Scientific Forecaster Discussion
fxus62 ktbw 180804
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
304 am EST Sat Nov 18 2017
Short term (today - sunday)...
a mid level ridge over the Gulf of Mexico and Florida
Peninsula today will get pushed southeast tonight and Sunday
as a strong trough swings east through the eastern Continental U.S..
the surface ridge is currently positioned northeast of
Florida, setting up light easterly low level flow. This
surface ridge will drift south across the state today as a
cold front associated with the mid level trough approaches
from the northwest. Under this ridging, rain free
conditions with mostly clear skies will continue today and
tonight, with temperatures continuing to moderate and
running near to a few degrees above normal.
On Sunday, the cold front will quickly move southeast across
the area. Limited moisture will be sufficient to allow for
chances of showers and thunderstorms moving north to south
through the area, with the highest chances farthest to the
north. High temperatures will be cooler behind the front on
Sunday north of Interstate 4, but the front will generally
arrive too late to limit high temperatures to the south.
Long term (sunday night - friday)...
a cold front will be exiting to the south of the forecast
area Sunday night. In the wake of the front much cooler
and drier air will advect into the region on a breezy
northerly wind flow as surface high pressure builds in
across the southeastern U.S. And northern Gulf with very
pleasant dry weather expected through Monday night as the
high slides east toward the mid Atlantic coast.
On Tuesday the surface high along the mid Atlantic coast
will slide east into the Atlantic during the day as a
short wave energy slides eastward across the area. The cold
front which had moved south of the region Sunday night will
lift back to the north as a warm front during the day.
Increasing lift along the northward moving warm front
combined with increasing low level moisture within the
return east-southeast wind flow around the departing surface
high and the short wave energy aloft will support scattered
showers (pops in the 40 to 50 percent range) developing
across the region during the day along with moderating
temperatures and increasing humidity levels.
During Tuesday night into Wednesday models show another and
more vigorous positively tilted short wave trough and
possible closed low moving from the Southern Plains across
the lower Mississippi Valley and into the west central Gulf
of Mexico. The European model (ecmwf)/GFS and Canadian models continue to
struggle with the evolution and timing of this system, with
the GFS now the most aggressive, intense, and fastest in
moving this system eastward while the Euro and Canadian are
slower and more open with the upper trough vs closing off a
closed low as depicted by the GFS. Despite these differences
though the models do agree that the short wave trough and
or closed low will deepen over the west central Gulf during
Wednesday night into Thursday with surface cyclogenesis
likely occurring somewhere over the eastern Gulf during
Wednesday night or early Thursday morning, with this low
then intensifying some as it moves east northeast toward and
across the region during Thursday night and Friday via a
blend of the model solutions, although exact location and
movement of the surface low is still uncertain at this time,
thus confidence in anyone solution remains low at this
Regardless of which solution pans out increasing moisture
within a deep layered southwest wind flow ahead of the
above mentioned features combined with increasing large
scale lift and upper level divergence should support
increasing rain chances (pops 50 to 70 percent) across the
forecast area Wednesday night through Thanksgiving day and
continuing into Friday as this storm system affects the
Below normal temperatures with chilly readings in the lower
to mid 40s from the I-4 Corridor North into the Nature
Coast, upper 40s to lower 50s central interior, and mid to
upper 50s south early Monday morning will quickly moderate
back to slightly above normal on Tuesday and Wednesday as
the flow become east southeast. Temperatures should then
fall back to near or slightly below normal during Thursday
and Friday as rain chances increase across the area.
patchy fog will continue to be possible through just after
sunrise, most likely around klal and kpgd, with MVFR or IFR
conditions possible. Otherwise, VFR conditions will hold
through the next 24 hours, with mostly clear skies.
high pressure will gradually settle south across the waters
today and tonight, with light and variable winds
continuing. A cold front will move southeast through the
coastal waters on Sunday, with winds increasing and becoming
northerly before turning to northeasterly Sunday night.
Cautionary, or low end advisory level winds will be possible
Sunday and Sunday night. High pressure will then fill in
north of the area Monday and Tuesday, with east winds around
15 knots or less.
some patchy fog will be possible early this morning.
Otherwise, no fire weather concerns expected through the
Preliminary point temps/pops...
tpa 78 66 77 52 / 0 10 40 10
fmy 80 63 80 59 / 0 0 20 10
gif 80 60 78 50 / 0 0 40 10
srq 76 64 76 54 / 0 10 40 10
bkv 79 60 76 46 / 0 10 40 0
spg 78 66 76 55 / 0 10 40 10