615
FXPQ50 PGUM 181942
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
542 AM ChST Sat Apr 19 2025

.Marianas Update...
Little change was made to the forecast as a fairly quiet pattern
persists. A weak area of surface convergence ahead of a trade-wind
trough is approaching from the east, and IR satellite shows a patchy
band of clouds increasing over and east of Saipan and Tinian coastal
waters early this morning. Doppler radar reveals isolated showers in
the area, mainly over Saipan and Tinian waters, and west and south of
Guam. Showers and clouds look to diminish this afternoon before
increasing once more tonight. The forecast reflects only isolated
coverage through the period, although showers may become low-end
scattered (30 percent chance) from time to time with weak passing
features. For tonight, latest model guidance points to a build-up of
showers from around midnight through early tomorrow morning as a weak
convergence boundary crosses the area, mainly around Saipan, Tinian,
and Rota.

Nearby buoys show combined seas of 5 to 7 feet around the Marianas,
which will gradually diminish this weekend as trade winds and swell
subside, falling to between 3 and 5 feet next week. Gentle to
moderate trades will become mostly gentle early next week.

&&

.Fire weather...
0.04 inches of rain fell at the Guam International Airport
yesterday. This allowed the KBDI to increase slightly with today`s
reading at 643, which is in the high category. Gentle to moderate
trade winds with occasional fresh gusts are expected for today as
generally dry conditions continue, maintaining an elevated fire
threat. Critical Red Flag conditions are not expected to be met over
the next few days with trade winds decreasing through the weekend,
although afternoon relative humidity values will continue to fall
near 60 percent. Trade winds will become mostly gentle early next
week, with little change expected in the dry pattern.

&&

.Eastern Micronesia Update...
No significant changes were made. A surface trough has developed
along an area of surface convergence southwest of Kosrae, which will
not be a factor there. Another trough, also in an area of surface
convergence, should affect Kosrae later tonight, and it may clip
Majuro (mainly for the southern coastal waters). As such, scattered
showers are in the forecast tonight for both locations.

&&

.Western Micronesia Update...
Palau:
An area of surface convergence is located east-southeast of
Koror/southeast of Yap near 140E. This should reach Palau tonight,
and scattered showers are in the forecast. The models have increased
thunder probabilities as well, as moisture advects back into the
region, helping to increase moisture quality and depth while
destabilizing the atmosphere somewhat. Although widespread
thunderstorms aren`t expected, we do expect a few thunderstorms to
develop. As such, isolated thunderstorms are also possible.

Yap and Chuuk:
No significant changes were made to the forecast. You`ll continue to
remain removed from the deeper moisture and areas of convergence
(troughs). Thus, isolated showers look to be the best we can hope
for.

&&

.Prev discussion... /issued 700 PM ChST Fri Apr 18 2025/

Marianas Synopsis...
Moderate to fresh trade winds and isolated showers prevail across the
region this afternoon. Buoy data indicates combined seas are 5 to 7
feet.

Discussion...
Relatively quiet weather continues for the region. Model guidance
shows weak convergence ahead of a trade-wind trough, currently
located well to the northeast, possibly bringing brief upticks in
clouds and showers this weekend. Currently the forecast reflects
isolated showers over the next several days, but will keep an eye on
satellite and model trends that will help narrow down any periods of
low-end scattered showers.

Marine/Surf...
Combined seas of 5 to 7 feet gradually diminish over the weekend as
trade winds and swell subside, falling to between 3 and 5 feet next
week. Moderate to fresh trade winds will decrease into the gentle to
moderate range by Saturday, then becoming mostly gentle early next
week. A moderate risk of rip currents will continue along north and
east facing reefs through at least the weekend. Ritidian and Tanapag
buoys showed a bump in north-northwest swell energy this morning.
This, as well as daytime surf observations, still suggest a moderate
risk of rip currents along western exposures as well through tonight,
then decreasing to low by Saturday as this pulse of northerly swell
subsides. Over the weekend and early next week, wave models show minor
northeast swell moving through the region, but the primary trade
swell is expected to diminish a bit, leading to an overall decrease
in surf heights, possibly decreasing the risk of rip currents to low
on north-facing reefs.

Fire weather...
As of this afternoon, only 0.02 inches of rain has fallen at the
Guam International Airport today. The unlikelihood of achieving a
wetting rain today would allow the KBDI to rise from 639, currently
in the high category for fire danger. Over the weekend and into next
week, abnormally dry conditions continue, which would bring
afternoon relative humidities near 60 percent, although winds are
expected to settle back down to gentle to moderate, trending away
from critical Red Flag conditions for now.

Eastern Micronesia...
The dry pattern may well be coming to an end across eastern
Micronesia over the next several days. Latest satellite imagery shows
weak troughs moving into Kosrae and Majuro, bringing increased
showers to both locations. For Majuro, this will mark the start of a
wetter period that is expected to last through the middle of next
week. For Kosrae, there will be another brief dry period Saturday,
before a wet pattern establishes over the State, that looks to last
through the end of next week. The increase in convection is due to a
band of trade-wind convergence that is currently seen south of the
Marshalls. This convergence pattern looks to spread west and north
over the next few days, with the band expanding in width. As weak
trade-wind troughs traverse the band of convergence, expect flare ups
of heavier showers. Pohnpei looks to remain fairly dry for the next
couple of days before the convergence pattern spreads into the State.
Pohnpei can expect to see increasing convection early next week,
most likely around Tuesday, though this could change over the next
few days. Overall, more rainfall is expected across eastern
Micronesia!

Relatively benign marine conditions are expected over the next
several days, with moderate to fresh winds becoming gentle to
moderate over the weekend. Combined seas of 5 to 7 feet look to
slowly subside over the next few days, dropping to between 4 and 6
feet for the Marshall Islands and to between 3 and 5 feet for Pohnpei
and Kosrae.

Western Micronesia...
The proximity to a nearby convergence zone and developing NET will
keep patchy showers near and over Palau through the weekend into next
week. Meanwhile, Yap will sit in a pocket of diffluent trades to the
north-northeast, allowing just a few light showers to develop over
the next few days. A similar diffusive pattern is expected over Chuuk
through the weekend into early next week, followed by an ITCZ-like
pattern developing that may bring on-and-off showers in the second
half of next week.

Combined seas of 5 to 7 feet near Palau and Yap, and 6 to 8 feet near
Chuuk, are expected to slowly taper down over the weekend, becoming
3 to 5 feet across the region by early next week.

&&

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

$$

Marianas Update: DeCou
East/West Micronesia Update: Doll
Marianas: Cruz
East Micronesia: Kleeschulte
West Micronesia: Montvila