Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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359
FXUS62 KTBW 250111
AFDTBW

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
812 PM EST Fri Feb 24 2017

...Updated Aviation Section to mention lower Cigs already moving
into Tampa Bay area terminals...

.UPDATE...
Only updates this evening to inherited forecast was an
uptick in sky cover by second half of the overnight and the
expansion fog potential over portions of the marine
zones...especially north of Englewood.

There is no doubt that NWP is notoriously over-aggressive
when it comes to marine stratus/fog development, however, we
already have a large area of stratus just offshore this
evening...and a flow pattern that will be increasingly
favorable for this areas movement/expansion eastward into
the FL west coast. We are already seeing this expansion
beginning on last few IR satellite images since the sun set.
This process is likely to accelerate overnight...especially
second half of the night.

Even taking the aggressive bias into account...the signal
for the ensemble data (SREF/NARRE)...along with other
deterministic solutions suggests strongly that we will see
more and more stratus overnight...and eventually the
potential for some visibility problems. Fog and especially
marine fog are some of the most difficult things to
forecast...so a careful monitoring of observations and
satellite data will be required the next several hours and
beyond. However, to avoid a sudden huge change to the
forecast that could be impactful, have started the trend
toward foggier and cloudier conditions overnight into
Saturday morning. The economic impacts of sea-fog to areas
such as Port Tampa and elsewhere also suggest not waiting
any longer to address the potential.

Will make additional updates as necessary...and try my
hardest to stay ahead of the game.

&&

.AVIATION (25/01Z through 26/00Z)...
Honest truth...this is not an easy aviation forecast through
tomorrow morning. Determining factor is the exact evolution of lower
stratus deck offshore Gulf...and now moving ashore in Pinellas
County. Most of the guidance is showing this deck making a full move
back to the coast...resulting widespread MVFR/IFR...LIFR potential.
However...NWP is also notoriously over aggressive with marine
stratus/fog. Have updated KTPA/KPIE/KSRQ to include the already
observed low MVFR/IFR cigs moving ashore for rest of the evening.
Thereafter...Have gone with the ensemble solution...but backed off
full restriction potential. Feel it might still be more prudent to
monitor satellite trends a few more hours before going even more
pessimistic. However, because of the potential for greater
restrictions after 06Z than currently shown, pilots should check
back before finalizing plans. If the marine stratus/fog does come
inland...coastal terminals are likely to have a slow recovery back
to VFR tomorrow morning/midday.

&&

.MARINE...
WEAK HIGH PRESSURE WILL REMAIN OVER THE WATERS THROUGH
SATURDAY. A COLD FRONT WILL PUSH ACROSS THE WATERS SATURDAY
NIGHT WITH INCREASING NORTHWEST THEN NORTHERLY WINDS BEHIND
THE FRONT THROUGH SUNDAY MORNING. HIGH PRESSURE WILL BUILD
BACK OVER THE WATERS IN THE WAKE OF THE FRONT LATER SUNDAY
AND MONDAY.

THE POTENTIAL THAT AREAS OF MARINE FOG WILL DEVELOP OVERNIGHT
INTO SATURDAY MORNING APPEARS TO BE INCREASING...ESPECIALLY TO THE
NORTH OF ENGLEWOOD. MARINE FOG THAT DOES DEVELOPS IS USUALLY
DENSE IN NATURE. THEREFORE...MARINERS ARE URGED TO MONITOR THE
LATEST FORECASTS BEFORE FINALIZING PLANS FOR SATURDAY
MORNING.

&&

.Prev Discussion... /issued 649 PM EST Fri Feb 24 2017/

AVIATION (25/00Z through 26/00Z)...
Honest truth...this is not an easy aviation forecast through
tomorrow morning. Determining factor is the evolution of
lower stratus deck offshore Gulf. Most of the guidance is
showing this deck making a move back to the
coast...resulting widespread MVFR/IFR...LIFR potential.
However...NWP is also notoriously over aggressive with
marine stratus/fog. Have gone with the ensemble
solution...but backed off full restriction potential. Feel
it might be more prudent to monitor satellite trends a few
more hours before going even more pessimistic. However,
because of the potential for greater restrictions after 06Z
than currently shown, pilots should check back before
finalizing plans. If the marine stratus/fog does come
inland...coastal terminals are likely to have a slow
recovery back to VFR tomorrow morning/midday.

Prev Discussion... /issued 204 PM EST Fri Feb 24 2017/

SHORT TERM (This afternoon-Saturday)...
Upper ridging continues to build into and over the region from
the S Gulf and N Carib while weak surface high pressure remains
in the area between the low pressure features in the Great
lakes and W Atlantic. This stacked ridging overhead will
produce dry subsidence aloft while abundant surface moisture
keeps warm and humid conditions in place under the low level
inversion. Expect overnight fog and low clouds to once again
develop areawide especially thick over interior areas early
Saturday morning that should burn off/mix out mid morning
for another warm and partly sunny afternoon.

Long Term (Saturday Night-Friday)...
A nearly zonal or weakly southwest flow aloft will remain over the
state through the end of the weekend. At the surface, a dry cold
front will move through the region Saturday night and will be south
of the forecast area by Sunday morning, with high pressure then
shifting into the southeast. For Monday through Wednesday, mid/upper-
level ridging will build over the Caribbean into the Gulf of Mexico
and over Florida. This will lead to significant warming for the
first few days of the week, with temperatures into the upper 80s
across the interior. Some locations could even approach 90,
especially during Tuesday and Wednesday afternoon.

Another storm system will move across the northern portion of the
country toward the end of the week, with a trailing cold front
moving through the state on Thursday. Timing with this front remains
a bit uncertain, but it does look like this will be our next shot
for rain, and will keep slight chance to chance PoPs in the forecast
for now. High pressure building into the southeast looks to give us
a quick cool-down for Friday, although temps are currently forecast
just to get back down to normal.

FIRE WEATHER...
Abundant low level moisture through Saturday with dense fog
possible tonight. Cold front Saturday Night to bring much
drier airmass over the N FL Peninsula Sunday with min RHs
in the 25-30% range over the Nature Coast.

&&

.Preliminary Point Temps/PoPs...
TPA  64  77  57  77 /  10   0   0   0
FMY  63  81  60  81 /   0   0   0   0
GIF  62  82  56  77 /   0   0   0   0
SRQ  61  75  58  76 /   0   0   0   0
BKV  57  78  50  76 /  10   0   0   0
SPG  64  76  60  75 /   0   0   0   0

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...Beach Hazards Statement through Monday evening for Coastal
     Charlotte-Coastal Sarasota.

Gulf waters...None.

&&

$$

UPDATE/AVIATION/MARINE...Mroczka
PREVIOUS DISCUSSION...DAVIS/CARLISLE



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