Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
752 PM EDT Mon Jun 06 2022
Valid 12Z Fri Jun 10 2022 - 12Z Tue Jun 14 2022
...Overview and Guidance Evaluation/Predictability Assessment...
Today's guidance maintains some broad themes in the overall
pattern, featuring northern coast energy that should settle over
or near the Bering Strait in the form of a closed low while
northwestern Canada upper ridging eventually builds over at least
a portion of the mainland, along with a slow-moving upper low over
the northeastern Pacific. The northern upper low should promote a
northward shift in the main axis of lowest surface pressures over
the mainland, from southern areas late this week into the
central/north-central latitudes by the weekend. The Panhandle and
southern mainland should see the main focus for precipitation
during the period, with relatively higher totals late week into
the weekend versus early next week.
Within the general evolution, the fairly good agreement along with
mostly just refining continuity adjustments from 24 hours ago have
given way to more noticeable differences and run-to-run changes
for some aspects of the forecast. Latest runs have tended to be
slower/farther east with the northern coast to Bering Strait upper
low with some spread and variability, ultimately providing a
modest delay for the upper ridge expected to build over the
mainland from northwestern Canada. As of the 12Z cycle, the
operational model average was a bit east of the ensemble means but
west of the old 00Z ECMWF after Sunday. Arrival of the 12Z ECMWF
mean/18Z GFS add support for an intermediate solution. Meanwhile
consensus has trended a little faster to eject the northeastern
Pacific upper low. The majority of guidance has suggested the
system will take a track south of the Panhandle but the 12Z ECMWF
shifted farther northward, and its ensemble mean did as well.
Over recent days the mid-latitude Pacific has generally been out
of play with respect to Aleutians weather, but recent northward
trends for a system tracking well south of the region during the
weekend could bring at least some peripheral influence to the
eastern Aleutians/Alaska Peninsula by early next week. ECMWF runs
have stayed well south while the 12Z GFS offered a compromise
between the ECMWF and 06Z GFS/12Z CMC/18Z GFS that were all
farther north to varying degrees. Thus far the ensemble means
have not favored the northern side of the current spread.
By early next week the guidance shows increasing spread and
significant run-to-run variability for how upstream flow could
amplify into the larger scale Bering Sea mean trough. Lack of
confidence in any specific scenario favors trending the forecast
toward a more general model/mean blend in that time frame.
Today's forecast started with a composite of the 12Z GFS/ECMWF/CMC
early in the period. The 12Z UKMET could not be used as it
differed from other guidance over the Bering Sea, emphasizing a
separate upper low near 60N latitude versus the consensus feature
farther north-northeast. This blend transitioned toward a half
models/half means (12Z GEFS/00Z ECens for the latter) by day 8
Tuesday.
...Weather and Hazard Highlights..
The deep-layer low initially over the northeastern Pacific should
favor continuation of precipitation across the Panhandle late this
week into the weekend, while moisture within the far northern
periphery of the broad cyclonic flow should also contribute to
episodes of rainfall over parts of the southern mainland. Some
locally enhanced totals may be possible but it will take into the
short range period to refine specifics. Weakening and departure
of this system should yield a lighter and more scattered trend for
Panhandle/southern mainland activity early next week. Other areas
of precipitation are possible as the wavy front initially over the
southern mainland lifts northward and a front sets up over the
western mainland, on the eastern side of the Bering Strait upper
low/associated trough. Recent trends have increased the
possibility that the eastern Aleutians/Alaska Peninsula could see
some light precipitation on the northern side of a mid-latitude
Pacific system early next week. However this is quite uncertain
with dry weather also still a plausible scenario.
From late this week into the weekend, expect below normal highs
from the North Slope across the eastern mainland through the
Panhandle and above normal readings over southwestern areas. The
forecast pattern evolution should lead to a cooler trend over the
west and moderation closer to normal over the north and east from
the weekend into next week. Low temperatures will tend to be
above normal over southern areas, and below normal but moderating
with time across the North Slope and vicinity.
Rausch
No significant hazards are expected over Alaska during this
forecast period.
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