Area Forecast Discussion
Issued by NWS Melbourne, FL
FXUS62 KMLB 171503
Area Forecast Discussion
National Weather Service Melbourne FL
1000 AM EST Tue Jan 17 2017
Current...The persistent local wx pattern featuring the Atlantic
high pressure ridge at the surface coupled with a strong mid level
ridge over the top of Florida continues to remain in place.
Morning RAOB data shows the cap has risen to 830-800MB, while both
RAOB/DRWP data show the low-mid level winds starting to veer out of
the SE and south. Early visible satellite imagery showed mostly
sunny skies with some thin CI streaming overhead. A large disparity
in temps currently exists, ranging from the L60s over the interior
north to the M-U70s along the Treasure Coast.
Rest of Today...Little change expected today, other than winds being
slightly more veered and max temps a degree or two warmer. Expect
partly to mostly sunny skies with maxes near 80F along the coast and
in the L80s inland.
.AVIATION...VFR. Patchy/shallow mist possible over the northern
interior aerodromes overnight/ 08Z-13Z
.MARINE... Local buoys indicate combined seas of 3FT near shore,
building up to around 4FT well offshore. Spectral density plots
paint an interesting picture this morning. Contribution to wave
energy has gradually transitioned from 8-9s pd swell to 4-5s pd wind
chop, especially near the coast, as seen in local data buoys. Since
sea heights are on top of the current forecast, no changes will be
forthcoming there. However, will go with the shorter wind chop pd as
the dominant one for the morning update.
LONG TERM/IMPACT WX...Lascody
.PREV DISCUSSION... /issued 245 AM EST Tue Jan 17 2017/
...Above Normal Temperatures will continue this week...
Tonight...Sfc and low level ridge axis near the area will allow for
lighter boundary layer flow and increased chance for fog development
after midnight especially across the interior. Will forecast areas
of fog inland and patchy fog near the east coast. Lows will drop
into the 50s most areas except in the lower 60s along the Martin
Wed-Wed night...Flat ridging in the mid-levels early in the period
ahead of shortwave ridging later in the period as a potent shortwave
trough moves off of the mid Atlc coast and into the western Atlc. At
the surface, weak high pressure ridging across the central FL
peninsula continues to slide southward toward the southern
peninsula. General subsidence continues with fair/dry conditions and
partly cloudy skies. Winds will begin SW remaining generally below
10 mph during the day, except backing to ESE along the
Space/Treasure coasts in the afternoon with development of the east
coast sea breeze. Winds fall to near calm at night.
The biggest weather concern remains fog potential early in the
period and again overnight. Fog, should it develop, may become
locally dense in favored prone locations over the interior. Highs
continue well above normal in the U70s to L80s areawide. Lows also
mild and generally ranging from the U50s to L60s, except normally
cooler locations across the interior that may realize M50s.
Thu-Mon...Ridging aloft will slowly migrate east of the Florida
peninsula by late Thu. The W/SW flow aloft will allow for periodic
shortwave impulses to traverse the deep south and Florida peninsula
through Sat. The pattern in the mid-levels across the CONUS remains
active as a strengthening wave moves out of the Desert Southwest Sat
night and travels eastward across the Gulf Coast States on Sun/Sun
evening. While the upper low associated with this deepening upper
trough lies over the Tennessee Valley early Mon morning, expect the
trough itself to move across the FL peninsula Mon morning/early
afternoon becoming negatively tilted as it moves east away from the
area Mon night.
At the surface, an area of low pressure over the ArkLaTex region
with associated upper energy will lift northeastward into the Ohio
Valley Thu night while weakening, which will keep the Deep South in
the warm/moist sector through the weekend. If fact, any frontal
activity over the Deep South will not be able to dive southward
toward ECFL until very late Sun overnight and Mon morning. The
pressure gradient remains relatively weak thru Sat night with
generally light winds. The flow picks up on Sun out of the south and
southwest ahead of the approaching cold front. Westerly winds will
follow behind the front on Mon.
Deep layer moisture values will steadily increase into the weekend
with PWAT values increasing in upwards of 1.40-1.60 inches on Sat
and again on Sun aftn. PWAT values may surge up to around 1.80-1.90
inches out ahead of the front late Sun/Sun night. For PoPs, Thu
still looks dry and will keep low shower chances Fri afternoon and
evening across the I-4 corridor. On Sat, enough moisture and
heating, combined with some weak energy aloft may allow for some
convection Brevard-Osceola counties northward, mainly in the
afternoon and early evening. Have recently added thunder mention to
grids/zones north of a KISM-KTTS line for Sat aftn/evening. Have
kept showery precipitation in for the I-4 corridor early on Sun with
isolated thunder possible Sun afternoon here as well.
Precipitation chances go up considerably Sun night areawide as a
potentially organized squall line over the eastern Gulf moves
onshore WCFL, then across ECFL overnight into early Mon morning.
Expecting 50 to 60 percent PoP chances for the Sun night period.
Storms will be included in the forecast and cannot rule out a few
strong storms Sun night/Mon morning. It remains too early to pin
down exact storm threats just yet. Best guess for Mon morning is
that heaviest activity will favor areas south of Orlando by around
sunrise. Decreasing precipitation chances will follow from north to
south through the morning/early afternoon.
Little change in temperatures indicated through the period, meaning
they will remain well above normal thru Sun night. Highs look close
to 80 degrees each day with overnight lows around 60 to the mid 60s.
If the next frontal passage verifies for Sun night-early Mon, max
temps may drop back close to normal on Mon/Mon night.
Some brief MVFR to IFR fog may develop across nrn terminals early
this morning from 09z-12z. VFR conditions from late morning into the
evening. Areas of fog expected late Tonight across the interior...
with possible IFR VSBY/CIGs late for interior terminals.
Today/Tonight...SE/S winds to 10-14 knots Today will become
southerly around 10 knots Tonight around the high pressure center
east of the area. Seas 3-4 ft this morning will decrease to 2-3 ft
this evening and overnight.
Wed-Sat...The surface ridge axis across the waters early in the
period will continue to sag south and east into Thu. The pressure
gradient remains relatively weak into at least Fri evening with wind
speeds generally AOB 10 kts with directional component often
variable. Speeds may average around 15 kts over the open Atlc
briefly Fri overnight into early Sat morning before relaxing a bit
again. Seas AOB 3 ft thru Thu night, with some possible 4 ft seas
well offshore Fri-Sat night. A small threat for offshore moving
showers/ISOLD lightning storms are forecast Sat aftn/Sat night and
generally north of the Cape.
.PRELIMINARY POINT TEMPS/POPS...
DAB 80 58 79 60 / 0 0 0 10
MCO 81 59 82 61 / 0 0 0 10
MLB 79 60 81 60 / 0 0 0 10
VRB 80 59 81 58 / 10 0 0 0
LEE 81 60 81 61 / 0 0 0 10
SFB 81 59 81 61 / 0 0 0 10
ORL 81 61 81 62 / 0 0 0 10
FPR 79 58 80 57 / 10 0 0 0