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473
FXCA62 TJSJ 191805
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
205 PM AST Mon Oct 19 2026

...New SHORT TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER...

.KEY MESSAGES...
Issued at 159 PM AST Mon Oct 19 2026

* Slow-moving thunderstorms will maintain the potential for
  locally heavy rainfall and flooding through this afternoon,
  particularly across interior and western Puerto Rico. Stronger
  storms may produce frequent lightning and gusty winds.

* Dangerous coastal conditions will develop late tonight and
  continue through at least Wednesday morning. Breaking waves of 8
  to 12 feet are expected from Rincon to Fajardo, with localized
  beach erosion and life-threatening rip currents along Atlantic-
  facing beaches of Puerto Rico and the U.S. Virgin Islands.

* A long- period north-northwesterly swell will produce hazardous
  seas across the Atlantic waters and exposed passages, peaking
  Tuesday and becoming northerly Wednesday.

* Rainfall coverage and flooding potential decrease Tuesday into
  Wednesday. Heat impacts will primarily affect heat-sensitive
  individuals without adequate cooling or hydration.

&&

.Short Term(This evening through Wednesday)...
Issued at 159 PM AST Mon Oct 19 2026

Mostly clear skies early this morning gave way to showers
downwind of the U.S. Virgin Islands and across portions of Puerto
Rico by midmorning. Nearly stationary thunderstorms developed
early this afternoon over western Puerto Rico, the southern
slopes, and near the San Juan metro area as terrain effects and
sea breeze convergence provided lift within weak steering flow.
Rainfall totals of 12 inches, with locally higher amounts,
prompted a Flash Flood Warning for portions of San Juan, Carolina,
and Trujillo Alto. Winds remained light and variable with a weak
east-southeast background flow. Hot and humid conditions primarily
affected heat-sensitive individuals without adequate cooling or
hydration.

This afternoon, daytime heating and local convergence will
support showers and thunderstorms, particularly across interior
and western Puerto Rico. Weak steering flow may favor slow-moving
cells and repeated development, producing locally heavy rainfall
and an elevated flooding threat across west-central and
northwestern Puerto Rico. Urban and small stream flooding is
possible, with isolated flash flooding where heavier rainfall
persists. More localized rainfall impacts are possible across
northeastern Puerto Rico and portions of the U.S. Virgin Islands.
Thunderstorms may also affect adjacent waters, producing lightning
and gusty winds. Activity should gradually diminish tonight,
although occasional showers will remain possible over the local
waters and windward areas.

On Tuesday, increasingly southerly flow aloft may shift afternoon
convection toward northern Puerto Rico. The flooding threat
should decrease and become more localized, mainly across
northwestern and northeastern sections, while thunderstorms remain
possible across the northern half of the island. Drier air
arriving Tuesday night into Wednesday will further reduce shower
coverage. The 06Z GFS indicates precipitable water values falling
to around 1.31.5 inches Wednesday, accompanied by pronounced mid-
level drying. This improvement will be brief, as moisture
increases Wednesday night into Thursday, with precipitable water
exceeding 2 inches.

Warm conditions will continue, particularly across northern
coastal and urban areas. Heat impacts should primarily affect
heat-sensitive individuals without adequate cooling or hydration,
especially during the late morning and early afternoon.

&&

.Long Term(Thursday through Monday)...
Issued at 130 AM AST Mon Oct 19 2026

No major changes to the long-term forecast. A southeast to
southerly steering flow will persist across the region due to the
interaction between a deep-layer low moving across the eastern
CONUS and surface high pressure over the central Atlantic. Deep
tropical moisture will return Thursday, with precipitable water
values generally around or exceeding 2 inches through much of the
period. Although a mid-level ridge is expected to build over the
eastern Caribbean, abundant moisture, daytime heating, sea breeze
convergence, and local topographic effects will continue to
support scattered to numerous showers and thunderstorms. Passing
showers will favor windward areas during the overnight and morning
hours, followed by afternoon convection across interior Puerto
Rico, spreading toward northern and western sections. Increasing
steering winds Thursday through Saturday should favor more
progressive convection. However, weakening winds late in the
weekend into early next week may allow slower-moving or repeatedly
developing thunderstorms, increasing localized rainfall
accumulations. The main hazards will be lightning, urban and
small-stream flooding, and isolated flash flooding where heavier
rainfall persists, particularly during the afternoon hours.
Meanwhile, the prevailing southeast to southerly flow will
maintain hot and humid conditions, especially across northern
coastal and urban areas of Puerto Rico. Heat impacts will
primarily affect heat-sensitive individuals outdoors without
effective cooling or adequate hydration during the late morning
and early afternoon.

&&

.AVIATION...
(18Z TAFS)
Issued at 159 PM AST Mon Oct 19 2026

VFR conds should cont across most TAF sites throughout the fcst prd,
though MVFR/IFR conds are likely across JSJ and JBQ due -TSRA/+TSRA
near the sites through at least 19/21z. AMDs may be issue if
required. By 19/22-23z, ESE-SE winds will weaken, becoming VRB and
light, with VCSH across USVI and windward PR sites. Winds should
strengthen btwn 7  - 12 kt around 20/13-14z. VCTS cannot be ruled
out across PR terminals aftr 20/16z.

&&

.MARINE...
Issued at 159 PM AST Mon Oct 19 2026

Low pressure and an associated frontal boundary over the western
Atlantic will maintain a weak local pressure gradient, supporting
gentle to moderate east to southeast winds through midweek. A
long-period north-northwesterly swell will arrive late tonight,
peak Tuesday, and become northerly by Wednesday, producing
hazardous seas across the Atlantic waters and exposed passages.
Showers and thunderstorms may produce locally gusty winds,
lightning, and reduced visibility, particularly this afternoon and
evening.

&&

.BEACH FORECAST...
Issued at 159 PM AST Mon Oct 19 2026

A moderate risk of rip currents will continue this afternoon
along Atlantic-facing beaches of Puerto Rico and the U.S. Virgin
Islands. Conditions will deteriorate late tonight as a long-period
north-northwesterly swell arrives, builds Tuesday, and becomes
northerly by Wednesday.

A High Surf Advisory is in effect from 2 AM AST Tuesday through 6
PM AST, covering the area from Rincon to Fajardo. Dangerous
breaking waves of 8 to 12 feet are expected, along with possible
localized beach erosion. High Rip Current Risk is in effect along
the Atlantic shoreline of Puerto Rico and the U.S. Virgin Islands
from late tonight through at least Wednesday morning. Beachgoers
should remain out of the water and away from exposed rocks and
jetties.

Afternoon and evening thunderstorms may also bring lightning and
gusty winds; seek shelter in a substantial building or enclosed
vehicle when thunder is heard.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk from late tonight through Wednesday
     morning for PRZ001-002-005-008-010-012.

     High Surf Advisory from 2 AM to 6 PM AST Tuesday for PRZ001-002-
     005-008-010.

VI...High Rip Current Risk from Tuesday evening through Wednesday
     morning for VIZ001.

AM...None.
&&

$$

KEY MESSAGE/SHORT TERM/MARINE/BEACH FORECAST...CAM
LONG TERM....MRR
AVIATION...MNG

NWS SJU Office Area Forecast Discussion