Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 212342

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
642 PM EST Sat Jan 21 2017

22/00Z-23/00Z. VFR conditions until AFT midnight when patchy
BR begins to form...although winds stay high enough to
limit BR except at fog prone LAL and PGD where MVFR settles
in. BR lifts 12-14Z followed by increasing clouds spreading
south with MVFR CIGS. Approaching cold front with a squall
line will provide VCTS/TSRA starting 12-14z in the north and
18-20Z in the south...and continuing through 00Z. southerly
winds slack some over night then then pick back up in the
morning with significant gusts...and become S-SW in the


.Prev Discussion... /issued 240 PM EST Sat Jan 21 2017/

..Enhanced Risk of Severe Thunderstorms Sunday...
..Hazardous Coastal Marine Conditions early Sunday through
..Hazardous Lake Conditions Sunday through Tuesday...

SHORT TERM (Tonight - Sunday)...
A significant storm system is expected to develop and move through
the area beginning tonight through Sunday and will bring an enhanced
chance of severe weather to west central and southwest Florida.
Upper level ridging has moved off the east coast and will carry with
it the surface high to our east that has been giving us pleasant
weather the past several days. The real story for the next 36 hours
is with a deep upper level trough out west that will lend support to
a major storm system that will move through the region. This trough
further deepens and closes into an upper low by late Saturday
evening over northern Texas. By Sunday evening, this upper low will
be located over northern Alabama with significant troughing into the
northern gulf waters west of the Florida peninsula. As this upper
low moves north of the area, a strong 110+ knot jet will be located
over the northern gulf coast waters. A little closer to the surface,
a 55kt low level 925 mb jet located over central and southwest
Florida will only enhance the chance of damaging winds making it
down to the surface in strong thunderstorms.

On the surface, a major storm system develops to the northwest.
Models are in good agreement with developing a surface low near the
northern Texas/Oklahoma panhandle by Saturday evening. Models
continue to be in agreement placing the low near western Tennessee
by Sunday morning with a cold front extending southwest over the
Florida panhandle. This low will combine with energy from another
disturbance that moved through the southeast earlier today making it
an even more potent system. SPC currently has the northern portion
of Florida from the I-4 corridor northward in an Enhanced Risk for
severe thunderstorms including high winds and risk of possible
tornadoes starting at 12z on Sunday. As this front approaches the
region, the squall line will possibly produce gusty winds in the 20-
30 kt range as it moves over the coastal waters and approaches the
inland areas. Region wide rainfall of 1-2 inches can be expected
with locally higher amounts expected in stronger thunderstorms.

LONG TERM (Sunday Night - Saturday)...
At the start of the period strong to severe storms will be ongoing
and moving south through south-central and southern portions of the
forecast area along a pre-frontal squall line. This convection
should move south of the region by mid to late evening with the main
cold front moving south through the forecast area overnight into
early Monday morning as deepening surface low pressure lifts
northeastward up along the mid Atlantic coast. With the upper trough
axis associated with a strong closed upper level low over the lower
TN valley/southeastern states still to our west lingering showers
will continue to be possible over the forecast area overnight into
early Monday morning before all of the rain finally comes to an end
from north to south by mid to late morning as the trough axis shifts
eastward and drier air advects into the region.

In the wake of the cold front a very strong westerly wind flow will
advect in somewhat cooler and drier air into the region. The strong
onshore flow will support very hazardous marine conditions over the
adjacent Gulf waters where frequent wind gusts to gale force along
with seas building into the 10 to 15 foot range will be likely. The
strong onshore flow will also bring a threat of some minor coastal
flooding especially at times of high tides Sunday night into Monday,
as well as high surf and a high risk of rip currents along area
beaches. The strong and gusty winds will also lead to hazardous
boating conditions on area lakes as well and a lake wind advisory
will likely be required for much of the region, with breezy to windy
conditions expected through Monday.

During Tuesday and Wednesday pleasant dry weather with diminishing
winds will return to the forecast area as high pressure surface and
aloft builds in over the region. By late Wednesday the high will
shift east into the Atlantic as another cold front approaches from
the west. Unlike yesterday the GFS is now more in line with the
ECMWF with the timing of the front, with a blend of the models
moving the front into the Nature Coast during Thursday afternoon,
then sinking it south through the central zones Thursday night, and
then across the southern peninsula on Friday bringing with it a
slight chance (Pops 20 percent) of showers.

By late Friday and into Saturday a drier and cooler airmass will
advect into the region in the wake of the front on a breezy
northerly wind flow with dry cool and below normal temperatures
expected on Saturday as high pressure builds in from the northwest.

