Advisory FFA Flood Watch — Fri Nov 4, 2022 12:26 PM

FFASJU) for
Flash Flooding will continue in effect from this afternoon and
continuing through through Monday afternoon.

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.AVIATION UPDATE...
VFR conditions will prevail. However FQT passing SHRA/Isold TSRA
with SCT-BKN multi lyr cld lyrs nr FL025...FL050...FL090 across
the local flying area. SHRA/Isold TSRA will cont in and around the
USVI and terminals, with increasing aftn convection fcst to
affect the eastern, central and nrn half of PR, including the
TJSJ/TJBQ/TJNR terminals. Brief MVFR expected durg the rest of the
prd at most terminals with Mtn Top obscr across the ctrl mtn
range of PR. E-SE wnds btw 12-20 kts with ocnly hir gusts
especially with convective activity.

&&

.MARINE UPDATE...
No change to previous marine discussion. Marine conditions will
continue to deteriorate through the weekend, due to combination
of increasing winds and an arriving northerly swell. Seas will
increase 6 to 8 feet with occasional seas up to 10 feet. Small
Craft Advisory is in effect for most of the local waters. Please,
refer to the Marine Weather Message (MWWSJU) and the Coastal Water
Forecast (CWFSJU) for more info.

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From previous discussion sent at 449 AM AST Fri Nov 4 2022

.SYNOPSIS...

The combination of a polar trough and increasing moisture will result
in favorable atmospheric conditions for flooding rains. The unsettled
weather pattern will continue to today and extend through Monday evening.
Puerto Rico and the U.S. Virgin Islands have saturated soils from last
week`s rain event. In addition, river streamflows are near to above-
normal. Therefore, A flash Flood Watch is in effect Friday afternoon
through Monday evening due to the elevated risk of rapid river rises,
flash flooding, mudslides, and urban flooding.

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.SHORT TERM...Today through Sunday...

The forecast remains on track. The tropical wave with axis southwest
of Puerto Rico promoted shower and thunderstorm activity across the
Caribbean waters during the overnight hours. Showers will persist
during the morning hours affecting mostly the south and east Puerto
Rico, Vieques, Culebra and U.S. Virgin Islands. Weather will further
deteriorate throughout the day as the upper-level polar trough with
axis currently southeast of Florida continues to strengthen while
sinking southward and settling over Hispaniola by Saturday. The
positioning of the trough will be favorable as it promotes a
diffluence and divergent pattern aloft with steep low- to mid-level
lapse rates. At low-levels, a southerly flow will enhance moisture
convergence over the CWA. Widespread convective activity with the
potential of frequent lightning, gusty winds, and heavy rain is
expected to peak between late afternoon through Saturday evening.
Therefore, a Flash Flood Watch will come into effect by this
afternoon. Given the vulnerable state of many areas across the
islands, there is an increased potential for urban, river and life-
threatening flash flooding, as well as debris flow and rockslides.
Please continue to monitor for any advisories or warnings issued by
our office as this event unfolds.

Higher uncertainty remains for Sunday as models now have the area of
highest moisture convergence east of the local islands. However, the
deep-layered polar trough, although weaker, will maintain unsettled
weather conditions across the northeastern Caribbean as it combines
with plenty of low-level moisture. Therefore, a continuation of a
wet and unstable weather pattern is anticipated for the latter part
of the short-term period, although with less coverage of active
weather compared to previous day.

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.LONG TERM...Monday through Friday...

The unsettled weather conditions may continue on Monday. Suppose
the flooding rains event occurs throughout the weekend. In that
case, saturating even more the soils and increasing the
streamflows along local rivers, the risk of flash flooding and
mudslides will extend through at least Monday evening. The
confidence in the model guidance is moderate because the event is
tight to the upper-level feature`s final position and the
surface`s low-pressure evolution. That non-tropical low is being
monitored by the National Hurricane Center (NHC) and might develop
near the Northeast Caribbean or the Western Atlantic. It has a
low chance of tropical cyclone formation in the next five days (30
percent). Please refer to the latest Tropical Weather Outlook
(TWOAT) issued by the NHC.

This non-tropical low plays an essential role in the islands`
weather scenario. Therefore, the confidence in next week`s weather
scenario is even lower due to high uncertainty about this
system`s future path/intensity. However, GFS solution insists on a
southerly to southwesterly wind flow through late Wednesday
night, from the southeast on Thursday, and more easterly by
Friday. Moisture content is now even lower than the previous run
cycle, and the upper-level dynamic seems weaker. Therefore, this
period could be a transition to better weather conditions with
just the typical afternoon convection.

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.AVIATION...

An unsettled weather pattern will persist through the forecast
period. Sct-Num SHRA/SCT-TSRA will develop after 04/17z thru
05/06z with areas MVFR/IFR conds and widespread mtn obscurations.
Sfc winds less than 8 kts thru 04/14Z bcmg ESE 8 to 16 kt aft
04/14Z with sea breeze variations, but locally higher near/in
TSRA.

&&

.MARINE...

Marine conditions will gradually deteriorate this weekend, due to
combination of increasing winds and an arriving northerly swell.
Seas will increase 6 to 8 feet with occasional seas up to 10 feet.
Small Craft Advisory is in effect for most of the local waters.
Please, refer to the Marine Weather Message (MWWSJU) and the
Coastal Water Forecast (CWFSJU) for more info.

A mid to upper-level trough with abundant tropical moisture and a
surface low pressure over the southeastern Caribbean will result
in unsettled weather conditions and increased thunderstorm
activity across the regional waters throughout the weekend.

For beachgoers, the risk of rip currents is moderate along the
Atlantic Coastline of Puerto Rico, Vieques, Culebra, and the
Virgin Islands. The risk of rip currents will increase to high
this weekend into early next week for most of the beaches.

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.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flash Flood Watch through Monday afternoon for PRZ001>013.

VI...Flash Flood Watch through Monday afternoon for VIZ001-002.

&&

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