Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 170737
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
337 AM EDT Thu Aug 17 2017

.DISCUSSION...
...Highest Heat Index Readings Between 101 and 106 Today...

Current...Weak surface high pressure ridging lies across the south-
central FL peninsula this morning with light/variable surface winds.
East-west oriented mid-level ridging remains across the northern FL
peninsula. 915 MHZ Cape wind profilers show a very weak wind profile
with speeds around 5 kts and direction varying from SW-W. Conditions
remain warm and moist with temperatures and dewpoints well into the
70s areawide. Skies are partly cloudy with some high-level cirrus
overhead.

Today-Tonight...The surface high pressure ridge axis remains
forecast to lift very slowly over the next 24 hours from south-
central FL into the central peninsula. The pressure gradient also
remains very weak with light/variable winds carrying into the
afternoon over the interior. Winds will become onshore near the east
coast late morning/early afternoon (with deeper inland push
southward again). Winds will generally become light S/SW this
evening and overnight. Mid-level high pressure ridging east-west
oriented continues north of central FL, though the center does
retrograde from the FL Panhandle to near the Louisiana coast by the
end of the period. 500 mb temps are forecast a little cooler at -
6.5C/-7.5C. PWATs are forecast to be in excess of 2 inches over much
of the coverage warning area, especially northward, though the GFS
hints at some drier air intrusion overnight southward across the
Treasure Coast and Okeechobee County.

The lighter offshore flow again today will allow earlier
onset/inland push of the east coast sea breeze with various
afternoon/early evening boundary collisions allowing climo PoPs of
50 to 60 percent, at least for areas near Okeechobee County
northward. The Cape southward through the Treasure Coast will have
the lowest PoP chances (20-40pct), unless late day boundary
collisions push some convection back towards the coast here. Storm
threats continue to be locally heavy downpours, lightning, and gusty
winds up to around 35 to 45 mph. With the deep moisture and very
weak overall wind profile, cannot rule out a waterspout or two near
the east coast or around Lake Okeechobee.

General storm steering flow remains forecast at around 5 mph with
variable direction again at best and direction ultimately dictated
by stronger afternoon/early evening boundary collisions. The local
HRRR is again showing the greatest coverage late today from Lake
George southward through Osceola County and along the Kissimmee
River into Okeechobee County.

Highs continue in the 90s with overnight lows in the 70s. The
combination of hot temperatures and high humidity may create a
dangerous situation in which heat illnesses are possible. Drink
plenty of fluids, stay in an air-conditioned room, stay out of the
sun, and check up on relatives and neighbors. Highest heat index
values will soar to between 100 and 106 from late this morning into
early evening across much of east central Florida.

Friday...The models show little change with tutt cell forecast to
be in the vicinity of western Cuba and a mid level inverted
trough extending northward across the Florida peninsula. Overall
moisture is not forecast to be quite so high, as some drier air
aloft is forecast by the models pushing in from the east/southeast.
MOS POPs have trended lower which looks reasonable so will adjust
current values downward to a max of 50 percent over interior
sections.

Weekend-next Thu...The 00z GFS showed mid level inverted trough
shifting west over the Gulf of Mexico early in the period, with
ridge building in behind it over Florida. Meanwhile, the surface
ridge axis will lift into north Florida Sunday, which would
generate an onshore wind flow.

The latest models showed highest moisture values from Sat (in the
south) into Sunday as area comes under east side of the inverted
trough. Lower POPs are anticipated Mon as mid level ridge covers
the area. These climo or slightly below normal POPs will continue
into mid week, except the northward nudge of the subtropical ridge
may allow for the northern extension of a tropical wave to affect
southern areas Tue into Wed. Frontal trough is shown dropping
into the southeast states Thu and suppressing surface ridge back
to the south. This would signal a return to higher than normal
POPs for east central Florida.

&&

.AVIATION...Generally light morning winds with a degree of variability
into the afternoon and a very weak pressure gradient in place. Winds
will become onshore near the coast late morning/early afternoon,
beginning with the Treasure Coast, then northward. SCT- NMRS mainly
aftn/early evening showers/storms with continued deep moisture in
place. Highest coverage again late in day/early evening surrounding
additional/larger - sea breeze/mesoscale boundary interactions.
This greater coverage should be near/north of a KISM- KTIX line
and potentially southward to along the Kissimmee River.


&&

.MARINE...
Today-Tonight...High pressure ridging over the south-central FL
peninsula remains forecast to make slow progress northward toward
the central peninsula over the next 24 hours. The pressure
gradient remains very weak so expect light morning offshore flow
to turn onshore, once again, in the afternoon along the coast with
the sea breeze development. Expect earlier formation of the sea
breeze along the Treasure Coast again and quicker push inland
there as well. Over the open Atlc this afternoon winds will
average around 5 kts with mainly a variable direction. Winds
becoming S/SW this evening while still generally AOB 10 kts. Seas
1-2 ft near shore and around 2 ft offshore.

The greatest chance for offshore moving afternoon storms should be
from about Canaveral northward. Marine interests should also be
alert for the potential of waterspouts today into early this evening.

Fri...Surface ridge axis is forecast to extend across the central
waters. This will produce a southwest wind flow in the north and
southeast in the south. Speeds look 10 knots or less with
continued rather benign seas. The chance for offshore moving
afternoon storms looks low and mainly from about Canaveral
northward.

Weekend-Mon...Little change in the models showing axis of surface
high pressure ridge nudging north into the northern waters Sat and
then north of the waters on Sunday. Speeds look 10 knots or less,
except up to 10-15 knots in the south half Sun-Mon. The more
southeast wind component should bump up seas slightly to near 3
feet offshore and maybe 4 feet by Mon. A weak low pressure wave
should increase shower/storm coverage in the southern waters Sat
and central/north waters Sunday. Drier conditions are expected
Mon.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  92  76  92  76 /  60  40  40  20
MCO  94  76  94  76 /  50  30  40  20
MLB  92  76  91  78 /  30  30  40  10
VRB  92  75  92  76 /  20  20  30  10
LEE  94  77  94  77 /  60  30  50  20
SFB  95  77  94  77 /  60  30  40  20
ORL  95  78  95  78 /  50  30  40  20
FPR  92  74  92  76 /  20  20  30  10

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&

$$

SHORT TERM...Sedlock
LONG TERM....Lascody


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