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Southcentral and southwest Alaska forecast discussion 
National Weather Service Anchorage Alaska
352 PM akdt Sat Jul 23 2016

Analysis and upper levels...
the low that brought rain to much of southcentral Alaska has
pushed off into the eastern Gulf bringing the bulk of that rain
with it. Another system is making its way toward southwest Alaska
from the north with rain already spreading across the area.
Between these two systems is weak ridging that is helping to clear
things out over southcentral Alaska. Out west, ridging sits to the
south of the western Aleutians which is bringing northwest flow
across the Bering and Aleutians.

&&

Model discussion...
for the most part the models are in good agreement. However, there
are some issues with the low tracking south across southwest
Alaska tonight. They do not seem to quite now how to handle the
various shortwaves swinging around the main low which is causing
problems as to when rain will start for southcentral Alaska.

&&

Fire weather...
the drier conditions observed over parts of southcentral this
afternoon will wrap up overnight tonight, as the weak ridging
pushes further eastward, and a slightly more potent upper level
low begins to move in from the west. This system will bring
another round of rain, which may be heavy at times, to much of
southcentral Alaska. This wet pattern will continue through the
beginning of next week. Winds along Turnagain Arm will shift from
the southwest to southeast overnight tonight, and become more
gusty throughout the day Sunday, and again on Monday.

&&

Short term forecast southcentral Alaska (days 1 and 2)...
weak upper level ridging over southcentral will quickly exit to
the east, making room for an upper level trough to swing in from
the west overnight tonight. This system will bring another round
of rain, which can be heavy at times, to much of southcentral
Alaska through Monday. In addition, there will be sufficient
pressure gradients to support local gap winds from the building
coastal ridge.

&&

Short term forecast southwest Alaska (days 1 and 2)...
a continuation of the cloudy and wet pattern is in store for
southwest Alaska in the coming days as a broad upper level trough
will bring another round of widespread rain to southwest Alaska
tonight and Sunday, with precipitation transitioning to a more
showery regime with the passage of the trough. Showers will begin
to diminish in coverage from west to east by Sunday night as the
trough evolves into a closed low and sinks southward towards
Bristol Bay and the Alaska Peninsula, however this diminishing trend
will be short lived as an easterly wave on the northern periphery
of the large scale feature once again enhances shower coverage on
Monday.

&&

Short term forecast Bering Sea/Aleutians (days 1 and 2)...
the trough moving over the southwest Mainland will also bring
showery conditions to the eastern Bering through Sunday afternoon
as it dives southward towards the Alaska Peninsula, with conditions
improving through Monday across much of the Bering as drier north
to northwesterly flow develops in the wake of the trough. In the
meantime, a weak North Pacific front will bring steadier rain to
portions of the western and central Aleutians tonight into Sunday
morning before sinking south of the area on Sunday afternoon.

&&

Long term forecast (days 3 through 7)...
there is a northeasterly 80 knot jet streak over the y-k Delta
streaming into the eastern Bering, and northwesterly 100 knot jet
positioned over the western Aleutians on Monday. These synoptic
features merge into one jet streak as they dig into the base of
the longwave trough located south of the central Aleutians. By
Tuesday evening heading into Wednesday this jet streak transitions
to a 100 knot southwesterly jet streak south of the eastern
Aleutians. By Wednesday this feature will be streaming through the
Gulf into the southeast Panhandle. Meanwhile, an upper level
closed low will be over the eastern Aleutians before tracking into
the North Pacific Ocean by Tuesday. This feature will move into
the northern Gulf by Thursday before dissipating by Friday. While
a second upper level low will form in the base of the longwave
trough before moving to the eastern Gulf by Friday afternoon. This
will coincide as a deep southwesterly flow develops in the North
Pacific Ocean, and extends into the eastern Gulf region by the
midweek time-frame. Therefore, resulting in a wetter pattern as
shortwaves track through the southwest Alaska region, and swings
around the base of the longwave trough before moving through the
southcentral region. This synoptic scenario will bring abundant
moisture, and precipitation to the southwest/southcentral regions
through Friday. The rest of the Bering and the Aleutians will have
northerly flow with a showery weather regime. While some marine
layer stratus/fog will filter into the region associated with the
high pressure just west of Shemya.

&&



Afc watches/warnings/advisories...
public...none.
Marine...none.
Fire weather...none.

&&

$$

Synopsis and model discussion...dk
southcentral Alaska...pepe
southwest Alaska/Bering Sea/Aleutians...cb
long term...pd

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