Area Forecast Discussion
Issued by NWS Miami, FL

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348
FXUS62 KMFL 270100
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
900 PM EDT Sat May 26 2018

.AVIATION...
Trends in the model suggests more precipitation is possible
through the night into Sunday.


&&

.UPDATE...
Raised rain chances overnight to nearly 100 percent as nearly
certain widespread rain will continue. Latest convective band is
pushing into far southern Florida nearly 1z and additional banding
is likely toward early morning. 0z RAOB indicates increasingly
favorable airmass for rotating updrafts as supplemented by HRRR
and other CAMs. Target time for enhanced tornado risk appears to
be 5z-13z, so will be continuing to closely monitor. SPC continues
with Slight Risk of tornadoes and damaging winds south and west of
a Naples to Miami line overnight, with Marginal Risk for remainder
of CWA. Flood Watch and Small Craft Advisory continues areawide.
High Risk of Rip Currents on East coast through Monday, with High
Risk Sunday for Gulf Coast. Will be also monitoring for minor
tidal inundation along the Gulf coast Sunday, particularly around
high tide with is roughly midday. A Coastal Flood Statement is in
effect along the Gulf coast where a foot or so of inundation is
possible. Last but not least, Tropical Storm Warning in effect for
outer Gulf Waters, beyond 20 nm offshore. Latest observations from
buoys in the Gulf and also in and near the Keys should tropical
storm force wind gusts are likely already occurring in this area.
8PM NHC advisory on Subtropical Storm Alberto reveals weak,
disorganized storm with max. sustained winds of 40 mph, though
highest winds are present well east of the center. Alberto should
make its closest approach to South Florida during the morning
Sunday.

&&

.PREV DISCUSSION... /issued 349 PM EDT Sat May 26 2018/

DISCUSSION...
The National Hurricane Center shows Alberto continuing to move north-
northwestward over the eastern Gulf waters through the rest of the
weekend. At the same time, an area of high pressure continues to
remain over the western Atlantic just to the east of the Florida
peninsula. This set up will allow for a south southeasterly wind
flow to continue and it will keep a steady flow of deep tropical
moisture in place through the Memorial Day weekend.

With all of this moisture in place, rain chances will remain high
through the rest of the weekend. Of particular concern is that for
late tonight and Sunday, South Florida will lie under a region of
upper-level divergence to the east of the deepening mid/upper level
low pressure over the Gulf of Mexico associated with Alberto, as
well as increasing low-level convergence and wind fields around the
periphery of Alberto`s large-scale circulation. This synoptic setup
is conducive for bands of rain and a few embedded thunderstorms to
not only increase in coverage but also in intensity as they move
north across the area. The end result is that our flood threat will
increase beginning late tonight and continue through Sunday, and
possibly Sunday night as well. The Flood Watch will remain in place
at least through Sunday evening, and we will continue to closely
monitor the threat of heavy rain and flooding even into Monday as
Alberto continues to affect the northern Gulf coast.

Along with the increasing threat of flooding, the potential for
isolated tornadoes will increase late tonight in response to the
strengthening low-level wind profiles, helicity values and
increasing instability. The highest tornado threat appears to be
late tonight and Sunday over Southwest Florida, but notable as well
over Southeast Florida. This corresponds well with SPC`s marginal
risk area over all of South Florida.

Both of the latest GFS and ECMWF show Alberto moving across the
Southeastern portion of the country early next week. This should
also allow for a deep swath of moisture across South Florida as the
flow should remain out of the south southwest at least through the
middle of the week. By the end of next week, the swath of deeper
moisture should slowly move northward out of the region, which
should allow for a return to a more typical summertime pattern with
scattered showers and thunderstorms developing along the east and
west coast sea breezes.

MARINE...
The offshore Gulf waters are under a Tropical Storm Watch
through midday Sunday due to its closer proximity to the outer
tropical storm force wind field. Wind speeds will be between 25 and
30 knots across the Gulf waters, with higher gusts even outside of
any rain bands. Over the Atlantic waters, South-Southeast winds of
20 to 25 knots tonight and continuing through late Sunday. Wind
speeds gradually decrease to 15 to 20 knots late on Memorial Day,
except over the offshore Gulf waters where winds will remain around
20 knots.

A Small Craft Advisory will be in effect for all the coastal waters
through at least Sunday night.

BEACH FORECAST...
Tides have been running about a half-foot above normal along the
Southwest Florida coast based on data from NOAA tide gauges. As
Alberto moves northward over the eastern Gulf, consensus of the
latest model guidance shows that the water levels could go up a
little bit more, as much as 1.5 to 2 feet above mean higher high
water (MHHW) across portions of the Southwest Florida coast during
the high tide cycle Sunday morning through midday. This will
allow for the possibility of some minor coastal flooding and minor
beach erosion especially in the vulnerable areas along the
Collier County coast. We will continue to monitor this, however if
this trend continues, a coastal flood statement will need to be
considered for Sunday. There will be a high risk of rip currents
along the Atlantic Coast beaches through Sunday evening. The
threat for rip currents will also begin to increase late tonight
and Sunday along the Gulf coast beaches, probably to a high risk.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  73  83  75  84 /  90  90  60  90
Fort Lauderdale  75  82  77  83 /  90  90  70  80
Miami            74  83  75  84 /  90  90  70  80
Naples           72  84  74  85 /  90  80  60  80

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through Sunday evening for FLZ063-066>075-168-
     172>174.

     High Rip Current Risk from 8 AM EDT Sunday through Monday
     afternoon for FLZ069-075.

     High Rip Current Risk through Monday afternoon for FLZ168-172-
     173.

AM...Small Craft Advisory until 8 AM EDT Monday for AMZ610-630-650-
     651-670-671.

GM...Tropical Storm Warning for GMZ676.

     Small Craft Advisory until 8 AM EDT Monday for GMZ656-657.

&&

UPDATE...23/SK
DISCUSSION...55/CWC
MARINE...55/CWC
AVIATION...67/MT
BEACH FORECAST...55/CWC






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