Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 031937
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
937 AM HST Sat Dec 3 2016

.SYNOPSIS...
An rather unsettled weather pattern can be expected over the next
several days as a trough of low pressure lingers near the area.
Locally heavy rainfall can be expected at times though not all
locations will experience these conditions. There will be breaks
in the weather at times with some sunshine possible as well.
Winds will be rather light for the most part favoring daytime sea
breezes and nighttime land breezes.

&&

.DISCUSSION...
A weak low level trough is in place over the area. Thus winds are
light favoring daytime sea breezes and nighttime land breezes.
This low level trough is expected to linger over or just west of
the islands over the next several days.

Water vapor imagery shows two distinct upper troughs in our
vicinity. One trough is currently located just to the east of The
Big Island with a second trough seen digging down west of Kauai.
The trough east of The Big Island is moving toward the north and
will have less of an influence on our weather. The trough digging
down west of Kauai will be the main player for our weather over
the next few days.

With these features in place, a rather unsettled weather pattern
can be expected at times across the area. There is an abundant
amount of moisture in the island vicinity with satellite derived
precipitable water values of between 1.5 inches and 1.8 inches.
Thus there is a chance for locally heavy rainfall which is the
reasoning for the Flash Flood Watch. There is also a slight chance
for thunderstorms with lightning currently being detected over the
waters west of Niihau.

The Winter Storm Warning as been cancelled for The Big Island
summits as the deepest moisture moves away to the north. However a
Winter Storm Watch is in effect for Sunday and Sunday night as
another round of deep moisture is expected to move over the area,
especially on Sunday. There may still be a few light snow showers
over the summits today but no significant accumulation is
expected.

A brief break in the unsettled weather is expected later Monday
and on into Tuesday as the best upper dynamics pull away to the
north. However winds will remain light with some showers still a
possibility.

By Wednesday, global models indicate a broad low level trough
will be located near or just west of the state. This will continue
to place the islands in moist southerly flow, though winds will
generally be light. A broad upper level trough will also be in
place in the island vicinity with its axis centered northwest of
the area. Thus periods of unsettled weather can be expected at
times though pinpointing the finer details such as timing and
location is problematic in the extended periods.

&&

.AVIATION...
Clouds and showers continue to bring MVFR and occasional IFR
conditions to the islands. Conditions have improved somewhat over
the islands, but an upper level system moving in from the west
will continue to keep an unsettled airmass over the region.

AIRMET SIERRA remains in effect for mountain obscuration across
the Big Island and Maui. Conditions have improved and the AIRMET
may be dropped for these areas this afternoon. A new AIRMET for
mountain obscuration may be needed for areas later tonight or
tomorrow.

AIRMET TANGO remains in effect for moderate upper level
turbulence across the entire state between FL240 and FL400 due to
an upper level disturbance and upper trough in the vicinity of the
islands. These conditions are expected to remain in place through
the day.

AIRMET ZULU remains in effect for light to moderate icing over
Maui and the Big Island and adjacent waters between 120 and
FL200. Conditions have been improving with the greatest threat of
icing to be over the windward waters of these islands. Conditions
are expected to continue to improve today, but will likely
deteriorate tonight from west to east as the next disturbance
moves over the islands.

&&

.MARINE...
East facing shores remain under a High Surf Advisory through
today due an east swell. Buoys exposed to this swell continue to
show seas near 7 to 8 feet, but the swell will decrease today and
tonight as the upstream fetch weakens. A Small Craft Advisory for
most waters will remain through today due to a combination of the
east swell, a moderate northwest swell and local wind waves. The
SCA and High Surf Advisory are likely to be dropped this
afternoon. Winds will be light and variable over the next few
days.

Unsettled weather across the islands is expected Sunday due to an
upper level trough passing over the area. Heavy rain and
thunderstorms will be possible.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Sunday afternoon for all Hawaii
islands.

High Surf Advisory until 6 PM HST this evening for Kauai
Windward-Oahu Koolau-Olomana-Molokai Windward-Maui Windward West-
Windward Haleakala-South Big Island-Big Island North and East.

Winter Storm Watch from Sunday morning through late Sunday night
for Big Island Summits.

Small Craft Advisory until 6 PM HST this evening for Kauai
Northwest Waters-Kauai Windward Waters-Kauai Channel-Oahu
Windward Waters-Kaiwi Channel-Maui County Windward Waters-
Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward
Waters-Big Island Southeast Waters.

&&

$$

Synopsis/Discussion...Burke
Aviation...M Ballard
Marine...Foster


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