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Lake Effect Showers Downwind of the Great Lakes through Sunday; Wet Weather Approaches the Pacific Northwest

Cooler weather returns for the northeast through Sunday where some lake effect showers are expected downwind of the Great Lakes. Meanwhile, high pressure will provide tranquil and near seasonable weather conditions for the center of the nation. A Pacific system approaches Sunday with the increase chance for wet conditions. Read More >

FXZS60 NSTU 160132

Area Forecast Discussion
National Weather Service Pago Pago AS
232 PM SST Fri Oct 15 2021


Satellite imageries (IR & Vis) show open cumuli clouds to the east
and north streaming across the area. These clouds are likely to
produce brief isolated to scattered showers (15% to 50% chance)
once they reach the mountaintops. They are also associated with
the high pressure centered south of the regioin. This high
pressure will dominate weather conditions for the entirety of the
forecast period. Gentle to moderate (10 to 15 mph) easterlies
increasing to fresh breeze (20 mph) is expected on Saturday into
the new week. Upper air data from this afternoon`s (16/00Z)
balloon release show a slightly unstable atmospheric profile. The
Galvez-Davison Index (GDI) model data shows a dry trend for the
forecast period, except the passing showers embedded within the
easterly flow. Thus, expect isolated to scattered showers with
gentle to fresh breeze for the short term forecast period.

As the high pressure continues to migrate eastward, another high
pressure from the southwest will follow suit. Model data is
showing a trough to the north or the territory by midweek. If and
when the high pressure exits the region, the chance for this
trough to descend south and across the islands will bring adverse
weather conditions. Otherwise, moderate to fresh east-southeasterlies
with scattered showers will prevail through the midweek before
decreasing to gentle breeze Wednesday night through the end of the
forecast period.


The latest set of data from the PacIOOs buoy near Aunu`u Island
show seas in the 5 to 7 feet range with long periods. White caps
are currently observed in the open waters from the station. This
is largely due to the gentle to moderate (10 to 15 knots) easterlies
in the hourly observations, and will continue to increase to
fresh (20 knots) breeze on Saturday. The model projects combined
seas to build to 7 to 9 feet Saturday through at least Monday.
However, long periods (>13 seconds) are shown in the PacIOOs data.
This feature will likely enhance surfs as they reach shorelines.
Seas will subside starting Monday night through the rest of the
forecast period. Therefore, an advisory for small crafts will be
in effect through Wednesday night. Will continue to monitor and
issue alerts when warranted.



A Small Craft Advisory is in effect.