Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
754 PM EDT Mon Mar 14 2022
Valid 12Z Fri Mar 18 2022 - 12Z Tue Mar 22 2022
...Overview...
The most notable feature over Alaska for the medium range period
will be an upper low with possibly multiple centroids at times
meandering in the Gulf of Alaska as a potent upper-level shortwave
diving southward across the Bering Sea as well as energy along an
active storm track across the northeastern Pacific will serve to
redevelop and reinforce the closed low through early next week.
This pattern will 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 period.
...Guidance/Predictability Assessment...
Model guidance shows fairly good agreement with the overall
pattern of a reloading upper low over the Gulf, with perhaps a bit
more spread compared to the past couple of days with the details.
By Day 5/Saturday, GFS runs are showing more of a double barreled
upper low as energy approaches from the Bering Sea, while the
ECMWF/CMC/UKMET have more interaction and one combined low. The
latter solution is closer to continuity and shows more agreement
overall, so leaned toward a more combined low feature, but even
the ECMWF does have some energy lingering over Bristol Bay, so a
compromise of deterministic guidance including the ECMWF, GFS,
CMC, and UKMET seemed like a good middle ground to indicate this
possibility but not jump on it.
Troughing should amplify across the state and southward well into
the Pacific as Bering Sea ridging builds early next week. Embedded
within the trough, the low may reform or retrograde west of Kodiak
Island Sunday/Monday due to additional energy interaction from the
northeastern Pacific, and slowly track eastward Tuesday over the
Gulf. The 12Z ECMWF appeared to be somewhat of an outlier by
Monday-Tuesday as it drifts the original upper low east more
quickly. Farther north, the GFS indicates stronger energy diving
into the trough for interior Alaska around Sunday compared to
other guidance, which is possible if arctic energy combines that
way but uncertain at this point. The overall meandering and energy
interactions aloft lead to surface low position and strength
differences as well. Thus WPC forecast phased in about half of the
GEFS/EC ensemble means by days 7-8 to alleviate the individual
model differences, while maintaining some operational guidance in
the blend for strength of systems.
...Weather/Hazard Highlights...
Precipitation is expected to focus along southern parts of Alaska
given the northern Pacific storm track. Southcentral Alaska to the
Panhandle in particular should see rounds of enhanced
precipitation, with increasing and decreasing intensity depending
on location of the surface lows and the orientation of the upper
trough/low. While precipitation does not appear to be very
intense, recent heavy rain/snow across the area could make it more
sensitive to additional impacts, and amounts may pick up by early
next week. In addition, brisk winds are expected with the approach
of a surface low Friday-Saturday with some gusty winds possible
across the Panhandle. On the other side of the lows, periods of
breezy northerly winds are expected over the Aleutians, along with
some chances of snow showers. Snow is also possible for the
eastern mainland over the weekend.
Colder than average high temperatures are forecast for much of
Alaska given troughing aloft, with highs generally 10-20F below
normal for mid-March across the southwestern mainland and Alaska
Peninsula on Friday and Saturday as a reinforcing cold front comes
through. These cooler temperatures will spread into much of the
interior as well. However, low temperatures should be closer to
normal with some areas even above normal for lows. The North Slope
and the southeast mainland are forecast to be closest to average.
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