Near seasonal level temperatures through mid week will fall to below
normal Friday and into next weekend as cooler drier air moves into
the region in the wake of the cold front.

VFR conditions can be expected through early Sunday morning. Gusty
south-southwest winds at 15-20 knots this afternoon will subside
briefly overnight, then becoming gusty again by 12Z tomorrow morning
as a strong frontal boundary approaches the area. Some of these
gusts could reach near 30 knots through the morning and into Sunday
afternoon. MVFR/LIFR conditions can be expected by 12z for the
northern terminals and by 17z for the southern terminals.
Thunderstorms can be expected tomorrow, but will just hold VCTS
starting after 12Z and will adjust with TSRA for timing with the
later TAFs. So all in all, today will be VFR, giving way to
inclement flying weather after 12z tomorrow for all terminals.

Interaction between high pressure over the Bahamas and an
approaching storm system to the northwest will produce gusty
southerly winds starting at SCEC level this evening, then rapidly
increasing to SCA level after midnight and lasting through Tuesday
morning. A potent squall line is expected to approach the coastal
waters beginning late Sunday morning along the northern coastal
waters near the nature coast, then approaching the waters off Tampa
Bay by the afternoon and moving through the waters off of Charlotte
Harbor by Sunday evening. With this squall line, you can expect
heavy downpours in thunderstorms, deadly lightning, gusty winds 20-
30 knots with higher gusts and very rough seas. Sustained south-
southwest winds near gale force will be possible just before frontal
passage on Sunday afternoon lasting through the evening hours. This
has warranted the issuance of a Gale Watch beginning on Tuesday
afternoon at 18Z lasting through Monday night. During this time, you
can still expect Small Craft winds of 20-30 knots with higher gusts.
Mariners should remain in port until conditions improve. By Tuesday,
winds begin to subside, but residual long period swells will
continue in the eastern Gulf. High pressure moves into the region
late Tuesday, which will produce much lighter winds and decreasing
seas through the middle of the week.

No fire weather hazards are expected through the weekend as relative
humidity values will remain above 35 percent each day.


.Preliminary Point Temps/PoPs...
TPA  68  78  64  71 /  10  80  70  20
FMY  67  81  67  75 /  10  40  80  20
GIF  65  82  62  72 /  10  70  80  20
SRQ  68  78  67  72 /  10  70  70  20
BKV  65  80  60  71 /  10  80  70  20
SPG  67  79  64  70 /  10  80  70  20


FL...Beach Hazards Statement through Monday evening for Coastal
     Manatee-Coastal Sarasota.

     Lake Wind Advisory from 10 AM Sunday to 7 PM EST Monday
     for Coastal Charlotte-Coastal Citrus-Coastal Hernando-
     Coastal Hillsborough-Coastal Lee-Coastal Levy-Coastal
     Manatee-Coastal Pasco-Coastal Sarasota-DeSoto-Hardee-
     Highlands-Inland Charlotte-Inland Citrus-Inland
     Hernando-Inland Hillsborough-Inland Lee-Inland Levy-
     Inland Manatee-Inland Pasco-Inland Sarasota-Pinellas-

     High Rip Current Risk through Tuesday evening for Coastal
     Charlotte-Coastal Hillsborough-Coastal Lee-Coastal
     Manatee-Coastal Sarasota-Pinellas.

Gulf waters...Gale Watch from Sunday afternoon through Monday evening
     for Coastal waters from Bonita Beach to Englewood FL
     out 20 NM-Coastal waters from Englewood to Tarpon
     Springs FL out 20 NM-Coastal waters from Tarpon
     Springs to Suwannee River FL out 20 NM-Waters from
     Bonita Beach to Englewood FL out 20 to 60 NM-Waters
     from Englewood to Tarpon Springs FL out 20 to 60 NM-
     Waters from Tarpon Springs to Suwannee River FL out
     20 to 60 NM.

     Small Craft Advisory from 4 AM to 1 PM EST Sunday for
     Coastal waters from Bonita Beach to Englewood FL out
     20 NM-Coastal waters from Englewood to Tarpon Springs
     FL out 20 NM-Coastal waters from Tarpon Springs to
     Suwannee River FL out 20 NM-Waters from Bonita Beach
     to Englewood FL out 20 to 60 NM-Waters from Englewood
     to Tarpon Springs FL out 20 to 60 NM-Waters from
     Tarpon Springs to Suwannee River FL out 20 to 60 NM.

     Small Craft Advisory from 10 AM Sunday to 7 PM EST Monday
     for Charlotte Harbor and Pine Island Sound-Tampa Bay



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