Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 191944
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
944 AM HST Thu May 19 2022

.SYNOPSIS...
Moisture along a weakening front will maintain higher shower
chances for Kauai through tomorrow, with flooding rainfall and
thunderstorms possible this afternoon. The rest of the state will
experience mainly spotty afternoon showers under decreasing
southeast to south winds. Layered clouds will gradually diminish
today as humid conditions persist through Friday. Moderate trade
winds will build during the weekend and will hold into next week.

&&

.DISCUSSION...
Humid southerly winds will produce areas of heavy showers today,
especially around Kauai, while layered mid to high clouds thin.
Active showers persist along a stalled front just northwest of
Kauai, though little rainfall is occurring from Oahu to the Big
Island this morning. The strong upper level trough that brought
stratiform rainfall to mainly Kauai and Oahu yesterday is pushing
east of the state this morning. Mid to high clouds will slowly
thin, but conditions will remain somewhat unstable as the upper
trough slowly departs. As a result, expect low clouds and spotty
heavy showers to develop over the islands this afternoon,
especially around Kauai where a Flash Flood Watch remains in
effect due to the proximity of the lingering deep moisture. There
could be areas of gusty south winds to the north of terrain on
Kauai and Oahu today, but as winds decline this afternoon, sea
breezes should dominate over most areas. With dew points hovering
in the lower 70s, humidity will remain high.

Tonight and Friday, a humid land and sea breeze regime will
prevail from Oahu to the Big Island, while a band of moisture
along the dissipated front stalls over Kauai. Upper level ridging
will be slowly building, but a lingering mid level trough will
maintain some instability. As a result, expect clouds and spotty
showers, some briefly heavy, to develop over most islands in the
afternoon and diminish during the overnight hours. Cloud cover
and shower chances will remain highest over Kauai. There does not
appear to much of a flood threat on Kauai tonight and Friday
morning, but heavier rainfall possible Friday afternoon could lead
to short term flooding concerns.

An increasingly stable trade wind flow will build during the
weekend. High pressure far northeast of the state will strengthen,
causing trade winds to slowly increase and push the deeper
moisture west of the state. A mid level ridge will also build
overhead and bring increased stability. The result will be a
return to typical trade wind weather that will hold into next
week.

&&

.AVIATION...
A broad field of gentle background ascent within the established
moist southerly flow regime will result in periodic low clouds
and showers focusing over leeward zones. A few showers may be
locally heavy, mainly near Kauai which is located within the
eastern edge of the deepest moisture. Likewise, Kauai will
experience a greater frequency of MVFR through the forecast
period. Showers will further increase over Kauai tonight as a
remnant front approaches from the west.

AIRMET Sierra for mountain obscuration is in effect for Kauai &
Lanai, and will likely remain in effect for Kauai through tonight.

Light icing is possible within the 14.5-25kft mid/upper cloud
layer.

&&

.MARINE...
Strong southerly winds will continue over Kauai waters today as
a slow moving cold front stalls just west of Kauai. The southerly
winds and a long period south swell are producing rough seas over
southern leeward waters near Kauai and Niihau that are normally
protected during a typical trade wind weather pattern. A Small
Craft Advisory (SCA) remains in effect for all waters around Kauai
through this afternoon. Expect locally higher winds and seas near
heavy showers and thunderstorms. The front is expected to weaken
as it lifts northward later this evening with a sharp drop in
southerly winds by tonight. High pressure will begin to build back
over the region Friday with easterly trade winds strengthening
from east to west across the area this weekend. SCA conditions
will likely return to the typical windier waters and channels
around Maui County and the Big Island as this happens.

Surf heights along south facing shores will remain elevated into
the weekend as the current south swell becomes reinforced today.
In the long range, models show quite a bit of activity in the
southern hemisphere, which could translate to a few south shore
surf events over the next week or so.

Surf along north and west facing shores will trend up today as a
small, medium-period northwest (300-320 degrees) swell arrives. A
return to small, summer-like conditions is expected over the
weekend and into the first half of next week as this swell energy
fades.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 6 PM HST this evening for Niihau-Kauai-

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

&&

$$

DISCUSSION...Wroe
AVIATION...JVC
MARINE...TS


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