Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
659 PM EST Fri Mar 11 2022
Valid 12Z Tue Mar 15 2022 - 12Z Sat Mar 19 2022
...Overview...
All of the model guidance continue to support the general idea
that a compact shortwave trough over the Arctic Ocean will dive
south across mainland Alaska Tuesday, reaching the Alaskan
Peninsula by early Wednesday as it evolves into a closed low. The
closed low will then interact with an active storm track across
the northeastern Pacific to bring a sustained period of inclement
weather through the Panhandle and occasionally up into the
southern coasts for much of the workweek.
...Guidance/Predictability Assessment...
The ensemble means show very good agreement on the aforementioned
synoptic evolution in the vicinity of Alaska through the
medium-range period. The deterministic runs exhibit larger
run-to-run variability regarding how far west/east the upper low
will track through the Alaskan Peninsula on Wednesday.
Nevertheless, the spread is quite reasonable given the forecast
lead time. Toward the end of the forecast period, model consensus
indicates that the upper low should drift eastward into the Gulf
of Alaska as it interacts with various low pressure systems that
are forecast to track through the northeastern Pacific. An omega
block will appear to set up across the Aleutian toward
northeastern Siberia by the end of next week. The GFS and GEFS
(especially the 12Z run) are fast with placing this block farther
east than the ECMWF, EC mean, and the CMC mean. Therefore, the
slower 06Z GEFS was used in place of the 12Z GEFS for Days 7-8.
The WPC forecast grids for Alaska was based on 40% from the 12Z
ECMWF/00Z EC mean, 40% 12Z GFS/12Z GEFS, and 20% from the 12Z
CMC/CMC mean for Days 4-6, transitioning to including more of the
ensemble means for Days 7-8 as well as replacing the GEFS with the
06Z run as mentioned above. The results look very compatible to
continuity.
...Weather/Hazard Highlights...
Much of the mainland should see dry conditions during the period,
as precipitation is expected to focus along southern parts of
Alaska given the northern Pacific storm track. The Panhandle in
particular should see steady precipitation becoming heavier on
Tuesday ahead of a stronger albeit weakening low pressure system.
Heaviest amounts are expected to occur on Wednesday. Although the
precipitation does not appear to be very intense through the
period, recent heavy rain/snow across the area could make it more
sensitive to additional impacts. The precipitation will tend to
linger through late next week across the Panhandle with perhaps a
gradual downward trend as the low slowly weaken. In addition,
brisk winds are expected with the approach of the low with gusty
winds. On the other side of the low, breezy northerly winds are
expected over the Aleutians by later in the week.
A transition to colder than average temperatures is forecast next
week for much of Alaska with troughing aloft. This will
particularly be true in terms of highs, which could be 10-30F
below normal for mid-March. The North Slope will be the main area
that can expect near to above normal temperatures. Meanwhile, the
Panhandle should see below normal highs through the period and a
mix of above and below normal lows.
Kong
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 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