Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
710 AM EST Tue Dec 26 2017

Valid 00Z Wed Dec 27 2017 - 00Z Wed Jan 03 2018

Shortwave expected to cross Hawai'i today through early Wed, with
an additional shortwave amplifying just north of the Islands early
Thu. In general, models and ensemble show good agreement with
respect to both of these features. The primary exception was the
00Z UKMET, which appeared to be overly amplified with both waves.
At the surface, expect a cold front to pass through the state
Wed/Wed night, with low-level flow veering from southerly today
and tonight to northerly or northeasterly in the wake of the cold
front. Expect convection to accompany the front across Hawai'i.
Satellite loop early this morning shows an active area of
convection in association with the frontal system. This should
continue as the front crosses the Islands, with the GFS and ECMWF
in general agreement on this scenario, indicating the potential
for 1-2 inches of rainfall, and localized higher amounts.

From Fri night onward through the middle of next week,
models/ensembles are in good agreement on building upper ridging
from west of Hawai'i eastward across the state. Low-level
easterlies should resume as the surface high initially north of
Hawai'i moves eastward. This feature should keep a source of
low-level dry air in place into next week, with shower activity
rather sparse, and limited to the typical favored east-facing
terrain.

Ryan