Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
616 PM EST Mon Feb 28 2022
Valid 12Z Fri Mar 04 2022 - 12Z Tue Mar 08 2022
...Pattern Overview...
Multiple storm systems are forecast to traverse the North Pacific
and impact the Aleutians, portions of the western mainland, and
the southern Coast during the extended range period
(Friday-Tuesday). The first will bring a storm system to southwest
Alaska, and southerly flow ahead of this combined with another low
will bring possibly heavy precipitation to parts of the southern
coast and Panhandle. Mean troughing over the Aleutians will
facilitate several low pressure areas rotating through the base of
the trough. Weak troughing replaces upper ridging briefly this
weekend, with the upper ridge building back in by early next week
and above normal temperatures prevalent.
...Guidance/Predictability Assessment...
The guidance overall shows reasonable synoptic scale agreement on
the main weather features, however continue to exhibit a ton of
run to run variability in the details which leads to a low
confidence forecast, especially the second half of the period. On
Friday-Saturday (day 4-5), a surface low is forecast to lift
across the eastern Aleutians, into the Bering Sea, and skirt the
west coast of Alaska. The past couple of days models have shown
some placement differences, but today they seem to better converge
on a surface low center a little closer to the mainland. The next
low into the Gulf this weekend also shows decent agreement on
placement, but the 12z CMC was notably slower/south of the
consensus.
The greatest forecast concerns during this period seem to surround
various low pressure systems in and near the Aleutians. Models are
struggling with placement/track of the first low... the UKMET and
CMC both are displaced north of the Aleutians on Sunday, while the
ECMWF/GFS and ensemble means support something farther south.
After Sunday, things get pretty chaotic across the region as this
low should weaken in favor of the next one in line entering the
region early next week, and another possible low (which gets
washed out by the ensemble means) lifting northward towards the
Peninsula. Amongst the deterministic guidance, there is a lot of
uncertainty in the details and timing of these systems.
The WPC forecast leaned mostly on the deterministic solutions days
4-5 (with more weighting on the GFS/ECMWF) which allowed for a
good middle ground placement on the Bering low and the Gulf low.
After day 5, increasing ensemble mean weighting was included to
help mitigate the late period uncertainty. Did continue to include
some smaller amounts of the GFS/ECMWF for added system definition.
...Weather/Hazard Highlights...
Low pressure lifting across the eastern Aleutians into the Bering
Sea will bring light to moderate precipitation to parts of the AK
Peninsula and southwest Alaska, along with a period of gusty winds
into Friday. Southerly flow ahead of this system and combined with
another low lifting towards the Gulf into this weekend will also
keep precipitation in the forecast from the Southern Coast to
northern Panhandle region with moderate to heavy precipitation
possible, but dependent on exact low track. A parade of lows
rotating through the base of the mean Aleutians trough will likely
keep conditions generally unsettled into early next week from the
Aleutians to the Peninsula. Elsewhere, most of interior
central/eastern Alaska should remain mostly dry through the period
besides some light precipitation associated with weak troughing
this weekend.
Above average temperatures should prevail across much of Alaska
into early next week, both for daytime highs and overnight lows.
The warmest anomalies are expected to be over the northern and
western parts of the state where daytime highs 10-20 degrees (and
locally higher) are possible. The exception to this will be across
the Panhandle and southeastern Mainland where near or below
average temps are expected due to increased onshore flow and
periods of upper level troughing.
Santorelli
Hazards:
- Heavy precipitation across portions of southern mainland Alaska,
Thu-Fri, Mar 3-Mar 4.
- Heavy precipitation across portions of the Alaska Panhandle and
southeast mainland Alaska, Sat, Mar 5.
- High winds across portions of southwest mainland Alaska and the
Aleutians, Fri, Mar 4.
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