518
FZMY50 PGUM 180625
CWFGUM

Coastal Waters Forecast for the Mariana Islands
National Weather Service Tiyan GU
425 PM ChST Mon Aug 18 2025

Marianas Waters out to 40 nautical miles

PMZ150-182200-
425 PM ChST Mon Aug 18 2025

.Synopsis for Marianas Waters...A tropical disturbance is
expected to move south of Guam overnight, producing a period of
locally heavy showers with occasional strong to gale-force gusts
across the region, especially for Guam and Rota waters. A Small
Craft Advisory will be in effect for Guam and Rota from late
evening through Tuesday morning. Combined seas are also expected
to peak to between 5 and 7 feet tonight and Tuesday. Afterwards,
conditions are expected to subside to light to gentle winds and 3
to 5 foot seas around midweek.

$$

PMZ151-152-182200-
Guam Coastal Waters-Rota Coastal Waters-
425 PM ChST Mon Aug 18 2025

...SMALL CRAFT ADVISORY IN EFFECT FROM TONIGHT THROUGH TUESDAY
MORNING...

.TONIGHT...East wind 15 to 25 kt. Occasional gusts to 35 kt near
heavier showers. Seas 5 to 7 ft. Wave Detail: East 5 ft at 8
seconds and east 5 ft at 6 seconds. Isolated thunderstorms.
Scattered showers this evening, then widespread locally heavy
showers starting late evening.
.TUESDAY...Southeast wind 15 to 25 kt. Seas around 5 to 7 ft.
Wave Detail: East 5 ft at 8 seconds and southeast 5 ft at 5
seconds. Isolated thunderstorms. Numerous showers becoming
scattered around noon. Locally heavy showers possible in the
morning.
.TUESDAY NIGHT...Southeast wind 5 to 15 kt. Seas 4 to 6 ft. Wave
Detail: East 5 ft at 8 seconds and southeast 3 ft at 4 seconds.
Scattered showers with isolated thunderstorms.
.WEDNESDAY AND WEDNESDAY NIGHT...Northeast to east wind 5 to 10
kt. Seas 3 to 5 ft. Wave Detail: East 4 ft at 8 seconds and
northeast 2 ft at 4 seconds. Isolated thunderstorms.
.THURSDAY AND FRIDAY...East wind 5 to 10 kt. Seas 3 to 4 ft. Wave
Detail: East 3 ft at 8 seconds and east 2 ft at 4 seconds. A
slight chance of thunderstorms. A chance of showers Thursday night
and Friday.
.SATURDAY...East wind 5 to 10 kt. Seas around 3 ft. Wave Detail:
East 3 ft at 8 seconds and east 2 ft at 4 seconds. A slight
chance of thunderstorms.

$$

PMZ153-154-182200-
Tinian Coastal Waters-Saipan Coastal Waters-
425 PM ChST Mon Aug 18 2025

.TONIGHT...East wind 15 to 20 kt. Occasional gusts to 30 kt near
heavier showers. Seas 5 to 7 ft. Wave Detail: East 5 ft at 8
seconds and east 4 ft at 6 seconds. Scattered showers and isolated
thuderstorms. Locally heavy showers possible around midnight.
.TUESDAY...East wind 10 to 20 kt. Seas 5 to 7 ft. Wave Detail:
East 5 ft at 8 seconds and east 4 ft at 5 seconds. Scattered
showers with isolated thunderstorms.
.TUESDAY NIGHT...Southeast wind 10 to 15 kt. Seas 4 to 6 ft. Wave
Detail: East 5 ft at 8 seconds and southeast 3 ft at 4 seconds.
Isolated thunderstorms.
.WEDNESDAY AND WEDNESDAY NIGHT...East wind 5 to 10 kt. Seas 3 to
5 ft. Wave Detail: East 4 ft at 8 seconds and east 2 ft at 4
seconds. Isolated thunderstorms.
.THURSDAY AND FRIDAY...East wind 10 kt. Seas 3 to 4 ft. Wave
Detail: East 3 ft at 8 seconds and east 2 ft at 4 seconds. A
slight chance of thunderstorms.
.SATURDAY...East wind 5 to 10 kt. Seas around 3 ft. Wave Detail:
East 3 ft at 8 seconds and east 2 ft at 4 seconds. A chance of
showers with a slight chance of thunderstorms.

$$