Scientific Forecaster Discussion
fxus62 kmlb 191507 cca
Area forecast discussion...updated to correct wwa
National Weather Service Melbourne Florida
1005 am EST sun Nov 19 2017
..cold front will sag south through the region this afternoon and
early evening with a slight shower threat...
..wind/sea conditions will become poor behind the front tonight
Current...14z/9am position of the approaching cold front was near a
kx60-k28j-ksgj line. Visible satellite shows some clouds developing
out ahead of the boundary over North Lake/Volusia counties, clear
skies out ahead it. Prevailing SW to west-southwest flow and mild temps out
ahead of the boundary, with the air mass still quite dry (0.80" to
0.90") and mild, with temps a couple degrees either side of 70f.
As expected...local radars across north-central Florida show a weak,
unimpressive band of light showers along the front.
Remainder of today...dry pre-frontal air mass and paucity of decent
low level moisture convergence along the front is expected to limit
diurnal reinvigoration of showers along the front as sags through
the northern and central County Warning Area today. Pops of 20 to 30 (at best) north
looks fine. Only grid adjustments will NE to make near term tweaks
to clouds/winds/temps/dew pts using a mix of analysis, 2-6km model
output and some interpolation between the two.
Aviation...VFR to start. Initial cigs bkn060-080 klee-kded-kdab
sagging south across kism-kmco-ktix through 19-20z with MVFR cigs
bkn015-025 trailing behind by about 20-30sm. Spotty MVFR vsbys in
showers. From 19z-24z, expect multilayered MVFR to VFR cigs near
bkn025-030 bkn060 to sag south into the kmlb-ksua with weakening
band of isolated-widely scattered MVFR showers.
Marine...with winds having turned offshore, seas have dropped to
around 2-3ft near shore, and any 4ft seas pushed toward the outer
reaches of the 60nm legs. Some increase in winds should bring seas
back up to around 4ft or so across the Volusia waters by late in the
afternoon, however boating conditions will be pretty benign for most
of the area, especially from the Brevard waters south.
Disappointing to see both wave models, especially the Swan, show
such a high bias in this pattern. Seas on average were 1-2ft lower
than progged for several days, since the previous Small Craft Advisory event ended
Previous discussion... /issued 302 am EST sun Nov 19 2017/
..periodic unsettled weather conditions return Tuesday through
Thursday with potential lightning storms and higher rain chances...
Monday-Monday night...the area of high pressure over the southeast
U.S. Will push eastward and off of the mid Atlc coast Mon night.
North/NE winds will veer easterly through the day. The previous front
remains stalled across the Florida Straits into Mon night, but deep layer
moisture will begin to return overnight with some showery
precipitation developing over the coastal waters and potentially
along the Treasure Coast. Highs in the low to mid 70s. Milder lows
generally in the 60s, except u50s north of I-4.
Tuesday...an inverted trough with a weak surface low over the
northeastern Gulf of Mexico will support a southerly flow with
additional moisture. The weak surface low is forecast to move across
North Florida during the afternoon and evening. This combined with
the enhanced moisture and impulses of shortwave energy aloft will
lead to high rain chances areawide. Rain chances taper off gradually
farther south as distance from the weak surface low increases. Will
keep a slight chance for thunderstorms.
Wednesday-Friday...guidance generally agrees that multiple pieces of
mid/upper level energy will shift down The Rockies/plains and carve
out the base of a larger scale trough over the Gulf. Will continue
to chance pops from mid to late week as consensus suggests multiple
opportunities for precipitation, particularly on Thursday.
Saturday-Sunday...a brief, weak ridge of high pressure will build
across the region providing a dry weekend with a return to
Aviation...continued mainly VFR. Stronger wind speeds above the
surface may limit fog formation this morning. SW/west flow around 10
kts today ahead of a cold front will veer to northwest/north behind it later
today/tonight. Brief MVFR shower potential along a narrow band of
moisture associated with the front. Skies becoming mclear tonight
again behind the boundary (from north to south).
Marine...today-tonight...SW/W winds ahead of an approaching cold
frontal boundary. This feature will reach the northern waters by
early afternoon, then continue to slide southward and should
approach Sebastian Inlet by around 7pm/00z tonight. Winds will veer
northwest/north behind this feature through late evening and then north-northeast/NE
overnight. Wind speeds will approach 15-20 kts over the open Atlc,
north of the cape from mid-late afternoon and continue to spread
southward over the waters into the evening. While cautionary
statements may be necessary offshore, north of the cape later in the
afternoon, will go ahead and initiate an Small Craft Advisory for
both marine legs, north of Volusia-Brevard County line at 7pm/00z,
then spread southward across the remainder of the waters at
10pm/03z. Winds will reach 20 kts in the advisory with frequent
higher gusts, but seas will be slower to respond. Expect seas over
the Gulf Stream to reach 6-7 ft over the Gulf Stream by daybreak Mon
morning. The north wind (opposing the Gulf stream) and developing
shorter period seas this evening/overnight will also make for rough
small craft boating. A narrow band of light, showery precipitation
will accompany the front.
Monday...the Small Craft Advisory continues thru Mon night as winds
continue to veer toward the east and approach 20 kts sustained with
higher gusts likely. Seas build to 5-7 feet over the Gulf Stream and
5-6 ft near shore.
Tuesday...poor to hazardous boating conditions as seas of 5-6 feet
in the offshore waters will continue to build to 7-8 feet. Winds and
seas gradually diminish through the day on Tuesday, but high rain
chances along with a few thunderstorms will keep conditions less
Wednesday-Friday...guidance indicates multiple weak troughs or lows
in vicinity of our waters. Some increase in winds possible on
Thursday if the low pressure becomes better organized. Expect winds
to be generally from the north to northwest with seas 3-5 feet until
Friday when seas build due to increasing winds.
Am...Small Craft Advisory from 7 PM this evening to 4 am EST Tuesday
for Flagler Beach to Volusia-Brevard County line 20-60 nm.
Small Craft Advisory from 10 PM this evening to 4 am EST Tuesday
for 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.