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Southcentral and southwest Alaska forecast discussion 
National Weather Service Anchorage Alaska
544 am akst Thursday Nov 26 2015

Analysis and upper levels...
an upper level trough currently moving over Kodiak Island is
bringing rain throughout much of the south Mainland to the east of
the Alaska Range under deep...moist...and warm southerly flow. The
exception to this remains for the higher elevations of the Susitna
Valley and Copper River basin which continue to experience
snowfall...though rain is starting to mix at higher elevations as
the column warms. A gale force coastal jet and tight pressure
gradient ahead of this low is still bringing hear high winds to
gap wind areas of the Gulf Coast such as Turnagain Arm. Winds over
the Anchorage bowl have however have weakened substantially since
yesterday as the low position near Kodiak Island is bringing
stronger down inlet flow. Cloud cover and rainfall in the area
however are keeping temperatures above freezing in most areas
overnight. Behind the low...skies are clearing under weakening winds
as a shortwave ridge moves in from the eastern Bering. This is a
very brief period of quiet weather as the next system is already
passing through the eastern Aleutians. This low will continue
tracking into North Pacific today...keeping active weather for
much of the south Mainland into this weekend.


Model discussion...
the models remain in great synoptic agreement until Saturday
morning when there begin to be discrepancies with the timing and
intensity of the next low moving into the western Aleutians. There
are however some small scale issues in the early term...mainly
with regards to the development of precipitation associated with
the upper trough over the southwest Mainland this morning.
Previous model runs had brought this precipitation as far west as
Dillingham...however recent models have trended much further to
the east...keeping most of the precipitation confined to eastern
Bristol Bay.


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

A low pressure system located just to the north of Kodiak has been bringing
widespread heavy rain across southcentral overnight...with snow
falling to the north and west of Talkeetna. As this low progresses
towards Matanuska Valley today...this low pressure system will
continue to bring heavy rain and snow along the Gulf of Alaska
coast...with heavy snow expected through Thompson Pass. In
contrast...precipitation is expected to continue to weaken across
the Matanuska Valley...and as a result the advisory has been

In addition to supporting heavy precipitation...this low pressure
system will increase winds through local gaps...and support
sufficient winds for downsloping across the Anchorage bowl and
western Kenai Peninsula by this afternoon. A weak wave will
again enhance precipitation along the Gulf Coast beginning early
Friday and continuing Friday afternoon. This wave will also
increase pressure gradients and bring gap winds beginning early
Friday morning before weakening Friday afternoon.


Short term forecast southwest Alaska (days 1 and 2)...
the remnants of a weak low pressure over the lower Cook Inlet
will bring wrap-around moisture into the region resulting in mixed
precipitation along the Alaska Peninsula and the Aleutian Range
through Thanksgiving day. By late Thursday evening a storm force
low will be located near Dutch Harbor with an associated front
moving into the Alaska Peninsula region. This synoptic feature
will bring warmer temperatures as the front moves into the Bristol
Bay interior. This will bring precipitation in the form of rain
and will move spread northward. The temperatures in the lower
Kuskokwim valley will be cooler resulting in a mixture of snow and
freezing rain as we head into the weekend.


Short term forecast Bering Sea/Aleutians (days 1 and 2)...
the storm force low located near Atka this morning will continue
to track parallel along the chain before moving near the Shumagin
Islands by Friday morning. The winds in the Bering Sea will shift
from northeasterly to predominantly northwesterly direction by
Friday as the low pressure system tracks along the eastern
Aleutians. This will continue to bring a showery weather regime
along the chain and throughout the Bering Sea heading into the


Long term forecast (days 3 through 7)...

Models are in excellent agreement that by Friday evening the low
moving along the Aleutians will reach the akpen...and then move
into the eastern Bering where it will dissipate along the coast
Sat afternoon. The next low...however...contains abundant tropical
moisture from the western Pacific and as a result is increasing
model uncertainty. The GFS and ec bring the low to the eastern
Aleutians on Sat...and then they hint at moving the low to the
eastern Bering/Aleutians with different solutions. Wpc utilized
their ensemble approach...keeping the low south of the chain as it
travels to near Kodiak Island and eastern Bristol Bay Tuesday through
Thursday. The forecast uses this solution...especially confident
in the eastward progression of the low.

The east domain will be under the influence of strong, warm,
southerly flow through Sat with the first low...and then again
late Sat into Wednesday with the second. This will bring rain to the
coast changing to snow over much of the Susitna Valley and Copper
River basin through the middle of next week.

The west will have small craft winds associated with the initial
low and then potential gales early next week on the backside of
the second low. Rain along the eastern flank of the second low
will spread across the chain through the weekend...with a mix of
rain and snow on the backside beginning sun and lasting through


Afc watches/warnings/advisories...
Marine...storms 119 177
gales 120 125 130 155 165 170 171 172 173 174
175 176 178 185 351 352 411 412 413 414
heavy freezing spray 180 181



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

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