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fxus62 ktbw 210813 
afdtbw

Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
313 am EST Tue Nov 21 2017

..increasing rain chances today through Friday...

Short term (today - wednesday)...
surface high pressure just offshore the mid Atlantic coast
early this morning will slide further to the east over the
Atlantic the remainder of the today as a short wave trough
within the amplifying upper level trough over the west
central Gulf of Mexico approaches and slides east-northeast
across the region through tonight. Increasing low level
moisture within a southeast to southerly wind flow combined
with increasing ascent associated with the approaching short
wave, and the remnant frontal boundary to the south lifting
back to the north as a warm front should all help to
generate numerous showers and isolated storms over the
region today, with the showers first developing across
southwest Florida by mid morning as it will take a while
longer for the current dry and stable airmass to moisten up
enough to support rain, with the activity then spreading
north across the remainder of the forecast area during the
afternoon as the above mentioned features affect the region.



With some rather cold temperature aloft (-10 to -11c at
500mb) and decent shear via forecast soundings, a few
strong storms will be possible. Model pop guidance remain
fairly similar to previous days with pops in the 60 to 70
percent range areawide. Max temps today should run close to
normal despite increasing cloud cover and rain chances with
highs topping out in the mid to upper 70s in most locations
along with increasing humidity levels.

Tonight the rain chances will taper back into the isolated
range (20 percent) as the upper level support and deepest
moisture axis shifts northeast into the Atlantic overnight
with mostly cloudy mild and muggy conditions expected. Dew
points increasing into the mid 60s along with light winds
will likely support some fog development over inland areas
and in fog prone areas overnight and will introduce into the
grids and zones. Low temperatures will run above normal for
this time of the year with lows generally in the 60s
areawide.

On Wednesday rain chances will remain elevated (pops in the
30 to 40 percent range) across the forecast area as upper
level troughing persists over the southeastern U.S. And Gulf
of Mexico. Sufficient moisture combined with the lingering
frontal trough and additional upper level disturbances
moving across the region should again help to generate some
scattered showers and isolated storms across the region
during the day under mostly cloudy skies, but some dry mid
level air (via model sounding and time cross-section data)
may support somewhat lower convective coverage compared to
today. Temperatures on Wednesday will be similar to today
with highs again climbing into the mid and upper 70s north
into central zones and around 80 far south during the
afternoon.

Long term (wednesday night through monday)...
a strong mid level shortwave trough will be digging into the
central Gulf of Mexico Wednesday night, and will slowly
shift east through the Florida Peninsula through the rest of
the week. This trough will be fueling a surface low that
will lift northeast through northern Florida Thursday and
Friday, bringing ample moisture into the forecast area.
Showers and thunderstorms will be possible at any time
through Friday afternoon, with the highest rain chances
expected Thursday and Thursday night. Despite the prolonged
wet period, column moisture will only be sufficient to
support light to moderate rainfall rates, with occasional
heavy downpours, so it does not look likely that any area
will see a washout.

Surface high pressure will build into the Gulf and northern
Florida Friday night and Saturday, with rain chances
drying out from north to south. Another mid level shortwave
will quickly follow the first, providing a reinforcing shot
of cool and dry air Sunday and Sunday night. This will bring
temperatures down to a few degrees below normal, with lows
Monday morning in the 40s and low 50s, and afternoon highs
in the mid to upper 60s.

&&

Aviation...
VFR conditions this morning will give way to brief MVFR
cigs/vsbys after 14z at kfmy, krsw, and kpgd terminals and
after 17z from ksrq north to ktpa, kpie, and klal as
moisture and rain chances increase across the region during
the day. Some isolated tsra will be possible after 18z and
have handled with thunderstorms in the vicinity for now. Outside of the convection
VFR will prevail with cigs aoa 050. East winds in the 5 to 7
knot range will veer to the southeast at 7 to 10 knots
after 15z with higher gusts possible in the vicinity of tsra
after 18z. Light and variable winds will return to all
terminals after 00z tonight.

&&

Marine...
surface high pressure just offshore the mid Atlantic coast
is supporting east winds in the 15 to 20 knot range over
the offshore Gulf waters early this morning. As the high
moves further to the east during the day winds should
diminish as the gradient relaxes as winds veer to the
southeast and south. In the interim though current wind and
sea states (via offshore buoys) supports maintaining
cautionary headlines for the offshore waters through early
afternoon, with east to southeast winds in the 10 to 15 knot
range closer to shore diminishing to around 10 knots during
the afternoon. Increasing moisture and lift associated with
an upper level disturbance approaching from the west will
support increasing rain chances over the waters through the
day with higher winds gusts likely in the vicinity of
thunderstorms.

Tonight through Wednesday an area of low pressure is
expected to develop over the eastern Gulf of Mexico, with
this low then tracking east-northeast across the peninsula
during Thursday and Thursday night. Although winds and seas
are not expected to significantly increase with this low
rain chances will remain elevated through the period with
scattered to numerous showers and isolated storms expected
as this storm system affects the region. A trailing cold
front from this low will move south through the waters on
Friday bringing with it drier weather and northwest to north
winds in the 10 to 15 knot range. High pressure with dry
conditions and northwest winds will continue on Saturday,
with a slight uptick in wind speeds expected on Sunday as
another reinforcing dry cold front moves south through the
waters during the day.

&&

Fire weather...
increasing low level moisture and rain chances will keep
humidity values well above critical levels today and
through the remainder of the week with no fire weather
issues expected.

&&

Preliminary point temps/pops...
tpa 76 64 77 66 / 70 30 40 30
fmy 81 65 80 66 / 50 20 30 20
gif 77 62 78 63 / 70 30 40 20
srq 77 65 77 64 / 70 20 40 20
bkv 76 61 77 61 / 70 30 40 40
spg 76 65 76 65 / 70 30 40 30

&&

Tbw watches/warnings/advisories...
Florida...none.
Gulf waters...none.
&&

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