Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 241858

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
258 PM EDT Wed May 24 2017

...Severe Storms Possible Through Tonight...
...Minor Coastal Flooding Possible Through Early Tonight...

.SHORT TERM (Tonight - Thursday)...
A potent upper level trough and closed upper level low over the
lower Mississippi valley will move across the southeastern states
tonight, then lift out to the northeast on Thursday becoming
negatively tilted as it does with a zonal flow developing over the
region in its wake. At the surface low pressure over the TN/OH
valleys will deepen as it lifts north into the eastern Great Lakes
region through the period. A trailing cold front from the surface
low will move into the forecast area tonight and then south of the
region on Thursday.

Ample moisture combined with sufficient instability, embedded vort
maxes rotating through the base of the upper trough and decent upper
level divergence will continue to support showers and isolated
thunderstorms over the forecast area the remainder of the afternoon
and into early tonight, with highest rain chances across central and
southern zones. Strong wind fields associated with the upper trough
(850MB winds in the 45-55 knot range) will support strong shear
within the atmosphere which will continue to favor some organized
convection with the possibility of severe storms through early
tonight with damaging winds the primary hazard along with a low
potential for a tornado or two. Given the ongoing and expected
convective trends and after coord with SPC severe thunderstorm
watch number 265 will be in effect for Sumter, Polk, Hardee,
Highlands, Desoto, Charlotte, and Lee counties until 11 PM EDT

In addition to the severe threat some locally heavy rainfall will be
possible which may produce some minor flooding of low lying and poor
drainage areas, as well as the ponding of water on roadways.

Strong and gusty south to southwest winds will continue to support
rough boating conditions over the adjacent Gulf waters with
hazardous surf and a high risk of rip currents continuing along area
beaches through early Thursday morning, and plan to extend the rip
current risk through 14Z on Thursday. In addition, the strong
onshore flow will continue to cause tides to run some 2 to 3 feet
above normal at times of high tide along the Levy and Citrus county
coasts where a coastal flood warning remains in effect until 5 PM
EDT this evening, with 1 to 2 feet above normal tides expected
further to the south. Given ongoing and expected wind and sea
conditions plan to maintain the Coastal hazard message until 12Z
on Thursday for the risk of elevated water levels along the coast
during this time frame.

Residents living along the coast should continue to monitor water
levels and be ready to move to higher ground if flooding is
observed. The strong and gusty winds will also continue to produce
very hazardous boating conditions on area lakes and a lake wind
advisory will remain in effect for the entire area until 10 PM EDT

On Thursday lingering showers and storms across the south-central
portion of the forecast area in the morning will gradually end by
early afternoon as the front continue to move to the south. Drier
air filtering into the region in the wake of the front on a breezy
west to northwest wind flow will support increasing amounts of
sunshine across the Nature Coast and into the central zones during
the afternoon, with southwest Florida clearing out last during the
mid to late afternoon with pleasant dry weather expected for
Thursday night as surface high pressure builds in over the region.
Temperatures will be noticeably cooler on Thursday compared to the
high temperatures we have been experiencing of late with highs
topping out in the lower to mid 80s area wide.

.LONG TERM (Thursday Night - Wednesday)...
An upper ridge from central Mexico to the upper Great Lakes slowly
slides east and flattens...settling in across the Gulf and eastward
to the Bahamas through the weekend. At the surface - Atlantic high
pressure reaches west across the Gulf of Mexico with a ridge axis
initially across south Fl that drifts into the central part of the
state and meanders there...with a relaxed gradient.

For about the first half of next week - The upper ridge shifts east
across the southern half FL and extends out over the Atlantic as an
upper low tracks along the Great Lakes with troughing spreading down
into the western Gulf. This troughing will usher a frontal boundary
into the western Gulf coast and the Deep South...with the surface
ridge axis dropping down into southern FL.

The end of the week wraps up with a dry and stable airmass and
temperatures running close to normal. The weekend continues with
near seasonable temperatures but a slight increase in moisture...
but not enough for any precipitation. For the start of next week
the moisture continues to increase with some showers and a few
thunderstorms mainly in the afternoons. With the ridge axis over
or near the area the flow will be light and dominated by sea breezes
that will tend to keep the higher coverage of showers/storms inland.


Prevailing MVFR cigs and vsby with brief IFR conditions associated
with rain and embedded thunderstorms will impact the terminals
through 03Z tonight. Southwest winds in the 20 to 25 knot range with
frequent gusts above 30 knots will continue through 01Z tonight
before winds begin to diminish some overnight into Thursday morning
as they shift to the west and northwest. VFR should return to KTPA,
KPIE, and KLAL after 09Z, and from KSRQ south to KPGD, KFMY, and
KRSW terminals between 13 and 16Z as drier air moves into
the region.


Hazardous marine conditions will continue over the Gulf waters
tonight into early Thursday as a cold front moves south through the
waters. South to southwest winds in the 20 to 25 knot range with
frequent gusts up to gale force this afternoon will gradually shift
to the west and northwest as the front moves south through the
waters with diminishing winds expected on Thursday as the gradient
weakens. Much lighter winds and seas are expected across the waters
Thursday night into the upcoming holiday weekend and continuing into
early next week as high pressure builds in over the waters with no
additional headlines expected.


Drier air will filter into the region on Thursday in the wake
of the cold front, however humidity values are expected to
remain above critical levels with no red flag conditions expected.
20 foot winds and transport winds will remain elevated on
Thursday which will support high dispersion indices across
the forecast area. Lighter winds will return for Friday.
On Friday a few hours of critically low humidity values below
35 percent will be possible over central interior zones during
the afternoon, however with lighter winds and ERC values remaining
below critical levels no fire weather issues are expected.


.Preliminary Point Temps/PoPs...
TPA  74  82  68  86 /  50  20   0   0
FMY  76  83  69  90 /  70  50   0   0
GIF  71  83  65  89 /  50  20   0   0
SRQ  76  82  68  84 /  60  20   0   0
BKV  70  80  59  86 /  50  20   0   0
SPG  75  81  71  85 /  50  20   0   0


FL...High Rip Current Risk through Thursday morning for Coastal
     Charlotte-Coastal Hillsborough-Coastal Lee-Coastal
     Manatee-Coastal Sarasota-Pinellas.

     Lake Wind Advisory until 10 PM EDT this evening 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-

     Coastal Flood Warning until 5 PM EDT this afternoon for
     Coastal Citrus-Coastal Levy.

Gulf waters...Small Craft Advisory until 8 AM EDT Thursday for Charlotte
     Harbor and Pine Island Sound-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-Tampa Bay waters-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.



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