060
FXPQ50 PGUM 301945
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
545 AM ChST Thu Jul 31 2025

.Marianas Update...
Little change has been made to the forecast. After a line of showers
makes its way across Guam and Rota in a few hours, it is expected to
remain mostly dry until the afternoon, when island-induced showers
and thunderstorms may develop during peak heating hours. This is
dependent on winds remaining light and variable, and expected
clearing of the skies that should allow added island heating for said
island showers to develop.

In addition, the marine forecast remains unchanged; oscillating
water levels induced by tsunami waves earlier have stabilized enough
to allow the rip current risk to decrease to moderate along all reefs
of the Marianas. The moderate risk of rip currents is expected to
continue along all reefs the next few days, as a dominant westerly
swell and secondary easterly swell continue to produce elevated surf
along all reefs. Rip current risk is likely to drop to low along east
and south facing reefs by Friday, once the westerly swell weakens
enough to minimize wrap-around effects across the Marianas.

&&

.Eastern Micronesia Update...
Pohnpei Waters will have scattered showers through Friday night, then
could be isolated for Saturday, then back to scattered for Sunday and
Monday. Winds will be variable 5 to 10 knots and seas will be 5 feet
through Sunday dropping to 4 feet Monday.

Kosrae will have scattered showers through Saturday then isolated for
the beginning of next week. Winds will be 5 to 10 knots mainly from
the east or southeast, with possibly a brief blip of westerlies. Seas
will be 5 feet through Sunday, then diminish to 4 feet Monday,
similar to Pohnpei.

Majuro will also have scattered showers through Saturday, which could
become numerous Friday. They will then be isolated for Sunday and
Monday. Mainly east winds will start out at 10 to 15 knots then
diminish to between 5 and 10 knots Friday night. Seas will be around
5 feet through the period.

&&

.Western Micronesia Update...
Western Micronesia is being affected by the same ridge that has built
in south of the monsoon trough that has been over them for the last
few to several days.

Koror Palau will have isolated showers today as partly sunny skies
will likely hold island convection to a minimum. Showers could nearly
dry up tonight, then return as isolated through Saturday, and could
become scattered for Sunday and Monday. This is a decrease of PoPs
from the previous forecast. Winds will be 5 to 10 knots, mainly from
the southeast, and seas will be capped at 3 feet through Friday night
then diminish to 2 feet for the weekend. What little swell there is
looks to be southeast at 2 to 3 feet, which then disappears after
Friday.

Yap is liable to have isolated showers through Friday night, then
scattered showers over the weekend, probably as the ridge begins to
break down. Winds will be variable at 5 knots. Seas will start at 4
feet with a west to northwest swell, then after tonight will be down
to 3 feet.

Chuuk will probably have isolated showers today, then scattered
tonight and Friday, followed by isolated Friday night and Saturday,
then scattered Sunday through Monday. Winds at Chuuk could reach as
high as 15 knots today, but will otherwise be capped at 10 knots.
Seas of 5 feet will diminish to 4 feet around Saturday.

&&


&&

.Prev discussion... /issued 532 PM ChST Wed Jul 30 2025/

Marianas Synopsis...
Satellite and radar this afternoon reveal scattered showers over Guam
coastal waters, with isolated showers further north over the CNMI.
Cloud cover is widespread in the middle and upper levels across the
region, but was a bit more sparse over Guam around mid-day. This,
along with light and variable winds, allowed island convection to
develop through the afternoon. Now, showers are drifting slowly west
through the area.

Discussion...
Light and variable winds are expected to continue for the next few
days with a col set up near the Marianas. A weak trough southeast of
the islands looks to slightly nudge into the area tonight,
maintaining scattered showers near Guam. Tomorrow afternoon could see
another round of island convection during peak heating hours, even as
models show a slight decrease in moisture through the next day or
two. Shower chances increase toward the weekend as a series of
trade-wind troughs push west into the area.

Marine/Surf...
A Tsunami Advisory remains in effect for Guam and the CNMI. Tsunami
waves are already being observed in Marianas coastal waters late this
afternoon, and may continue into the evening. There will be little
direct effect felt over the open ocean away from shorelines. However,
even after the initial set of tsunami waves, oscillating water
levels may continue to generate strong currents in the coastal
waters. As such, a high risk of rip currents was issued for all reefs
of the Marianas through late tonight. The high rip current risk is
not associated with elevated surf, and is expected to come back down
to moderate for Thursday.

Generally light winds are expected for the next few days with a
ridging pattern in place across the area. A weak trough southeast
of the Marianas may bring a slight risk of lightning for Guam
coastal waters tonight. Combined seas of 5 to 7 feet are expected
to relax over the next few days as the dominant west-northwest
swell gradually diminishes, while the trade swell remains weak.

Eastern Micronesia...
The main items of interest are a surface trough moving through
Majuro tonight, and an area of increased convergence crossing the
Date Line. Both will create locally-enhanced rainfall potential from
time to time over the next couple of days.

Otherwise, clouds remain plentiful across the region as seasonably
deep moisture, relatively light winds, and divergence aloft from an
upper-level trough to the northeast of Pohnpei/north of Kosrae will
low-end scattered shower coverage at Pohnpei the next couple of days,
with only isolated showers at Kosrae due to increased distance from
the base of the trough.

Then, towards the end of the week, the Majuro trough and area of
convergence behind it will increase rainfall potential across all of
eastern Micronesia. Seas will hold in the 3 to 5 foot range. Winds
will be light to gentle at Pohnpei and Kosrae, and gentle to
moderate at Majuro the next few days, before decreasing into the
light to gentle range for the end of the week.

Western Micronesia...
Satellite analysis shows isolated showers and partly cloudy skies
across Palau and Yap. Mostly cloudy skies are seen near Weno with
scattered showers in Weno`s western coastal waters. Altimetry and
buoy data show combined seas between 2 to 5 feet across the region.

The quiet pattern continues for Palau and Yap with isolated to low
end (20 to 30%) scattered showers generally favored over the next
few days. There were some messy island showers that developed across
Palau today and Time-Heights due suggest winds below 10 knots
through at least 700mb. The Time-Heights also suggest more moisture
being available for Palau tomorrow compared to today, so the
forecast was bumped up to scattered (30%) chance for island showers
and isolated thunderstorms. Shower activity looks to increase late
this weekend for Palau and Yap and into the weekend as guidance
shows low level convergence returning to both locations.

For Chuuk, guidance continues to show increasing showers tonight
becoming numerous tomorrow. There are hints on satellite that shower
coverage is increasing with scattered showers seen across the
western half of Weno`s coastal waters and a cumulus field growing
further east. The active pattern looks to continue for Chuuk through
Friday before a short lull this weekend.

A tsunami risk will continue for western Micronesia this evening,
however, minimal threats are expected onshore, but we continue to ask
people to stay out of the water. Otherwise, benign seas of 2 to 5
feet look to continue through the next several days.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
MP...None.
Marianas Waters...None.
&&

$$

Marianas Update: Montvila
East/West Micronesia Update: Stanko
Marianas: DeCou
East Micronesia: Doll
West Micronesia: Williams