Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 101406
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
905 AM EST Sun Dec 10 2017

.UPDATE...

Current...Quite cold and dry this morning as pre-dawn temps dropped
into the U30s-L40s across all but the far SE CWA. Minimum WCIs in
the Advisory area look like they right on top of the forecast/30-35F.

Surface analysis shows a large cP surface high extending from the
breadth of the Continental Divide S/SE into the GOMEX and eastward
across the SE CONUS/FL. Morning RAOBs show an anomalously cold/dry
air mass with peninsular PWATs all less than 0.25". Interestingly
the 0.15" at KXMR this morning is a scant 0.03" above the all time
record low ever measured there (0.12" twice, 12/29/?? and 03/06/??).

Remainder of today...Cold start to the day will maintain itself into
this afternoon. Despite full sun, a chilly NW breeze will keep the
diurnal temp rise in check, with max only reaching the U50s across
most of the CWA and L60s from Lake Okeechobee to the Treasure Coast.

Tonight (previous)...Surface ridge axis will settle into north
Florida and cause surface winds to diminish. Skies will remain
clear, so good radiational cooling is indicated. This will bring a
threat of frost across much of the area. Boundary layer winds are
forecast to be north near 10 knots though, so expect the frost will
occur mainly in the normally colder locations. Hence will maintain
the previous forecast which calls for patchy frost. This low level
wind pattern should keep the main threat for freezing temps west of
the mid Florida ridge, though some normal cold spots could touch the
freezing mark, particularly in north Lake and western Volusia Cos.

&&

.AVIATION...VFR/SKC.

&&

.MARINE...Current buoy and C-MAN observations show NW-N winds of 15-
20KT near shore and around 20KT offshore, with seas up to around 8FT
in the Gulf Stream. Winds and seas will gradually subside into this
afternoon, but will need to hold onto the SCA through the rest of the
day, and will likely need a cautionary statement for much of the
MAOR early this evening, especially in the Gulf Stream, where 7FT
seas will likely linger.

&&

SHORT TERM/AVIATION...Cristaldi
LONG TERM/IMPACT WX...Johnson

&&

.PREV DISCUSSION... /issued 311 AM EST Sun Dec 10 2017/

...Remaining Cooler than Normal into Late Week...

Mon-Mon Night...The flow remains zonal aloft as an east-west
elongated piece of energy continues to weaken over the central FL
peninsula during the 24 hour period. PWAT values generally one half
inch or less and will keep conditions dry as weak surface high
pressure holds in place. Winds will be light WNW/NW during the day
and light SW/WRLY at night.

After a very chilly start to the day, highs will recover into the L-
M60s areawide. Overnight lows warmer than the previous two nights
and generally in the L-M40s, but do suppose normally cooler rural
locations may realize U30s, but at least no threat for freezing
temps, frost, or wind chill concerns. Skies MSunny during the day
and MClear at night.

Tue-Wed...Mainly zonal/near zonal flow aloft during this period. A
piece of upper energy pinwheeling around a fairly strong upper low
over the Great Lakes will drive a reinforcing cold front down the FL
peninsula late on Tue with high pressure over the Deep South and
north GOMEX building in from the west overnight Tue thru Wed. PWAT
values may increase to around 0.75 inches, but more cooling/drying
behind this latest system will drive values back to 0.25-0.35 inches
overnight Tue. Conditions appear to remain mainly dry over land.
Moderate SW/WSW flow ahead of the front on Tue will veer to WNW/NW
behind it with winds becoming light.

Highs on Tue ahead of the front will rebound into the L70s areawide,
with lows behind the front Tue night falling back into the L-M40s,
except U40s/L50s immediate Treasure Coast and adjacent barrier
islands. A chillier day Wed once again with highs in the L-M60s and
chilly overnight into Thu morning, lows U30s/L40s interior with
immediate coastal lows along the Space/Treasure coasts in the M-U40s.

