Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 221436
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
935 AM EST Sun Jan 22 2017

.DISCUSSION...

.UPDATE...

...Severe Weather and Tornado Risk Increasing into Late Afternoon
and Evening...

Main forecast updates this morning were to increase severe weather
risk across the area during the late afternoon through around
midnight Tonight as a potent weather system tracks across the
southeast states. SPC Day 1 update has upgraded the northern FL
peninsula to a HIGH RISK for severe weather including significant
long track tornadoes and the significant severe weather risk extends
south into east central FL by late afternoon into Tonight. Deepening
surface low pressure will eject northeast toward north GA into late
afternoon/evening while deepening to 981-986 mbs (NAM/GFS) progs.
Mid layer H7-H5 flow will increase to 65-70 knots from the SW by
late afternoon and evening across nrn sections with 850mb winds as
high as 50-60 knots across nrn sections by 21-00z. The strengthening
environmental wind profiles and shear will support very fast moving
storms with the potential for damaging winds and also isolated
strong tornadoes. Some of these have the potential to be long
tracked and significant. Tornado Watches will likely go into effect
across portions of the area later into the afternoon. Pre squall
line convection is expected to develop across northern portions of
east central FL into the mid to late afternoon and then the squall
line is expected into nrn sections by the very late afternoon or
early evening and it will move through east central FL through the
late evening hours and then through the late evening to around
midnight across the Treasure coast. Heed any warnings this afternoon
and seek sturdy shelter quickly if warnings are issued for your
area.

Previous discussion...

Today/Tonight...Area will be under increasing S/SW flow, squarely
within the warm sector, as low pressure deepens over the southeast
US. Once daytime heating commences, the stronger winds will mix
down to the surface and produce a windy/gusty day requiring a Wind
Advisory for all counties. Surface heating will be maximized over
southern sections with a little more cloudiness across the north.
Nonetheless, near record high temperatures are expected in the low
to mid 80s. At least the first half of the day looks rain free.

But conditions remain quite favorable for a powerful and fast
moving squall line to develop this afternoon over the Gulf of
Mexico ahead of a cold front. Models exhibit some timing
differences with this important feature but this is to be expected
in such strong deep layer wind fields. The best timing remains
late this afternoon through this evening, pushing offshore Martin
county around or just after midnight. Once the squall line
develops later today, it will be trackable and timing confidence
will increase.

Once formed, the squall line will race E/SE across the area with
widespread strong wind gusts of 40-50 mph along its leading edge.
Bowing segments along the line will be capable of 60-80 mph wind
gusts. Cold temperatures aloft and excellent ventilation will
produce a large (1") hail threat. Isolated tornadoes will be
possible particularly in any storms that develop ahead of the
squall line in more preferred low level shear environment. Not
surprisingly, a Tornado or Severe Thunderstorm Watch is very
likely to be issued for most if not all of EC FL later today,
probably after noon.

Intense rainfall can also be expected but given the fast forward
motion, amounts should not be excessive with widespread one half
inch accumulations and locally up to 2 inches.

Monday...Windy conditions will exist across the area Monday as a
strong westerly flow ushers in drier/cooler air behind the front.
Another Wind Advisory may be needed across the area as winds are
forecast to reach near 25 mph with gusts to 30-35 mph. Lingering
low clouds and areas of light rain/isolated showers may continue
into the morning hours as axis of low aloft pushes across the
state. Rain chances should then end into the afternoon, with skies
gradually clearing into the evening. Highs will reach the low to
mid 70s with temperatures falling into the upper 40s to low 50s
over much of the region Monday night.

Tuesday-Wednesday...High pressure will approach the area from the
west Tuesday, then will continue eastward across the state and
offshore into mid week. This will lead to decreasing winds through
the period, shifting from the W/NW Tuesday to S/SW on Wednesday.
Drier airmass across the area will keep rain chances out of the
forecast, and temperatures will gradually increase from near normal
on Tuesday/Tuesday Night to slightly above normal into Wednesday.

Thursday-Saturday...Warmer than normal conditions will continue
across the area Thursday before a cold front moves southward through
the region late in the day through Thursday night. Rain chances
remain rather low with this frontal passage, and any rainfall looks
to be rather light. Cooler/drier conditions then expected across
the area behind the front late week into Saturday.

&&

.AVIATION...
MFVR CIGs poss thru 15Z or so in increasing moist southerly flow.
Sustained winds 20 knots with gusts 30 knots expected during the
day. Squall line is forecast to move in from the Gulf late this aftn
spreading E/SE into tonight. Have a 2-hr TEMPO group in each TAF for
thunder and strong wind gusts but these will likely need to be
adjusted once the squall line forms and it can be tracked. There is
potential for damaging winds greater than 50 knots assocd with the
squall line.

&&

.MARINE...

Update...Little changes for morning CWF update with Gale Warning
going into effect late this afternoon. Severe storms may reach the
waters by around sunset into this evening. Previous discussion...

Today/Tonight...Tightening S/SW pressure gradient will produce
wind speeds 20 to 25 knots today so a Small Craft Advisory remains
in effect. Winds will increase 30 to 35 knots offshore this
evening and overnight. Frequent gusts to Gale Force (34 knots)
expected over the nearshore waters. As a result, have upgraded the
Gale Watch to a Warning and expanded it to include all the waters
beginning at 4 pm. Seas building to 7 feet this afternoon
offshore, then 10-11 feet tonight. The offshore flow will suppress
seas nearshore to 4-5 feet.

Monday...Very hazardous boating conditions will continue across
the waters, as strong W/NW winds up to 25-30 knots persist,
maintaining seas of 9-11 feet offshore. A Gale Warning will remain
in effect over the waters through the late evening.

Tuesday-Thursday...High pressure will shift eastward across the Gulf
Tuesday and then cross the state and push offshore into mid week.
This will allow W/NW winds and seas to gradually decrease into
Tuesday, but poor to hazardous boating conditions will likely
persist. As winds decrease even further and switch to the S/SW into
mid week, boating conditions will become more favorable.

&&

.CLIMATE...
Record highs for Today:

DAB 83 1937
MCO 87 1929
MLB 86 2007
VRB 86 2007

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  83  61  71  47 /  70  80  20   0
MCO  83  62  72  50 /  70  90  20   0
MLB  85  64  75  50 /  50  90  20   0
VRB  85  65  74  50 /  40  90  20   0
LEE  81  60  70  49 /  80  70  20   0
SFB  83  62  72  49 /  70  80  20   0
ORL  83  62  72  50 /  70  80  20   0
FPR  85  65  75  48 /  30  90  20   0

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...Wind Advisory from 10 AM this morning to 6 PM EST this evening
     for Coastal Volusia County-Indian River-Inland Volusia
     County-Martin-Northern Brevard County-Northern Lake County-
     Okeechobee-Orange-Osceola-Seminole-Southern Brevard County-
     Southern Lake County-St. Lucie.

AM...Small Craft Advisory until 4 PM EST this afternoon 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.

     Small Craft Advisory from 11 PM Monday to 9 AM EST Tuesday 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.

     Gale Warning from 4 PM this afternoon to 11 PM EST Monday 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.

&&

$$

Volkmer/Ulrich


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