Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 280711 CCA
AFDTBW

Area Forecast Discussion...Corrected
National Weather Service Tampa Bay Ruskin FL
309 AM EDT Tue Mar 28 2017

.SYNOPSIS...
07Z water vapor and H4 RAP analysis shows an amplified by
progressive mid/upper level pattern over north America early this
morning. Main features include a short-wave trough evolving through
the TN/OH Valleys...with a weak trough extension down to northern
Florida...followed upstream by synoptic ridging through the Plains
states and mid/lower MS valley...and finally followed upstream by a
sharp trough digging through the inter-mountain west/SW states. The
influence of the shortwave trough entering the eastern states is
staying just north of our region early this morning and will be
passing to our east this morning. This evolution will allow the
ridging to our west to build over the region during today. The
secondary trough out west will evolve into the central/southern
plains later today/tonight with an expected severe weather outbreak
across portions of that region. This trough and its associated
inclement weather will not be a concern for our region anytime soon.

At the surface...High pressure off the eastern seaboard continues to
ridge back to the southwest over the Florida peninsula and eastern
Gulf of Mexico. The synoptic gradient within this ridge position is
providing a light easterly to variable flow this morning.

&&

.Short Term (Today through Wednesday)...
As weak troughing pulls away from the region this morning...heights
will again rise in response to mid/upper level ridging evolving
eastward form the central Gulf of Mexico over our region. The
synoptic pattern by late today will again feature stacked ridging in
place...keeping our weather dry and warm through the middle of the
week.

Although significant troughing will be evolving into the central
plains during the next 24-36 hours...the slow evolution of this
system will allow the strong upper ridging to remain in control of
the FL peninsula through Wednesday. This ridging should exert enough
large scale suppression, keep the moisture layer shallow enough, and
maintain a hostile enough thermodynamic environment above 6-8KFT to
prevent even isolated deep convection along the sea-breeze the next
couple of days. Therefore...despite expected very well-defined sea-
breeze boundaries and strong BL focus along the boundaries evolving
inland the next couple afternoons...PoPs will remain under 10%...and
the resulting cu fields should remain shallow and highly suppressed.

High temperatures the next couple of days will be well into the 80s
inland...and generally lower 80s at the coast. Shelf waters
temperatures are still generally in the lower to middle 70s...so
expect temperatures at the beaches to drop from the lower 80s to the
mid/upper 70s after the onset of the sea-breeze each afternoon. Low
temperatures tonight will be seasonable, with mid/upper 50s north to
the I-4 corridor...and upper 50s to lower 60s further south.
Normally warmer locations with E-SE nocturnal flow, such as southern
Pinellas County, and the Capes of Charlotte Harbor will likely not
drop below the middle 60s.

&&

.MID/LONG TERM...
Mid/upper level ridging will be in place at the start of the
extended forecast period with dry weather and above normal
temperatures expected on Thursday. Temps will top out in the 80s
across the area with upper 80s expected across the interior zones.
Afternoon seabreeze will keep temps cooler along and near the coast.
On Friday, a mid/upper level trough will dig into the SE U.S.
allowing a surface trough to move through our area bring some
increased rain chances. Models are in better agreement now compared
to a few days ago so have increased PoPs a bit compared to previous
forecasts. Upper ridging quickly builds back over the region for the
rest of the weekend and into Monday keeping us dry with above normal
temps continuing.

As we get into the early part of next week, greater forecast
uncertainty exists. Global models have been persistent on the
development of a significant shortwave trough / cut-off low feature
across the western U.S. later this weekend and take the feature
eastward into the southern U.S. at the start of next week. While
both global models show this feature, there are major discrepancies
between them on timing, location and strength of this feature. All
of which will have impacts on our forecast. For now, have low end
rain chances on Monday and Tuesday until models have a better handle
on things.

&&

.AVIATION (28/07Z through 29/06Z)... Once again the main
forecast parameter for this TAF package is a wind forecast
related to timing of the sea-breeze. A brief period of MVFR
vis is possible at KLAL/KPGD toward dawn this morning, but
no significant restrictions are expected. Light E-SE flow
this morning will shift SW-W for coastal terminals during
the early to mid afternoon as the sea-breeze develops and
evolves slowly inland. KPIE will likely go briefly northeast
around midday with initial bay breeze before the Gulf sea-
breeze arrives and turns winds westerly. Similar conditions
tonight with patchy areas of MVFR visibility, mainly for
KLAL/KPGD in the few hours surrounding sunrise.

&&

.MARINE...
Benign marine forecast the next several days as high pressure
dominates the region. Light east to southeast flow overnight into
the morning hours will turn west and southwest near the coast each
afternoon with sea-breeze development...and then expand offshore
with time through the afternoon/early evening hours. No rainfall is
expected through at least Thursday. Confidence then
increases that the approach of a cold front Thursday night
into Friday will bring an increase in southerly winds,
possibly to cautionary or advisory levels, and a potential
round of thunderstorms over the eastern Gulf of Mexico.

&&

.FIRE WEATHER...
High pressure keeps the weather dry and warm through the next
several days. The next potential for any rainfall will not arrive
until at least Friday. Relative humidity is expected to briefly
approach or drop just under 35% away from the coast each of the next
two afternoons, however, extended durations of critical RH, and only
light forecast winds will keep red flag conditions from being met.

Fog Potential...Patchy fog is expected away from the coast early
this morning, and again early Wednesday morning. However, widespread
and/or dense fog is not anticipated.

&&

.Preliminary Point Temps/PoPs...
TPA  81  65  82  66 /   0   0   0   0
FMY  84  63  84  64 /   0   0   0   0
GIF  85  63  88  65 /   0   0   0   0
SRQ  77  64  78  63 /   0   0   0   0
BKV  83  57  85  58 /   0   0   0   0
SPG  80  67  81  68 /   0   0   0   0

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.

&&

$$

SYNOPSIS/SHORT TERM/AVIATION/MARINE/FIRE WX...Mroczka
MID TERM/LONG TERM/DECISION SUPPORT...McKaughan



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