Scientific Forecaster Discussion
fxus62 ktbw 181832
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
232 PM EDT Fri Aug 18 2017
..a few strong storms possible this afternoon...
Short term (tonight - saturday)...
a large upper level low located offshore the northern Cuba
coast with a trough axis extending north-northeast into
the Florida Peninsula this afternoon will continue to move
slowly to the west northwest and into the Gulf of Mexico
tonight through Saturday. Cooler and drier mid level air
wrapping into the region around the upper level low combined
with steep lapse rates will favor some robust convection
across the forecast area the remainder of the afternoon with
some strong storms possible with strong downburst winds,
frequent lightning, and small hail possible. Slow and
erratic storm motion will also favor some locally heavy
rainfall amounts in some locations.
Tonight the showers and storms will gradually wind down by
mid evening as boundary interactions weaken and loss of
daytime heating occurs with convective debris cloudiness
thinning out with skies becoming partly cloudy overnight. It
will be a warm and muggy night with overnight low
temperatures in the mid 70s inland areas, and upper 70s to
around 80 along the coast.
On Saturday the upper level low will continue to move to
west-northwest across the south-central Gulf as surface
high pressure persists from the Atlantic across the Central
Peninsula and into the eastern Gulf. Drier mid level air
associated with the upper low will suppress rain chances
with only isolated to low end scattered (pops in the 20 to
30 percent range) shower and storm coverage expected along
the sea breeze circulations during the afternoon. With lower
rain chances temperatures will soar into the lower to mid
90s along the coast, and mid to upper 90s inland with high
humidity levels supporting heat indices in the 105 to 108
degree range during the afternoon.
Long term (saturday night through friday)...
in the mid/upper levels, an upper level low over the eastern
Gulf of Mexico will continue moving westward toward Texas
through the beginning of next week. Mid-level ridging near
Bermuda extends west- southwest over eastern Florida. As the
upper low moves toward Texas next week, the high pressure
ridge settles in over the southeast U.S. Through the middle
of next week. On Thursday, the ridge shifts slightly to the
south as deep troughing moves through the eastern half of
the U.S. On the surface, subtropical high pressure near
Bermuda ridges west-southwest over Florida and into the Gulf
of Mexico. This will produce a predominant easterly wind
flow over the Florida Peninsula. This will favor the
development of thunderstorms early in the afternoon along
the East Coast and later evening along the West Coast of
Florida as the storms move westward. Temperatures will
remain around seasonal averages with daytime highs in the
low 90's and overnight low in the mid to upper 70's.
brief MVFR cigs/vsbys may impact the terminal sites through
00z as scattered showers and thunderstorms move across the
region outside of the convection VFR will prevail. West to
northwest in the 7 to 9 knot range will prevail through 00z
with gusts up to 40 knots possible in the vicinity of tsra.
Light to calm winds will return to all terminals after 02z
tonight, becoming southwest to west at 5 to 7 knots after
14z on Saturday.
high pressure from the Atlantic extending west across the
central Florida Peninsula and into the eastern Gulf of
Mexico will maintain light winds and slight seas over the
Gulf waters tonight through the upcoming weekend with a weak
pressure pattern supporting an onshore sea breeze component
developing along the coast each afternoon. A subtle uptick
in winds and seas will occur early next week as the gradient
tightens a bit between high pressure across the north
central waters and lower pressure to the south. Although
winds will increase some and will be higher in the vicinity
of thunderstorms, no headlines are anticipated.
ample moisture combined with daily rain chances will keep
humidity levels above critical levels through early next
week with no fire weather issues expected.
Preliminary point temps/pops...
tpa 79 93 79 92 / 20 20 20 50
fmy 76 95 77 91 / 30 20 30 60
gif 76 95 77 92 / 40 20 20 60
srq 77 93 78 92 / 10 10 20 60
bkv 74 94 74 93 / 20 30 30 50
spg 80 93 80 92 / 20 10 20 50