Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
644 PM EST Sat Feb 05 2022
Valid 12Z Wed Feb 09 2022 - 12Z Sun Feb 13 2022
...Overview...
The pattern over Alaska during the latter half of next week into
the weekend will feature an elongated upper trough over parts of
the mainland, which is likely to have an embedded upper low over
the Bering Sea near the western mainland Wednesday-Thursday of
next week. Meanwhile overall ridging builds across the eastern
Pacific and into northwestern North America. This pattern will
allow for a surface low pressure system to track into
south-central and southeastern Alaska around midweek, and a series
of additional lows are likely to progress south of the state
through the weekend. These will spread precipitation especially
into southern Alaska, with some snow farther north in the mainland
particularly Wednesday and Thursday.
...Guidance/Predictability Assessment...
The guidance consensus since yesterday has shifted somewhat with a
surface low position 12Z Wednesday. Yesterday's forecast showed
the low going into the southwest mainland but is now closer to
Kodiak Island on the southern side of the Alaska Peninsula. The
ECMWF and EC mean are a bit east with this feature compared to the
GFS/CMC, given lingering differences in the Bering Sea upper low
and the shortwave energy passing through on the southern side,
though the EC is supported by the UKMET. Leaned a bit toward the
western position shown by the GFS/CMC suite. Guidance is becoming
somewhat more agreeable in converging on a middle ground position
for the Bering upper low at least initially on Wednesday, not as
far west as previous GFS runs and not as far east as previous
ECMWF runs. The position of the NAEFS mean worked well for this
feature. That upper low drifts northeast and likely weakens for
the latter part of the week, but still with notable timing
differences when it lifts out and how much energy is left behind.
Farther south, a storm track south of the Aleutians will take
rounds of troughing and surface lows through the northern Pacific
and possibly near the Aleutians/southern coastal Alaska. Some of
these surface lows could be potent, but there is considerable run
to run and model to model variability in their placement and
strength through the end of the week. In fact the best signal for
a deep storm system (deterministic models show the low in the
950s) is not until next Sunday, when guidance agrees better on a
position well south of the Aleutians but still may be large enough
to affect the region with strong winds. Thus the WPC forecast
began with a blend of mainly deterministic models but including
the NAEFS mean even at the beginning, and increased the proportion
of ensemble means to 50 percent by day 6 and beyond given the
large differences in the details among deterministic guidance.
...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 during most of next week. 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 Wednesday into 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 in the Aleutians if
the current forecast storm track occurs. Below normal temperatures
are likely across northern and western parts of the state around
midweek given the upper low in the vicinity, which should
gradually moderate by the end of the week and confine the below
average temperatures to the far western mainland. Near to above
average temperatures are forecast elsewhere, with the largest mild
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