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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KMLB 181955
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
355 PM EDT Sun Apr 18 2021

.DISCUSSION...

...HEAVY RAINFALL AND STRONG STORMS EXPECTED TO IMPACT EAST
CENTRAL FLORIDA THROUGH MID WEEK...

Rest of Afternoon-Mon...A frontal boundary which was analyzed
over northern FL this morning/early afternoon is forecast to
slightly push south towards the Orange/Cape line tonight. As we
sit on the warm sector in a SW flow and PWAT values of an inch and
a half with dew points in the mid60-near 70 this afternoon, we
expect another round of showers and thunderstorms to develop from
Osceola/Lake counties to the northeast. These will be moving to
the northeast and reach the coastal counties from Brevard to
Volusia and the Atlantic waters. Strong to nearly severe gusty
winds and small to isolated large hail remains possible with these
storms. This round, reaching the Atlantic, could end later this
evening.

Then short term models show another round of a line of storms
reaching the west coast around midnight and pushing east overnight.
This will originate from the convection currently over the
eastern gulf and it will bring heavy rain for most of the
forecast area through Mon afternoon. So the start of the work
week will be a messy one, as these storms will have the potential
to generate heavy rain and thunderstorms causing localized
flooding and strong gusty winds.

Tuesday-Wednesday...Early to mid week trends are holding steady,
as the frontal boundary dominating the local pattern dances over
the FL peninsula. Late Monday night, the boundary will drop
towards south FL, sending PoPs of 70-80% across the southern Space
and Treasure Coasts overnight. The upper level support for strong
to severe storms through the day exits over the Atlantic waters
in the late evening hours, which may curb the potential for thunder
towards midnight and through the early morning hours. The boundary
then switches gears into reverse, trekking back northward on
Tuesday, leading to the third consecutive day of PW values above
1.8-2.0" pumping across the Gulf of Mexico. These values are the
90th percentile for mid April, and close to daily maxima for the
period of record. Needless to say, the threat for widespread heavy
rain looks to be probable through mid week, especially on
Tuesday, however, antecedent soil conditions suggest that the
flood threat will remain marginal, largely dependent on rain
totals over the next 48 hours. For now, do not anticipate the need
for a Flood Watch, however, urban flooding could prompt the need
for flood warnings, especially in training thunderstorms.

Axis of broad mid-level trough crosses FL by late Wednesday, forcing
surface front to drop south of the CWA by late in the day. Moisture
axis gradually lessens, but still enough moisture convergence and
lift for high POPs across the southern CWA (50-70%), with shower
coverage lowering/ending across the north during the day (20-40
percent).

Temperatures Tuesday fall to the low to mid 70s in the afternoon
across the north and reach the mid 80s over the southern Treasure
Coast following the movement of the boundary. Temps even out on
Wednesday, reaching the low 80s areawide on Wednesday. Lows in the
low to mid 60s.

Modified Extended Discussion:

Thursday-Friday...Zonal, unperturbed flow returns aloft with post-
frontal surface high pressure well to the north ensuring a couple
dry and relatively cool days/nights. Max temps ranging from lower
70s north to near 80 far south Thursday, and upper 70s/near 80 CWA-
wide Friday. Thursday and Friday morning mins in the 50s, except 60-
65 along the coast south of the Cape.

Longer range guidance suggests another mid-level trough approaches
next weekend, with surface front and possible weak gulf low crossing
the peninsula. This pattern would return rain chances and warmer
temps starting Saturday.

&&

.AVIATION...
Convective activity took a pause early this afternoon but it
should restart after 20z and impact KISM and KMLB northward. A
few rounds of SHRA/TSRA with gusty winds are possible to impacts
this afternoon, causing brief MVFR/IFR conditions. Then after
midnight, another more widespread round of showers and storms will
move in from the west and affect most of the terminals through Mon
afternoon. These could reduce visibilities and cigs to IFR in
pockets of heavy rain and produce strong gusty winds.

&&

.MARINE...
Tonight-Mon...Conditions across the local Atlantic waters will
appear to be good for boating but as storms developing over east
central FL move onshore, locally strong winds and higher seas
will quickly change marine conditions. Outside any storm activity,
winds will be variable up to 15 kt tonight and becoming SW
towards Mon morning. Then a shift from the NW is forecast to start
in the late afternoon from Volusia waters southward. Seas will be
2-3 ft outside any storm.

Tuesday-Thursday...Prolonged period of daily scattered to numerous
showers and strong thunderstorms will last through Wednesday,
with the front finally pushing south of the area by Wednesday
evening. Southeast winds 10-15 knots will veer NW on Wednesday as
the front begins the southward shift, becoming NW to N by early
Thursday and increasing over 15 knots. Seas Tue- Wed of 2-4 ft,
increasing seas 4- 5 ft nearshore and up to 6 ft in the offshore
waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  65  76  63  77 /  80  80  60  80
MCO  68  79  66  79 /  80  80  70  80
MLB  68  82  67  82 /  80  80  70  80
VRB  69  85  66  84 /  50  80  70  80
LEE  67  75  65  76 /  80  80  60  80
SFB  67  77  65  78 /  80  80  70  80
ORL  70  79  67  80 /  80  80  70  80
FPR  67  86  67  85 /  40  80  70  70

&&

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

$$

Negron/Smith/Leahy/Haley