Flood Potential Outlook
Issued by NWS San Juan, PR

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FGCA72 TJSJ 280921

National Weather Service San Juan PR
521 AM AST Tue May 28 2019

...Saturated soils and potential for heavy rain through midweek may
cause flooding and mudslides...

The latest guidance continues to suggest periods of heavy rainfall
across Puerto Rico on Wednesday and Thursday, and the U.S. Virgin
Islands may also observe periods of heavy rainfall on Thursday.

Current observations show that there is a higher than normal
available moisture and this moisture will linger through early
Friday. An upper level trough digging into the western Caribbean
is causing showers and thunderstorms across the Caribbean waters,
but the local islands are under the upper level ridge, which is
causing cloudiness over the local islands. This could limit
shower and thunderstorm development to just a few areas today,
mainly across the northwestern quadrant of Puerto Rico and
portions of the central interior. However, this upper level trough
in the Caribbean is expected to weaken by Wednesday afternoon,
which could cause less cloud cover in the morning which would aid
with the development of thunderstorms during the afternoon. Then
on Thursday, a shortwave trough with its axis just west of Puerto
Rico would further increase instability, causing showers and
thunderstorms to develop over Puerto Rico, especially across the
eastern half and possibly over the U.S. Virgin Islands as well.

The potential exists for rainfall totals to exceed 1-3 inches with
isolated higher amounts on Wednesday and Thursday. Although there
is a good chance of significant rain today, the jury is still out
on whether we will observe heavy rain across more than just a few
areas due to the aforementioned factors. Emergency managers and
others that could be affected should make the necessary plans in
case this active weather pattern materializes.

Due to the fact that the soils are already saturated, it does not
take much rain to have a significant impact. The potential
impacts include rapid river rises, urban and small stream flooding
as well as mudslides in areas of steep terrain.



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