Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
649 PM EDT Thu Apr 15 2021
Valid 12Z Mon Apr 19 2021 - 12Z Fri Apr 23 2021
...Overview and Guidance/Uncertainty Assessment...
Latest guidance continues to depict a blocky regime during the
period. This pattern will be highlighted by upper ridging that
covers the mainland and western Canada and eventually joined by
another ridge that builds over the western Bering Sea/eastern
Siberia, while a consolidating Pacific mean low aloft should
settle into a position south of the eastern Aleutians and Alaska
Peninsula. Shortwave energy within progressive flow around the
north side of the upper ridge may push a cold front into the
northern/eastern mainland by Tuesday-Thursday. Most of the state
should be fairly dry for most of next week, with the best
potential for precipitation along coastal locations shifting west
to east from the Aleutians to Southern Coast to Panhandle.
Overall, the guidance shows fairly good agreement through much of
the period and continues to trend towards a stronger ridge aloft.
For days 4-6, the WPC blend favors a majority deterministic
guidance (GFS/ECMWF/CMC). After this, the ECMWF (and to some
degree the ECENS mean) want to break down the ridge a little too
fast, thus the forecast leans more heavily towards the GFS/GEFS
solutions which hold onto the ridge/blockiness a little longer.
This approach fits well with yesterdays WPC continuity as well for
days 4-7.
...Weather/Hazards Highlights...
Most precipitation should be confined to the Aleutians/Alaska
Peninsula and vicinity, with a fairly persistent flow of moisture
carried in the gradient between one or more Pacific lows and high
pressure well to the north. Light to moderate amounts are most
likely but some locally higher totals could be possible depending
on exact strength and track of Pacific systems. By the end of the
week, lighter precip may begin shifting east towards the Southern
Coast region and the Panhandle. The rest of the mainland should
remain dry throughout the entire week.
Most of the state should see above normal temperatures at the
start of the period Sunday, with the warmest anomalies over the
North Slope and for morning lows. A gradual cooling trend with
time will tone down the warm anomalies somewhat while possibly
bringing at least high temperatures to near or below normal first
over parts of the southeastern quadrant of the mainland and the
Panhandle an then eventually much of the eastern half of the
mainland by next Wednesday-Friday.
Santorelli
No significant hazards are expected over Alaska during this
forecast period.
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