Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 110840
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
440 AM EDT Sat Aug 11 2018

.DISCUSSION...

Today-Tonight...
Currently, the Bermuda ridge is broken into two parts, a closed H100-
H70 anticyclone extending from the MS/AL bootheels acrs the Bahama
Bank, and the wrn flank of the primary ridge just E of the Bahama
Bank. Btwn the two, as weak trof/col is positioned over the nrn
Bahamas. This trof retrograde into the FL Peninsula thru late aftn
as a broad frontal trof over the Appalachian region digs into the
Deep South. These two WX features will merge along the spine of the
peninsula overnight, which in turn, will allow the wrn flank of the
primary Bermuda ridge to rebuild into S FL.

H100-H70 mean flow will be W/NW today, backing to W/SW overnight.
While NW flow patterns are climatologically not all that favorable
for diurnal precip, coverage on Fri was higher than anticipated when
the flow had an even more pronounced northerly component. With the
north component expected to diminish thru the day as the trof works
its way into the peninsula, expect the lcl storm environment to
become even more favorable for precip. Evng RAOBs measured PWat
values arnd 2.00" acrs central and north FL...latest RAP40 analysis
confirming this with values approaching 2.25" north of the I-4
Corridor. H100-H70 mean RH values btwn 70-80pct, and H85-H50
dewpoint depressions arnd 5C, suggesting an airmass primed for
convection.

H70 temps btwn 8-9C and H50 temps arnd -7C will yield meager lapse
rates btwn 5.5-6.0C/KM. However, with low pres digging into the Deep
South and weak troffing pushing in from the east, FL will become
sandwiched btwn two areas of high pres, leaving the peninsula in an
induced area of favorable storm formation. Will go with likely PoPs
areawide, 60pct over the I-4 Corridor and Cape Canaveral area, 70pct
to the south. Lcl HRRR/WRF models suggesting a fairly early start to
diurnal convection, as early as midday north of I-4. This would tend
to burn up available energy before sunset, leaving little for any
convection to linger into the evng. Will go with 20/30pct btwn
sunset and 02Z, but the bulk of the precip should be done by 00Z.
Temps near avg with aftn maxes in the U80s/L90s, overnight mins in
the L/M70s.

Sun-Sun Night...
The area will remain under low level southwest flow with surface low
pressure across the Carolinas and the surface ridge just south of
the state. PWAT values from 2.0-2.2 inches across central/nrn
sections will support likely rain chances for much of the area with
scattered storm coverage for the Treasure coast. Mid level steering
flow will be from the south across srn sections and SW north of the
Cape which will allow storms to track back toward the east coast in
the mid to late afternoon across nrn sections. Highs will be in the
upper 80s to lower 90s.

Mon-Tue...
The low level ridge axis will begin to move northward across south
FL into early next week with low level SSW/SW flow Monday becoming S
to SW into Tuesday. Moisture levels are forecast to lower some
allowing rain chances to lower into the scattered range. Mid level
winds will remain from the southwest with the mid level ridge across
the Atlantic beginning to build toward S FL into Tuesday. Highs will
be in the lower 90s.

Wed-Sat...
The mid level Atlantic ridge east of the area on Wed will build over
central FL into late week. The low level ridge will be near central
FL Wed and then lift northward toward the nrn peninsula. The
influence of the ridge aloft and developing onshore flow will lower
moisture levels and reduce POPs from the 20-30 percent range Wed to
10-20 percent for Thu-Sat. The lower coverage of storms/cloud cover
will also allow for warmer temps with highs into the mid 90s across
the interior and lower 90s near the east coast from mid week onward.
Lows will range from the mid 70s interior to upper 70s near the east
coast.

&&

.AVIATION...Thru 12/12Z.
Sfc Winds: Thru 11/12Z...S/SW 3-6KTS. Btwn 11/12Z-11/15Z...bcmg W/SW
6-10KTS. Btwn 11/16Z-11/19Z...coastal sites bcmg S/SE 7-11KTS. Btwn
11/22Z-12/01Z...bcmg W/SW 3-6KTS.

Vsbys/WX/Cigs: Btwn 11/12Z-11/16Z...cigs AOA FL120...slgt chc MVFR
shras/IFR tsras. Btwn 11/16Z-11/20Z...cigs btwn FL060-080...N of
KISM-KTIX nmrs MVFR shras/IFR tsras slgt chc LIFR tsras with sfc
G35KTS...S of KISM-KTIX sct MVFR shras/IFR tsras. Btwn 11/18Z-
11/22Z...cigs btwn FL060-080...S of KISM-KTIX nmrs MVFR shras/IFR
tsras slgt chc LIFR tsras with sfc G35KTS...N of KISM-KTIX chc MVFR
shras/IFR tsras. Btwn 11/22Z-12/02Z...cigs btwn FL100-120...coastal
sites chc of MVFR shras/IFR tsras...interior sites slgt chc MVFR
shras/IFR tsras.

&&

.MARINE...
Today...Weak trof over the nrn Bahamas will combine with a broad
anticyclone over the GOMex to generate a light to gentle W/SW breeze
acrs the lcl Atlc thru midday. Weak sfc pgrad will allow the east
coast sea breeze to form along the Treasure Coast by early aftn,
zippering up the Brevard/Volusia Co coasts by mid aftn... sfc/bndry
lyr winds bcmg a light to gentle S/SE breeze as is does. Seas AOB
2FT. Primary boating hazard will be sct/nmrs shras/tsras moving
offshore btwn midday and early evng.

Tonight...Pgrad will tighten slightly as a broad trof over the
Appalachian region digs into the Deep South and interacts with the
wrn flank of the Bermuda ridge.  Winds bcmg a gentle to moderate
S/SW breeze. The offshore wind component will keep the lcl Atlc
fetch protected with seas holding AOB 2FT. However, dominant pds
will shorten to AOB 5sec, resulting in choppy conds.

Sun-Sun Night...SSW winds to around 10 knots will become southerly
in the afternoon and increase to 10-15 knots. Seas 1-2 ft near shore
to 2 ft offshore. Expect some late afternoon storms to approach the
intracoastal and near shore waters mainly north of Sebastian Inlet.

Mon-Wed...Southwest winds to 10 knots will become southerly into
Tuesday-Wed as the low level ridge begins to move northward from
south FL. Scattered storm coverage Mon-Tue will decrease some by Wed
as mid level dry air begins to limit convection into mid week.

&&

.HYDROLOGY...The St Johns River at Astor has fallen just below Flood
Stage and the River Flood Warning has been cancelled. However, this
are is forecast to remain within Action Stage into next week.

The St Johns Above Lake Harney near Geneva, near Sanford, and near
Deland are forecast to slowly decrease into next week, with the
point near Deland receding below Action Stage this weekend.

Refer to the latest Hydrologic Statements (RVSMLB) for the latest
stage and forecast information.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  90  75  90  75 /  60  30  60  40
MCO  90  75  92  74 /  60  20  60  30
MLB  92  74  90  75 /  70  30  60  30
VRB  91  72  91  74 /  70  30  50  30
LEE  90  75  92  76 /  60  20  60  30
SFB  91  75  92  75 /  60  20  60  40
ORL  91  75  92  76 /  60  20  60  30
FPR  91  71  91  73 /  70  30  40  30

&&

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

&&

$$

Short Term/Aviation...Bragaw
Long Term/Impact WX...Volkmer


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