Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
455 AM EST Tue Jan 20 2026

Valid 00Z Wed 21 Jan 2026 - 00Z Wed 28 Jan 2026

An upper trough axis is forecast to be atop Hawaii through late
week. After some light scattered showers on Tuesday, a more
organized moisture plume is forecast to move into Kauai Tuesday
night just ahead of a cold front, bringing a line of showers
including possibly locally heavy rainfall. The front is forecast
to move south toward Oahu Wednesday with winds turning to show a
northerly component, but with temporarily weakening moisture. But
by Thursday and especially Friday a secondary front pushed along
by the upper trough is forecast to reinforce the boundary and pool
higher moisture levels across the state, especially as a surge of
moisture comes in from the west. Instability is forecast to
increase broadly Friday into Saturday as well. Thus in general the
pattern becomes more favorable for widespread rain, which could
be locally heavy, across much of the state late week into Saturday
and perhaps Sunday.

Into early next week, the upper trough should be moving east,
with possible ridging building in from the west. This leads to
drying conditions in general. That said, there is ample model
spread with the details of the pattern, including another possible
front moving through the state around Monday per the ECMWF and
AIFS, so continue to monitor for forecast updates.

Tate