic waters while weakening during the next few days. Sea fog
development is possible over the near shore waters this morning,
especially from Mayport northward through the waters adjacent to
southeast Georgia. Sea fog may linger in these areas through this
afternoon, and may expand southward throughout the near shore
waters adjacent to northeast Florida tonight. Meanwhile, a cold
front will enter the southeastern states on Tuesday and will stall
just to the north of the southeast Georgia waters by late
Wednesday. Offshore winds are expected from Tuesday night through
early Thursday. Another cold front will approach our region from
the west on Friday, with offshore winds resuming and potentially
strengthening. Winds and seas will remain below caution criteria
Rip currents: a long period easterly ocean swell will keep a
moderate risk in place at area beaches today. The easterly swell
will begin to fade on Tuesday, but a lingering moderate risk is
anticipated at the northeast Florida beaches.
Preliminary point temps/pops...
amg 76 53 78 56 / 0 0 0 0
ssi 69 58 72 56 / 0 10 10 0
jax 78 55 80 56 / 0 0 0 0
sgj 75 60 77 57 / 0 0 0 0
gnv 80 53 80 54 / 10 0 0 0
ocf 79 55 81 56 / 0 0 0 0