Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 202339
AFDTBW

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
639 PM EST Sat Jan 20 2018

.AVIATION...
Some brief MVFR/IFR vsbys from fog may impact KLAL and KPGD
terminals between 09-13Z, otherwise VFR will prevail at all
sites during the next 24 hours. Light and variable winds the
remainder of tonight will become east to southeast at 7 to
10 knots after 15Z on Sunday.


&&

.Prev Discussion... /issued 205 PM EST Sat Jan 20 2018/

SHORT TERM (Tonight - Sunday)...
Mid/Upper-level trough moving eastward across the Gulf is
resulting in broad weak ascent from the central Gulf
northeast across most of Florida. The main impact is
widespread mid and upper-level cloudiness, but a few drops
of light rain may occur here and there through this evening.
The lower levels are too dry to support significant shower
activity, but it wouldn`t be out of the question to see a
more pronounced band of light showers along the nature coast
later tonight as the main energy moves across north
Florida. Have introduced a chance of showers there, but will
keep amounts well under a tenth of an inch.

Any lingering light rain or showers should end by early
Sunday with skies clearing from west to east as the upper
trough moves into the Atlantic. For those waiting for warmer
days, this one is for you. Temperatures will climb into the
middle to upper 70s over most of the region. Easterly winds
should be strong enough to keep the sea breeze offshore for
most of the day, but a late-afternoon wind shift is
possible, and this would result in a rapid drop of
temperatures right at the beaches.

LONG TERM (Sunday night through next Saturday)...
Through Tue: An upper low over the central plains...with a
surface reflection trailing a cold front that reaches down
to Mexico... tracks across the lower Great Lakes into
Quebec with the front sweeping across The Gulf of Mexico
then FL on Tue. In response an upper ridge from the eastern
Gulf of Mexico to the Mid-Atlantic states along with surface
high pressure on the VA/NC coast both slide east. As the
high moves offshore the low level flow shifts from east to
southeast then southerly and provides increasing moisture.
This will result in patchy fog Sun night-early Mon on land.
As the flow becomes southerly Mon night it will be streaming
across cooler waters with with some sea fog forming on the
Gulf that may drift on shore for part of Tue. The
approaching front and southwesterly to westerly flow flow
aloft adding some additional moisture will provide a slight
chance to chance showers though Tue. But as the front moves
in it will bring somewhat drier air on northerly
flow...helping to dissipate the fog and to push decreasing
chance of showers into the south Tue night. Temperatures run
above normal but begin a slow trend down later Tue.

Wed-Thu: Broad troughiness aloft continues over the eastern
U.S. as a short wave trough pushes into the central Gulf
coast. An Atlantic ridge over Cuba builds west across the
Yucatan. Surface high pressure in the central plains treks
eastward to the Mid-Atlantic coast. The front that moved
through Tue lingers south of the Florida Keys. The high
pressure moving fairly rapidly across the southeast quarter
of the nation will turn winds to northeasterly for much of
this period with temperatures slightly below normal but
increasing back to around normal. Trailing moisture in the
wake of the Florida Keys front will support isolated to
scattered showers for the southern counties.

Fri-Sat: A Canadian upper trough drops into the Pacific
northwest then moves to the Upper Midwest as it extends
south to Mexico. The upper ridge over Cuba builds north over
the eastern seaboard then shifts out into the Atlantic. The
Mid-Atlantic coastal high pressure slips out over the
Atlantic while ridging back over the eastern states and much
of the Gulf of Mexico. The upper trough approaching over
the nation/s mid-section and the ridge over then off the
east coast will begin to bring in some deeper moisture on
southwesterly flow aloft...supporting slight chance to
chance showers. The surface high results in easterly then
southeasterly low level flow... reaching caution to advisory
speeds on the Gulf at times. Temperatures above normal
slowly increase. While guidance have come into slightly
better agreement on the latest run...compared to earlier
ones...some uncertainty continues with the very end of the
period.


MARINE...
Easterly winds will become southerly ahead of a cold front
Monday and Monday night. Sea fog is possible ahead of the
front as warmer and more humid air moves over the cooler
shelf waters. The cold front is forecast to move through the
waters Tuesday with northeast winds increasing to between
15 and 20 knots behind the front Tuesday night which will
continue through Thursday.

FIRE WEATHER...
Relative humidities should stay above critical values
through at least the middle of next week.

&&

.Preliminary Point Temps/PoPs...
TPA  68  55  75  60 /  10   0   0   0
FMY  72  57  79  60 /  10   0   0   0
GIF  70  54  76  58 /   0   0   0   0
SRQ  68  54  76  58 /  10   0   0   0
BKV  69  50  75  53 /   0  10   0   0
SPG  66  55  74  61 /  10   0   0   0

&&

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

$$
AVIATION...57/McMichael
SHORT TERM/MARINE/FIRE WEATHER...Jillson
MID TERM/LONG TERM...Rude



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