FXHW01 KWNH 160749
PMDHI

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
349 AM EDT Thu Apr 16 2026

Valid 00Z Fri 17 Apr 2026 - 00Z Fri 24 Apr 2026

The trades that have been disrupted significantly lately, associated
with the stalled front/shear line north and west of the islands,
will begin to return to more normal by the weekend as surface high
pressure builds to the north of the state near 40N and the
stalled front/shear line dissipates.

Models continue to show a new mid-upper level low forming along
approximately 170W by Friday, remaining there through Saturday
before becoming absorbed by a full-latitude trough which will
gradually advance toward the islands. As the trough approaches, low-
level flow will veer more S-SW by late in the weekend (western
islands) and early next week (eastern islands). As this occurs the
PWAT plume will elongate poleward, averaging around 1.5 to 1.75"
and thereby continuing 2-2.5 standard deviations above normal for
mid April. In terms of more organized rainfall, outside of the
typical upslope trades precipitation distribution, the trough will
likely generate more widespread showers with locally heavy
rainfall across the western islands early next week.

Hurley