Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
439 am akst Sat Feb 13 2016
Analysis and upper levels...
The remnants of a low and its front has pushed onshore along the
north Gulf Coast through Prince William Sound. The upper trough is
moving across northern Cook Inlet tonight. A strong onshore push
of moisture has produced rain across much of the north Gulf Coast
with snow at higher elevation of the coastal mountains. This upper
trough extends back to the west over Bristol Bay. Precipitation
has spread across the Aleutian mountains into the Bristol Bay
region and moisture is advecting to the west as the upper trough
pushes through tonight.
Out west is a complex of three lows south of the central Aleutians
with an elongated front to a low about 300 miles south of Kodiak
Island. This is resulting in clouds and precipitation along the
central to western Aleutians with moderate winds as the gradient
is weak along this elongated front. Another low is just west of
the southern Kamchatka peninsula.
An upper low is near Cape Lisburne with a trough that extends
across northwest Alaska through the Kuskokwim Delta resulting in
some showers across the Delta this evening.
the models remain in good agreement through Sunday then begin to
diverge on the solution of the next system moving into the
southern Gulf of Alaska early next week. The GFS and NAM stay in
good agreement while the European model (ecmwf) is the outlier with a faster
solution resulting in the low being about 300 miles further to the
northeast by Tuesday morning. This does have implications for the Gulf
of Alaska offshore wind direction and speed. We are staying the
course using the wpc/European model (ecmwf) guidance for this low's location and
intensity. The models have come into excellent agreement with the
movement of the low toward Kodiak Island tonight and remain in
excellent agreement with the main low moving toward Unalaska
tonight as well.
Short term forecast southcentral Alaska (days 1 and 2)...
a fairly potent shortwave is moving over southcentral Alaska
early this morning. Temperatures are rather warm behind this
feature causing most of the precipitation at sea level to fall as
rain. Temperatures will remain warm through the weekend across
most of the area. The Copper River basin will be the exception
where temperatures should remain below freezing.
The main surface low is south of Kodiak Island and will make it
to the southern tip of the Kenai Peninsula Sunday. This will bring
in another shot of precipitation to the area much like this
Short term forecast southwest Alaska (days 1 and 2)...
as a weak disturbance (which brought light snow showers to the
Kuskokwim Delta during the overnight hours) exits to the north...
another wave starts to push through the Bristol Bay area. Light
snow and rain showers over the Bristol Bay area are expected as
this wave pushes further inland...with little or no accumulations
expected. However...areas along the Aleutian/Alaska Range will see
slightly drier conditions due to weak downsloping...along with
gusty gap winds increasing today and persisting through Sunday
morning. As the low near Kodiak Island starts tracking inland over
the Bristol Bay area Sunday morning...moisture will spill over
into the southwest Mainland...keeping a chance of precipitation
over the area through Monday morning.
Short term forecast Bering Sea/Aleutians (days 1 and 2)...
a complex North Pacific low south of the central Aleutians will
consolidate and move over the eastern Aleutians Sunday morning...
then begin to dissipate over the Alaska Peninsula Monday morning.
This system will keep showery conditions along the eastern
Aleutians and akpen through Monday morning...with showers tapering
off from west to east as ridging builds over the western
Aleutians/Bering Sunday afternoon and push eastward over the
central Aleutians by Monday morning. A frontal system associated
with a low near the Kamchatka peninsula will start to bring some
rain and gale force winds to the western Aleutians come Monday
Long term forecast (days 3 through 7)...
Starting Monday the persistent pattern of a broad trough over the
Bering with ridging over the western North American coast will
begin to break down as a cold upper level trough begins to dive
into southern Gulf and the northeast Pacific...while a sharp and
narrow ridge of high pressure aloft builds over the eastern Bering
and western Alaska Mainland. This will allow for a shift to
northwesterly flow aloft over southern Alaska...bringing colder
air back to the Mainland. Meanwhile...southerly flow will increase
over the western and central Bering as low pressure systems move
from Kamchatka into the Bering Sea. This system looks to impact
the Bering Sea with gale force winds and rain/snow on Monday and
Tuesday...while weak high pressure over the Mainland should bring
sunny skies and cooler temperatures.
As this system crosses the Bering toward the southwest Mainland
and weakens toward mid-week...a triple point low pressure will
form over the southern Gulf and northeast Pacific. This will
likely allow for more seasonable colder air to filter into
southwest and southcentral Alaska toward the end of next week.
This will also offer little chance of ending the consecutive days
streak without measurable snow in Anchorage.
heavy freezing spray...185.
Synopsis and model discussion...surface observation
southwest Alaska/Bering Sea/Aleutians...tp