Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 171931

Area Forecast Discussion
National Weather Service Honolulu HI
931 AM HST Sat Mar 17 2018

Trade winds will gradually return over the next few days. A
moisture band will pass southward across the islands tonight and
Sunday, ushering in a slight increase in showers and sky cover. An
approaching front will stall west of Kauai by midweek, causing
local winds to veer a bit to southeasterlies and re-introducing
the possibility of wet weather for the second half of the work


Light winds around the smaller islands will allow development of
sea breezes across leeward areas this afternoon, while light to
moderate trade winds across far eastern waters push clouds and
light showers across windward areas of the Big Island. Models show
that weak low pressure near 30N150W, northeast of the main
Hawaiian Islands, will move to the east today through early next
week, allowing trade flow induced by high pressure far to our
north to spread westward across the chain. The cloud cover expected
this afternoon across mauka areas should decrease as the trades
spread westward this evening.

GFS depicts a narrow but distinct band of moisture moving
southward across the islands tonight and Sunday, likely an old
frontal remnant. In contrast, ECMWF shows a much less distinct
feature moving across the chain. Our forecast follows GFS but,
either way, the increase in trade flow mentioned above will be
most noticeable as this moisture band passes by. We also expect
increased associated shower activity overnight and Sunday.

A front expected to stall just west of Kauai will cause winds to
veer to southeasterlies near Kauai beginning Tuesday, while
moderate trades continue elsewhere. GFS and ECMWF are in rather
close agreement concerning the timing of this front`s movement,
with both stalling it 300 to 500 miles west of Kauai by midweek.
Moisture brought northward by the southeasterlies expected near
Kauai may increase rainfall across the western islands during the
second half of the coming work week. Both models want to push the
front over Kauai next weekend, likely extending and expanding the
area affected by increased rainfall.


High pressure building well to the north of the state will bring
returning trades today, although a few areas may see sea breezes
develop prior to the trades setting in. Generally VFR conditions
are expected at the TAF sites over the next 24 hours, although
some MVFR cigs will likely affect PHNY during the day. A band of
clouds and showers will shift southward into the island chain
tonight and Sunday, bringing an increase in trade wind showers
along with some MVFR cigs/vsbys to windward areas.

No AIRMETs are currently in effect.


No marine warnings or advisories are in effect today. Light winds
will give way to moderate trades beginning late in the day today,
which will persist through Tuesday. Winds may approach Small
Craft Advisory (SCA) levels in the windy zones around Maui County
and the Big Island Monday or Tuesday. Winds will begin to shift
out of the southeast late Tuesday or Wednesday through the second
half of the upcoming week as a front approaches from the west and
stalls. The front may bring a period of wet weather during the
second half of the week.

A series of small northwest swells has begun filling in across the
area. Surf will remain well below advisory levels along north and
west facing shores with these swells over the next several days.

A broad low is forecast to develop and move into the northeast
Pacific late this weekend and direct a large swath of gale force
winds towards the islands. This should translate to a building
north-northeast swell late Tuesday, and could bring advisory
level surf to north and east facing shores.

Small long period south swells should provide above null surf for
the south facing shores over the next few days.





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