Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
707 PM EDT Fri Oct 8 2021
Valid 12Z Tue Oct 12 2021 - 12Z Sat Oct 16 2021
...Active pattern continues with periods of gusty winds and
precipitation across southern Alaska...
...Pattern Overview and Model Guidance...
Progressive and energetic flow aloft will lead to multiple surface
low pressure systems affecting portions of Alaska through the
period. A strong low pressure system is expected to affect the
northern Gulf region on Tuesday and then rapidly weaken on
Wednesday. Another low should move across the Bering Sea and then
cross into the Gulf over the Alaska Peninsula by midweek, and this
low pressure in the Gulf is likely to linger through the end of
the workweek. Areas of enhanced precipitation and/or strong winds
are likely with each system.
In terms of the models, there is good overall synoptic scale
agreement through midweek regarding the evolution of the main low
pressure systems. By Thursday, the CMC becomes more amplified
than the model consensus with the upper level trough over the Gulf
and thus a stronger cold front, and this becomes even more
pronounced by next Friday, and the CMC also has a stronger
downstream ridge over the Aleutians. There was enough agreement
among the 12Z UKMET/ECMWF/GFS to merit a blend of those models
through Thursday morning, before transitioning to mainly GFS/ECMWF
and their respective ensemble means for the remainder of the
forecast period.
...Weather/Hazard Highlights...
The strong surface low development in the Gulf of Alaska is
expected to result in enhanced precipitation early in the week
across coastal portions of southern Alaska and the southeast
panhandle, with the potential for a few inches of rain near the
coast and heavy mountain snow, along with strong winds. The next
low pressure system should bring precipitation and windy
conditions to the Aleutians and the western mainland through
midweek, while persistent low pressure in the Gulf keeps the moist
inflow into the Panhandle and thus precipitation chances there
through late week with additional heavy totals possible where
orographic enhancement is maximized. Temperatures should
generally be cooler than normal through next week for much of the
southern part of the mainland and the Panhandle, particularly in
terms of highs. For the northern two-thirds of the state, near
average highs are forecast with a mixture of slightly below and
slightly above normal readings.
Hamrick
Hazards:
- Heavy precipitation across portions of mainland Alaska, Mon-Tue,
Oct 11-Oct 12.
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Mon-Thu, Oct 11-Oct 14.
- Heavy rain across portions of the Alaska Panhandle, Mon-Thu, Oct
11-Oct 14.
- High winds across portions of mainland Alaska and the Aleutians,
Mon-Tue, Oct 11-Oct 12.
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