Text Products for AFD Issued by GUM

Area Forecast Discussion
Issued by NWS Tiyan, Guam
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
000
FXPQ50 PGUM 232048 CCA
AFDGUM

Area Forecast Discussion...CORRECTED
National Weather Service Tiyan GU
648 AM ChST Wed Apr 24 2024

Corrected typo in Fire Weather section.

.Marianas Synopsis...
A trough starting to pass to the west of the Marianas is producing
heavy showers across Guam and coastal waters, and decreasing in
coverage and intensity northward, with showers becoming isolated at
Tinian and Saipan. Moderate trades prevail across the waters and seas
are about 5 to 7 feet.

&&

.Discussion...
Showers have increased greatly in intensity and coverage around Guam
as westerly winds in the upper levels (around 250 mb) have increased,
suggesting an upper-level jet streak has cut-off from the
subtropical jet and strengthen over the Marianas. This increased
divergence aloft, above the surface trough just west of Guam, helping
to support heavier showers around Guam, and brought the potential
for thunderstorms to Guam and surrounding waters. Rota is seeing some
scattered shower this morning, but so far nothing has heavy has over
Guam, and satellite shows isolated showers for Tinian and Saipan.
Expecting showers to decrease across Guam and Rota tonight as the
surface trough currently just west of Guam, continues to pull way to
the west, and allows the drier trade-wind pattern to move back into
the Marianas for the rest of the week.

&&

.Marine...
Moderate trades will prevail in the region for much of the week,
briefly becoming fresh Friday. Combined seas of 5 to 7 feet are
expected through the weekend. A passing trough is will produce
scattered showers in Guam and Rota waters for most of the day.
Isolated thunderstorms were also observed just outside the coastal
waters of Guam and Rota overnight, so isolated thunderstorms are
possible today for Guam and Rota waters.Surf is expected to taper
down slightly along all reefs, allowing the rip current risk to drop
along north reefs around Friday. Afterwards, a strengthening trade
swell during the weekend may increase surf along north and east reefs
once again.

&&

.Fire weather...
A passing trough brought some showers to Guam yesterday evening, and
showers are continuing to move across this island this morning.
As of midnight, 0.15 inches of rain fell yesterday, but was not
enough to stop the KBDI from increasing slightly to 725. With rain
falling overnight and some rain gages in central and northern Guam
have seen between 0.70 to 2.5 inches in the past 12 hours. This will
cause the risk for fires to spread rapidly to decrease as vegetation
is wet. However, automated rain gages this morning in the southern
parts of the island have recorded less than 0.20 inches in the past
12 hours. Given this large gradient in rainfall, keeping the Red Flag
Warning out until 7PM, mostly for southern Guam.

&&

.Eastern Micronesia...
An active weather pattern continues over the region and is expected
to persist the weekend. Satellite analysis overnight showed deep
convection ongoing over and south of Majuro, south of Kosrae, and
over and south of Pohnpei. Models continue to show periods of
showers and isolated thunderstorms due to surface convergence along
and ahead of multiple surface troughs in the region persisting
through at least early next week.

Combined seas of 5 to 7 feet and mainly moderate winds are expected
at Kosrae and Pohnpei. For Majuro, combined seas of 5 to 7 feet with
seas possibly reaching 7 to 9 feet around the weekend.

&&

.Western Micronesia...
Satellite analysis this morning shows multiple areas of showers and
isolated thunderstorms along a couple of surface troughs in the
region. The first is just east of Chuuk, while the other is located
near Palau. The aforementioned troughs will provide chances for
scattered showers and isolated thunderstorms at Palau and Chuuk. For
Yap, the best chance for a wetting rain over most of Yap state will
be today before the axis of deeper moisture and convergence shifts
southward with the best chance in the southern islands of Yap Proper
through the weekend.

Gentle to moderate trades and benign seas are expected to persist at
Chuuk, Yap, and Palau through next weekend.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...Red Flag Warning until 7 PM ChST this evening for GUZ001.

MP...None.
Marianas Waters...None.
&&

$$

Marianas: Schank
Micronesia: Kelly
National Weather Service Regional Headquarters
