451
FXCA62 TJSJ 250936
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
536 AM AST Mon Nov 25 2024

.SYNOPSIS...

Breezy conditions across coastal areas early in the period.
Locally induced afternoon convection is expected each day. A
wetter pattern is expected for the latter part of the workweek
into the weekend. A northerly swell will fill in today,
deteriorating the local marine and coastal conditions through at
least mid-week.

&&

.SHORT TERM...Today through Wednesday...

Variably cloudy skies prevailed across Puerto Rico and the U.S.
Virgin Islands during the overnight hours. Localized showers
persisted over the northern and eastern coastal municipalities of
Puerto Rico, and across the U.S. Virgin Islands. Observed rainfall
amounts were from a tenth of an inch in St. Croix to near a quarter
of an inch over El Yunque area. Minimum temperatures were between
the upper 60s across the higher elevations to the upper 70s across
the lower elevations. The wind was from the east up to 10 mph, with
gusts up to 26 mph near showers.

A weak surface high pressure north of the region will strengthen
over the central Atlantic by Wednesday. A frontal boundary south of
the high is expected to remain mainly above 20N. Meanwhile, a broad
surface low is expected to build just south of Jamaica during the
short-term period. This will promote moderate to locally fresh
easterly trades across the region through at least Tuesday, with a
more southeasterly component on Wednesday as the high shifts over
the central Atlantic. Although moisture has increased over the area
during the early morning hours, the increasing trades will push the
best moisture content west of the area. However, the precipitable
water content is expected to range between 1.75 and 2.25 inches from
Tuesday through Wednesday. This moisture content in combination with
daytime heating and the sea breeze convergence will cause afternoon
shower and thunderstorm development over portions of the interior
and western PR. At upper levels, a polar trough is expected to
remain far north, and the sub-tropical jet should remain northwest
of the area as a ridge builds over the eastern Caribbean for most of
the period. In response the 500 mb temperatures will increase by a
degree or two, fluctuating between -5 and -6 degrees Celsius, enough
to support afternoon convection.

High temperatures are expected to range between the upper 80s and
low 90s in general across the urban areas and lower elevations of
the islands.

&&


.LONG TERM...Thursday through Monday...

A variable weather pattern is expected for the latter part of the
workweek into the weekend. A building surface high pressure over the
central Atlantic and a broad surface low south of Hispaniola and
Jamaica will maintain an east-southeasterly flow, bringing pulses of
moisture over the region. The latest model guidance suggests that
Precipitable Water (PWAT) values will gradually increase above the
climatological normal. Additionally, the Galvez-Davison Index
suggests deep convection activity, particularly on Saturday and
Sunday. The abundant moisture content and instability aloft will
promote moderate to heavy showers and thunderstorms through the
weekend and early next week, increasing the potential of flooding
over the eastern sections of Puerto Rico and the USVI in the morning
hours and the interior and western Puerto Rico in the afternoon.
Ponding of water on roads and poorly drained areas is very likely,
enhancing urban and small stream floods. Winds will shift from the
east, and patches of dry air will filter into the region by the end
of the forecast period.

&&

.AVIATION...

(06Z TAFs)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, trade wind SHRA may cause brief
MVFR cigs across the USVI and eastern PR terminals thru 24/13z, and
afternoon SHRA with possible iso TSTMs can develop near the vcty of
TJBQ btw 24/16z-22z. E winds btw 15-20 knots with sea breeze
variations and stronger gusts aft 24/14z.

&&

.MARINE...

A frontal boundary extending from the windward passage into the
Atlantic Ocean north of PR and the USVI will induce a pre-frontal
trough near the islands, promoting shower activity across the local
waters and passages. A north northwesterly swell will gradually fill
today and deteriorate the local marine and coastal conditions
through at least mid-week. The frontal boundary will linger north of
the islands while a surface high pressure builds from the western
Atlantic to the central Atlantic, with moderate to locally fresh
trade winds.

&&

.BEACH FORECAST...

The risk of rip currents will remain high across the north-facing
beaches of Puerto Rico, including Vieques and Culebra, and across
the Virgin Islands through at least Tuesday afternoon. Another
long-period swell from the north will arrive later in the week,
so it is likely that the risk will have to be extended through the
end of the week. For a more detailed forecast, please refer to the
latest Surf Zone Forecast (SRFSJU) and the Coastal Hazard Message
(CFWSJU).

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Tuesday afternoon for PRZ001-002-
     005-008-010-012.

     High Rip Current Risk through late tonight for PRZ013.

VI...High Rip Current Risk through Tuesday afternoon for VIZ001-002.

AM...Small Craft Advisory until 6 PM AST Tuesday for AMZ711-712-716-
     723.

&&

$$

SHORT TERM/AVIATION...DSR
LONG TERM...MNG
MARINE...DSR/MNG