Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
513 PM EDT Sun Apr 3 2022
Valid 12Z Thu Apr 7 2022 - 12Z Mon Apr 11 2022
...Overview...
A deep upper level trough and closed low is expected to be in
place across western Alaska and the eastern Bering on Thursday,
and a weakening surface low will affect southeastern portions of
the state. By Saturday, the polar low continues to govern the
weather pattern across the North Slope region, while an upper
ridge axis tries to build in across the Aleutians and the southern
Bering, and a second Gulf low likely develops and tracks in the
general direction of the southeast Panhandle region. There is
also a model signal for a low pressure system approaching the
Aleutians by the beginning of next week.
...Guidance/Predictability Assessment...
The 12Z model guidance suite continues to show fairly good
synoptic scale agreement with the overall pattern through the end
of the week, and a general deterministic blend represents a good
forecast starting point through Friday. The 12Z CMC is
considerably closer to the model consensus compared to its
previous 00Z that was more out of phase across the Aleutians and
Bering. By the weekend, models struggle with shortwave energy
crossing the northern periphery of the Aleutians upper ridge, with
the 12Z ECMWF considerably faster compared to the GFS and CMC.
There is also a good deal of longitudinal spread in the main polar
low by Sunday, but there is still decent agreement on the upper
ridge in place across southwest Alaska. Due to these
uncertainties in the later half of the forecast period, the WPC
forecast leaned increasingly more towards the ensemble means to
help mitigate these differences.
...Weather/Hazard Highlights...
A corridor of moderate to locally heavy coastal rain and mountain
snow between the Kenai Peninsula and the Alaska/Yukon border
should be abating by early Thursday as the Gulf low steadily
weakens. However, another round of organized precipitation
(mainly light to moderate) is likely for the southeast Panhandle
region Thursday night into early Friday as a second low approaches
the region. Patchy areas of light snow are likely across southern
portions of the Interior going into the weekend, and mainly dry
conditions farther north. Depending on the eventual evolution and
track of the next low reaching the Aleutians by next
Sunday/Monday, widespread showers and some gusty winds can be
expected for these islands.
Most of central and eastern Alaska will likely have readings
slightly above normal for the beginning of the extended period and
below average for the western mainland. A gradual cooling trend
appears likely across much of the mainland going into next weekend
as the polar trough over northern Alaska keeps readings in check.
Temperatures should also be generally a bit below average for
southern coastal areas owing to increased cloud cover and
precipitation.
Hamrick
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook 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