Miami, Florida

New AVIATION

• Flood watch in effect for the eastern half of South Florida through Monday as the potential for isolated flash flooding increases.
• Minor to Moderate coastal flooding expected during times of high tide.
• Dangerous marine and beach conditions are expected across the Atlantic coast.

Satellite imagery and model analysis data show a shortwave moving into the eastern Gulf and assisting with the development of deep convection. Another shortwave can be found in WV imagery over central AR. Together, these waves are responsible for the dip in the longwave upper-level trough over the Southeast. A CONUS-scale surface analysis by the WPC depicts a large ridge centered over the Mid-Atlantic/Northeast, that sits under a mid/upper ridge axis that stretches from the Northern Plains, through the Midwest, and off the Mid-Atlantic coast. A hand analysis of the surface pattern across the local area reveals a persistent trough along the eastern FL coastline (along the Gulf Stream). The strong easterly flow across this trough is resulting in bands of shower activity developing near, and moving over SE FL.

Through today, the leading shortwave will cross the Peninsula as the trailing shortwave elongates and moves into the eastern Gulf. Stable layers in the mid-levels are preventing a robust surface response to these upper-level shortwaves. However, the affect of the shortwaves will be in the addition of moisture to the column and the contribution to ascent in areas where convection is ongoing. Thus, for the surface forcing today we`ll rely on low-level isentropic ascent and mesoscale boundaries. Where these features develop is uncertain; but while the development pattern is similar to recent days, the coverage may be a bit higher, the thunderstorm threat will be higher, and the potential for heavy rainfall will be higher. Global ensembles, even in the day 1-2 period, have a rather large spread on QPF amounts. This is likely due to the lack of a clear, synoptic-scale surface forcing mechanism. However, the majority of the ensemble members would suggest that 1-2" of rain will be a common amount for locations across south Florida over the next 48 hours. Common high-end amounts for localized areas could be on the order of 2-4", with reasonable worst case scenario that a location or two could get 5-7" of rain over 48 hours. How it`s determined how much you get will be based on whether you`re impacted by a stray shower now and then, a couple back to back heavy showers, or a banding feature setting up across your specific location. All of these scenarios are probably, but pinning down the location for each is quite difficult. The current suite of hi-res data, and trends over the last several hours, would indicate that Broward county probably has the greater chance for those high-end amounts today. Hi-res guidance would also indicate this axis of heavy rain may shift north overnight tonight, with Palm Beach county having the greatest chance for heavy rain overnight. How wet Monday will be is also a source of spread in the ensembles in the near term. Some of this uncertainty is whether or not a part of the second shortwave cuts off and meanders over the SE Gulf/Straits, or stays connected to the mean trough and moves a bit further eastward. Either way, showers are still expected as we remain in the persistent low-level easterly flow regime. The question is just how widespread and how heavy they may be.

Bottom line (at the end), is that the next couple days will be characterized by showers and isolated storms across South Florida, with the main threat being periods of heavy rainfall.

A brief period of mid/upper level ridging is expected early to mid-week, with low-level easterly flow continuing around the surface ridge. This will likely keep us from completely drying out through early next week. However, by mid-week, a frontal system moving through the central CONUS is forecast to start pushing the low-level ridge northeastward. This will give us a more southerly component to the low-level winds and end the persistent shower activity. It`ll still be humid, just not as wet. There is a ton of model divergence on how that central CONUS system evolves, but it seems like the majority of the solutions bring a pretty weak frontal boundary through Florida by the end of the week.

SCT to BKN MVFR ceilings today with NE winds 10-15 kts and gusting to around 25 kts. Scattered thunderstorms today may result in brief flight restrictions and erratic winds.

Strong easterly flow over the Atlantic will keep seas elevated through early this week. Advisory conditions are expected to continue, with hazardous conditions for small craft. Showers and storms are expected to be widespread today and tomorrow. Calming winds and lowering seas are expected starting around mid-week.

The onshore flow and elevated winds and seas will keep a High Risk for rip currents across Atlantic beaches well into this week. Large breakers are expected through at least today across Broward and Palm beaches, with a high surf advisory in effect for these locations. Higher than usual tides will also create elevated water levels near the coast. Dangerous beach and swim conditions are expected through mid-week.

Believe it or not we`re nearing the ebb of the astronomical tides between the full and new moons. While we may briefly (and barely) drop below moderate flood levels on Monday, probabilities of at least reaching low-end moderate flood levels appear too high to let the Coastal Flood Advisory drop. Water levels are forecast to gradually start climbing again by mid-week as we draw closer and closer to the New Moon on Nov 9. Hopefully we`ll be able to remove the strong onshore wind component and pull back some of the heavy rain potential as astronomical tide levels start to rise again.

Miami            82  74  81  74 /  80  70  90  70
West Kendall     84  74  82  74 /  80  70  90  50
Opa-Locka        83  74  82  74 /  80  70  90  70
Homestead        84  74  83  75 /  70  80  80  60
Fort Lauderdale  81  73  80  74 /  80  80  90  80
N Ft Lauderdale  82  73  81  74 /  80  80  90  80
Pembroke Pines   84  73  82  73 /  80  70  90  70
West Palm Beach  82  73  81  73 /  60  70  80  80
Boca Raton       82  74  81  74 /  70  80  90  80
Naples           84  71  82  71 /  70  60  70  30

FL

Flood Watch from 10 AM EST this morning through Monday afternoon for FLZ067-068-071>074-168-172>174.

Coastal Flood Advisory until 7 PM EST Monday for FLZ168-172-173.

High Rip Current Risk through Monday evening for FLZ168-172-173.

High Surf Advisory until 7 PM EST this evening for FLZ168-172.

AM

Small Craft Advisory until 7 PM EST Monday for AMZ650-651-670-671.

GM

None.