Thu-Sat...W/NW flow aloft continues with another piece of energy
diving southward and driving another cold frontal boundary down the
FL peninsula on Fri with high pressure building in once again
promoting a pleasant day Sat. Less than a 20pct chance for a light
shower surrounding this next front, as moisture remains limited,
otherwise continued dry conditions for ECFL. Temps will rebound into
the U60s-L70s for highs with mins generally in the 50s, except some
normally cooler rural locations may realize U40s overnight.

&&

.AVIATION...VFR with diminishing northwest winds.

&&

.MARINE...
Today-Tonight...High pressure ridge over the deep south will
maintain a breezy northwest/north wind flow through this morning,
then as the ridge axis sags into north Florida, winds will start to
ease gradually. Will not make substantial changes to the previous
forecast, which has an advisory through 10 am nearshore and
through 4 pm offshore.

Mon-Thu...Weak high pressure across the region on Mon and early Tue,
then another cold front will be driven southward down the peninsula
late on Tue with high pressure building back in again for Wed/Thu.
NW winds Mon 10-14 kts will back Mon night to WRLY into Tue with
speeds increasing during the day on Tue 15-20 kts near shore and 20
kts offshore as the pgrad tightens ahead of/behind next front. Tue
evening winds will veer more WNW/NW with speeds potentially 20-25
kts over the open Atlc finally decreasing during the day on Wed into
Thu. Initial seas 2-3 ft near shore and 4 ft Gulf Stream will build
2-4 ft near shore and 4-5 ft by the end of the day on Tue continuing
to respond to the increasing winds Tue night, 4-5 ft near shore and
6-8 ft well offshore. As winds slowly decrease Wed-Thu, seas will
gradually begin to subside to AOB 3 ft areawide Wed evening thru
Thu. SCEC/SCA will be necessary for Tue into at least a portion of
Wed for the local coastal waters.

&&

.FIRE WEATHER...
Today...Northwest/north winds will ease, but steady cool/dry air
advection will continue. Min RH values will drop to the upper 20s
to lower 30s this afternoon over the interior. Recent rain wetting
will keep fuel moisture high enough to preclude any significant
fire weather concerns.

Mon-Thu...Persistent dry conditions on Mon will drive RH values into
the 20s/L30s interior and M30s near the coast. Another cold front
will push thru the area late on Tue with moderate westerly winds and
higher dispersion values for Tue. Much of the area will again
realize RHs in the 30s again for Wed.

&&

.CLIMATE...The record cool high temperature for Sanford today is
57 degrees set in 1957. Our forecast is close to that temperature.
Other sites aren`t anywhere close to the record cool highs for today.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  56  35  63  44 /   0   0   0   0
MCO  57  38  66  43 /   0   0   0   0
MLB  60  36  65  44 /   0   0   0   0
VRB  62  37  66  42 /   0   0   0   0
LEE  57  37  64  44 /   0   0   0   0
SFB  57  37  64  44 /   0   0   0   0
ORL  57  40  64  45 /   0   0   0   0
FPR  62  37  66  42 /   0   0   0   0

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...Wind Chill Advisory until 8 AM EST this morning for Coastal
     Volusia County-Indian River-Inland Volusia County-Northern
     Brevard County-Northern Lake County-Okeechobee-Orange-
     Osceola-Seminole-Southern Brevard County-Southern Lake
     County.

AM...Small Craft Advisory until 10 AM EST this morning for Flagler
     Beach to Volusia-Brevard County Line 0-20 nm-Sebastian
     Inlet to Jupiter Inlet 0-20 nm-Volusia-Brevard County Line
     to Sebastian Inlet 0-20 nm.

     Small Craft Advisory until 4 PM EST this afternoon for Flagler
     Beach to Volusia-Brevard County Line 20-60 nm-Sebastian
     Inlet to Jupiter Inlet 20-60 nm-Volusia-Brevard County Line
     to Sebastian Inlet 20-60 nm.

&&

$$



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