Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
626 PM EST Thu Nov 05 2020
Valid 12Z Mon Nov 09 2020 - 12Z Fri Nov 13 2020
...Guidance/Predictability Assessment...
Progressive and active pattern is still forecast for Alaska next
week. Lead system will be in the exit phase on Monday with its
surface low in the Gulf and front moving through the Panhandle.
Consensus of the 12Z guidance sufficed there. To the west, a
robust Bering system from the west will move eastward as the
parent low moves northeastward toward the Gulf of Anadyr. GFS
continues to be just different enough from the
ECMWF/UKMET/Canadian that it was excluded from the blend, but was
not necessarily unreasonable. 12Z GEFS mean was close to the GFS
on timing and was not preferred initially. Deterministic models
strongly suggest a surface wave along the front Tuesday along the
Aleutians that will move into the Gulf early Wednesday, spreading
another round of coastal rain and inland snow with windy
conditions to Southcentral. Yet another system may follow along
the Aleutians to the AKPen around next Thursday to the Gulf around
next Friday. ECMWF and Canadian paired fairly well with theses
systems but relied much more on the ECMWF ensemble mean and GEFS
mean as it fell back into good agreement from its earlier fast
bias. This maintained good continuity from the forecast 24 hrs ago
aside from the surface wave on Tuesday over the central
Aleutians/southern Bering (hinted at yesterday but uncertainty had
been high in the details). Still believe there are details on
which the models will not yet have a handle, so features in the
day 6-8 period will likely shift around. To the north, weak
troughing and ridging will settle towards troughing by the end of
the week as a surface boundary slowly decays.
...Weather/Threats Highlights...
System in the Bering Sea Mon-Tue will spread an area of
precipitation and strong winds across the Bering
Sea/Aleutians/AKPen/western coastal Alaska. Trailing surface wave
could bring additional modest precipitation to the region as it
becomes the main low into the Gulf, spreading coastal rain and
inland snow across Southcentral. Lingering precip will slowly face
from northwestern areas (Seward Peninsula area) as the old parent
low dissipates. Next system across the Aleutians around Wednesday
will bring a quick round of rain/snow to the region again, ending
into the Panhandle around next Friday.
Above normal temperatures are forecast to remain over much of the
Interior (generally west and north of the Alaska Range) next week.
By contrast, below normal temperatures are expected over the
Panhandle and through portions of Southcentral.
Fracasso
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Sun-Mon, Nov 8-Nov 9.
- High winds across portions of mainland Alaska, Tue-Wed, Nov
10-Nov 11.
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