Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
630 PM EDT Thu Sep 30 2021
Valid 12Z Mon Oct 04 2021 - 12Z Fri Oct 08 2021
...Pattern Overview and Guidance/Predictability Assessment...
An active weather pattern can be expected during the extended
forecast period across the Alaska domain with a large storm system
crossing the Bering and then reaching mainland western Alaska.
This will be the extratropical version of what is now Typhoon
Mindulle, and a trailing low is likely behind this along with a
reinforcing cold front. Another low pressure system may affect
the Gulf region as a triple point low may develop.
Model guidance is initially well clustered with the arriving
extratropical low through Tuesday and also with the decaying low
over the Gulf region. There is also relatively good agreement
with a secondary low and front that will be trailing the initial
storm system across the Bering Sea. A 12Z deterministic model
blend was incorporated through Tuesday night. Towards the end of
the forecast period next Thursday/Friday, the model signal is
becoming a bit more clear regarding a potential triple point low
forming over the Gulf region, although still uncertainty remains
with low placement and magnitude. There are even more substantial
differences with a potential third storm over the Aleutians/Bering
by next Friday, with the GFS appearing to be a strong outlier, so
leaning more towards the ensemble means seems prudent for days 7
and 8.
...Weather/Hazard Highlights...
A period of dry weather can be expected for most of the state on
Monday before precipitation associated with the Bering Sea storm
arrives across western Alaska by Tuesday. The main concern will
be strong winds and very rough seas across the Aleutians and
extending up the Alaska coast towards Nome. Moderate to heavy
snow can be expected for the higher elevations of the Interior by
the middle of next week as the moisture surge moves inland.
Additional heavy rain and mountain snow is becoming more likely
from the Kenai Peninsula to the southeast Panhandle for next
Wednesday and Thursday with the potential offshore low
development. Temperatures are expected to initially be quite
chilly for most of the state through Tuesday before a slight
moderating trend ensues ahead of the Bering Sea storm system
across the western half of the state.
Hamrick
Hazards:
- High winds across portions of mainland Alaska and the Aleutians,
Mon-Tue, Oct 4-Oct 5.
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Wed-Thu, Oct
6-Oct 7.
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