Flooding in Florida, October 23, 2020

Area Forecast Discussion...UPDATED
National Weather Service Miami FL
1052 AM EDT Fri Oct 23 2020

.Update...
A generally dry start to this Friday except for a band of showers
that has persisted over southern Palm Beach County this morning.
Have tweaked the hourly PoPs to account for this continuing
activity. Otherwise, the previous forecast philosophy is on track
with no additional updates anticipated through midday. Updated
zones have been transmitted also showing these changes for the
rest of the morning. Have a wonderful Friday!

&&

.Prev Discussion... /issued 756 AM EDT Fri Oct 23 2020/

Aviation...
Generally VFR though some showers and storms are possible with a
focus around PBI this morning. Additional activity is possible
later in the day including the late morning, afternoon, and
evening. Greater convective coverage returns late in the forecast
period on Saturday. Generally easterly flow will continue through
the period. Sub-VFR possible around convection with short-fused
amendments necessary for IFR/LIFR impacts.

Prev Discussion... /issued 319 AM EDT Fri Oct 23 2020/

.FLOOD WATCH FOR SE FLORIDA CONTINUES INTO THE WEEKEND...

Discussion...

Short Term (Friday-Saturday):

Models begin the forecast period by depicting a deepening large mid
level trough across the central CONUS, with an associated frontal
boundary stretching from the Great Lakes region down to northern TX.
Meanwhile, the western edge of a broad ridge remains right along the
eastern seaboard, and Hurricane Epsilon gradually migrates into the
eastern Atlantic.

The described synoptic scenario will bring one more day of robust
easterlies across SoFlo, but with less gusty periods as pressure
gradients begin to relax. This is in response of the departure of
Epsilon, and the migration southward of the aforementioned front,
which will begin eroding the ridge to our north. Today, the easterly
flow will keep bringing moisture advection from the Atlantic, with
POPs in the 30-40% range from advection alone.

There is the possibility of having an area of disturbed weather over
the western Caribbean trekking mainly NW and passing very close to
SoFlo during the weekend. This will further enhance the deep
moisture over the area, bringing chances of rain into the likely
range on Saturday. So, even in the short term, there is plenty of
uncertainty since models still have a hard time showing consensus on
the potential for development of this feature. The National
Hurricane Center will continue to closely watch the progress of this
feature, currently labeled as a trough of low pressure. But it seems
prudent to follow the increasing trends in models towards higher
rain coverage Saturday afternoon and carry POPs in the 60-70 percent
range for much of the CWA at least.

With all this in mind, the Flood Watch currently in effect will be
extended through the weekend, since even with a break today from
widespread heavy downpours, seems that the threat for localized
flooding will again be in place on Saturday. Also, with all the rain
from previous days, many locations remain saturated and it won't
take much for water to start ponding on metro areas.

Temperatures remain warm with highs in the mid to upper 80s each
afternoon.

Long Term (Sunday-next Friday):

Sunday

A low-level trough originating in the Carribean waters is forecast
to progress northeastward into the southern Atlantic waters. This
feature has tropical characteristics, with forecast PWI
(precipitable water indices) as high as 2.5 ins. in some prog
solutions. Furthermore, a stout low-level (850 hPa) jet appears
intact on the easterly periphery of this feature, which will be
capable of impressive moisture flux quantities and supportive of
deep tropical convection. While widespread rainfall will likely
encompass this feature, there is very low spatial certainty
(regarding impacted locations). The GFS suggests that the wave stays
well east of South Florida, generally affecting the Bahamas. ECMWF
resembles more of a "reasonable worst-case" scenario, where the
surface trough lingers much closer to the southeast Florida
coastline.

The primary concern through the end of the weekend is localized
flooding, which may become more of an areal threat if the feature
nears southeastern Florida. There could also be a low-end severe
weather threat, with some model solutions (particularly ECMWF)
indicating SFC-6km bulk shear values in the 20-25kt range with a 500
hPa shortwave trough lingering over the region. This threat is very
conditional however, and confidence is presently low.

Monday through Friday

The aforementioned 500 hPa shortwave trough progresses easterly into
the western Atlantic, with height rises aloft in it's wake. Synoptic
scale subsidence will cause the low-level wave to becomes diffuse,
quickly losing it's robust tropical nature. Rain chances still
remain possible Monday, however much lower, with PoPs generally no
greater than 40 across South Florida.

