Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 250756
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
356 AM EDT Mon May 25 2020

.DISCUSSION...
...Heavy Rainfall, Localized Flooding, and a Few Tornadoes Possible
Today into Tonight...

Today-Tonight...A wet Memorial Day for all of east central Florida
as a vigorous tropical wave moves from the Florida Straits north
across the peninsula. Deep tropical moisture will surge into our
area, with model soundings indicating 2.30-2.40" PWAT values -
record territory for us in late May. Virtually all of the model
guidance now shows this tropical wave moving north, with either a
weak surface low or inverted surface trough developing somewhere
along or near the southern peninsula. As this feature moves north,
it will drag incredible amounts of moisture leading to numerous
heavy rainfall and the potential for localized flooding. Aloft, a
negatively tilted 500mb trough will swing across the Florida
peninsula this morning and afternoon, producing considerable
divergence aloft - directly atop the warm front at the surface.

A Flood Watch is in effect for Martin, St. Lucie, Indian River,
Okeechobee, Brevard, Osceola, Orange, and Seminole Counties until
Tuesday morning. Up to 4 inches of rain fell yesterday in Martin
County between Tequesta and south Palm City. Multiple rounds of
heavy rainfall will move into the area this morning, continuing
north through the afternoon. The high moisture content means these
storms will be efficient rain producers with rainfall rates of 2-3"
per hour possible.

Widespread rain amounts of 4-6" with isolated amounts up to 8-10"
through Tuesday morning from Brevard/Osceola counties southward,
with 2-4" with isolated amounts up to 6" for Orange and Seminole
Counties. Areas that experience heavy rainfall could see localized
flooding, with the main impacts being water on roadways, flooding
of low-lying/poor drainage spots, and rises of water levels in
small streams/canals. Persistent rainfall in urban areas may cause
more significant issues with high water on area roads. This
threat is currently highest in Martin County where up to 4" of
rain fell yesterday.

A few tornadoes are possible today, mainly along the northward
moving warm front where helicity/shear are maximized. There has
been strong rotation in cells offshore of Southeast Florida, and
expect this trend to continue as the warm front lifts north. Even
with low instability the potential exists for a few embedded, low-
topped supercells that carry a tornado/waterspout risk.

Rain chances are high, around 80-90 percent for much of the region
with a chance of thunderstorms. Highs around 80 degrees this
afternoon. Becoming breezy this afternoon as well. Sustained winds
increase to 15-20 mph inland and 20-25 mph along the coast with
higher gusts. Some daily rainfall records could be broken today,
especially from Melbourne south (see climate section below).

By this evening, as the inverted trough approaches the Cape, a
majority of the models indicate strengthening pressure gradient
along the trough axis. If this were to occur, we could see windy
conditions develop along the coast, and especially over the coastal
waters. This is something that needs to be watched as this system
develops. Regardless, widespread rainfall is expected to continue
into this evening, then slowly decreasing through the overnight
hours. Rain-cooled temperatures tonight around 70 degrees.

Tue-Wed...Avbl guid continues to suggest a well defined sfc wave
or perhaps low pressure early Tue wl be located just north of the
area. The feature will drift slowly away to the north leaving a
rather high PWat environment. This in combination with an
upstream mid level trough will lead to the likelihood of
afternoon development of showers and storms across the area with
Westerly component steering winds favoring the east side of the
peninsula. PoPs range from 60-80 Pct from W-E. At midweek,
a favorable setup remains for another round of afternoon storms
with continuation of broad mid level troughing across the SE and
Gulf of Mex, and westerly component steering level winds. Storm
coverage forecast a little lower than Tue, however Sct to Nmrs
showers and embedded storms should occur during the diurnal window
from around 1 PM through 8 PM.

