Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
731 PM EDT Fri May 21 2021
Valid 12Z Tue May 25 2021 - 12Z Sat May 29 2021
...Overview and model guidance...
The 12Z model guidance suite continues to indicate a broad upper
low over the Aleutians/Bering Sea and a downstream ridge over
parts of mainland Alaska will be the dominant upper features
during this forecast period, but some important specifics vary.
One of the uncertainties is the role individual waves emerging
from the western Pacific will play, including whether they merge
with the mean low over the Aleutians/Bering or remain separate.
This pattern will tend to focus episodes of precipitation from the
Aleutians into the Alaska Peninsula, and eventually farther east
along the southern coast.
In terms of model choices, the WPC medium range forecast started
with a blend of the 12Z ECMWF/GFS/UKMET for the early-middle part
of next week. The CMC differed more from the ensemble means along
with greater timing differences, so it was not favored for this
forecast cycle. Beyond that time, the forecast trended to
included more of both the ECENS and GEFS mean to account for
timing differences with individual shortwaves and amplitude. Some
previous WPC continuity was also included.
...Weather/Threats Highlights...
Initial low pressure and associated frontal system over the
Aleutians/Bering Sea as well as one or more trailing systems that
may merge into the overall mean low should bring periods of
unsettled weather to areas from the Aleutians through at least the
Alaska Peninsula and eventually southern coast. Some moisture may
extend into parts of the western and southern mainland as well.
Fronts/embedded waves may provide localized enhancement of
precipitation and winds at times. The best signal for highest
totals during the five-day period exists from the Alaska Peninsula
to Kenai Peninsula and over favored terrain just north of Bristol
Bay. In terms of temperatures, the Panhandle and portions of the
southern mainland as well as parts of the North Slope will tend to
see slightly below normal high temperatures during the period.
Other locations will likely experience above normal highs with the
greatest anomalies over the western part of the state, though some
moderation may occur after midweek.
Hamrick/Rausch
Hazards:
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