By Tuesday, the upper ridge of high pressure elongates, with South
Florida generally under the eastern periphery of this feature. Dry
air will usher in beneath this feature, which will generally quell
any widespread storm activity. Storms that do develop will generally
be short-lived and benign in nature, bereft of sufficient moisture,
instability, and shear to sustain themselves. This pattern generally
remains dominant through at least the middle of the week, and
possibly through Friday as well.

Maximum temperatures are forecast to be in the mid 80s for most of
the region, which is slightly cooler than seasonable for this
weekend due to the increasing cloud cover/rainfall with the surface
trough. An increasing trend into the upper 80s ensues Monday with
higher pressure building back in.

Marine... Abundant moisture over the area will allow for scattered
to numerous showers and storms to continue through much of the
forecast period. Winds and seas could be locally higher in and
around any shower or thunderstorm. Meanwhile, a trough of low
pressure in the western Caribbean is being monitored by the National
Hurricane Center for any potential development as it gradually
migrates closer to the area during the weekend.

Beach Forecast... Swells from Hurricane Epsilon and persisting
robust easterly winds will again combine today to keep a high rip
current risk through this evening along the Atlantic beaches. It is
possible that the high risk will be extended through Sunday. As we
move on from the new moon and approach the first quarter moon, the
astronomically high tides should begin to diminish closer to
predicted values.

&&

.Preliminary Point Temps/PoPs...
West Palm Beach  84  75  85  74 /  30  20  60  50
Fort Lauderdale  86  77  85  76 /  40  30  70  60
Miami            86  77  85  76 /  40  30  70  60
Naples           88  73  88  73 /  30  20  50  30

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through Sunday evening for FLZ068-072>074-168-
     172>174.

     High Rip Current Risk until 8 PM EDT this evening for FLZ168-172-
     173.

AM...None.
GM...None.

&&

Update...02/RAG

Hazardous Weather Outlook for South Florida
National Weather Service Miami FL
403 AM EDT Fri Oct 23 2020

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676-
232015-
Lake Okeechobee-Biscayne Bay-
Coastal waters from Jupiter Inlet to Deerfield Beach FL out 20 NM-
Coastal waters from Deerfield Beach to Ocean Reef FL out 20 NM-
Waters from Jupiter Inlet to Deerfield Beach FL from 20 to 60 NM-
Waters from Deerfield Beach to Ocean Reef FL from 20 to 60 NM
excluding the territorial waters of Bahamas-Glades-Hendry-
Inland Palm Beach-Metro Palm Beach-Coastal Collier-Inland Collier-
Inland Broward-Metro Broward-Inland Miami-Dade-Metro Miami-Dade-
Mainland Monroe-Coastal Palm Beach-Coastal Broward-Coastal Miami-
Dade-Far South Miami-Dade-
Coastal waters from Chokoloskee to Bonita Beach FL out 20 NM-
Coastal waters from East Cape Sable to Chokoloskee FL out 20 NM-
Waters from Chokoloskee to Bonita Beach FL from 20 to 60 NM-
403 AM EDT Fri Oct 23 2020

...Coastal Flooding and High Rip Current Risk Atlantic Beaches...
...A Few Strong Thunderstorms Possible Today...

This hazardous weather outlook is for South Florida.

.DAY ONE...TODAY AND TONIGHT

Rip Currents: There is a high risk of Rip Currents along the
Atlantic beaches.

Coastal Flooding: Higher than normal tides could lead to minor
coastal flooding around periods of high tide.

Flooding: Heavy rainfall may lead to localized flooding, especially
along east coast metro and coastal areas. A Flood Watch remains in
effect.

Thunderstorms: A few thunderstorms are possible. The primary hazards
are lightning, gusty winds, and urban flooding.

Wind: Gusty winds in excess of 20 to 25 knots across South Florida
waters.

Waterspouts: There is a slight chance of waterspouts over South
Florida waters, mainly associated with thunderstorms and gusty
showers.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A trough of low pressure in the western Caribbean is being monitored
by the National Hurricane Center for potential tropical development
over the next several days. This feature could provide for an
increased chance of showers and thunderstorms this weekend. Flooding
is the primary concern.

The elevated risk of rip currents could continue over the Atlantic
beaches through the weekend.

.SPOTTER INFORMATION STATEMENT...

Widespread spotter activation is not anticipated. However,
individual spotters especially east coast metro areas are encouraged
to report high wind, waterspouts, and flooding to the National
Weather Service forecast office in Miami. Please relay any
information about observed severe weather to the NWS while following
all local, state, and CDC guidelines.

For more information...visit the National Weather Service in
Miami website at www.weather.gov/miami.