329
FXPQ50 PGUM 021844
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
444 AM ChST Thu Apr 3 2025

.Marianas Update...
A High Risk of Rip Currents is now in effect for the Marianas.

Overall, no significant changes to the forecast were needed tonight.
A small trough will be passing through CNMI today. CNMI will have
scattered showers today. Guam will be but just south of the passing
trough. A second trough can be seen on satellite imagery just
crossing 150 E. Altimetry shows seas to the east of the Marianas of
around 7 to 9 feet.

&&

.Eastern Micronesia Update...
The main change was to lower rainfall potential in the short term, as
surface analysis doesn`t show much of a trigger for a more widespread
potential. Additionally, Convection has also collapsed between
Pohnpei and Kosrae, which was an additional factor as some mid-level
subsidence may persist through the afternoon , limiting convective
potential. That said, we went with isolated coverage at Pohnpei
today/20 percent potential, increasing to scattered coverage/40
percent potential tonight. At kosrae, we lowered the rainfall
potential to 30 percent (low-end scattered coverage).

A modest area of convergence in the trades is located southeast of
Majuro, but it should be close enough to maintain scattered shower
coverage with perhaps a thunderstorm or two.

&&

.Western Micronesia Update...
No significant changes were made to the forecast. We`ll need to keep
an eye on Chuuk as surf looks to increase briefly tonight, but it
still looks to remain below headline criteria. Otherwise, the best
rainfall potential will be across East Central Yap State, as a
surface trough continues to cross the region. Temperatures were
adjusted down slightly (a degree or two) at Chuuk due to abundant
cloud cover that is anticipated to stick around today.

&&

.Prev discussion... /issued 553 PM ChST Wed Apr 2 2025/

Marianas Synopsis...
Isolated showers and partly cloudy skies are seen across the
Marianas. Surface observations and ASCAT reveal moderate trade winds
with occasional fresh gusts. A band of scattered showers and patchy
cloud cover is seen just east of the Marianas, oriented northwest to
southeast, with the northern edge of the showers passing just over
Alamagan this afternoon.

Discussion...
The band of showers seen east of the Marianas are expected to cross
the area overnight into early tomorrow morning, with low-end
scattered (30 percent chance) showers expected for the CNMI north of
Guam. These showers are located at the leading edge of a decaying
surge in trade winds, and some higher winds and gusts will be
possible as showers move through, especially over Tinian and Saipan
coastal waters. Thereafter, a quiet trade-wind regime will dominate
the forecast period, with only isolated showers expected Thursday
night onward.

Marine...
Nearby buoys and altimetry indicate combined seas of 5 to 7 feet,
which look to remain in that range through tonight. A pulse of long-
period northeast swell will bring seas up slightly for the latter
half of the week. Gentle to moderate trade winds are expected for
much of the forecast period. Winds could become fresh at times with
occasional strong gusts tonight and Thursday morning over mainly
Tinian and Saipan waters as a decaying surge in trade winds moves in,
bringing an uptick in showers. As the long-period northeast swell
arrives tomorrow, surf will increase along north and east facing
reefs, leading to a high risk of rip currents along east reefs, and
maintaining the moderate risk along north reefs. Swells and
corresponding surf are expected to diminish this weekend.

Fire weather...
Winds continue to trend downward with gentle to moderate speeds
expected through the forecast period, but fire danger remains high
for Guam with dry conditions anticipated to continue. This will be
especially true across higher terrain where winds will be higher.
Passing weak troughs over the next day or so could potentially
provide a brief wetting rain, but shower chances remain at only 20
percent for Guam and Rota through the forecast period. Only a trace
of rain fell at the Guam International Airport yesterday, and the
KBDI (currently in the high category at 630) is expected to continue
to rise, with afternoon relative humidity values dropping below 60
percent.

Eastern Micronesia...
A trade-wind trough is moving into the Marshall Islands. This trough
is packing scattered showers and a few thunderstorms. The
thunderstorms are mainly east of the Date Line. Put a FM group in
the TAF and scattered showers after midnight in the public and marine
forecasts. Afterward, fairly wet weather is expected through Friday
night, then drier through Monday.

An ITCZ (Inter Tropical Convergence Zone) fragment really fired up
today, especially near Pohnpei. Had to update the previous forecast
from scattered to widespread, and the Pohnpei Office put out flood
products. For tonight, worded the forecast numerous becoming
scattered. The event is winding down, it`s just taking its time doing
it. Kosrae is at the far eastern edge of this fragment.
Nevertheless, as the trough arrives and due in part also to the
fragment, Kosrae can expect wet (scattered to numerous) showers
through Sunday, then could get a chance to dry out Monday. Meanwhile,
Pohnpei will be in the wet and wild weather through Monday and even
beyond.

Majuro Waters will have winds of 15 to 20 knots with occasional
gusts to 25 knots. Seas will start at 5 to 7 feet then become 7 to 9
feet over the weekend, easing Monday as winds become 10 to 15 kt with
occasional gusts to 25 kt. This will result in conditions
challenging to operate small craft in, just short of a Small Craft
Advisory.

Kosrae Waters will see 15 knot winds with occasional gusts to 25
knots through Sunday, which will then diminish to between 10 and 15
knots on Monday. Seas will start at 5 to 7 feet, build to between 6
and 9 feet, then diminish again to between 5 and 7 feet. The gusts
and elevated seas will create conditions challenging for the
operation of small craft, as in Majuro Waters.

Pohnpei Waters will receive winds of 10 to 15 knots, with occasional
gusts to 25 knots tonight. Seas of 5 to 7 feet will build to between
6 and 8 feet Thursday night, then diminish to between 4 and 6 feet
early next week.

Western Micronesia...
Scattered showers and isolated thunderstorms are developing across
Chuuk and eastern Yap State, along an area of trade-wind convergence
north of the near-equatorial trough and buffer circulation that are
hugging the equator well south of Palau and Yap. This convergence is
starting to build into Palau, but remaining south of Yap, so while
Palau is starting to see increased cloud cover and scattered showers,
the weather at Yap Proper is expected to remain on the drier side
for the next couple of days. Satellite imagery shows a cluster of
numerous locally heavy showers near Pohnpei, along an ITCZ fragment,
and this area of heavier showers looks to be drifting westward
towards Chuuk, causing showers to become numerous across Chuuk
tonight. Outflow from these heavier showers are expected to some
gusty winds, so added gusts to tonight`s forecast for Chuuk. As the
ITCZ fragment continues to drift west and starts to morph more into a
trade-wind trough, a wet pattern is expected for much of the region
through the rest of the week and into early next week, with the
potential of thunderstorms increasing at Palau and showers even
lifting up towards Yap Proper by the weekend.

Buoy and altimetry data show seas of 4 to 6 feet near Palau and Yap
Proper, increasing to 6 to 8 feet around Chuuk State. A pulse of
long-period northeast swell late this week may slightly add to seas
near Chuuk, but will mainly contribute to an increase in surf heights
along north and east facing reefs. Wave models shows this northeast
swell peaking at a swell height of 4 feet with periods around 14
seconds Friday. This currently keeps surf below 12 feet for east-
facing reefs, just below 9 feet for north-facing reefs of Chuuk, so
continuing to hold off on any high surf advisories, but surf will be
elevated and currents will be strong along cuts in the reefs.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk through Saturday afternoon for GUZ001.

MP...High Rip Current Risk through Saturday afternoon for MPZ001>003.

Marianas Waters...None.
&&

$$

Marianas Update: Bowsher
East/West Micronesia Update: Doll
Marianas: DeCou
East Micronesia: Stanko
West Micronesia: Schank