Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
658 PM EST Sat Mar 12 2022
Valid 12Z Wed Mar 16 2022 - 12Z Sun Mar 20 2022
...Overview...
The most notable feature over Alaska for the period will be an
upper low meandering slowly southeastward over the Alaska
Peninsula midweek and eastward across the Gulf of Alaska by next
weekend. The initially closed low will interact with an active
storm track across the northeastern Pacific to support a series of
surface low pressure systems and bring a sustained period of
inclement weather through the Panhandle and occasionally up into
the southern coasts for much of the week.
...Guidance/Predictability Assessment...
Overall model guidance has rather good agreement for a medium
range Alaska forecast throughout most of the period. The closed
upper low appears well handled by the guidance especially through
Wednesday-Thursday as it drifts from the southwest mainland to
near Kodiak Island. Thus the WPC forecast was able to use a
multi-model deterministic blend led by the 12Z ECMWF early on. By
early Friday, the GFS/GEFS runs appeared a bit slower with the
upper low as it moves into the Gulf compared to other models, but
still with relatively small differences for Day 6. The 06Z GFS
does seem to be against the consensus in its handling of the Gulf
surface low (farther south) by Friday-Saturday, so did not prefer
it there. However, farther west and along the northern Pacific
storm track, the 06Z GFS looked better clustered with other
guidance than the 12Z GFS with another upper/surface low south of
the Aleutians during that timeframe. By next weekend, energy from
the northern Pacific storm track and some spilling southward
across the Bering and western mainland could both interact with
the original upper low, and this leads to more spread in the
details overall. But the general idea is there for the upper low
to persist over the Gulf, which is shown by the agreeable ensemble
means as well as the deterministic guidance though they vary with
the specifics. The WPC forecast gradually transitioned a blend of
about half GEFS/EC ensemble means and half operational models by
Days 7-8, continuing to favor the ECMWF as the model closest to
the means with placement of features, but giving some added depth
to the systems. The results are similar to continuity.
...Weather/Hazard Highlights...
Much of the mainland should see dry conditions during the period,
though perhaps with increasing snow showers by next weekend in the
eastern mainland, as precipitation is expected to focus along
southern parts of Alaska given the northern Pacific storm track.
The Panhandle in particular should see rounds of enhanced
precipitation, with the heaviest amounts currently expected on
Wednesday with the initial surface low. The precipitation will
tend to linger through late next week across the Panhandle with
rounds of increasing and decreasing intensity depending on
location of surface lows, but with perhaps a gradual downward
trend overall. While precipitation does not appear to be very
intense, recent heavy rain/snow across the area could make it more
sensitive to additional impacts. In addition, brisk winds are
expected with the approach of the initial low with gusty winds
possible for the Panhandle on Wednesday, and possibly again later
in the week. On the other side of the lows, periods of breezy
northerly winds are expected over the Aleutians.
Colder than average temperatures especially in terms of highs are
forecast for much of Alaska with troughing aloft, with highs
10-30F below normal for mid-March across the southwestern mainland
and Alaska Peninsula on Wednesday, and again there and spreading
east for Friday-Sunday as a reinforcing cold front comes through.
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.
Tate
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