Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
754 PM EDT Sat Oct 24 2020
Valid 12Z Wed Oct 28 2020 - 12Z Sun Nov 1 2020
...Guidance/Predictability Assessment...
The forecast period begins on Wednesday with a lingering surface
low over the northern Gulf of Alaska, and a surface high building
over the Interior by the middle to end of the week. Meanwhile, an
active weather pattern is likely for the Arctic Coast region with
a couple of shortwave disturbances. Deterministic guidance
indicates reasonable mass field agreement through Thursday night,
and then normal levels of model spread become apparent. This
holds true with the next and stronger storm system to pass south
of the Aleutians, with the 12Z GFS considerably slower than the
ECMWF/CMC and the ensemble means. By the end of the forecast
period next weekend, a third system is forecast to approach the
western Aleutians, with surprisingly better model agreement
regarding location of the surface low, with the 12Z ECMWF faster
than the model consensus, but not to the same degree as the 00Z
run. The WPC fronts and pressures forecast was primarily derived
from the 12Z CMC/ECWMF/EC mean, and with time increasing the
weighting of EC mean along with some of the NAEFS mean. Some
previous WPC continuity was also incorporated into the forecast.
...Weather/Threats Highlights..
Some lingering rain and mountain snow is expected across the
southeast panhandle and portions of the southeastern Mainland
through mid-week as the surface low over the northern Gulf
gradually weakens, with onshore flow to the east of the low. Some
snow showers and gusty northwest winds are likely across the
Arctic Coast region as a couple of disturbances pass north of the
region. Very little in the way of snow is expected for the
Interior as high pressure will govern the overall weather pattern.
The coldest temperatures are expected to be across the
east-central portion of the state, especially for the latter half
of the forecast period where some sub-zero high temperatures will
be possible. Depending on the track of the Aleutian storm system
next weekend, strong winds may materialize across this region,
although confidence in this remains limited for now.
Hamrick
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
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