Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
630 PM EDT Mon Apr 05 2021
Valid 12Z Fri Apr 09 2021 - 12Z Tue Apr 13 2021
...A cold pattern for Alaska with deep maritime storms...
...Guidance/Uncertainty Assessment...
Guidance shows an amplified large scale pattern this week aloft,
with a cold trough dug through Alaska from the high Arctic and a
ridge over the Bering Sea/Aleutians Day 4/Friday. The ridge is
expected to gradually be worked eastward into the mainland this
weekend by ample but still uncertain upper trough energies that
feed back into the Bering Sea. Model solutions are well clustered
Friday and seem quite reasonable. Differences become increasingly
significant days 5-8 (Saturday-next Tuesday), but recent runs of
the ECMWF/Canadian remain better aligned with ensembles than the
GFS. This is mainly evident with system and flow transition and
progression from the Bering Sea/Aleutians to the mainland and Gulf
of Alaska. Accordingly, the WPC Alaskan product suite was
primarily derived from a blend of the 12 UTC
GFS/ECMWF/UKMET/Canadian Day 4 and the 12 UTC ECMWF/Canadian and
the GEFS/ECMWF ensemble means Days 5-8 amid growing forecast
spread.
...Weather/Hazards Highlights...
High Arctic troughing digging over Alaska this week will spread
and maintain significant cooling over much of the state into early
next week. Digging and phasing energies will support deep
cyclogenesis over the northern Gulf of Alaska later this week.
This will favor adverse maritime conditions, strong backside winds
through southern Alaska, and periods of terrain enhancing
precipitation (mainly snow) for Southeast Alaska and the
Panhandle. The mainland should dry out this week as frigid high
pressure settles in. This will allow below normal temperatures to
expand across much of Alaska, with the coldest anomalies (as much
as 20-30+ below normal) across the Interior. Systems entering the
Bering Sea later week and the weekend are less certain, but will
bring quite unsettled maritime conditions. Enhanced winds and
precipitation will also progress across the Aleutians and are
expected to work in earnest into the mainland next weekend and
emerge into the Gulf of Alaska next week along with additional
storm energies up from the north Pacific.
Schichtel
Hazards:
- Heavy snow across portions of the Alaska Panhandle, Thu, Apr 8.
- High winds across portions of mainland Alaska, Thu-Fri, Apr 8-9.
- Much below normal temperatures for parts of the Alaskan
Panhandle and mainland Alaska, Thu-Sun, Apr 8-11.
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