Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 140926
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
426 AM EST Fri Dec 14 2018

...STRONG TO SEVERE STORMS POSSIBLE LATE THIS AFTERNOON AND
EVENING...
...HAVE MULTIPLE DEPENDABLE WAYS TO RECEIVE TIMELY WEATHER ALERTS...

.DISCUSSION...
Current...An impressive and still deepening low/mid tropospheric
cyclone over Texas continues to "bowl" east southeast this morning.
Strongly diffluent flow ahead of the low is aiding vigorous convection
over the eastern Gulf of Mexico in a region of increasingly warm
and unstable air. Mid- and upper-level convective debris is
spreading over much of the peninsula given strong west-southwest
winds aloft. Closer to the surface, low-level winds continue to
veer southerly as temperatures linger in the mid to upper 60s.

Today-Tonight...Broadly cyclonic flow and large-scale ascent ahead
of the closed low will support several waves of showers and
thunderstorms over the eastern Gulf of Mexico today. Meanwhile, a
pre-frontal trough trailing from a secondary surface wave should
act as a focusing mechanism for a north-south oriented line of
convection across the eastern Gulf later this morning. Strengthening
wind fields aloft will help sustain the line as it pushes onshore
and inland from the west coast this afternoon; however, widespread
debris cloudiness and weak mid-level lapse rates will temper
instability at least somewhat and likely cause the complex to
weaken as it progresses east this evening and overnight. Even so,
a threat for isolated strong to damaging wind gusts along with a
very low risk for tornadoes will exist as the line moves across
the area, particularly from about the Interstate 4 corridor north
as outlined in the most recent Storm Prediction Center (SPC) Day 1
Outlook.

A majority of convective-allowing mesoscale models indicate the main
squall line approaching our far northwest zones after sunset;
however, models typically underestimate the forward propagation
of MCS/squall-line cold pools and as a result are often too slow.
Taking into account the aforementioned timing bias, believe the
greatest threat for storms will materialize between 4:00-8:00 pm
along and northwest of I-4 and from 8:00 pm to midnight southwest
to Osceola and Brevard Counties. A chance for storms will continue
overnight as activity pushes south and east; however, the threat
for severe weather will likely have diminished.

Residents and visitors within east central Florida should monitor
forecast updates and remain weather aware this afternoon and
evening. Ensure you have a severe weather plan in place that
includes multiple ways to receive timely weather warnings (i.e.
Wireless Emergency Alerts [WEA], text messaging services or phone
apps from local emergency management or media outlets, NOAA
Weather Radio, etc.) especially given the potential for hazardous
weather after sunset.

Breezy southerly flow will allow temps to warm rapidly today,
especially across central and southern areas where some breaks in
the clouds are expected. In fact, high temperatures may come
within a few degrees of record levels at Melbourne and Vero Beach
(see climate section below).

Saturday-Sunday...Large/potent deep layer low centered over northern
AL will lift NE across the TN Valley and offshore the Delmarva
region this weekend. Its attendant cold front will move across the
peninsula during the late afternoon and evening. Despite cooler max
temps (L70s north to U70s south), sufficient moisture ahead of the
front should maintain support for scattered-numerous showers and
perhaps an isolated storm early, decreasing in coverage by afternoon
and moving offshore by early evening as NW post-frontal winds usher
in a drier/cooler air mass into ECFL. Partly-mostly sunny drier and
a big cooler still for Sunday.

Monday-Friday...Zonal flow pattern develops behind the weekend storm
system. This will push the large post-frontal surface high pressure
ridge eastward across the central/eastern CONUS through mid week,
keeping conditions dry through Wednesday with moderating temperatures.
Beginning Wednesday night, the Nino-esque southern stream begins to
buckle once again as a large trough digs into south central CONUS.
Global models show a huge disparity in the strength and progression
of this feature through the end of the week. Op-model Solutions
range from a slowly progressive full latitude trough (ECMWF) to a
slower moving cutoff low (CMC), to a trough fracture with a broad
upper low getting left behind over old Mexico. As is usually the
case, a low confidence, likely to change extended forecast will
trend toward slowly increasing rain chances with near normal
temps.

&&

.AVIATION...
VFR into this afternoon with increasingly gusty south winds.
Several rounds of showers and thunderstorms will develop over the
eastern Gulf of Mexico and move mainly to the north of our
aerodromes through mid afternoon. Eventually, a line of showers
and embedded thunderstorms will cross central Florida beginning
late this afternoon and continue into this evening. Some fast-
moving strong to severe storms are possible mainly along and north
of a KISM-KTIX line from 21-02Z. Have included TEMPOs at most of
these airfields where there is higher confidence. Expect
widespread SHRA and isolated TSRA overnight to spread south and
east toward KMLB-KSUA.


&&

.MARINE...
Today-Tonight...A potent storm system transiting the Gulf Coast
will generate breezy south winds today and tonight, 15-20 knots
nearshore and 20-23 knots away from the coast. Advisory
conditions remain in play offshore where seas will approach 7
feet, otherwise, small craft should continue to exercise caution.
Fast-moving late afternoon and evening convection will affect
near shore boaters with locally heavy rain, gusty winds over 35
knots, and frequent lightning.

Saturday-Sunday...S-SW flow will veer offshore and weaken
slightly Saturday afternoon behind the pre-frontal trough passage,
then shift to NW behind the trailing cold front, though it
appears it will be absent a significant increase in speeds. Seas
3-4FT near shore and 5FT well offshore.

Monday-Tuesday...NW winds gradually slacken/veer more northerly on
Tuesday and northeast by Tuesday night. Seas subsiding to 2-3FT.

&&

.CLIMATE...High temperatures may come within a few degrees of record
levels at Melbourne and Vero Beach on Friday.

Record High Temps...
DAB 14-Dec  85 1991
MCO 14-Dec  86 1972
SFB 14-Dec  86 2016
MLB 14-Dec  85 2015
VRB 14-Dec  85 2015
FPR 14-Dec  86 1991


&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  80  65  73  55 /  60  80  70  10
MCO  80  66  74  57 /  50  80  60  20
MLB  82  68  77  59 /  20  70  70  30
VRB  83  68  78  59 /  10  60  70  30
LEE  77  64  72  56 /  70  90  50  10
SFB  79  65  74  56 /  60  80  60  10
ORL  79  65  74  57 /  50  80  60  10
FPR  83  69  79  59 /  10  60  70  30

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory until 4 AM EST Saturday 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.

&&

$$

Short Term...Ulrich
Mid/Long Term...Cristaldi


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