Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
634 PM EST Tue Jan 11 2022
Valid 12Z Sat Jan 15 2022 - 12Z Wed Jan 19 2022
...Guidance/Uncertainty Assessment...
Generally, the synoptic pattern for this cycle shows average to
above average agreement across Alaska. Early on, a pair of weaker
shortwave troughs will pass through, one affecting the southern
mainland while another wave lifts into the Panhandle region. Both
of these systems gradually become absorbed into the mean flow.
Afterward, guidance continues to show a deep, large closed low
settling across the western Aleutians becoming occluded by day 4.
Model spread within this feature is high, with several embedded
pieces of vorticity rotating through the flow that are difficult
to time and pinpoint in the time range. There are signals of low
pressure developing on the southern periphery of this system that
then lifts northeast toward the mainland. Most of the
deterministic models have this signal but with wide range in
timing and track. As a result, the WPC blend initialized with a
blend of the latest available deterministic guidance but then
became heavily weighted towards the ECENS and GEFS means for days
6-8 given the higher than normal spread and affects to sensible
weather.
...Weather/Hazard Highlights...
A series of low pressure systems will impact the Alaska panhandle
for the first few days of the medium range period, the first
arriving late on day 3 into day 4. It is quickly followed by
another system for the 16th/17th, both of which could bring
widespread moderate to locally heavy precipitation (mountain
snow, valley rain) as well as high winds and waves along the
coast. The rest of the mainland is expected to be relatively dry
(a weakening system will pass through the southern mainland days
3-4) as a closed low settles over the Aleutians. By the end of
forecast period, waves of low pressure will become possible
underneath the closed low and this could bring widespread
precipitation to the eastern Aleutians and the southern mainland
days 7-8. Some of this precipitation could be heavy along with
high winds and waves.
Taylor
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle,
Fri, Jan 14.
- High winds across portions of the Alaska Panhandle, Fri, Jan 14.
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