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Southcentral and southwest Alaska forecast discussion 
National Weather Service Anchorage Alaska
432 PM akdt Monday Oct 24 2016

Analysis and upper levels...

An upper level ridge currently encompasses Mainland Alaska and is
supporting widespread sunny skies across much of the state. With
high pressure over the Mainland and low pressure over the Gulf of
Alaska, widespread offshore winds are well-established across the
region. Due to light winds and relatively dry air, fog has been
limited across southcentral, and temperatures have plummeted in
places in low lying valleys such as the Copper River basin.
Meanwhile, a potent low west of Shemya is curving towards the
northwest. Currently its associated front is supporting strong
gusts as it pushes eastward across the western Aleutians, and
wind gusts are rapidly increasing as the front approaches the
central Aleutians. &&

Model discussion...

Models are in generally good agreement in the short term as the
western Aleutian low spirals to the northwest towards the
Kamchatka peninsula, and the associated front surges towards the
eastern Aleutians. The GFS model has shown good consistency and
indicates slightly weaker winds and was the model of choice for
both the east and west domains.


for Anchorage...VFR conditions with light winds will continue.

Short term forecast southcentral Alaska (days 1 and 2)...
high pressure over southcentral Alaska will keep clear skies and
below normal temperatures over the region the next few days. There
is some patchy fog near Knik Arm but otherwise the area should
remain free of fog. Outflow winds will persist over the Gulf Coast
through tomorrow and then the pressure gradient should diminish
causing these winds to decrease. Blowing dust out of the Copper
River Delta is easily seen on visible satellite and will continue
until winds diminish tomorrow.


Short term forecast southwest Alaska (days 1 and 2)...

Some fog may redevelop this evening in the Kuskokwim Delta before
the next front brings increasing winds to the southwest Alaska coast.
On Tue this front will slowly move inland with rain and wind
through Tue night. By Wed the front will weaken, with rain
diminishing in the north but remaining over the Bristol Bay zone.


Short term forecast Bering Sea/Aleutians (days 1 and 2)...

The front moving across the Bering will continue to bring warning
level winds to the central Aleutians through this evening before
slowly weakening on its way east. Rain will also be associated
with this front through Tue. Gale force westerly winds behind the
front will slowly weaken through Wed. Showers in this flow behind
the front will be scattered across the Bering through Tue,
becoming more numerous as the next low moves to the western
Aleutians on Wed.


Long term forecast (days 3 through 7)...
overall there has been very little change in the long term
forecast thinking since yesterday. The persistent pattern with a
high-amplitude trough over the Bering with a blocking ridge over
the Mainland will continue into the middle of this week. This will
bring yet another gale-storm force low through the Bering/Aleutians
starting Wednesday, which will then spread to the southwest coast
late in the work week. To the east of this system, ridging over
southcentral and the Gulf will keep most of the active weather
confined to the Bering or North Pacific. This will allow for the
current sunny, dry and offshore flow pattern to persist into late
this week.

Starting this weekend, there remains good agreement that the
the blocking ridge will begin to shift to the east, allowing the
amplified trough to become much more broad, possibly bringing more
active weather into the Gulf and possibly into southcentral. There
is significant differences in the models as to how much
development will take place in the Gulf, especially between the
GFS (most aggressive over the gulf) and the ec (most aggressive
over the bering). The GFS however begins to have significant run-
to-run inconsistency issues beginning this weekend, and as a
result was treated as an outlier for much of the long term
forecast in favor of ensembles and heavy use of wpc guidance. As a
result in of this inconsistency in the models, the confidence in
the long term forecast begins to decrease significantly beginning
this weekend.


Afc watches/warnings/advisories...
public...High Wind Warning...187.
Marine...storm...173 174 175 176 179 181 185 412 413 414.
Gale...127 165 170 171 172 177 178 180.



Synopsis and model discussion...en
southcentral Alaska...ez
southwest Alaska/Bering Sea/Aleutians...ds
long term...dek

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