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RH96 %
WindSSE 1 mph
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Hawaiian Islands Synoptic Discussion and Guidance

911
FXHW60 PHFO 221934
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
934 AM HST Mon Jan 22 2018

.SYNOPSIS...
Trade winds will continue today with clouds and showers focused
over the windward sides of the islands. And upper level
disturbance could enhance shower activity through midweek. Some of
the layered clouds on the Big Island could spark a thunderstorm or
two, and could even bring some snow or freezing rain to the
summits. Lighter winds with land and sea breezes are forecast
during the second half of the week.

&&

.DISCUSSION...
As mentioned in the update around 730am, the Winter Weather
Advisory was updated to include lower snow totals, and adding in
the threat for freezing rain. The cloud band near and over the Big
Island has broken up some in the last few hours. Some towering
cumulus remains near the Big Island and is moving in, however the
little deep layer moisture is making its way to the summits.

The clouds and showers moving over the windward side of the Big
Island will continue through much of the morning, and likely into
this afternoon. Satellite shows a break in the cloud band about 50
miles east of the Big Island, which could result it some tapering
off of some of the showers. Clouds and showers are also being
carried in on the trades to the windward sides of Oahu and the
islands of Maui County this morning, and are expected to continue.
Kauai is starting the day with the fewest clouds overhead, but
suspect clouds and showers will form over the windward side
shortly.

The surface ridge to the north of the islands is expected to move
to the east during the second half of the week, which will allow
the background flow to become southeasterly and weaken. This will
likely result in local land and sea breezes over the islands.
Expect more clouds and showers during the afternoon hours, and
some clearing overnight.

&&

.AVIATION...
An area of clouds and showers continues to affect windward and
southeast portions of the Big Island and appears to be spreading
westward toward the smaller islands. Except for Hilo, the terminal
will be predominantly VFR.

AIRMET Sierra is in effect for mountain obscuration across
windward sections of the Big Island. These conditions are
expected to persist through the day and possibly through the
overnight hours as well. The mountain obscuration AIRMET may be
needed this afternoon for leeward sections of the Big Island.
Additionally, the AIRMET may need to be expanded to include
windward sections of the smaller islands this afternoon and
tonight.

AIRMET Tango remains in effect for moderate low level turbulence
over and downwind of the terrain of all islands. The AIRMET is
expected to remain in place through through tonight.

AIRMET ZULU is in effect for light icing in clouds around the Big
Island from 12000 to 20000 feet. This AIRMET will likely be
continued through today.

&&

.MARINE...
A Small Craft Advisory remains posted for most Hawaiian coastal
waters. This is due to several factors including a moderate east
swell, locally windy conditions around Maui County and The Big
Island, and a new moderate size northwest swell. These conditions
are expected to continue through Tuesday afternoon. The new
northwest swell will will gradually lower later on Tuesday so the
Small Craft Advisory may be lowered over those exposed waters.
However, locally windy conditions and the moderate size east swell
are expected to continue through at least Wednesday.

A High Surf Advisory is posted for most north and east facing
shores and for west facing shores from Molokai westward. The
current east swell will continue to produce hazardous surf along
east facing shores with the largest waves expected over the east
end of the island chain. The new moderate size northwest swell
will produce advisory level surf along exposed shorelines through
Tuesday with the largest waves expected over the west end of the
island chain. There will also be a small south swell affecting
exposed shorelines through Tuesday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST Tuesday for Niihau-Kauai
Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu
Koolau-Olomana-Molokai-Maui Windward West-Maui Central Valley-
Windward Haleakala-South Big Island-Big Island North and East.

Winter Weather Advisory until 6 PM HST this evening for Big
Island Summits.

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


&&

$$


DISCUSSION...M Ballard
AVIATION...
MARINE...

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office