Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
536 PM EST Wed Jan 13 2021
Valid 12Z Sun Jan 17 2021 - 12Z Thu Jan 21 2021
...Active Gulf of Alaska early next week will shift focus to the
Bering Sea...
...Overview and Guidance/Uncertainty Assessment...
Deep troughing will move out of eastern Asia later this week and
across the northern Pacific this weekend, promoting split flow
across the Dateline. This will drive one system into the Gulf of
Alaska on Monday before a lead then trailing Bering system from
the west become the focus. The models and ensembles generally
showed this evolution, but continued to differ on timing of the
systems, especially in the Bering Sea. For the Gulf, guidance has
mostly converged on a track/speed given the lead time (somewhat in
between the quicker ensembles and slower deterministic guidance 24
hrs ago) and a blend of the 12Z models sufficed. Front will lift
steadily northeastward into the southeastern mainland and the
Panhandle late Monday but will pack a bit of a punch with strong
winds and modest to heavy precipitation. For Tue-Thu, upstream
pattern will transition from strongly zonal ahead of a deep trough
in eastern Asia to increasingly amplified. This will favor
building ridging into the mainland from the south even as
shortwaves pass through and weaken. Good ensemble agreement exists
even by next Wed-Thu with a second Bering system on the heels of
the first, and used their consensus to form most of the
frontal/low placement.
...Weather/Hazards Highlights...
Gulf system on Monday will bring modest to locally heavy
precipitation to the southeastern Kenai Peninsula/southeastern
mainland Alaska/coastal Panhandle. Winds to gale or perhaps storm
force will accompany the area of low pressure--see the Ocean
Prediction Center for more information. Bering systems will bring
in light to moderate precipitation along the Aleutians next week,
perhaps enhanced with the second system as it may tap more
subtropical moisture. Temperatures will be well above average for
most areas of the mainland during the period owing to ridging
nosing into the area from the southeast. The Panhandle and
Aleutians may see near to even below normal temperatures at times
as systems pass through.
Fracasso
Hazards:
- High winds across portions of southern mainland Alaska, Sat, Jan
16.
- High winds across portions of northern mainland Alaska, Sat-Sun,
Jan 16-Jan 17.
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Sat-Tue, Jan 16-Jan 19.
- High winds across portions of the Alaska Panhandle and mainland
Alaska, Mon, Jan 18.
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards 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