115
FXPQ50 PGUM 190601
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
401 PM ChST Thu Jun 19 2025

.Marianas Synopsis...
Satellite and radar observations show a few clouds with isolated
showers across the Marianas. Ritidian and Ipan buoys show combined
seas between 2 and 4 feet.

&&

.Discussion...
The dry trade-wind pattern continues across the region. Isolated
thunderstorms remain in the forecast for Friday. However, Both MIMIC
TPW and Blended TPW show PWATS below 2.00 inches across the Marianas
today, which aligns with this morning`s upper air sounding. Both
MIMIC and Blended TPW show PWATS as low as 1.75 inches moving into
the Marianas. Although thunderstorms are still possible at these
PWATS, without a forcing mechanism to assist in convective
development, confidence is low in thunderstorms occurring tomorrow.
For now, thunderstorms remain for consistency, but it may need to be
removed with the next forecast update if PWATs continue to trend
drier.

Looking ahead, there are signs that the pattern may flip back to
being very active towards the middle and end of next week. It`s too
early to get into the details, but both the GEFS and EPS are starting
to show increased precipitation across the Marianas. For now,
handled the end of the period with 30% PoPs, but changes are likely
as we approach the latter half of next week.

&&

.Marine...
Marine conditions remain benign with combined seas between 2 to 4
feet. Combined seas look to remain steady over the next several days.
That said, models appear to hint towards a slight increase in trade
swell sometime this weekend, while winds remain light. This could
allow surf to rise and lead to the risk of rip currents to briefly
become moderate along east facing reefs.

&&

.Eastern Micronesia...
An active pattern will develop across eastern Micronesia through the
weekend into next week. Multiple surface troughs will pass west
across the region through a convergence zone. In addition, upper-
level winds will increase at times as the Tropical Upper-Tropospheric
Trough (TUTT) occasionally dips south, enhancing the lift and
instability across the region. Expect generally scattered showers and
isolated thunderstorms through the period, with Probability of
Precipitation (PoPs) fluctuating between 30 to 40 percent through
early weekend. Showers could become high-end scattered to possibly
numerous at times (PoPs 50-60 percent) late weekend into next week as
the models are showing the Inter-Tropical Convergence becoming
better developed and creeping north towards the forecast points.

Combined seas of 4 to 6 feet will dip 1 to 2 feet through the
weekend for Pohnpei and Kosrae as the trade swell subsides, but look
to linger for Majuro as the trade swell remains slightly elevated. As
the ITCZ creeps north next week, the background south to southeast
swell looks to increase. Combined seas and surf along south-facing
reefs/beaches could rise slightly as a result. Winds will remain
gentle to moderate for the period.

&&

.Western Micronesia...
A generally unsettled weather pattern persists across far western
Micronesia. A surface convergence boundary is focusing scattered to
numerous showers and isolated thunderstorms over and west of the
Republic of Palau, as a trade-wind trough moves in from over Yap
State. Scattered showers are seen near and west of Yap Proper, but
look to be gradually diminishing this afternoon. Palau will likely
remain in an area of convergence and shower development through
later tonight, but both locations will see a gradual easing of
showers tonight through the remainder of the week, with coverage
possibly dropping to isolated at times this weekend. To the east,
isolated to scattered showers are seen near Chuuk with a series of
outflow boundaries crossing the area from east to west. Chuuk Lagoon
can expect on-and-off scattered showers through the next few days as
it remains just on the outer periphery of the features causing them.
A disorganized ITCZ looks to briefly build north into the area around
Friday, diminish this weekend, before re-emerging Monday. Models
suggest a more robust ITCZ disturbance or two may cross the area next
week, sometime during the midweek onward.

There was little to no change to the marine forecast. Benign marine
conditions continue, with combined seas of around 3 to 4 feet near
Palau and Yap, and 4 to 6 feet near Chuuk, expected to gradually
diminish about a foot or so over the next few days. Mostly gentle
winds persist for Palau and Yap, with moderate to fresh winds over
Chuuk waters tonight expected to diminish to gentle to moderate
through the weekend.

&&

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

&&

$$

Marianas: Williams
East Micronesia: Slagle
West Micronesia: DeCou