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000
FXHW60 PHFO 141400
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
400 AM HST Sun Apr 14 2024

.SYNOPSIS...
The potential for heavy rainfall and thunderstorms associated
with a front will continue through Monday, initially over the
western end of the state through tonight, then over the eastern
end on Monday. Conditions will gradually improve from west to east
through the first half of the week as high pressure builds to the
north in the wake of the front. Breezy southerly winds ahead of
the front will hold today, then ease into the light to moderate
range as they shift to the north, then to a more typical trade
wind direction around midweek. Expect a more typical trade wind
pattern to return with showers favoring windward and mauka
locations through the second half of the week.

&&

.DISCUSSION...
The short-term guidance remains in good agreement and depicts the
active weather pattern persisting through Monday due to an upper
low to the northwest and its attendant surface front forecasted to
slowly advance down the island chain. A shortwave pulse rotating
through the base of the upper-level trough to the northwest has
triggered the next round of heavy showers and storms that is
spreading northward over Niihau and Kauai. Provided the saturated
soils and elevated streams from the recent heavy rainfall over
the past few days, it won`t take much for them to respond this
morning. Expect this threat to reach Oahu later this morning, then
to Maui County later today through Monday. As a result, the Flood
Watch has been expanded and now includes all of the smaller
islands.

In addition to the expected heavy rainfall, a few thunderstorms
could become strong provided the instability and shear profiles,
particularly over Kauai and Oahu today. Also, breezy southerly
winds could translate to strong downsloping winds over windward
areas through this time, especially in the heavy showers/storms
moving through.

A drying trend is anticipated from west to east, beginning over
Kauai late tonight, then over Oahu through the day Monday as the
front advances eastward to Maui County and the Big Island.
Conditions should steadily improve over the eastern end of the
state Tuesday through Wednesday as the upper level trough exits
or shifts northeastward and away from the state. The low-level
flow will return to a more typical trade wind direction Wednesday
through the second half of the week as surface high pressure
builds north of the state.

&&

.AVIATION...
The tail end of a Central Pacific cold front will strengthen as it
passes over the western Hawaiian Islands today. An organized band
of intense showers associated with with the leading edge of this
front can be seen on late night radar slowly approaching western
Oahu. These showers, which are accompanied by isolated embedded
thunderstorms, are pressing quickly eastward even as they expand
to the south.

Surface winds will veer from southeast to west-southwest with the
frontal passage. Ahead of the front, light showers will favor
south and southeast facing slopes and coasts. Behind the front,
moderate showers and embedded thunderstorms will favor west and
southwest facing slopes and coasts.

We anticipate issuing AIRMET Sierra for mountain obscuration for
Kauai and Oahu later this morning. It will likely need to be
expanded to included Molokai and Maui sometime this afternoon.

AIRMET Tango remains for moderate upper level turbulence as been
canceled, but conditions are likely to redevelop later today as
a new upper level trough approaches from the northwest.

AIRMET Zulu remains in effect for moderate rime icing in cloud, in
precipitation, between FL230 and FL280 due to upper level layered
clouds. This AIRMET will likely be needed through today and into
tonight.

&&

.MARINE...
South to southeast winds will strengthen ahead of an approaching
front today. A Small Craft Advisory remains posted for coastal
waters west of and including the Kaiwi Channel due to winds. The
front will slowly push southeast late today through Monday,
before stalling out and slowly dissipating near the Big Island
Tuesday and Wednesday. Light to moderate west to northwest winds
will fill in behind the front. Winds will become rather light by
Monday night and continue through Wednesday, with moderate trades
potentially returning for the latter part of the week.

North shore surf will remain small today. Surf will trend up
tonight and Monday as a medium-period northwest swell arrives.
Surf could reach low end advisory levels along north facing shores
Monday night and Tuesday as a second, more north-northwest pulse
arrives. This swell will then decline Wednesday through late in
the week. Surf along east facing shores will continue to slowly
decline today and Monday, with only small very small surf expected
through the remainder of the upcoming work week. Small, medium to
long period south swell will keep some small surf rolling into
south facing shores through late in the week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for Niihau-Kauai-

Flood Watch through Monday afternoon for Oahu and Maui County.

Wind Advisory from noon today to 6 PM HST Monday for Haleakala
Summit.

Winter Weather Advisory until 6 AM HST Monday for Big Island
Summits.

High Wind Warning from noon today to 6 PM HST Monday for Big
Island Summits.

Small Craft Advisory until 6 PM HST this evening for Kauai
Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-
Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters-Kaiwi
Channel.

&&
$$

DISCUSSION...Gibbs
AVIATION...Bedal
MARINE...Jelsema