646
FXPQ50 PGUM 131755
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
355 AM ChST Sat Jun 14 2025

.Marianas Update...
There were no significant changes needed for this update. Pleasant
weather is in-store for the Marianas. Partly cloudy skies with
isolated showers are expected for the weekend and much of next week.
Seas are expected to remain benign with 3 to 5 feet sea heights. This
may fall by a foot or so by as early as Monday. The risk of rip
currents remains at moderate along east facing reefs, and low for all
other reefs.

&&

.Eastern Micronesia Update...
Pohnpei:
The main change to the forecast was to ramp up POPs (Probability of
Precipitation) to numerous coverage (70 percent probabilities) at
Pohnpei, as a surface trough slides overhead. The models quickly move
this feature west of the area tonight, but the day shift will need
to take another look at this, as we may need to increase shower
coverage from isolated to scattered for tonight.

Kosrae:
As one area of scattered showers associated with the trough mentioned
above, continues to move west away from the region, a new area of
convergence denoting the leading edge of the next trough looks to
move into areas south of Kosrae by late this afternoon. However, the
trough associated with this convergence will approach from the east
through this evening and then slide overhead tonight, with additional
convection currently developing in its wake as well to the southeast
of Majuro. Thus, scattered showers looks to be in your future for
the next 24 to 48 hours, possibly longer.

Majuro:
The deeper moisture and convergence will bypass you to the south,
with northing more than isolated showers expected through tonight,
and probably through Sunday as well.

&&

.Western Micronesia Update...
Palau and Yap:
Convection associated with a through continues to develop this
morning near Palau and Yap. Scattered showers and isolated
thunderstorms will continue at Yap through tonight. At Palau, showers
will increase from scattered coverage today to numerous showers and
isolated thunderstorms tonight. This is due to Palau being located
squarely in the center axis of the trough, compared to Yap being on
the northern end of it.

Chuuk:
Look for just isolated showers to develop today and tonight. A
thunderstorm or two may also develop tonight as moisture and lift
gradually increased ahead of the Pohnpei trough, which also looks to
increase shower coverage to Scattered on Sunday.

&&

.Prev discussion... /issued 406 PM ChST Fri Jun 13 2025/

Marianas Synopsis...
Satellite and radar observations show scattered showers across the
southern and eastern coastal waters of Guam and Rota, and isolated
showers across Tinian and Saipan. Ritidian and Ipan buoys show
combined seas between 3 and 5 feet.

Discussion...
Overall, only minor changes were made with this forecast package. The
main one was to reduce shower coverage for Guam and Rota after
midnight to isolated and drop isolated thunderstorms. Both the GFS
and ECMWF time heights show a growing mid-level dry layer, with
700-500 mb RH values falling below 60% after 12z tonight. This should
allow shower coverage to gradually decrease later tonight. However,
prior to the drier air moving in, MIMIC TPW does show a localized
increase in PWATS approaching Guam that could lead to locally heavy
rainfall during the evening time. Beyond tonight, both the GFS and
ECMWF show a dry season-like pattern for the Marianas with a sharp
decrease in RH values above 700mb through Tuesday. For now, kept
PoPs at 20%, but there could be some opportunities to reduce PoPs to
light showers at times.

Marine...
No changes were made to the marine forecast with this package. Benign
combined seas of 3 to 5 feet will continue through the weekend. The
weak westerly swell is expected to dissipate tonight, but an increase
in the easterly swell will keep combined seas nearly steady.

Eastern Micronesia...
An overall dry trade-wind flow is seen across eastern Micronesia this
afternoon. There is a finger of the Inter-Tropical Convergence Zone
(ITCZ) that extends across the Date Line into the region, but it is
south of the forecast points, seen east of Butaritari and Tarawa.
Very weak trade-wind convergence east of the ITCZ that is producing
only spotty showers south of Pohnpei, with a small band of stronger
convergence over Kosrae that is generating low-end scattered showers.
This feature looks to move west-northwest through the evening,
allowing showers to become isolated across Kosrae, with low-end
scattered showers moving into Pohnpei by midnight. Otherwise, weak
trade-wind troughs look to bring periodic showers and possible
thunderstorms to all three locations through the weekend. For next
week, models indicate a more organized convergence zone developing
over the region. This could become another ITCZ, however, latest
guidance indicates the winds will remain northeast to east.
Regardless, increased convection with a slight chance of
thunderstorms is on tap for at least the first half of next week.

Winds will generally be gentle to moderate, with seas of 4 to 6 feet
for Pohnpei and Kosrae through the middle of next week. For Majuro,
gentle to moderate winds with occasional fresh winds through the
the beginning of next week. Seas are expected to be between 5 and 7
feet and could reach as high as 8 feet early next week.

Western Micronesia...
A disorganized but generally unsettled weather pattern continues
across far western Micronesia. A trade-wind convergence boundary
extends roughly east-to-west from just south of Yap Proper to the
north of Koror, into a broad trough centered over the westernmost
Republic of Palau. Scattered to numerous showers and isolated
thunderstorms are seen across the region, loosely organized about
this convergence boundary and trough axis. Himawari visible satellite
and scatterometry indicate a weak circulation centered to the
southwest of Sonsorol, which the aforementioned trough extends south
into. This weak disturbance shows little, if any short-term
development in the latest model guidance, but it does look to
maintain an area of disorganized surface convergence and unsettled
weather near Palau and Yap over the next few days, as it gradually
meanders north-northwest. Locally heavy showers will be possible from
time to time, with shower chances slightly diminishing early next
week.

Quieter conditions are seen to the east over Chuuk, with isolated to
scattered showers seen near and northwest of Chuuk Lagoon,
associated with broad, weak trade-wind convergence across the region.
Chuuk will start to see increasing showers by Sunday as a series of
troughs begin to moves west through the region, while trade-wind
convergence increases nearby. Expect on-and-off scattered showers
through at least the middle of next week.

Benign marine conditions continue. Combined seas of 3 to 5 feet are
expected for Palau and Yap waters into the start of the weekend,
coming down a foot or so early next week. Combined seas of 4 to 6
feet near Chuuk are expected to diminish a foot or so through the
weekend as trade swell and wind waves relax slightly, with gentle to
moderate trades expected for the next few days. Palau and Yap can
expect mostly gentle, occasionally moderate easterly trades.

&&

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

$$

Marianas Update: Bowsher
East/West Micronesia Update: Doll
Marianas: Williams
East Micronesia: Kleeschulte
West Micronesia: DeCou