Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
732 PM EDT Sun Oct 10 2021
Valid 12Z Thu Oct 14 2021 - 12Z Mon Oct 18 2021
...Stormy Pattern Continues from the Aleutians through Southern
and Southeast Alaska...
... Guidance and Predictability Assessment...
The latest models and ensemble guidance over Alaska shows above
average agreement on the synoptic pattern as multiple low pressure
systems moving from the Bering Sea into the Gulf of Alaska
continue a stormy pattern. Models continue to show some timing and
detail differences, but nothing atypical for these time ranges.
The WPC Alaskan medium range product suite used the 12z GFS and
ECMWF deterministic models blended with their respective ensemble
means. More deterministic weighting was given during the early
periods with higher predictability, with slightly more weighting
towards the ensembles by the end of the period. This approach
maintains good continuity with yesterdays WPC forecast.
...Pattern Overview and Weather/Hazard Highlights...
An energetic and progressive flow aloft will support multiple
surface low pressure systems affecting portions of Alaska late
this week and into early next week. An initial strong low pressure
system will exit the eastern Gulf of Alaska by mid-late next week
as additional energies working from an unsettled Bering Sea and
Southwest Alaska/AKPen will act to reinforce mean low pressure
over the Gulf through the weekend. This should preserve a
favorable moisture and enhanced precipitation pattern for southern
and southeast Alaska.
Upstream flow is then expected to drive a deep storm into the
Bering Sea by next weekend with downstream energy transfer
allowing for triple point low developments which should work
across the eastern/central Aleutians and the AKPen region and
eventually into the Gulf of Alaska by next Monday. This should
again bring a coastal and maritime threat for heavy rainfall and
gusty winds to the Aleutians this weekend and the southern
coast/Alaskan Panhandle by early next week. There remains some
differences in exact placement of this low as it gets into the
Gulf, which of course would impact precipitation amounts along the
coast and also how far inland the precipitation shield extends.
Santorelli
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