Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
622 PM EST Tue Jan 04 2022
Valid 12Z Sat Jan 08 2022 - 12Z Wed Jan 12 2022
...Overview...
A blocky and persistent upper upper ridge over northeastern
Russia/the Bering Sea should finally weaken some and retreat
westward during the medium range period. This will lessen its
influence on Alaska and allow for lower mid-upper heights to come
into the state, with a busy storm track situated near/south of the
Aleutians and the northern Pacific/Gulf of Alaska. This will favor
increasing moisture and brisk winds into southern parts of Alaska
from the Aleutians into Southcentral Alaska and the Panhandle by
the weekend into early next week.
...Guidance Evaluation and Preferences...
The latest model guidance, particularly the ensemble means,
continue to show good agreement on the overall synoptic scale
pattern, but increasing uncertainty in the details. Nearly all of
the models agree that a blocky high over northeast Russia should
retreat westward by Saturday as an upper low retrogrades westward
across the mainland Alaska and into the southeast Bering through
Sunday. South of the Aleutians and into the Gulf of Alaska however
remains rather chaotic as the models struggle to resolve details
surrounding multiple streams/surface lows rotating around a main
region of upper level low pressure. Eventually, the mainland
system should merge into the broader low south of the Aleutians,
creating a persistent plume of moisture directed towards southern
Alaska. Model guidance remains incredibly varying with timing,
strength, and placement of the surface lows/frontal systems, but
with no clear outliers at this time.
With decent enough agreement days 4-5, WPC was able to utilize a
multi-model deterministic blend. After that, uncertainty increases
with various systems and shortwaves, and so a blend more towards
the ensemble means seemed the best starting point right now to
mitigate these differences. This approach maintained a fairly
consistent forecast with yesterdays WPC progs for days 4-7 as well.
...Weather/Hazard Highlights...
Increasing moisture is likely by the weekend across south-central
Alaska and the Panhandle as a warm front, stemming from low
pressure over the northern Pacific, pushes into the Gulf. The
frontal system should help direct a persistent plume of deep
Pacific moisture towards the region Sunday-Tuesday. There's a
pretty decent signal in the guidance for a potentially significant
precipitation event, with multiple days of moderate to heavy
precipitation from roughly Kodiak Island to much of the Panhandle.
A strong pressure gradient setting up between low pressure in the
Gulf and High pressure to the north of Alaska will result in very
windy conditions, with gusts has high as 60mph possible in some
places.
Elsewhere across Alaska, the weather should generally be dry, with
the exception of a few light showers across higher terrain inland.
The Aleutians should also remain rather unsettled and wet through
the weekend under the influence of low pressure south of the
region. Temperatures across the state should start out chilly and
much below normal, especially across western and eastern Alaska
where daytime highs could be 20-30 degrees below normal. However,
by early next week, temperatures should quickly moderate to above
normal across much of the state, except the North Slope region
which remains stuck beneath surface high pressure through much of
the period.
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
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Sat-Tue, Jan 8-Jan 11.
- High winds across portions of the Alaska Panhandle and mainland
Alaska, Sat-Sun, Jan 8-Jan 9.
- Much below normal temperatures across portions of mainland
Alaska, Fri-Sun, Jan 7-Jan 9.
- Much below normal temperatures across portions of mainland
Alaska, Fri-Sat, Jan 7-Jan 8.
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