Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
659 PM EST Tue Feb 08 2022
Valid 12Z Sat Feb 12 2022 - 12Z Wed Feb 16 2022
...Overview...
The extended range over Alaska begins this weekend with troughing
over the Mainland and a shortwave/frontal system moving quickly
through the Gulf of Alaska. Behind this, a strong ridge will build
in across the northeast Pacific increasing heights across the
Mainland which should hold until early next week. A large and deep
surface low will track towards the central/western Aleutians on
Monday, which eventually looks to weaken as it gets wrapped into a
second deep low approaching next Wednesday at the end of the
period. Given the size of these lows, regardless of the exact
track, they're likely to affect the Aleutians with high winds,
rough seas, and precipitation.
...Guidance/Predictability Assessment...
Recent model guidance has converged nicely over the past day and
is now in reasonably good overall agreement through most of the
the forecast period. For this weekend/days 4-5, a purely
deterministic model blend was used with the GFS, UKMET, CMC, and
ECMWF. The deterministic solutions also show excellent agreement
with position and strength of both surface lows approaching the
Aleutians next week. The first low should come in around Monday
and nearly all of the guidance shows the central pressure could
get down to near 950mb as it approaches the Aleutians. The only
notable difference with this low is the 12z UKMET was displaced
just west of the better consensus on day 6/Monday so it was not
used in the blend after day 5. The ensemble means are also quite a
bit slower, and farther east as it skirts the Aleutians
Monday-Tuesday, although likely due to depiction of a much weaker
system (as expected with ensemble means anyways). Therefore, a
deterministic model heavy blend was held through day 7 with much
smaller (20 percent) contribution from the means. Some larger
questions arise by next Tuesday-Wednesday with a developing
shortwave ejecting from the base of the Aleutians trough into the
eastern Aleutians/AK Peninsula region. The 00z and 12z ECMWF today
are a bit sharper with this shortwave which downstream also
affects how quickly the amplified ridge gets pushed east (also in
part due to a faster shortwave moving into the Mainland Alaska as
well). For the second deep low towards the Aleutians next
Wednesday, the GFS and ECMWF show very good agreement right now
while the CMC is depicting a little more elongated of a surface
low. For the day 8 blend, increased ensemble mean weighting to 40
percent to help smooth out some of the smaller scale detail
differences.
...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 this weekend. Highest totals are likely to be
from the southeastern coast through the Panhandle on Saturday.
This region should dry out next Monday into Tuesday, but another
round of moderate to locally heavy precipitation is likely next
Wednesday ahead of another shortwave moving into the Gulf. Across
the Aleutians, regardless of the exact track of the Aleutians low
pressure system, the pure massive size is likely to affect the
Aleutians with high winds, rough seas, and modest precipitation.
Winds are most likely to be the worst near the central and western
islands on Sunday, with several pieces of guidance indicating
gusts greater than 50 mph are possible. The winds should relax
Monday into Tuesday, but another round of gusty winds is possible
with the approach of the second low on Wednesday.
Northwest Alaska and the North Slope region should start out
chilly and much below normal this weekend, but should moderate
closer to normal early next week. The southern half of the
Mainland should be in a warming trend through much of the period
as a strong upper level ridge builds into the region. Daytime
highs near 10-20 degrees above normal are possible, with overnight
low anomalies even greater.
Santorelli
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
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle,
Fri-Sat, Feb 11-Feb 12.
- Much below normal temperatures across portions of mainland
Alaska, Fri-Mon, Feb 11-Feb 14.
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