Area Forecast Discussion
Issued by NWS
FXPQ60 PGUM 280700
Area Forecast Discussion
National Weather Service Tiyan GU
500 PM ChST Tue Mar 28 2017
A shear line near Saipan is slowly moving southward, with partly
cloudy skies south of the boundary, and mostly cloudy skies to the
north. Moderate to fresh trades and seas of 4 to 6 feet are found
in the Marianas waters.
The forecast for the islands is unchanged, with skies becoming mostly
cloudy tonight through Friday night as the shear line settles into
the region, but only isolated showers are expected for now. Winds
will be breezy up to 25 mph Wednesday, but will then gradually
diminish as the shear line weakens over the rest of the week.
Wednesday should see winds ramping up to 20-25 kt, which will require
a Small Craft Advisory. But these fresh to strong winds are expected
to be short-lived, falling back to 15-20 kt Wednesday night, and
diminishing further to 10-15 kt over the weekend. as a result, seas
are forecast to reach only up to 9 ft by Wednesday night, then fall
again Friday night and the weekend. But with seas reaching close to
the 10-foot threshold for a Small Craft Advisory, Wednesday`s
advisory will likely be for both winds and seas.
Trade-wind convergence is producing some heavy showers over Chuuk
State and western Pohnpei State this afternoon. Also, patchy showers
over the western and southern Marshall Islands are gradually moving
into Kosrae State. Fair skies are over Majuro for the near term, and
very dry weather persists over the far northern RMI. The areas of
showers are expected to continue moving westward, with a little
drier weather arriving from west to east the next couple of days.
Then, GFS model indicates a trade-wind trough will move across the
Date Line toward Majuro about Friday and continue moving west toward
Kosrae, Pohnpei and Chuuk this weekend into next week.
Trade-wind swell and waves will cause rough marine conditions for
Chuuk, Pohnpei, Kosrae and Majuro this week. Hazardous surf will
persist along east facing reefs of Kosrae through at least Wednesday.
While the surf is below high surf advisory criteria at Majuro, both
Kosrae and Majuro could see minor inundation on east facing shores
as the surf will combine with king tides through Wednesday afternoon
at Majuro and through Thursday at Kosrae.
ASCAT analysis shows a disturbance is centered well southwest of
Chuuk near 1N148E. Areas of heavy showers are near the disturbance
and over much of Chuuk State. Satellite shows patchy showers are
also near Yap and east of Koror this afternoon. GFS model indicates
the disturbance and areas of showers will move westward during the
coming days. The weather will become unstable over far Western
Micronesia on Wednesday through Thursday or Friday as a pattern of
convergent winds combined with moisture from an active equatorial
trough arrive from the east and southeast, respectively. There could
be times of heavy rainfall, especially for Koror about Thursday.
Seas will rise 2 or 3 feet at Koror and Yap as the disturbance moves
closer, and seas should then likewise fall 1 to 3 feet as it departs
the area this weekend.