Late Week...A Sfc ridge should begin to establish across the
peninsula to the gulf with lighter winds and a focus inland for
development of afternoon storms. Expect sct slow moving storms,
with slightly higher coverage inland due to expected boundary
interactions during heat of the day. Coverage will remain
slightly higher than normal Thu-Fri (Mid-Upr sct range) due to
less convective inhibition overall. Temperature near seasonal
norms.

Extended...Sfc ridge across the Western Atlc basin to the Gulf of
Mex will elongate while remaining the main map feature through
the weekend. This regime will lead to mentionable chc of diurnally
timed scattered showers and lightning storms light steering winds
should favor inland areas for higher chances of rainfall in
general with temperatures near to slightly above normal.

&&

.AVIATION...
Numerous showers with periods of heavy rainfall possible across much
of the area today into this evening. Difficult to time the heaviest
rainfall at this time, but TEMPO groups likely to be needed later as
storms get going in the area. Periods of reduced visibility and
ceilings to IFR/LIFR conditions is certainly possible, especially
along the coast from KMLB to KSUA. Conditions should start to
improve by this evening, but rain/showers linger into the
overnight.

&&

.MARINE...
Today-Tonight...A Small Craft Advisory goes into effect for all east
central Florida waters at 11 AM this morning. Poor to hazardous
boating conditions will develop by this afternoon as a tropical
wave/inverted surface trough moves north into our local waters by
this evening. Showers and scattered thunderstorms expected today
into tonight, with periods of heavy rainfall. ESE/SE winds 15-20
knots, then increase up to 20-25 knots and become east from the Cape
northward this evening. Seas build up to 5-6 feet this afternoon
across all the waters, then build up to 6-8 feet this evening.

Tue-Wed...Unsettled conditions ascd with sfc wave, or perhaps low
pressure north of the waters early in the period will produce
choppy seas with seas around 4 ft near shore and up to 6 ft Tue
diminishing to around 3-4 ft by Wed. Winds and seas locally
higher near numerous showers and embedded storms through midweek.

Late Week...High pressure wl begin to establish from the Wrn Atlc
basin toward the Gulf of Mex during the period, marine conditions
should correspondingly improve, with seas diminishing to 2-3 ft
Thu. Seas thereafter wl average around 3-4 ft into the weekend.
with and onshore wind.

&&

.CLIMATE...
SOME CURRENT RECORDS FOR TODAY:

LOC  DATE   HI-MIN   MAX PCPN

DAB 25-May  77 2005  1.01 1997
LEE 25-May  75 2014  1.85 1979
SFB 25-May  74 2000  2.91 1991
MCO 25-May  74 2014  1.52 2001
MLB 25-May  79 2015  2.01 2001
VRB 25-May  77 1991  2.30 1973
FPR 25-May  78 1933  3.10 1985

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  81  69  87  72 /  70  80  70  30
MCO  79  69  90  73 /  90  70  80  30
MLB  79  72  88  72 / 100  80  80  40
VRB  81  72  89  72 / 100  80  80  40
LEE  81  70  89  74 /  80  60  60  20
SFB  80  68  90  73 /  80  70  80  30
ORL  79  70  90  74 /  90  70  80  30
FPR  80  73  88  72 / 100  80  80  40

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through this evening for Martin-Okeechobee-St. Lucie.

     Flood Watch from 8 AM EDT this morning through this evening for
     Indian River-Northern Brevard-Orange-Osceola-Seminole-
     Southern Brevard.

AM...Small Craft Advisory from 11 AM this morning to 8 AM EDT Tuesday
     for Flagler Beach to Volusia-Brevard County Line 0-20 nm-
     Flagler Beach to Volusia-Brevard County Line 20-60 nm-
     Sebastian Inlet to Jupiter Inlet 0-20 nm-Sebastian Inlet to
     Jupiter Inlet 20-60 nm-Volusia-Brevard County Line to
     Sebastian Inlet 0-20 nm-Volusia-Brevard County Line to
     Sebastian Inlet 20-60 nm.

&&

$$

SHORT TERM...Rodriguez
LONG TERM....Pendergrast


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