Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
653 PM EST Sun Feb 06 2022
Valid 12Z Thu Feb 10 2022 - 12Z Mon Feb 14 2022
...Overview...
An active storm track is expected in the northern Pacific south of
the Aleutians late this week into early next week, with potential
for relatively weaker surface lows to approach the Gulf and
southern Alaska in southwesterly flow just east of an upper
low/trough weakening over northwestern Alaska and the Bering Sea.
These surface lows could enhance precipitation periodically in
southern Alaska especially from the Kenai Peninsula into the
Panhandle. The largest and deepest surface low should track south
of the Aleutians (likely somewhere between 40-50N latitude) early
next week, but given its breadth could still affect the Aleutians
with high winds, rough seas, and precipitation.
...Guidance/Predictability Assessment...
Recent model guidance still shows an upper low near the Bering
Sea/western Alaska embedded within an elongated upper trough over
northern and western parts of the mainland to start the period
Thursday. Then heights tend to rise as the period progresses,
though some level of troughing will be maintained. Meanwhile
overall ridging builds across the eastern Pacific and into
northwestern North America, but with increasing chances for it to
get disrupted by a shortwave around Sunday. Model guidance shows
relatively good agreement with this overall pattern. However,
plenty of differences remain in the details of individual
shortwaves and surface low pressure systems, especially as they
potentially approach southern AK. Today's guidance is generally
stronger with the aforementioned shortwave quickly moving across
southern Alaska/Gulf/northern Pacific over the weekend, but with
timing differences--the 12Z ECMWF and GFS were clustered east of
the 12Z CMC and 06Z GFS--so tried to take a middle ground
approach. This also maintains an occluded low pressure system in
the Gulf of Alaska longer than the previous forecast. While some
surface lows could be somewhat strong late week, but there is
considerable run to run and model to model variability in their
placement and strength. Guidance is most agreeable for a massive
and deep (likely in the 960 mb range) low centered south of the
Aleutians Sunday-Monday. However there are still considerable
differences in the placement of the low, with generally the
deterministic models north with its center compared to the
ensemble means. This could certainly affect impacts of the low
over the Aleutians, but given the breadth of the low the Aleutians
could still be impacted even if the low is well south. All
considered, the WPC forecast began with a blend of the
deterministic GFS/ECMWF/CMC, with the blending process smoothing
out some of the particulars of the individual models. Then
gradually phased in the GEFS and ECMWF ensemble mean guidance to
the majority by the end of the period.
...Weather/Hazard Highlights...
Southwesterly flow between the Bering Sea upper low/trough and the
East Pacific/far western Canada ridge will support wet weather
over southern Alaska continuing into the weekend. Individual
surface lows will periodically help to focus heavier episodes of
rain in low/coastal areas and heavy snow in higher elevations.
Highest totals are likely to be from the southeastern coast
through the Panhandle, particularly through Thursday, while
amounts over locations farther west will depend more on exact
storm tracks with the series of low pressure systems. Some snow
may extend farther north into the mainland especially mid-late
week. Each storm could also produce brisk to strong winds and
rough seas between the Aleutians/Alaska Peninsula and the
Panhandle, with the most likely period of high winds next
Sunday-Monday in the Aleutians if the current forecast storm track
occurs. Below normal temperatures are expected for the far western
mainland through the period underneath the trough. Near to above
average temperatures are forecast elsewhere, with the largest
above average anomalies across the southeastern mainland.
Tate
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:
https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html