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Area forecast discussion 
National Weather Service Honolulu HI
1007 am HST Sat Apr 25 2015

Synopsis...
a front approaching from the west is forecast bring showery weather
to the smaller islands through the weekend. A strong high
following the front will settle north of Kauai Monday and bring in
some breezy trades to the islands lasting through at least
Wednesday. A more typical trade wind shower pattern will return to
the islands after Monday with the showers favoring the windward
and mountain areas...especially nights and mornings.

&&

Discussion...
visible satellite shows a weak cold front just west of Kauai this
morning moving very slowly eastward. Broken low to midlevel clouds with
scattered showers associated with the front are impacting Kauai
and Niihau. A few pre-frontal clouds and showers are impacting
Oahu and Maui County earlier this morning...but are slowly moving
north of the area at this time. Meanwhile...a scattered clouds and
a few showers are located near the southeastern portion of The Big
Island. Early morning soundings showed a stable environment at
Hilo with an inversion at around 7500 with a normal 1.14 inches
precipitable water /pw/. Not surprisingly...the atmosphere is a
bit more moist and unstable near Kauai this morning with a nearly
absent low level inversion and a precipitable water value of 1.44 inches.

The front originates from a compact low pressure system currently
600 miles to the north northwest of Honolulu. This low is tracking
towards the northeast and is not expected to be a impact to Hawaii.
However...as the low lifts away...the weakening front will linger
across the islands into Monday. The front is expected to reach
Kauai early this evening...followed by Oahu Sunday morning...then
stall and dissipate over Maui County on Monday.

Without much upper level support...not anticipating thunderstorms
with this system. However...we could see some bouts of heavy
showers across the western half of the state today...and possibly
into Sunday as the moist southerly flow pushes frontal and
tropical moisture onto the islands. After observing a few moderate
showers popping up in the pre-frontal environment over Oahu and
Molokai this morning...there will be the potential for sea breeze
driven convection both this afternoon and Sunday afternoon. Voggy
and humid conditions will also continue through Sunday or Sunday
night.

A strong high pressure system to the northwest will build behind
the front beginning Sunday night. The high will push breezy trade
winds from west to east across the island chain on Monday through
Tuesday morning. With much of the moisture associated with the front
hung up over the smaller islands...expect the trade winds to focus
showers back onto the area...particularly for windward and Mauka
spots.

Anticipating a drier...and more typical trade shower pattern beginning
Tuesday afternoon. Showers will favor the windward and mountain
areas...especially during the nights and mornings. A few stray showers
may enter the leeward zone of the smaller islands but will be
relatively dry. Leeward Big Island will likely have daily isolated
to scattered afternoon and evening showers.



&&

Aviation...
an approaching cold front will move through Kauai tonight and Oahu
on Sunday. MVFR ceilings and scattered rain showers will become increasingly
likely along and ahead of the cold front. The highest probabilities
for reduced ceilings/visibilities are expected across Kauai today and
tonight...and over Oahu Molokai and Lanai tonight.

Airmet Sierra remains in effect for mountain obscuration across
Kauai Oahu Molokai and Lanai. Conditions should improve across Oahu
Molokai and Lanai over the next hour or two...but mountain
obscuration will likely continue across Kauai through the rest of
the day.



&&

Marine...
surf along south and east facing shores will subside through the
rest of the weekend as the winds and south southwest swell taper
off. A larger north northwest swell is set to arrive Sunday night
then shift from the by north Monday night. This swell will likely
produce surf above the advisory threshold along north facing
shores by Monday...and will likely rising to advisory levels along
east facing shores Tuesday as the swell direction shifts more
northerly.

A Small Craft Advisory /sca/ remains in place for the windward Big
Island waters due to the southeast winds accelerating along the
hamakua coast. The ascat pass during last evening showed 25
knot...Small Craft Advisory level winds...over the windward waters of Maui County and
waters off leeward The Big Island. The Small Craft Advisory for all these waters
will expire at 6 PM HST today.

Strong northeast winds behind the front will spread down the
island chain from Kauai to The Big Island from Sunday night
through Monday night. Small Craft Advisory conditions will likely return for some
of the coastal zones as the winds strengthen.



&&

Hfo watches/warnings/advisories...
Small Craft Advisory until 6 PM HST this evening for Maui County
windward waters-Big Island windward waters-Big Island leeward
waters.



&&

$$

Discussion/marine...Foster
aviation...jelsema

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