008
FXUS62 KMLB 141816
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
216 PM EDT Sun Jul 14 2024

...New DISCUSSION, AVIATION, MARINE...

.DISCUSSION...
Issued at 216 PM EDT Sun Jul 14 2024

KEY MESSAGES:

- Through this evening, scattered to numerous storms (40-80%) are
  expected to develop with the highest coverage along the I-4
  corridor. Heat and humidity have reached hazardous levels in a
  few locations, especially along the Treasure Coast.

- Unusually hot temperatures, even for Florida, continue this
  week. A risk for heat-related illness will extend to anyone
  without proper access to hydration and air conditioning.

- Daily scattered storms persist, but coverage is forecast to
  drop below normal by midweek before increasing again next
  weekend.

---------Synoptic Overview----------

Positive H5 height anomalies continue across the southern half of
the U.S. today with anticyclones located over NM and FL. Mid-level
heights will build over the W Atlantic this week as a longwave
trough forms over the Mississippi Valley. 14/00Z Cluster analysis
from the grand ensemble strongly suggests this trough will get stuck
well northwest of Florida. Therefore, the Bermuda High remains the
dominant influence on our weather. The near-surface ridge axis will
stay very close to Central Florida over the next week, allowing
light S/SE background flow in the lower troposphere.

Deep tropical moisture remains in place today (and tomorrow along
the I-4 corridor), but the middle troposphere dries out some as we
move into the work week. A propensity of members advect lower PW
(total moisture) values, perhaps as low as 1.4-1.5", across the
state through mid-week on the western flank of a weak TUTT.
Thereafter, moisture is forecast to increase late in the week (and
especially next weekend) out of the tropics.

H85 T`s remain near the maximum moving climatological average for
mid-July (+19 to +20C). Above-normal temperatures persist,
particularly through the work week as lightning storm coverage is
now expected to drop below normal for at least 2-3 days.

-----Sensible Weather & Impacts-----

Through Tonight...

A Heat Advisory continues for Indian River, St Lucie, Okeechobee,
and Martin Cos. for maximum heat indices locally exceeding 108F this
afternoon. Stuart (SUA) reported a heat index of 111F an hour or
so ago! A scattering of more reliable mesonet stations, including
the WeatherStem network, are also reporting heat indices of 108F
or greater in this area. The remainder of east Central FL is
reaching heat index readings of 102-107F, which can still be
dangerous but falls just below our advisory threshold. Be sure to
take frequent water breaks, seek shade and A/C, and listen to your
body: heat illness can creep up on you in a hurry.

A ribbon of higher moisture is pushing across the peninsula today,
evidenced by PW`s over 2" on this morning`s XMR sounding (14/10Z).
In addition, H7 RH values exceed 70% near and north of Melbourne to
Winter Haven. This is sometimes a good indicator of where convection
is favored. Beneath that, a robust sea breeze circulation is
underway, and an eventual collision should occur amid an uncapped
environment. A few storms have already bubbled up along the sea
breeze. Later this afternoon/early evening, our highest (60-80%)
rain/storm chances shift into a zone from near Daytona down
through Greater Orlando. Heavy rain is possible, with the 14/12Z
HREF indicating a reasonable worst-case scenario of 3"+ in 6 hours
from the strongest storms. This could lead to localized flooding.
Storms will diminish by mid/late evening, and it will be quiet
overnight with lows in the mid 70s.

Monday...

Quite a gradient in storm coverage tomorrow afternoon as drier
air aloft starts to drift overhead from the east. We have 30-40%
coverage for the Space/Treasure Coasts increasing to 50-70% near
and northwest of Interstate 4 where the deeper moisture looks to
reside a bit longer. Locally heavy rain and frequent lightning
will be the primary hazards from storms on Monday. High
temperatures should again reach 90-95F across the area, hottest
over the interior. Peak heat indices likely will rise to around
102-107F yet again as well.

Tuesday - Thursday...

Guidance has backed off on storm chances during the middle of the
week - especially Tue/Wed - as they hone in on this pocket of dry
air that floats across the peninsula. This required some changes,
namely taking out `likely` (>55%) coverage on storm potential on
Tue and Wed and pinning the highest coverage to areas west of
Orlando even into Thu. While widely scattered PM storms are still
forecast on the sea breeze, there will be a lot of dry time. Any
storm that manages to mature could produce gusty winds to 40-50
MPH as it collapses. The beaches may remain rain-free with quite a
bit of sunshine.

This downturn in rain/cloud coverage will have the opposite effect
on temperatures. Statistical guidance now indicates many areas
reaching 94-96F (except 90-93F along the coast) each afternoon. Heat
indices up to 107F will continue to occur, perhaps as high as 109F
especially near our lakes and on the advancing sea breeze. Little
relief is expected at night (mid/upper 70s), and our experimental
HeatRisk forecast (which considers climatology) is major to locally
extreme near Greater Orlando. This level of heat affects anyone
without effective cooling and/or adequate hydration.

Friday - Next Weekend...

Ridging will persist in the W Atlantic, nosing over Florida. Beneath
the upper high, some members hint that a low-amplitude easterly wave
will approach Florida from the tropics next weekend. Moisture would
increase in this scenario, leading to a return of more
scattered/numerous (50-70%) storm coverage. Highs are forecast to
remain in the low/mid 90s, hottest Friday before perhaps trending
down a couple degrees as storm chances pick up by Sat/Sun. Peak heat
indices will remain elevated, as high as 107F.

&&

.AVIATION...
(18Z TAFs)
Issued at 216 PM EDT Sun Jul 14 2024

VFR is forecast outside of storms. TAFs begin with VCTS and TEMPO
TSRA from 19Z-22Z for KDAB and at 20Z-23Z for inland sites.
Scattered storms are forecast to develop this afternoon/evening as
boundary collisions occur between the sea breezes and outflow from
previous storms. Generally ESE (except for KLEE) winds at 5-10kts
during the daytime become light and variable overnight.

&&

.MARINE...
Issued at 216 PM EDT Sun Jul 14 2024

Rather tranquil marine weather persists as a ridge of surface high
pressure extends westward into the local Atlantic through this week.
Isolated showers and storms are forecast, but long stretches dry
weather are likely. Southeast winds 5-12 KT through at least mid-
week, except ESE 10-15 KT nearshore in the afternoon as the sea
breeze forms. Seas 2-3 FT, except up to 4 FT well offshore north of
Sebastian Inlet through early Tuesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  75  93  76  93 /  30  60  20  40
MCO  77  95  76  95 /  50  60  20  50
MLB  77  91  76  90 /  20  40  10  30
VRB  76  92  76  92 /  20  30  10  30
LEE  77  95  78  95 /  50  70  40  50
SFB  77  94  76  95 /  40  60  30  50
ORL  77  95  78  95 /  50  60  30  50
FPR  75  92  75  91 /  10  20  10  30

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...Heat Advisory until 6 PM EDT this evening for FLZ058-154-159-164-
     254-259-264.

AM...None.
&&

$$

DISCUSSION...Heil
AVIATION...Fehling