Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
654 PM EST Thu Nov 11 2021
Valid 12Z Mon Nov 15 2021 - 12Z Fri Nov 19 2021
...Overview and Guidance Evaluation/Preferences...
Negatively tilted troughing across the Bering Sea/central-eastern
Aleutians to start the period on Monday will gradually weaken and
shift eastward sending a surface low pressure system into the Gulf
of Alaska by mid-week. This low should linger, in a weakened
state, through the remainder of the week as it interacts with more
amplified troughing digging south across the Mainland. Meanwhile,
upper ridging should slide eastward across the Aleutians ahead of
the next upper low which moves towards the region later next week.
For days 4-5/Monday-Tuesday, the guidance shows reasonable
agreement on this set-up to warrant a general deterministic model
blend. After this, the models begin to diverge with the typical
timing and detail differences regarding shortwave energy into the
Gulf and also energy/surface low south of the Aleutians next
Thursday-Friday. The biggest model concern is that the 12z ECMWF
drops a deep upper low north of Alaska into the Mainland by next
Wednesday. The GFS/CMC and the ensemble means support more
amplified troughing across the state while the core of the upper
low stays north of the state in the Arctic. As such, the WPC
forecast leaned away from the 12z ECMWF days 6-8 with more
emphasis towards the ensemble means.
...Weather/Hazard Highlights...
Generally dry conditions are likely for most of the mainland
through next week, other than a few possible snow showers. A
surface low exiting the Gulf on Monday may continue to bring some
light to moderate precipitation to the Panhandle region, though
the best precipitation chances should stay to the south.
Precipitation should accompany the next cold front, spreading
eastward from the Aleutians to the Peninsula region on Monday into
Tuesday. After a brief dry period, precipitation should once again
increase across the Panhandle by mid week as the surface low makes
its way into the Gulf and a stationary frontal boundary sets up
along the coast. The next system into the western Bering/Aleutians
should bring another round of unsettled conditions to the region
with light to moderate precipitation and gusty winds for the
western Aleutians and Bering Sea.
Below normal temperatures should prevail across much of Alaska
(with the exception of the North Slope region) through next week
as surface high pressure becomes established across much of the
state. The most pronounced anomalies should be over the western
and southwestern part of the state where daytime highs could be as
much as 15-30 degrees below normal. The north slope should begin
above normal, but quickly moderate back closer to normal the rest
of the week.
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
No significant hazards are expected over Alaska during this
forecast period.
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