Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
613 PM EST Sun Feb 27 2022
Valid 12Z Thu Mar 03 2022 - 12Z Mon Mar 07 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
(Thursday-Monday). An upper level ridge is expected to build over
eastern Alaska and western Canada by Friday and into next weekend,
keeping above normal temperatures in the forecast.
...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
Thursday into Friday (day 4-5), a surface low is forecast to lift
across the eastern Aleutians and towards the eastern Bering or
western Mainland. The past couple of runs of the ECMWF were
farther south and east with the low than the rest of the guidance,
but the 12z run today came into much better agreement. The ECMWF
and the UKMET are both a little farther east/closer to the West
coast with the system but a general model blend (between the 12z
GFS/ECMWF/CMC/UKMET) seemed to provide a good middle ground
solution.
By Sunday/day 7, models bring the next low pressure system towards
the Aleutians. There are some significant differences in timing
and strength of this system as it possibly crosses into the Bering
Sea and impacts the west coast again. The GFS is a little bit
faster with the energy, while the ECMWF is slower and keeps the
low center still south of the Aleutians by the end of the period
Monday/day 8. The WPC forecast days 7 and 8 leaned more towards
the ensemble means which creates a good middle ground position
(although considerably weaker in strength). Some inclusion of the
GFS and ECMWF were maintained though just for a little system
definition. The 12z CMC was much farther south, even from the
ECMWF, with the surface low and also had much weaker ridging over
the mainland as well, so it was not included in the blend after
day 6.
...Weather/Hazard Highlights...
Southerly flow from the Gulf of Alaska will advect moisture
northward and thus keep rain and snow chances in the forecast from
the Aleutians to the Alaska Peninsula, as a low pressure system
lifts northward and then enters the Bering Sea. Periods of
moderate to locally heavy rain/snow are possible, along with gusty
winds, and the locations of the heaviest QPF will be dependent on
the low track. Some at least light rain/mountain snow will likely
reach across western Alaska later next week and again next weekend
with the next surface low. Central and eastern portions of the
Interior should remain dry through the period underneath a
building upper ridge.
Above average temperatures will dominate much of Mainland Alaska
through the period, both for daytime highs and overnight lows. The
highest anomalies are forecast over the northern and western parts
of the mainland later in the week and into the weekend. The
exception to this will be across the Panhandle and southeastern
Mainland where near average temps are expected owing to more
onshore flow.
Santorelli
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