629 
FXUS62 KMLB 200901
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
500 AM EDT Fri Oct 20 2017

.DISCUSSION...

...First Significant Cold Front of the Fall Season Will Push Through 
Central Florida by Tuesday Night...

Today/Tonight...Drier air rounding the base of high pressure 
centered to our north will lessen PoPs further today, with limited 
low-level moisture keeping chances for light showers confined mainly 
our southern zones. Not expecting any deep convection (thunder) 
today as a building ridge aloft leads to significant subsidence and 
drying aloft. Will carry scattered PoPs (30-40%) across the Treasure 
Coast where enough 1000-850mb moisture remains to support low-topped 
marine showers moving onshore in the brisk east flow. Further to the 
north, measurable precipitation will be far more the exception than 
the rule, so will carry PoPs of 20% or less with the mention of 
isolated sprinkles. For the overnight, low-topped showers will 
remain isolated, with little in the way of measurable precipitation 
expected. A small chance has been drawn in along the coast south of 
Cape Canaveral. 

Afternoon highs will be within a few degrees of their late October 
average, ranging from the low 80s along the immediate coast to the 
mid 80s across the interior. 

Saturday-Monday...H50 high center over Florida and the southeastern 
CONUS will hold sway this weekend. The high will eventually give way 
to an amplifying trough, which digs SE into the lower MS Valley by
mid day Monday, then moves E-NE into the SE CONUS by Monday night.
Strong mid to upper level forced ascent will allow a surface low to 
develop along the central Gulf coast by Sunday night, then lift NNE 
rapidly through the TN/OH Valleys Monday and into the lower great 
Lakes Monday night. The low will drag the first significant autumnal
cold front toward central Florida, which will be preceded by a pre-
frontal trough, and likely a broken band of showers and storms on
Monday night.

In the interim, after one more day of onshore/easterly flow and 
spotty light rain showers moving onshore, mainly across the south, 
low level flow will veer to southeast Sunday-Sunday night, then 
southerly through Monday night ahead of the pre-frontal trough.

POPs from 15-20 north to 30-40 far Saturday, will increase to 40
south and 50-60 north on Sunday, owing to increasing moisture and 
weak warm frontogenetic forcing. Southerly flow with scattered 
showers and a few storms on Monday, with coverage increasing late
Monday night with the approach of the pre-frontal trough. Max temps
in the M-U80s each  day, with mins generally in the L-M70s (highest
along the coast).

Tuesday-Friday..Aforementioned mid level short wave trough dampens 
out rapidly as it lifts NE, courtesy of a deep, longer wave trough 
which amplifies across the eastern CONUS Wednesday-Thursday, while 
becoming negatively tilted. The prefrontal trough and trailing cold 
front move through the area Tuesday, which model guidance showing a 
reinforcing trough pushing through ECFL late Tuesday night-early 
Wednesday morning. Behind these boundaries, strong high pressure 
will build form the southern plains into the Gulf of Mexico and then 
Florida From Wednesday though  sunset Thursday. Modest return flow 
develops beginning Thursday night.

Both the mid/upper lift looks pretty respectable, and H85 LLJ (35-
45KT) look pretty respectable across north Florida from Late Monday 
night into early Tuesday. Thus, there seems to be at least some
potential for stronger storms from around the I-4 corridor north
during that time frame, before the stronger deep layer wind fields
lift out rapidly during the day. Something to keep an eye on.

Temps near climo norms of L80s/L-M60s through Tuesday night. On 
Wednesday-Thursday, 70s for highs and mainly 50s for mins, then
rebounding nicely closer to climo for next Friday.

&&

.AVIATION...Drier air filtering in from the northeast will limit the 
coverage of onshore-moving showers to our southern terminals, namely 
KVRB south. Will maintain VCSH there, otherwise, VFR expected to 
prevail with SCT clouds between FL020-030. Brisk onshore (east) flow 
will become gusty after sunrise.

&&

.MARINE...Today/Tonight...High pressure centered to the north will 
maintain a 5 to 6 mb gradient along the east coast of Florida, 
leading to brisk northeast-east winds 15-20 knots. A lengthening 
fetch of onshore flow will support seas 5-7 feet in the nearshore 
zones and up to 8 feet in the offshore zones. No changes to the 
Small Craft Advisory.


This weekend...Poor to hazardous boating conditions continue with 
winds/seas running near 17-21KT/5-7FT Saturday, then decreasing to 
around 14-18KT/4-6FT Sunday. SCA will continue through Saturday 
night, with cautionary conditions likely offshore on Sunday.
Scattered showers, with a few storms possible late Sunday.

Monday-Tuesday...Winds will veer to SE-S on Monday ahead of an 
approaching strong cold front, which will reach the northern waters 
Tuesday and push south of Jupiter Inlet by late Tuesday evening.
Expect increasing coverage of showers and a few storms Monday, with 
the front likely preceded by a more organized band of storms. Wind 
speeds 13-18KT Monday, dropping off some to 12-15KT Tuesday as they 
veer offshore. Seas 4FT near shore/6FT offshore Monday, subsiding a 
bit to 3-4FT nearshore/5-6FT offshore by Tuesday.

&&

.HYDROLOGY...The middle and upper Saint Johns River basins remain 
in flood. While additional light rainfall is in the forecast through 
the weekend, amounts look very light. Thus, the nearly steady or 
very slight fall we've had in river levels the last few weeks will 
continue.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  84  74  84  75 /  10  10  20  30 
MCO  85  71  87  73 /  10  10  20  20 
MLB  85  78  86  77 /  20  20  20  30 
VRB  85  77  86  76 /  20  20  30  30 
LEE  87  70  87  72 /  10   0  10  10 
SFB  85  71  87  73 /  10  10  20  20 
ORL  85  71  87  73 /  10  10  20  20 
FPR  84  77  85  76 /  30  20  30  30 

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory until 4 AM EDT Saturday for Flagler Beach 
     to Volusia-Brevard County Line 0-20 nm.

     Small Craft Advisory until 4 PM EDT Saturday for Volusia-Brevard 
     County Line to Sebastian Inlet 0-20 nm.

     Small Craft Advisory until 4 AM EDT Sunday for 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 20-60 
     nm.

&&

$$

SHORT TERM/AVIATION...Ulrich
LONG TERM/IMPACT WX...Cristaldi