Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
725 PM EDT Wed Mar 27 2024
Valid 12Z Sun Mar 31 2024 - 12Z Thu Apr 04 2024
...Holiday Weekend One-Two Storm Punch to offer Wind/Wave/Coastal
Flooding and/or Snow/Rain Threats from the Aleutians through
Southwest and Southern Alaska...
...Guidance Evaluation and Preferences...
Consensus keeps a general troughiness over the
Bering/Aleutians/Gulf region with multiple impulses moving through
the flow and the weakening of ridging over Southeast Alaska and
surrounding area; however the model spread has not improved much
beyond the start of the week resulting in an average/below average
confidence on the specifics. Maintained continuity by starting
with a combo of the ECWMF, GFS (12Z/6Z), CMC and UKMET through
Monday night/Tuesday morning before including/incrementally
increasing weighting of the GEFS/EC ensemble means through the end
of the extended period. The means comprised of 60% by the end of
the forecast period to account for the noise in guidance. The
means highlight a cooling Mainland as Arctic stream upper trough
energy works to dig southward and potential/eventual phasing to
some degree with Pacific stream energies into the Gulf of Alaska
and associated cold low developments offshore to monitor.
...Pattern Overview and Weather/Hazards Highlights...
High winds/waves and potential associated coastal flooding threats
up the coast of western/Southwest Alaska will likely be ongoing
from Friday/Saturday before losing this influence offshore over
the weekend. Meanwhile, guidance persists in strongly supporting a
solution with robust development of a trailing frontal wave back
over the north Pacific that suggests it will lift northward toward
the Alaska Peninsula Saturday as a potentially potent storm/high
winds threats, with subsequent track into Southwest Alaska and
into an unsettled/snowy Interior while slowly weakening. This
energetic scenario would focus a heavy snow threat over portions
of Southwest Alaska and into the Alaska Range. There would also be
a heavy rainfall and more inland/terrain heavy snow threats as
fueled by a channeled/deepened lead Pacific moisture feed up into
the Alaska Peninsula/Kodiak Island and south-central Alaska, and
to a much lesser extent Southeast Alaska through the weekend. 0.75
to 3+ inches may be possible along the southern coastline and
points adjacent this weekend with lighter amounts lingering into
next week.
Campbell
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