Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
758 PM EDT Tue Oct 25 2022
Valid 12Z Sat Oct 29 2022 - 12Z Wed Nov 02 2022
...A strong low will track across the Gulf of Alaska this weekend
causing high winds over parts of the Aleutians/AK Peninsula/Kodiak
Island and bringing heavy precipitation to the Panhandle...
...Overview...
Through the weekend, guidance continues to show a general Rex
Block configuration over the Arctic and Mainland Alaska, with the
active storm track across southern Alaska. There is better model
agreement today for a potent surface low to move across the Gulf
of Alaska this weekend and produce high winds from the Aleutians
and Alaska Peninsula as well as Kodiak Island, spreading some
gusty winds to the Alaska Panhandle as well but with heavy
precipitation likely the greater concern for the latter region.
After that by the first half of next workweek, weather is expected
to calm down in the eastern part of the state, while there is
still a general trend toward troughing developing across the
Bering Sea and Pacific tracking slowly toward western Alaska, but
with less confidence in the details.
...Guidance/Predictability Assessment and Preferences...
Fortunately model guidance has come into better agreement compared
to a day or so ago in terms of energy trekking across Southcentral
Alaska as the period begins Saturday, south of the upper low over
much of the mainland. There are some minor model differences
remaining though, with the 12Z GFS a bit slower to bring stronger
energy in to strengthen a surface low, but overall guidance tends
to show better consensus with the placement of the low over the
Gulf of Alaska tracking eastward over the weekend, and good
consensus for a strong low possibly in the range of 960-970mb for
a time. This low may remain near the eastern part of the Gulf
through early next week while gradually weakening. Thus the WPC
forecast blend was based on the deterministic multi-model
consensus since there was reasonable agreement.
Farther upstream, there is likely to be an upper low coming across
the Bering Sea by Monday, amplifying troughing across the western
mainland as it tracks somewhat slowly eastward through midweek.
Troughing could extend across the Aleutians and into the Pacific
but with more uncertainty farther south, as by Monday there are
already differences in individual models like the EC/CMC showing a
shortwave farther east over and to the south of the Aleutians
while the GFS runs are slower and more phased with the northern
stream. This also creates significant differences in surface low
placement. At least the ensemble means are in fairly good
agreement with indicating the trough and an albeit weak surface
low and their shift eastward with time, so the WPC forecast blend
incorporated and gradually increased the EC and GEFS ensemble
means in the blend by days 6-8.
...Weather/Hazards Highlights...
The Gulf of Alaska weekend low will be the main player causing
significant weather during the medium range period (after a potent
short range system as well). The tight pressure gradient with the
low will cause concerns for strong winds stretching across eastern
portions of the Aleutians into the Alaska Peninsula as well as
Kodiak Island beginning Friday; then even as the low pulls away,
northwesterly flow could cause gap winds issues in some of the
same areas. The low should tap into a long fetch of Pacific
moisture to cause heavy precipitation across the Panhandle
particularly Saturday and lingering into Sunday. Locations seeing
significant totals from the short range event may be sensitive to
the additional activity during the weekend. Some gusty winds are
possible there as well but may be less hazardous than farther
west. After that, there may be some wet periods early next week
across the Aleutians and perhaps the western mainland as troughing
shifts over the region.
Below normal high temperatures should persist over a majority of
the state including the Panhandle through the period, with the
greatest anomalies over southern areas. Locations near the
northern coast of the mainland may remain somewhat above normal.
Low temperature anomalies will likely be more moderate, but still
below average over most areas aside from the North Slope. The
Panhandle may see a mix of above/below average lows depending on
location, and should gradually increase in coverage of warmer than
average lows next week.
Tate/Rausch
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle,
Sun-Mon, Oct 29-Oct 30.
- High winds across portions of mainland Alaska and the Aleutians,
Fri-Sat, Oct 28-Oct 30.
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