Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
537 PM EST Sat Feb 27 2021
Valid 12Z Wed Mar 03 2021 - 12Z Sun Mar 07 2021
...Overview and Guidance/Uncertainty Assessment...
12 UTC GFS/ECMWF/UKMET/Canadian guidance seem quite well clustered
days 4-5 (Wed-Thu) and a composite for that period offers great
continuity in an amplified pattern with below normal forecast
spread and uncertainty. Pacific energy breaking through the flow
differences (mainly into the Gulf of Alaska) and more typical
smaller scale guidance variance days 6-8 (Fri-next weekend)
elsewhere portends preference for more of a generally compatible
GEFS/ECMWF ensemble mean solution. However, opted to keep some
deterministic model input in the blend since predictability still
seems above normal at mid-larger scales at these longer time
frames. WPC continuity is well maintained with this plan.
...Weather/Hazards Highlights...
The well defined circulation around a large and deep low will
influence the entire Gulf of Alaska through midweek before
gradually weakening/reforming to the southeast later next week
into next weekend as uncertain Pacific energies break through
amplified flow. While a prolonged but tempered maritime threat
over the Gulf of Alaska under a mean closed upper low/trough, this
overall evolution should limit most associated but waning onshore
precipitation to the southeast Panhandle during this period.
Meanwhile, energetic upstream energies are slated to work
northward into the Bering Sea on the western periphery of a highly
amplified midweek upper ridge position. The ridge shunts eastward
from the Bering Sea to western mainland and steadily erodes into
late week. While the brunt of storm energies focus west of the
state, a series of ejecting and weakening systems may bring
several rounds of modest precipitation increasingly onshore with
time.
Schichtel
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards 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