Area Forecast Discussion
Issued by NWS Melbourne, FL
FXUS62 KMLB 231838
Area Forecast Discussion
National Weather Service Melbourne FL
239 PM EDT SAT JUL 23 2016
Current-tonight...The 15Z KXMR sounding shows a PWAT of 1.56 inches
and 700/500mb temperatures respectively at +8.3C/-8.0C. Cape wind
profilers continue to show a very weak wind profile from the surface
up through 10.0Kft with generally an ESE or SE direction of 5 kts or
less. The weak pressure gradient across ECFL continues into tonight
with light and variable to calm winds. The east coast sea breeze is
venturing inland from the east coast with ENE-ESE winds of 8 to 12
mph in its wake. Shower and thunderstorm activity thus far has been
ISOLD to WDLY scattered with many cells short-lived, due to likely
lower deep layer moisture values and warmer temperatures aloft.
Water vapor imagery shows much drier air aloft infiltrating into the
ECFL peninsula this afternoon.
As the sea breeze moves inland showers/storms will follow it into
WCFL thru late afternoon/early evening. Highest POP chances will
remain well inland and generally south of Orlando. Threats continue
to be frequent cloud to ground lightning in a few storms, locally
heavy downpours with possible nuisance flooding of low-lying areas,
gusty outflow winds, and perhaps some small hail. Storm motion will
be slow/erratic. Few lingering storms possible into early evening,
mainly Lake County and near the Kissimmee River.
Overnight lows remain mild and generally in the L-M70s areawide.
Cloud debris will thin through the night.
...Previous Extended Forecast Discussion...
Sun-Sun Night...Unusually dry mid summer WX pattern to continue for
east central FL. An amplifying short wave trof over the Mid Atlc/New
England states will pull into the N Atlc, allowing a broad
anticyclone over the Deep South to lift into the Mid Atlc and merge
with the Bermuda Ridge. This merger will push a weak H100-H70 cut-
off low from the Carolina Coast to the S/SW into the nrn Bahamas/FL
Straits, effectively placing much of the central/north peninsula on
its descending left flank.
As the low drops into the region, it will drag a slug of rather low
RH air into the central/nrn peninsula. RAP40 analysis already
measuring H100-H70 RH values blo 60pct impinging on the I-4 corridor
with values as low as 50pct extending up the coast all the way to
the NC Outer Banks. Avg lyr dewpoint depressions are quite high with
H100-H70 values arnd 10C...H85-H50 values btwn 20-25C. GFS MOS
guidance continues to advertise 20-30 PoPs along the Treasure
Coast/Lake-O region...single digit PoPs along the I-4 corridor as
well as the Space Coast.
Can see no compelling reason to deviate very far from this solution
given the amount of dry air advection that is anticipated,
especially as winds thru the H100-H70 back to the E/NE, a direction
that climatologically is unfavorable for diurnal convection for east
central FL. GFS model soundings indicate PWat values in the 1.00"-
1.25" range over the central/nrn counties, increasing to arnd 1.75"
around Lake-O. Near full sun thru the peak heating hrs will couple
with the dry air advection to generate warm aftn temps over the
interior with maxes in the L/M90s, while the onshore component keeps
coastal temps in the U80s/L90s. Min temps near avg in the L/M70s.
Mon-Mon Night...Once the anticyclone over the Deep South merges with
the Bermuda Ridge, the cut-off low will steadily weaken into an open
inverted trof over south FL by daybreak. H100-H70 mean flow will
return to a S/SE direction that will pull a ribbon of moisture up
from the central Bahamas as the FL peninsula gains the ascending
flank of the trof. Sct PoPs areawide...30pct acrs Volusia/Nrn
Lake...increasing to 50pct Treasure Coast/Lake-O region. Maxes
U80s/L90s...a few M90s over the interior. Mins L/M70s.
Tue-Fri...Trof should dampen out completely by daybreak Tue as the
newly formed ridge shunts it into the GOMex. This will leave the
Bermuda Ridge as the dominant WX feature thru the remainder of the
week. Position of the ridge axis will meander acrs the FL peninsula,
as it is want to do this time of year. S/SErly flow will prevail
thru the H100-H70 lyr, a direction that favors the interior counties
for highest PoPs. Even so...will keep precip chances aob 40pct as
analysis of the tropical/subtropical Atlc shows a surprising amount
of dry air east of the Windward Passage assocd with the presence of
a large Saharan dust plume. Srly wind component will keep aftn maxes
in the U80s/L90s along the coast...L/M90s interior. Mrng mins in the
.AVIATION...VFR outside of convection. VCTS 18-23Z with MVFR CIGS
for mainly interior TAF sites. Winds light/variable to near calm
again tonight. Much drier air forecast to move north of KMLB and
west through the I-4 corridor on Sun, with afternoon storms favoring
south of here where moisture will remain deepest.
.MARINE...Current-tonight...ENE-ESE winds 8-12 kts along the coast
and 4-8 kts over the open Atlc. The weak pressure gradient will
allow winds to become light/variable again this evening with perhaps
an offshore flow at least near the coast overnight. Favorable seas 2-
3 ft. Isolated showers and storms, mainly over the Gulf Stream and
more favorable south from Sebastian Inlet.
...Previous Extended Marine Forecast Discussion...
Sun-Wed...Overall, favorable boating conds through the first half of
the upcoming week. Light to gentle Erly breeze on Sun will back to
the SE Sun Night as a weak inverted trof pushes acrs the FL
peninsula. Winds bcmg a gentle S/SE breeze on Mon as the trof
dampens out and the Bermuda Ridge rebuilds overhead. The ridge will
then meander acrs the FL Peninsula thru midweek...maintaining a
light to gentle SErly breeze. Seas 2-3FT. Sct shras/tsras Sun and
Mon...bcmg isold Tue and Wed.
.FIRE WEATHER...thru the weekend...Continued very light/variable
overnight/morning 20ft/transport winds becoming ENE-ESE with gradual
increase in wind speeds as the east coast sea breeze develops and
moves slowly inland each afternoon. Dispersion indices poor to fair
at best in the afternoon and poor overnight. Convection beginning
along the south Brevard County/Treasure Coast initially early in the
afternoon, then spreading inland with highest coverage south of
Orlando and well into the interior where deep layer moisture remains
greatest. Storm threats through the period include frequent cloud to
ground lightning in a few storms, heavy downpours, gusty outflow
winds, and perhaps some small hail. Fog not forecast but smoldering
brushfires may allow for settling of smoke locally.
.PRELIMINARY POINT TEMPS/POPS...
DAB 72 90 72 89 / 10 10 10 30
MCO 73 94 74 91 / 20 20 10 40
MLB 73 90 75 89 / 20 20 10 40
VRB 71 89 72 89 / 20 30 20 50
LEE 74 95 75 93 / 30 30 10 30
SFB 73 93 74 92 / 20 20 10 40
ORL 74 94 75 91 / 20 20 10 40
FPR 71 89 72 90 / 20 30 20 50