Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
456 PM EST Mon Feb 22 2021
Valid 12Z Fri Feb 26 2021 - 12Z Tue Mar 02 2021
...Quite a Stormy Pattern from the Bering Sea to the Mainland/Gulf
of Alaska...
...Overview and Guidance/Uncertainty Assessment...
Models and ensembles offer mid-larger scale solution evolutions
that are reasonably well clustered through medium range time
scales in an overall pattern with above average forecast
predictability. A 12 UTC GFS/ECMWF/UKMET/Canadian model blend
solution is quite representative day 4/Friday. However, prefer to
focus increasingly upon a better clustered GEFS/ECMWF ensemble
means composite days 5-8 to highlight the most predictable weather
features as numerous smaller scale system differences linger. A
smaller input of the still reasonably consistent deterministic
models days 5-8 offers a bit more system detail consistent with
uncertainty. The WPC medium range product suite was primarily
derived from these blends along with the 19 UTC National Blend of
Models. This forecast strategy maintains good WPC product
continuity.
...Weather/Hazards Highlights...
A deep lead low will work across the Bering Sea/Aleutians Friday.
This favors a downstream warming trend across southwest Alaska and
much of the Interior, but northern stream upper troughing may
inhibit North Slope/northwest Alaskan warming. The storm will
focus precipitation and wind/waves into the Aleutians, the AKpen
and southwest Alaska, with weekend energies to work inland across
the Interior to offer an enhanced snow threat. Deep low genesis
this weekend over an unsettled northern Gulf of Alaska will
support heavier precipitation into southern and southeast Alaska.
Upstream, there is a growing guidance signal early next week for
deep low development and track to the Aleutians/Bering Sea,
southwest Alaska/AKPen/Kodiak Island and then the northern Gulf of
Alaska. This offers maritime to onshore threats of heavy
precipitation and winds/waves into these areas and then
southern/southeast Alaska.
Schichtel
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Sat-Sun, Feb 27-Feb 28.
- High winds across portions of the Aleutians, Sun-Mon, Feb 28-Mar
1.
- Much above normal temperatures for parts of mainland Alaska,
Thu-Sat, Feb 25-Feb 27.
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