Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
311 PM EDT Tuesday may 21 2013
Short term (tonight - thursday)...weak middle-level low over North
Florida is forecast to remain nearly stationary through tonight then
move slowly northeast on Wednesday. Drier air has moved in behind
the low to the south of Tampa...but the airmass is not dry enough to
inhibit thunderstorm development this afternoon. Counter-clockwise
flow around the low will likely allow storms north of Tampa to move
back toward the coast while storms to the south push farther inland.
Weak steering flow in the middle means storm motion will be dictated
by outflow boundaries and therefore quite unpredictable.
Showers and storms wind down tonight with some patchy fog
developing...especially where the ground remains wet from previous
showers.
On Wednesday...a weak area of high pressure at the surface will be
in place over Florida and the eastern Gulf. This should allow
afternoon sea breezes to penetrate well inland and focus the storms
along The Spine of the peninsula. Steering level flow will be next
to nothing...so once again outflow boundaries will dictate where
storms move/develop during the late afternoon and evening hours.
Thursday will be similar...but the atmosphere between 700 and 850
mbs dries considerably. This will delay development as well as limit
the overall extent of storms. After a couple of days of scattered to
numerous showers and storms...it looks like Thursday will just have
isolated storms...and then mainly inland.
Long term (thursday night-monday)...
high amplitude pattern will persist with a l/west trough over the
eastern U.S. With a strong cut-off low developing Friday over the
middle Atlantic. As the trough axis pushes east of Florida on
Friday...a cold front will move across region with a slight chance
of thunderstorms. Surface high pressure will build over the
forecast area Friday night and Saturday with slightly drier air
advecting across the region. High pressure will move to the middle
Atlantic coast Sunday and over the western Atlantic Monday...while
u/l ridging over the central U.S. Will begin to gradually edge
east. This will keep broad easterly boundary layer flow across the
forecast area with subsidence aloft and a low chance of rain each
day.
&&
Aviation...
scattered showers and thunderstorms are expected to continue
through about 22/02z. Majority of this convection will be over
inland areas and should stay east of tpa...pie and srq...but could
impact lal...pgd...fmy and rsw causing some MVFR/local IFR
conditions. Otherwise...VFR conditions are expected.
&&
Marine...no issues through Friday as a weak area of high pressure
keeps winds light with some enhancement to onshore winds near the
coast during the afternoon sea breezes each day. A strong area of
high pressure will build north of the waters by Saturday morning
which will push a shear line through the region. The pressure
gradient will tighten significantly resulting in robust east to
northeast flow over the weekend...possibly requiring small craft
advisories at times.
&&
Fire weather...no humidity problems expected. Light transport winds
on Wednesday will lead to rather poor dispersions.
&&
Preliminary point temps/pops...
tpa 71 87 72 88 / 30 20 20 10
fmy 71 90 71 90 / 30 30 20 10
gif 69 89 70 91 / 30 60 20 20
srq 69 87 70 87 / 30 20 20 10
bkv 64 88 65 89 / 30 30 20 10
spg 74 86 75 86 / 30 20 20 10
&&
Tbw watches/warnings/advisories...
Florida...none.
Gulf waters...none.
&&
$$
Short term/marine/fire weather...jillson
long term...Oglesby
aviation...close
