Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
442 PM EST Sun Feb 28 2021
Valid 12Z Thu Mar 04 2021 - 12Z Mon Mar 08 2021
...Overview and Guidance/Uncertainty Assessment...
Latest 12 UTC GFS/ECMWF/UKMET/Canadian guidance seem quite well
clustered days 4-6 (Thu-Sat) and a composite for that period
offers great continuity in an amplified starting 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 7-8
(next Sun-Mon) elsewhere still portends preference for more of a
generally compatible 12 UTC GEFS/ECMWF ensemble mean solution.
However, opted to keep some GFS/ECMWF model input in the blend
since predictability still seems reasonable at mid-larger scales
at these longer time frames. WPC continuity is well maintained
with this plan.
...Weather/Hazards Highlights...
Deepened low influence focus over the Gulf of Alaska gradually
weakens or reforms over the eastern and southeastern Gulf later
week into next weekend as uncertain Pacific energies break through
amplified flow. While a prolonged but tempered maritime threat
remains over the Gulf of Alaska under closed upper low/troughing,
this overall evolution should limit most associated 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 an
initially 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 this week, a series of ejecting and
weakening systems will bring several rounds of moderate
precipitation increasingly onshore with time into the western
Interior and eventually late period also through southwest Alaska
and the AKPen as unsettled/amplified Bering Sea upper troughing
works eastward/inland. In this pattern expect a generally benign
weather pattern otherwise for much of the North Slope and Interior
where below normal temperature linger through late week. However,
increased flow into the region may act to moderate temperatures
next weekend.
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