Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 181839

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
239 PM EDT Sun Mar 18 2018


.SHORT TERM (Today - Monday)...
A closed upper low continues to spin over northern Quebec with
troughing extending south through the western Atlantic. A
predominant west-northwest to east-southeast zonal flow is over
Florida with ridging extending through the central U.S into the
Dakotas. Another closed upper low over the northwest U.S. and deep
troughing will move east through the period which will lend support
to our next significant weather system late Monday into Tuesday.

On the surface, high pressure over the eastern Gulf of Mexico will
produce pleasant weather conditions for the rest of today into early
Monday. The high shifts east over the Bahamas by Monday afternoon as
the next weather system approaches the area from the northwest. Most
of the associated weather with this system will stay north of Tampa
Bay on Monday, before the actual cold front moves through on
Tuesday. That is when the highest chances of severe weather with
damaging winds, possible tornadoes and large hail will be possible.
More on this in the long term discussion. Temperatures will be
around seasonal for the next couple of days until the front passes
on Tuesday. In the wake of the front, temps will cool down several
degrees below average.


.LONG TERM (Monday Night - Sunday)...
Models remain in decent agreement with synoptic scale features
during the long term period so a blend will be used. At the start of
the period a short wave trough will be moving east toward the TN
valley while an attendant deepening surface low moves east across
the the TN valley and toward the mid Atlantic coast with a trailing
cold front moving into the Florida Panhandle. Increasing moisture
and instability within the warm sector ahead of the front will
support increasing chances for showers and storms across the Nature
Coast and the adjacent Gulf waters during Monday night, with
increasing wind fields and shear increasing the potential for a few
strong to severe storms, especially from Citrus/Sumter counties
north to Levy county where currently a Marginal risk of severe
storms has been posted by the Storm Prediction Center.

On Tuesday a stronger shortwave trough will move east across the
southeastern states and northern Gulf coast. As this feature moves
eastward a broad area of surface low pressure will move east
northeast across GA/SC during the day with this low then moving
offshore the mid Atlantic coast Tuesday night. As the low moves east
northeastward the aforementioned cold front will get pulled
southeast through the eastern Gulf waters and west central and
southwest Florida. Ample moisture, instability, and increasing
ascent will support increasing chances (Pops 70 to 8 percent) for
showers and thunderstorms along and ahead of the front which will
spread south into west central and southwest Florida during the day.

Similar to yesterday model sounding data continues to indicate
increasing winds (in the 45-50 knot range in the 925-850mb level)
and increasing wind shear, steep mid level lapse rates, MUCAPE
values in the 1500-2000 J/kg range, and rapid cooling aloft (-13C at
500mb) overspreading the region on Tuesday which will increase the
potential for severe storms with damaging winds, large hail, and
perhaps a tornado or two the main hazards. The Storm Prediction
Center has placed the Nature Coast into an enhanced risk of severe
storms on Tuesday with a marginal to slight risk of severe storms
across the remainder of region. Given this all residents and
visitors should continue to monitor the latest forecast and be ready
to take immediate action if warnings are issued.

The severe threat along with rain chances will end from north to
south Tuesday night as the short wave trough exits to the east into
the Atlantic and the cold front moves to the south of the forecast
area. An increasing northwest to northerly wind flow in the wake of
the front will usher in much cooler and drier air Wednesday through
Friday as surface high pressure builds in from the west. The
increasing winds in the wake of the front will help to quickly
builds seas over the adjacent Gulf waters with a period of very
hazardous marine and beach conditions developing Tuesday night
through early Thursday with frequent wind gusts to near gale force
possible along with high surf and a high risk of rip currents
developing along area beaches.

High pressure over the peninsula on Saturday will move slowly
southeast into the Atlantic during the day as an area of low
pressure move offshore the mid Atlantic coast. Pleasant dry weather
with lighter winds and warmer temperatures are expected. On Sunday a
back-door type cold front will approach from the northeast during
the day. Limited moisture will preclude rain chances with the front
with pleasant weather continuing with just some clouds and a wind
shift into the northeast expected during the afternoon.

Above normal temperatures on Tuesday will fall to below normal
Wednesday through Friday in the wake of the front under cold air
advection with overnight lows falling back into the 40s and 50s,
with daytime highs in the upper 60s to lower 70s. Temperatures will
moderate back to above normal during next weekend as winds become


The fog and low ceilings from this morning have cleared up giving
way to VFR conditions for the rest of the day with light onshore
winds. Similiar conditions can be expected again on Monday morning
with more VSBY/CIG restrictions possible between 09-15Z.


High pressure is sitting east of Florida with perfect boating
conditions today. Rain free conditions can be expected with light
winds less than 10 knots and seas 2 feet or less. A slight uptick in
the winds and seas can be expected beginning Monday afternoon into
Tuesday as the next frontal boundary approaches the area. Rain
chances will also increase into Tuesday as the front approaches.
Boating conditions will deteriorate further late Tuesday into
Wednesday in the wake of this front with Small Craft Advisory
conditions expected.


Low level moisture continues to be on the rise and will remain above
critical levels today and Monday. Good rain chances Tuesday ahead of
a cold front. Very dry and cool high pressure to build into the
region Wednesday through the end of next week.


.Preliminary Point Temps/PoPs...
TPA  65  79  69  77 /  10  20  20  70
FMY  65  82  69  81 /  10  10  10  60
GIF  62  85  68  82 /  10  30  10  70
SRQ  64  76  69  77 /   0  10  10  70
BKV  62  81  67  78 /  10  40  30  70
SPG  65  79  69  77 /  10  20  20  70


Gulf waters...None.


LONG TERM/DECISION SUPPORT...57/McMichael is the U.S. government's official web portal to all federal, state and local government web resources and services.