Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
558 PM EST Wed Feb 24 2021
Valid 12Z Sun Feb 28 2021 - 12Z Thu Mar 04 2021
...Active Pattern from the Bering Sea/Aleutians to the
Mainland/Gulf of Alaska...
...Overview and Guidance/Uncertainty Assessment...
Upper pattern will be driven by a strong positive height anomaly
moving off Hokkaido this weekend (+3 sigma 500mb heights per the
ECMWF ensemble mean) will eventually translate eastward to the
western Bering Sea by the middle of next week. This will favor
downstream robust yet progressive troughing through the Bering
into western/southwestern Alaska and then into the Gulf of Alaska
in general west-to-east flow. With a rather defined wavelength,
the models/ensembles were in good agreement overall. A blended
mostly deterministic solution was preferred for the first few days
of the period Sun-Tue (12Z GFS/ECMWF/Canadian/UKMET). This fit
close to continuity as well with some expected timing differences.
Increased ensemble weighting by later in the period as uncertainty
increased in the Gulf with the digging upper trough and in the far
western Bering with the next system. Ensemble consensus was better
than average.
...Weather/Hazards Highlights...
Exiting system on Sunday will provide locally heavy rain/snow to
the Panhandle followed by more showery precipitation as the upper
trough moves through. Progressive pattern may limit excessive
amounts of precipitation. Next system will push swiftly through
the Bering Sun-Mon with windy conditions and rain/snow along the
Aleutians into southwestern Alaska. Models were in a bit better
agreement on light to modest QPF into the Interior Mon into early
Tue. Precipitation will then again focus on the Panhandle Tue-Wed
as the upper trough digs into the Gulf. Temperatures will
generally be below normal over much of the state next week,
focused over the western/southwestern portion of the state.
Fracasso
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Sat-Mon, Feb 27-Mar 1.
- High winds across portions of mainland Alaska and the Aleutians,
Sun-Mon, Feb 28-Mar 1.
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