Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
412 PM EST Sat Dec 07 2024

Valid 12Z Wed Dec 11 2024 - 12Z Sun Dec 15 2024

...Heavy precipitation along the southern coast through early next
week...
...Storm-force winds possible near the northern Alaska coast and
Gulf of Alaska coastline...

...Overview/Guidance Evaluation/Preferences...
Model guidance remains consistent and agreeable in showing a mid-
to upper-level ridge across mainland Alaska weakening as a trough
between the Sea of Okhotsk and the Gulf of AK team up with a
retrograding system across northern Canada to cause its erosion. 
Within the west-to-east trough, the main deep layer lows are
expected to be most persistent over portions of the Sea of
Okhotsk/Bering Sea and Gulf of AK/northeast Pacific, anchoring
troughs on either side of the Pacific.  While the broad flow is
agreeable, detail issues remain with individual cyclones and how
much upper level troughing is expected across Alaska itself.  For
the pressures, fronts, winds, and QPF/PoPs, used primarily a
compromise of the 12z runs of the GFS, ECMWF, UKMET, and Canadian
before including some 00z ECMWF/12z NAEFS means later in the
forecast to account for the uncertainty.  The remainder of the
grids were more 19z NBM heavy, as usual.



...Weather/Hazards Highlights...
Deep south to southeast flow should keep south-central AK and
Kodiak Island quite wet early, within 5-10" of liquid
equivalent/rain expected mid next week, before
rainfall/precipitation becomes less intense and moves eastward as
the Gulf of AK portion of the trough slowly edges east, making the
AK Panhandle wet, but not abnormally so.  A cyclone early on could
lead to storm-force winds near the Gulf of AK coast mid next week.
 Portions of southern and central AK should be relatively mild
early, but the beating down of the mid- to upper-level ridge and
the subsequent deeper layer flow becoming more northwesterly
should cause the arctic drape/colder air to shift south into the
far northern Gulf of AK by late next week, with outflow/gap winds
expected through the usual spots of Southeast AK/the AK Panhandle
from next Friday into next weekend behind the arctic front.  With
a stronger arctic high expected to build over the Arctic Ocean and
slip southeast, the threat of storm-force winds along the northern
AK coast is increasing.  This has also caused a cooling and
clearing trend for northeast AK when compared to yesterday's
forecast.  A new cyclone approaching the Aleutians from the
southwest next weekend looks strong enough, even with uncertainty
factored in, to bring a risk of storm-force winds to the Aleutians
and portions of the Bering Sea; at this range, the guidance can be
too strong and sometimes too far north with cyclones, so the
forecast bears watching as we get closer to next weekend.  The
general upper troughing near southern AK and the Bering Sea should
keep sea level pressure near to below average statewide.  The
stormy pattern should offer gales near most coasts and island
groups.

Roth

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