Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
751 PM EDT Sun Oct 25 2020
Valid 12Z Thu Oct 29 2020 - 12Z Mon Nov 2 2020
...Guidance/Predictability Assessment...
The forecast period begins on Thursday with a nearly stationary
surface low over the northern Gulf of Alaska, and a surface high
holding strong over the Interior through next weekend. Meanwhile,
an active weather pattern is likely for the Arctic Coast region
with a couple of shortwave disturbances. With the exception of
the faster 12Z CMC across the north Pacific with the storm system
crossing south of the Aleutians, the deterministic guidance
indicates reasonable mass field agreement for the end of the week,
and then normal levels of model spread become apparent. By the
end of the forecast period next weekend, a third system is
forecast to approach the western Aleutians, with decent model
agreement for a day 7 forecast regarding location and intensity of
the surface low, with the 12Z ECMWF/ECENS a little faster than the
model consensus. This is similar to the case with yesterday's
forecast. The WPC fronts and pressures forecast was primarily
derived from the 12Z GFS/ECWMF/EC mean, and with time increasing
the weighting of EC mean along with some of the GEFS mean. Some
previous WPC continuity was also incorporated into the forecast.
...Weather/Threats Highlights..
Periods of coastal rain and heavy mountain snow is expected across
the southeast panhandle and portions of the southeastern Mainland
through Friday, as the surface low over the northern Gulf produces
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, particularly for
the northwestern coast where some heavier snow will be possible.
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, where a strong low level temperature inversion will
likely develop for valley locations, especially for the latter
half of the forecast period. Depending on the track of the
Aleutian storm system next weekend, strong winds and rough seas
may materialize across this region, along with potentially heavy
precipitation.
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