Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 301952 CCA

Area Forecast Discussion...CORRECTED
National Weather Service Honolulu HI
952 AM HST Mon Mar 30 2020

Moderate trade winds today will give way to lighter winds by
Wednesday with increasing showers Tuesday and Wednesday, mainly
over windward areas. Even lighter winds for the end of the week
will allow showers to develop over interior and upslope areas in
the afternoons.


No changes to the forecast with the morning discussion, but will
be taking a closer look at the possibility of thunderstorms.
Currently the forecast has thunderstorms in for land on Wednesday
as winds start to weaken and we some instability works its way
into the area. However there are some indications that some
instability could spread across the area a little earlier, so will
be taking a closer look at that today.

A trough east of the islands continues to produce some
thunderstorms with it, but it will continue to move away from the
islands, and is no longer expected to have impacts on the local
weather. High pressure to the northeast is allowing trade winds
into the region again today, ushering in a dry airmass as
evidenced by satellite derived precipitable water (PW) readings
upstream of the islands.

A front to the northwest of the islands will move to the east,
disrupting the trade wind flow Tuesday and Wednesday. A weak
surface trough developing near the islands will dissipate with a
surface ridge moving over the islands for the end of the week.

For Tuesday and Wednesday, the winds will still predominantly be
out of the east, keeping showers focused over the windward sides
of the islands. An increase in low level moisture will mean an
uptick in shower activity. A weak upper level trough approaching
from the northwest will help to provide some instability to the
region, and thus we have the mention of thunderstorms for
Wednesday over land. As mentioned above, the recent model runs
indicate that threat could come in a little earlier. Most likely
will be expanding the mention to the coastal waters and
introducing it a little earlier.

Winds are expected to become weaker for the second half of the
week, which will lead to some land and sea breezes, which will
also mean cloud and shower developing over the interior and
upslope areas during the afternoon hours.

Another low and associated upper level feature approaching the
region from the northwest this weekend could bring another round
of moisture to the region. Still too far out in the forecast to
work out any details, but will likely be making some modifications
to the forecast to trend towards the latest model consensus for
the afternoon package.


Showers being carried in on the trade wind flow will produce some
passing MVFR conditions over the windward areas and mountain
slopes of each island. Lighter winds over the next few days will
result in land/sea breezes developing along more sheltered western
slopes of the islands each night/day with some interior cloud
buildups in the afternoons.

AIRMET Sierra in effect for tempo mountain obscuration over north
through east sections of Kauai and the Big Island, but should be
able to be dropped later this morning as showers decrease.


Moderate to locally fresh trade winds are expected to continue
into Tuesday, then weaken on Wednesday as a trough develops near
the islands. Winds will then become light and variable (favoring
a SE to S direction) Thursday and Friday as the trough dissipates
and a surface ridge moves over the islands. A disturbance aloft
may bring the potential for increased showers Tuesday into Wednesday.
Low pressure is expected to develop NW of the islands over the

Winds and seas will remain below Small Craft Advisory criteria
through the week. Surf will remain below advisory levels along
all shores through Friday, with potential for a NNW swell to bring
larger surf next weekend. Otherwise, surf highlights include a
small WNW swell from Tuesday into Thursday, lingering but
gradually diminishing short- and mid-period wind waves along E
facing shores the next couple of days, and small surf along S
facing shores.





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