Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
425 PM EST Sat Dec 14 2024
Valid 12Z Wed Dec 18 2024 - 12Z Sun Dec 22 2024
...Deep low to produce a high wind threat near the Bering Strait
and Gulf of Alaska from next Thursday through next weekend...
...Warm up for Alaska...
...Overview/Guidance Evaluation/Preferences...
The guidance is in broad agreement that a cyclone spanning much of
the Pacific late Monday into Tuesday will try to move eastward as
it lies in an unstable position aloft over a longwave ridge in the
mid-Pacific. Ultimately, its eastward progress will be halted by
a new cyclone moving into its southwest to southerly periphery,
which tries to yank it back west due to binary interaction,
leading to stalling while over the Aleutians. The guidance is
excellent agreement on this very large cyclone, but differs on the
spokes moving around its east side through the northeast Pacific
and possibly the Bering Sea on Thursday. To deal with the
uncertainly, used a blend of the 12z runs of the UKMET, GFS,
Canadian, and ECMWF before increasing the percentage of the 12z
NAEFS and 00z ECMWF ensemble means for the pressures, fronts,
winds, 500 hPa heights, and QPF. The remainder of the grids will
be 19z NBM heavy, as per usual.
...Weather/Hazards Highlights...
The slow east progression of the low near the Aleutians should
increase the strength of the roughly southeast flow from the
northeast Pacific into southern AK, causing increasingly cloudy
skies statewide and a warm up, which will be most pronounced in
the southern half of the state and slowest across northern and
eastern portions of AK. Winds near storm force are possible
across the Gulf of AK and near the Bering Strait from next
Thursday onward. Daily precipitation near south-central AK should
be the usual 1-2" per day in preferred terrain, though a spike in
amounts appears to be in the cards late next week. Despite the
forecasted spike, amounts were dropped somewhat from continuity as
a whole.
Roth
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook chart at: The WPC Hazards Outline
depicts these threats.
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