239
FXPQ50 PGUM 210833
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
633 PM ChST Fri Nov 21 2025

.Marianas Synopsis...
Partly cloudy skies with isolated showers and thunderstorms are shown
over the Marianas this evening by radar and satellite. A slug of
showers is moving toward Guam from the east-southeast, so if any of
the Marianas get involved in more showers, it will be Guam. With that
likelihood under consideration, split the grids for Saipan, Tinian
and Rota remaining isolated, and Guam will have scattered showers
developing, meaning they`re not there yet, but they are expected
later tonight. The buoys at Ipan and Ritidian on Guam show combined
seas of 7 to 9 feet.

&&

.Discussion...
In addition to the showers arriving for Guam, but much less so for
the CNMI, we had hazardous surf for the north facing reefs of the
Marianas. This required a High Surf Advisory which is currently
estimated to last through Monday night, but could continue into
Tuesday night. After this splash of showers mainly for Guam tonight
and Saturday, there could be another one next week. Overall though,
dry season, aka `Winder`, has arrived.

&&

.Marine...
For seas of 8 to 10 feet and winds up to 25 knots and gusts up to 30
knots, a Small Craft Advisory has been issued. The advisory remains
in effect through Saturday night, but could easily be extended. Keep
an eye out, and avoid unnecessary marine travel until the seas settle
back down.

&&

.Eastern Micronesia...
A trough is departing Pohnpei keeping scattered showers going through
tonight, with a few thunderstorms mixed in as well. For Kosrae, a
mid-level trough has lowered enough to get a line of outflow
boundaries to surge southwest per visible imagery. With this in mind,
have scattered showers in the forecast for tonight to cover this.
Otherwise, isolated showers will be the norm for the next few days,
until a surface trough east of Majuro brings in increasing rainfall
potential from a trough east of Majuro. This feature will increase
shower coverage there (Majuro) Saturday afternoon. This will then
reach Kosrae Sunday and Pohnpei Monday evening or Tuesday, with
upstream satellite imagery showing this should persist for a few
days.

As for marine conditions, winds will subside enough for the Small
Craft Advisory to be allowed to expire for Pohnpei by Saturday
evening, perhaps earlier. Also, as high pressure in the North Pacific
weakens some and lifts a little further away from the region, the
pressure gradient will weaken, supporting the idea of the winds
decreasing at Pohnpei. As for the High Surf Advisory, the current
headline looks good as the building surf (which should peak during
the next 48 hours) showed up nicely at the Pohnpei buoy. This along
with altimetry supports the current headlines, with wave forecasts
suggesting this will continue through at least Monday, possibly
longer.

As for winds, moderate to strong winds at Pohnpei will decrease into
the gentle to Moderate range Saturday night, with the latter
continuing at Kosrae and Majuro. Then, during the first half of next
week, continuing in mainly the gentle to moderate range area-wide for
the first half of next week.

&&

.Western Micronesia...
The Near-Equatorial Trough (NET) continues to extend across the
southern portion of the region, with ASCAT and satellite imagery
showing a broad circulation developing within the NET near 4N139E,
southeast of Palau. A trough extending north-northwest of the
embedded circulation produced scattered to numerous showers and
isolated thunderstorms around Yap earlier today, and now numerous
showers and isolated thunderstorms are shifting in Palau this
evening, with an overall decrease of showers at Yap. This trough and
associated showers are expected to push west of Palau overnight,
decrease showers back down to scattered later tonight, while
convergence north of the NET is expected to strengthen and bring
numerous showers back to Yap late tonight. As the embedded
circulation slowly develops and shifts west-northwest, models
support scattered to numerous showers and isolated thunderstorms
across Palau, and numerous to widespread showers and isolated
thunderstorms across Yap through the weekend. Models also show gusty
winds, supported by heavy convection and the strengthening pressure
gradient between the NET and the subtropical ridge, developing north
of the circulation which are expected to bring gusts of 25 kt to
Palau and to 30 kt at Yap. This will create choppy sea conditions
though seas are expected to peak around 7 at Palau and 7 to 9 feet at
Yap, with sustained winds of 20kt, below the hazardous threshold of
10 feet for seas and 22 kt for winds for a small craft advisory. As
the embedded circulation moves west of Palau and Yap and towards the
Philippines early next week, showers and the potential for gusty
winds will steadily decrease, likely leading to isolated showers and
winds around 5 to 15 kt around the middle of the week.

Across Chuuk, convergent flow between the NET and the trade-wind
surge mainly north of 8N is producing scattered to numerous showers
and isolated thunderstorms across portions of Chuuk State, and
producing occasional gusts around 25 kt. The northeast swell
generated by the trade-wind surge is also supporting elevated surf
along north and east facing reefs of Chuuk, but surf is expected to
peak around 8 feet along north facing reefs and 9 feet along east
facing reefs, below the hazardous threshold of 9 feet for north
facing reefs and 12 feet for east facing reefs. Winds of 15 to 20 kt,
and scattered showers and isolated thunderstorms will start to
subside late this week and into early next week as the trade-wind
surge begins to weak north of 8N, and as the circulation near Palau
shifts westward, drier air north of 10N is expected to be pulled
southward into Chuuk and helping to decrease the potential for
scattered showers and isolated thunderstorms. The weakening of the
trade-wind surge will also cause the northeast trade swell to also
subside.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk through late Monday night for GUZ001.

MP...High Rip Current Risk through late Monday night for MPZ001>003.

Marianas Waters...Small Craft Advisory until 6 PM ChST Saturday for PMZ151>154.

&&

$$

Marianas: Stanko
East Micronesia: Doll
West Micronesia: Schank