Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
714 PM EDT Sun Apr 25 2021
Valid 12Z Thu Apr 29 2021 - 12Z Mon May 3 2021
...Weather Pattern and Model Guidance...
The forecast period begins on Thursday with a closed upper low
over western Alaska, a weakening low 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. Meanwhile, the Aleutian low should continue slowly
eastward near 45-50 degrees north and reach the northern Gulf by
next Monday.
The 12Z deterministic guidance agrees well on the overall synoptic
scale pattern through next weekend, with the normal timing and
amplitude differences in individual lows and shortwaves. The GFS
remains more amplified with the first disturbance crossing the
Gulf for Friday/Saturday, but is in good agreement with the ECMWF
on the next system on Sunday/Monday, with the CMC a bit slower.
The greatest uncertainty resides across the Bering Sea and eastern
Siberia regarding a separate shortwave pivoting around the upper
trough over western Alaska. The WPC forecast leaned toward a
blend of the 12Z ECMWF/CMC/GFS for the Thursday through Saturday
time period, and then more of the EC/GEFS means beyond that.
...Sensible Weather...
Temperatures are expected to be on the cool side for many areas
under the influence of the upper level trough and mostly cloudy
skies, with highs generally in the 40s for most of the mainland,
and still remaining in the 20s north of the Brooks Range.
Widespread subfreezing lows are also expected for most of the
state, but nothing appears record breaking for now. The best
precipitation prospects will be from the Kenai Peninsula to the
southeast panhandle through Friday, and then across the Aleutians
and the Alaska Peninsula/Kodiak Island as the next storm system
approaches.
Hamrick
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