Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
703 PM EDT Tue Apr 27 2021
Valid 12Z Sat May 01 2021 - 12Z Wed May 05 2021
...Weather Pattern and Model Guidance...
The forecast period begins with a closed, elongated upper low over
western Alaska, a weakening trough over the Gulf and a large low
passing south of the central/western Aleutians. The upper
low/trough lingers over the Alaska mainland going into next
weekend, followed by potential upper level ridging early next
week. Meanwhile, the Aleutian low should continue slowly eastward
near 45-50 degrees north and reach the northern Gulf by next
Monday, albeit a little weaker by this time.
There continues to be spread with the amplitude and clustering of
lows associated with the Bering Sea/Gulf of Alaska system. The
ECMWF appears to be a tad less progressive and resembles the CMC
and UKMET solutions; whereas, the GFS tracks the low further south
through much of the extended period. The greatest uncertainty
remains across the Bering Sea and eastern Siberia regarding a
separate shortwave pivoting around the upper trough over western
Alaska, and how that eventually evolves. The preferred blend
utilized the 12Z ECMWF/CMC/UKMET/GFS initially with increasing
inclusion the ECMWF/GEFS means.
...Sensible Weather...
With the influence of an upper-level trough and persistent
cloudiness, much of the western Mainland will have cooler
temperatures; with near to slightly above normal for portions of
the North Slope and the eastern Interior. This pattern will favor
precipitation over parts of the southern Mainland and most of the
Southeast. There will be two main rounds, with the first round on
Friday/Saturday associated with the weakening disturbance from the
northern Gulf region and the second will likely affect locations
from the Alaska Peninsula to the southeast Panhandle as the next
storm system approaches from the Aleutians.
Campbell/Hamrick
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle,
Fri, Apr 30.
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