Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 251343
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
330 AM HST Sat Feb 25 2017

.SYNOPSIS...
A surface ridge north of the area will maintain gentle to moderate
trade winds over the islands through the weekend. The atmosphere
will remain rather dry through Sunday morning, so rainfall will be
light. On Sunday, a trough will deepen northwest of the islands
while high pressure builds far to the northeast. The atmosphere will
become more moist and unstable and heavy rainfall is possible
through the first half of next week, especially on the Big Island
and Maui. A ridge will build over the islands during the second half
of next week bringing light winds and dry, hazy weather.

&&

.DISCUSSION...
A surface ridge north of the area will maintain gentle to moderate
trade winds over the islands through the weekend. The atmosphere
will remain dry, so rainfall will remain light.

A trough aloft will deepen northwest of Kauai early next week
bringing increasing instability. Meanwhile, the low level flow near
the islands will shift out of the southeast. Precipitable Water (PW)
values will increase as tropical moisture streams in. The combined
instability and moisture will bring the threat of heavy showers...
especially for the Big Island and Maui Tuesday and Wednesday. The
moisture will likely be deep enough and the freezing level low
enough for snow on the Big Island summits.

A surface ridge building over the islands during the second half of
next week will keep winds light. The atmosphere will stabilize as
the trough northwest of the area lifts north. Afternoon clouds may
continue, but rainfall is expected to become light. The light winds
may allow vog to spread over the smaller islands through the second
half of the week.

&&

.AVIATION...
There are no AIRMETs in effect and none are expected over the next
24 hours. VFR conditions will prevail, but moderate east northeast
winds may carry enough clouds and showers over windward areas to
produce brief MVFR ceilings.

&&

.MARINE...
A storm east of the Kamchatka peninsula produced a large long-period
northwest swell that has been building overnight. This swell
is expected to peak today before slowly subsiding through Monday. A
gale north of the area has produced a smaller and shorter-period
north swell. That swell is expected to gradually shift out of the
north northeast. These two swells will combine to produce advisory
level surf along north and west facing shores of the smaller islands
through tonight.

An east to west surface ridge near 25N will maintain gentle to
locally fresh trade winds through Saturday night. Winds will weaken
and shift out of the southeast starting tonight as a trough deepens
northwest of the area. Winds and seas will remain below Small Craft
Advisory (SCA) speeds for the next several days.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Sunday for north and west facing
shores of Niihau, Kauai, Oahu and Molokai and north facing shores
of Maui.

&&

$$
Donaldson



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