Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
402 am EDT Tuesday Mar 11 2014
Short term (today-thursday)...
in the middle/upper levels a shortwave will move east across the deep
south and out into the Atlantic Wednesday quickly followed by a
deepening trough over the eastern U.S. Thursday. Meanwhile at the
surface an area of low pressure will develop over the central U.S.
And track east northeast across the Ohio Valley and eventually off
the New England coast Thursday dragging a cold front across the
region Wednesday night.
For today high pressure will hold on...but moisture will begin to
increase in the southwesterly flow ahead of the developing storm
system. It should remain dry...but could see a couple of showers
move into the northern and central coastal waters toward evening.
Clouds will begin to increase during the day with temperatures
warming into the upper 70s to lower 80s...except close to the Gulf
Coast where the sea breeze/onshore flow will keep readings in the
upper 60s to lower 70s.
Tonight into Wednesday deeper moisture associated with the
shortwave will overspread the area leading to mostly cloudy skies
and chances of showers and possibly a few thunderstorms. Best
timing for precipitation should be between 06z and 18z Wednesday
as shortwave energy moves by just to the north. Temperatures will
be above normal tonight with lows only falling into the upper 50s
to middle 60s...and still a couple of degrees above normal on
Wednesday with highs mostly in the middle 70s to lower 80s...except a
few degrees cooler close to the Gulf Coast.
Wednesday night the cold front will sweep across the region with
a band of clouds and possibly a few sprinkles associated with it.
Winds will shift to northerly and increase overnight as cooler
drier air begins moving into the area. Low temperatures will cool
into the middle 40s across the north to near 60 far south.
Thursday looks to be mostly sunny...breezy and cooler as high
pressure builds in from the northwest with temperatures only
climbing into the lower 60s north to lower 70s south.
Long term (thursday night-monday)...
models are in fairly good agreement through Friday night or
Saturday...then significant differences develop for the remainder
of the extended forecast.
The cold airmass will be sliding off to the northeast on Friday...
but not before giving US a chilly morning. Have kept temperatures
above freezing for now...but there is at least some chance that we
will see temperatures at or below freezing over Levy County.
Elsewhere...middle 30s to lower 40s will be common from north to
south...with temperatures holding near 50 right along the coast.
On Saturday...models begin to struggle with pieces of energy
ejecting eastward from a cut-off low that is forecast to be over
or near Southern California on Thursday. The GFS moves a slightly
better defined short-wave trough across the northern Gulf states
on Saturday whereas other models are weaker/flatter. The more
defined GFS solution would bring more clouds and perhaps even some
shower chances north of the Tampa Bay area while the European model (ecmwf) and
Canadian would favor dry weather with fewer clouds. 00z wpc
forecast also favors the drier scenario...so will optimistically
keep one of the weekend days dry.
On Sunday...a stronger short-wave in the northern stream digs
southward toward Texas...but what happens after that point depends
on the orientation of the polar low near Hudson Bay. The GFS has a
north-south orientation which begins to phase with the southern
stream. The European model (ecmwf) has more of an east-west orientation and does
not phase. This leads to timing differences throughout the
remainder of the extended period resulting in a rather low
Not going to try to get too detailed with all these differences...
but suffice to say that with a rather robust trough to our west
and a frontal boundary nearby...we will see our share of clouds
and rather high rain chances for March. The best rain chances
should be centered on Sunday and Monday with some improvement by
do not expect widespread fog this morning...but patchy shallow
ground fog has already made a brief appearance at pgd. The
normally fog prone locations of pgd and lal could occasionally
drop to MVFR or IFR...but expect predominantly VFR elsewhere.
All locations should be VFR by 14z.
the rather light flow will become more southerly during today with
the sea breeze developing near the coast during the afternoon. The
southerly flow will persist and increase some tonight before
shifting to westerly during Wednesday as a surface trough moves
across the waters. The real increase in winds and seas is expected
for Wednesday night into Thursday as the cold front moves across
the waters with northerly winds at Small Craft Advisory levels.
Winds and seas will begin to subside late Thursday and Thursday
and veer around to the northeast as surface high pressure moves by
to the north. A more easterly flow will become established over
the weekend with the West Coast sea breeze expected to develop
no fire weather concerns through Wednesday. On Thursday and Friday
much drier air will overspread the area with several hours of
critical relative humidity anticipated. However...winds and erc
values are expected to remain just below significant levels...so
no red flag warnings foreseen at this time.
Preliminary point temps/pops...
tpa 77 64 78 53 / 5 40 60 10
fmy 82 66 83 59 / 0 20 50 20
gif 81 63 81 53 / 5 30 50 10
srq 77 64 79 56 / 5 30 60 10
bkv 79 59 79 47 / 10 50 60 10
spg 77 66 77 55 / 5 40 60 10
Short term/marine/fire weather...69/close