Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 211445
AFDTBW

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
1045 AM EDT Mon Sep 21 2020

.UPDATE...
Another windy day on tap across the forecast area today as the
gradient between ridging extending south of a stout 1040 mb high
over New England and a lingering frontal boundary over the extreme
southern FL peninsula remains impressive. Per this morning`s
upper-air sounding, averaged winds over the lowest 1 km of the
column were out of the east-northeast right around 30 kts, with
35 to 40 knots around 925 mb. KTBW VAD wind profile has depicted
similar values this morning, which matches up fairly well with
most recent hi-res model depictions. Latest RAP guidance maintains
30- to 35-knot boundary layer winds throughout much of the day,
leading to frequent gusty conditions as some of this momentum
mixes to the surface through early evening. Last evening`s HREF
ensemble indicated max gusts generally in the 30- to 35-knot range
across most of the area with higher gusts along the coast and
over coastal waters, which also matches up pretty well with the
existing forecast.

PW values are down to around 1.8 inches this morning from 2.2
inches yesterday evening, and can expect noticeably drier air to
continue filtering into the peninsula into Tuesday, as PW values
may briefly drop below an inch early Tuesday. This is also
evident via observations of dewpoints currently in the mid 50s
across southern GA, where RAP mesoanalysis indicates PW values
hovering around an inch or less. Showers and an isolated
thunderstorm today will remain confined south of I-4 with the
greatest threat in the southern third of the forecast area. Temps
this afternoon will top out in the mid to upper 80s, although
with the stiff breeze likely will not feel quite as warm.

&&

.Prev Discussion... /issued 813 AM EDT Mon Sep 21 2020/

AVIATION...
Windy conditions across terminals with NE winds 10 to 15 knots
increasing to 15 to 20 knots during morning with gusts around 30
knots through the afternoon and into the evening before diminishing
to around 10 knots or less overnight. MVFR CIGs at southern
terminals through morning before joining remaining terminals in
VFR during afternoon...with VCSH/VCTS and brief MVFR/IFR possible
through afternoon...diminishing during evening.

Prev Discussion... /issued 343 AM EDT Mon Sep 21 2020/

SYNOPSIS...
Aloft, a weak 300mb anticyclone (keeping light/variable upper
level flow) is situated over the FL Peninsula, to south of a
trough currently off the New England coast. A weak area of surface
low pressure which formed Saturday night off the coast of
Melbourne has traversed westward along a stalled surface front
draped east/west across Lake Okeechobee. This area of low pressure
near SWFL is not expected to develop tropical characteristics.
Meanwhile, Tropical Storm Beta out in the northwest Gulf of Mexico
continues to move west-northwestward and is expected to make
landfall along the Central Texas coast likely sometime Monday
afternoon.

DISCUSSION...
Cyclonic flow around Hurricane Teddy out in the Atlantic along
with the periphery easterly flow feeding into Tropical Storm Beta
has developed an interesting mid-September pattern with a frontal
boundary continuing to gradually sag south of our CWA. The stiff
northeast flow behind the surface front, which is being aided by
Teddy`s flow, has created a cold air damming setup which can be
seen by a 7C difference of temps at 850mb between the western and
eastern foothills of the Southern Appalachians. This will filter
in drier (dewpoints in the 60s) and less hot (an emphasis on
wording) which will keep temperatures in the 80s areawide through
mid week and maintain lower heat index values. Lows tonight and
tomorrow night look to dip into the mid/upper 60s across much of
our northern and inland areas east of I-75 which will certainly be
a refreshing change when you head out in the morning. Tomorrow
night, isolated spots across the Nature Coast may reach the low
60s, perhaps even a stray 60 degrees if decoupling along with
pockets of clear skies can occur.

