000 
fxus62 kmfl 230834 
afdmfl 


Area forecast discussion 
National Weather Service Miami Florida 
434 am EDT Sat Sep 23 2017 


Discussion... 


Today through sunday: large trough extending across the eastern US 
is expected to develop into a weak upper level low that meanders 
along the northern Gulf Coast through the remainder of the weekend. 
Also in place will be a robust area of deep moisture across most of 
the state. Pwats from last evening's mfl sounding were around 2.2", 
with the potential for similar values today and tonight. 


Temps aloft were seasonably cool from the sounding at around -6c, 
but models show the potential for slight cooling to around -7c or so 
today with the upper level feature at its closest point to the 
region. While east-northeast flow will dominate, there will once again be the 
potential for a Gulf Breeze to develop near the coast. 


Scattered showers and storms will likely develop late morning near 
the East Coast then spread inland through the afternoon. Steering 
flow initially will be weak, with storms drifting SW, but 
expected to pickup later in the day as Hurricane Maria lifts 
northeast of the Bahamas and the local pressure gradient tightens. 


The concerns today will be for a few stronger storms given the 
proximity of the upper low, especially along boundary collisions, 
and heavy rainfall. Wpc has highlighted the eastern half of South 
Florida under a marginal risk for excessive rainfall, keying on 
the potential for coastal convergence and backbuilding storms 
along with slow storm movement. With drainage difficulties from 
sewers with debris still around from Irma, this could lead to some 
urban type street flooding, especially along the East Coast Metro 
areas. 


The NE flow will bring a few Atlantic and East Coast showers 
overnight. A similar pattern to today is expected on Sunday, though 
stronger winds should bring a little faster storm motion. 


Early to middle next week: Hurricane Maria is forecast to continue its 
northward track roughly parallel, but east of the US coast through 
mid week. As it lifts north of the region on Monday, west-northwest 
mid level flow in it's wake will bring a very dry airmass down the 
peninsula. Enough moisture lingers for scattered showers and storms 
Monday and Tuesday, with the steering flow favoring the East Coast. 
Coverage becomes more isolated Wednesday through Friday as pwats 
drop below 1.5", with areas north of the I-75 corridor 
potentially remaining dry. 


&& 


Marine...Hurricane Maria is forecast to move to the North Well east 
of Florida and the central Bahamas over the next few days. As the 
storm moves north of the Bahamas, we will see an increase in the NE 
swell that has been in place in the Atlantic. Seas may build to 5- 
8ft offshore Broward and Palm Beach counties, with swells 4-6ft at 
12-13 seconds from Sunday through midweek. Based on the timing of 
the seas, a Small Craft Advisory is now in effect for the Palm Beach 
waters starting this evening. 


Pressure gradient will be strongest today with NE winds 10-15kts in 
the Atlantic and around 10kts in the Gulf. Winds will diminish to 
around 10kts in the Atlantic and 5-10kts in the Gulf by Sunday, with 
prevailing winds becoming more northerly through early next week. 


&& 


Aviation...the winds will remain northeast at 5 to 10 knots today 
at all taf sites, except for kapf taf site where they will become 
westerly after 18z. Showers will develop today over all of the taf 
sites with even some thunderstorms over the East Coast areas between 
15z and 18z. Kapf taf site should see some thunderstorms between 18z 
and 24z. Therefore, a prob30 group has been added for all taf sites 
for the thunder threat. The ceiling and vis should remain in VFR 
conditions, but should fall down into MVFR conditions with the 
thunderstorms. 


&& 


Beach forecast...increasing northeasterly swells will be the 
concern into the upcoming week. Strong rip currents have continued 
to be reported along the Palm beaches, and will likely continue to 
through much of the upcoming week. A high risk for rip currents 
remains in effect for Palm Beach County today, which will likely 
have to be extended further south as we head into next week as the 
swells from Maria move in. 


With the northeast swell forecast to build to 5 to 6 feet, 
especially off Palm Beach County, there will be the potential for 
breakers over 10ft, especially at high tide, by Sunday night. High 
surf and beach erosion are a significant possibility, which may 
necessitate a high surf advisory as early as tomorrow.. 


&& 


Preliminary point temps/pops... 
West Palm Beach 88 77 90 76 / 60 40 40 10 
Fort Lauderdale 88 78 90 78 / 60 30 40 20 
Miami 90 78 91 78 / 60 30 40 20 
Naples 91 75 91 76 / 50 20 40 30 


&& 


Mfl watches/warnings/advisories... 
Florida...high rip current risk through this evening for flz168. 


Am...Small Craft Advisory from 8 PM this evening to 5 PM EDT Monday 
for amz650-670. 


GM...none. 


&& 



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