Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 211201
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
Issued by National Weather Service MIAMI FL
801 AM AST Thu Sep 21 2017

.AVIATION...
Visible satellite imagery this morning indicating high cloud tops
and likely heavy SHRA/TSRA over the middle of Puerto Rico
associated with a band on the back side of Hurricane Maria. MVFR
to locally IFR conditions expected over most of Puerto Rico
through the forecast period, although there may be a temporary
break in the 18z-00z time frame as slightly drier air moves in.
For the USVI and northern Leeward sites, better conditions
overall as deeper moisture stays over Puerto Rico. Winds mainly
140-160 degrees gusting to 25-35 knots early in the period,
gradually decreasing after 00z as Hurricane Maria continues to
move away from region. AMD NOT SKED remains for all terminals,
continue to check with authorities for airport closures.

&&

.PREV DISCUSSION... /issued 535 AM AST Thu Sep 21 2017/

DISCUSSION...As of 5 am, Hurricane Maria was located around 70
miles north of Punta Cana in the Dominican Republic. The
hurricane is expected to continue to move further away from Puerto
Rico and USVI today, with the strongest winds gradually
diminishing across the region later this morning. However, breezy
southerly conditions will continue into at least this evening,
and likely continue across the higher elevations through the day
on Friday.

The persistent heavy rainbands that have been lashing the western
side of PR overnight are expected to also lift north and west of
the island later this morning. While some areas may see a break in
precip, especially this morning, the concern for the remainder of
the day, and through the next few days, will be for more heavy
rainfall. Deep tropical moisture remains across the region, which
in combination with the southerly flow will lead to enhanced
rainfall along the southern slopes of PR, and across the south
side of the St Thomas/St John. Coverage and rainfall amounts are
likely to be higher during the afternoon/evening as less cloud
cover promotes some diurnal enhancement.

Any additional rainfall will aggravate the ongoing record
flooding along most of the rivers . While breaks in the rain may
allow for a brief respite, expect additional rapid rises with any
rainfall along with mudslides. Currently the Flash Flood Watch
continues through Friday afternoon, but may need to be extended if
the flow pattern holds through the weekend.

The Atlantic ridge begins to rebuild into mid next week, allowing
for a re-establishment of easterly trades. Models are in
agreement in showing a SAL layer arriving by Wednesday, which
should lead to much lower shower activity, potentially isolated at
best.

MARINE...Hurricane Maria will continue moving away from the local
waters allowing the ongoing tropical storm force winds with
occasional hurricane force gusts to subside in the the waters
northwest of Puerto Rico and in the northern Mona Passage by late
morning. Elsewhere a Small Craft Advisory is in effect with south
winds of 20 to 30 knots slowly lessening late this evening. More
moderate south-southeast flow is expected through the weekend with
seas continuing to subside.

Showers with periodic thunderstorms with heavy rain and locally
higher winds and waves are possible through this weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  83  77  88  78 /  40  20  30  30
STT  82  81  85  80 /  50  80  80  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flash Flood Watch through Friday afternoon for Central Interior-
     Culebra-Eastern Interior-Mayaguez and Vicinity-North
     Central-Northeast-Northwest-Ponce and Vicinity-San Juan and
     Vicinity-Southeast-Southwest-Vieques-Western Interior.

     Small Craft Advisory until 2 PM AST this afternoon for Southeast-
     Southwest.

VI...Flash Flood Watch through Friday afternoon for St Croix-
     St.Thomas...St. John...and Adjacent Islands.

     Small Craft Advisory until 2 PM AST this afternoon for
     St.Thomas...St. John...and Adjacent Islands.

AM...Flash Flood Watch through Friday afternoon for Coastal Waters OF
     Southwestern Puerto Rico out 10 NM-Coastal Waters of
     Northern USVI and Culebra out 10 NM-Coastal Waters of
     Southern Puerto Rico out 10 NM-Coastal Waters of Southern
     USVI Vieques and Eastern Puerto Rico out 10 NM.

     Small Craft Advisory until 2 PM AST this afternoon for Anegada
     Passage Southward to 17N-Caribbean Waters of Puerto Rico
     from 10 NM to 17N-Coastal Waters OF Northwestern Puerto
     Rico out 10 NM-Coastal Waters OF Southwestern Puerto Rico
     out 10 NM-Coastal Waters of Northern Puerto Rico out 10 NM-
     Coastal Waters of Northern USVI and Culebra out 10 NM-
     Coastal Waters of Southern Puerto Rico out 10 NM-Coastal
     Waters of Southern USVI Vieques and Eastern Puerto Rico out
     10 NM.

     Hurricane Warning for Atlantic Waters of Puerto Rico and USVI
     from 10 NM to 19.5N-Mona Passage Southward to 17N.

&&

$$

SHORT TERM...ALM
MARINE...ALM
AVIATION....Molleda



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