The main concern for the next day or two will be the winds as a
tight pressure gradient persists over the region. As we saw
yesterday, windy conditions will once again prevail on today so we
have hoisted another Lake Wind Advisory over land along with a
Small Craft Advisory for all of our coastal waters. Winds look to
increase further by late afternoon through the evening hours off
the coastal waters. As a result, a Gale Watch was issued for as
wind gusts will flirt with 34+ knots for a long period of time.
For Pinellas county, it was opted to exclude them from a Lake Wind
Advisory and instead issue a Wind Advisory. MOS guidance suggests
winds at SPG to be sustained between 28-30 knots. If this
materializes, portions of the county (especially across the
southern half) may see sustained winds in excess of 30mph with
gusts at or briefly above 40 mph, especially later in the
afternoon through early evening. High profile vehicles should use
caution if traveling over the Skyway Bridge. Nevertheless, any
activities on the water through at least Tuesday afternoon should
be reconsidered carefully.

Scattered showers and isolated thunderstorms will be confined
mostly south of I-4 during the day today. By tomorrow, a much
drier airmass (PWATs near 1 inch) will essentially choke off any
chance of rainfall with the exception of a few shallow-topped
showers moving westward off the Atlantic - but even these will be
confined to our eastern counties...

Relatively benign weather will be in place through at least
Wednesday as the dry airmass will maintain over the area and
northeast to east winds will persist... Thursday looks to be a
transition day as surface high pressure slides off the SE coast,
shifting winds out of the southeast. By Friday, a weak surface
trough looks to pivot on the western flank of the subtropical
ridge and move north out of the Caribbean into the SE Gulf of
Mexico. This will result in a return of a deep tropical airmass,
and accompanying rain, to be advected northward into the FL
Peninsula. Scattered showers and thunderstorms will persist
through the weekend as we say farewell to our short stint of this
week`s drier airmass...

MARINE... Poor marine conditions are expected for at least the
next 36 hours as strong northeast winds will persist across the
area thanks to strong high pressure to the north and a frontal
boundary to the south. Solid Small Craft Advisory conditions are
expected for all of the eastern Gulf waters, including the bays. A
Gale Watch has been issued for offshore areas beginning later
this afternoon and persisting through the evening as frequent wind
gusts around 34 knots are expected. Conditions will gradually
improve throughout the day on Tuesday but winds and seas are still
expected to remain elevated, especially during the overnight
hours as easterly surges bring headlines, if not brief advisory
conditions each night.

FIRE WEATHER...
Gusty northeast winds will prevail across the area for the next
couple of days. This will lead to very good afternoon and
overnight dispersions as transport winds will be strong.
Otherwise, adequate moisture over the last week or two precludes
any other fire weather concerns...

&&

.Preliminary Point Temps/PoPs...
TPA  88  72  87  71 /  20  10  10   0
FMY  88  73  88  71 /  70  20  10   0
GIF  86  69  85  69 /  20   0  20   0
SRQ  89  73  88  71 /  30  10  10   0
BKV  84  68  86  66 /  20   0  20   0
SPG  85  75  88  75 /  20  10  10  10

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...Lake Wind Advisory until 10 PM EDT this evening for Coastal
     Charlotte-Coastal Citrus-Coastal Hernando-Coastal
     Hillsborough-Coastal Lee-Coastal Manatee-Coastal Pasco-
     Coastal Sarasota-Inland Lee.

     Lake Wind Advisory until 8 PM EDT this evening for DeSoto-Hardee-
     Highlands-Inland Charlotte-Inland Citrus-Inland Hernando-
     Inland Hillsborough-Inland Manatee-Inland Pasco-Inland
     Sarasota-Polk-Sumter.

     Wind Advisory until 10 PM EDT this evening for Pinellas.

Gulf waters...Gale Watch from 5 PM EDT this afternoon through late tonight 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 until 5 PM EDT this afternoon 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 2 AM to 2 PM EDT Tuesday for 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 2 AM to 10 AM EDT Tuesday 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.

     Small Craft Advisory until 2 AM EDT Tuesday for Charlotte Harbor
     and Pine Island Sound.

     Small Craft Advisory until 10 AM EDT Tuesday for Tampa Bay
     waters.

&&

$$

UPDATE...Hurt
UPPER AIR/DECISION SUPPORT...McMichael



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