Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
507 PM EST Thu Jan 07 2021
Valid 12Z Mon Jan 11 2021 - 12Z Fri Jan 15 2021
...Deep lows offer heavy precipitation and wind/waves threats from
the Gulf of Alaska to Southern/Southeast Alaska Sun-Mon...
...Guidance/Uncertainty Assessment...
The WPC Alaskan product suite was derived from a composite of
reasonably clustered guidance from the 12 UTC
GFS/ECMWF/UKMET/Canadian and the 19 UTC National Blend of Models
(NBM) Monday before rapid transition to more compatible GEFS/ECMWF
ensemble means and the NBM Tue-next Fri. This Alaskan office
collaborated plan seems consistent with quick growing forecast
spread and avoids ugly embedded system run to run continuity
issues in the models. Offshore lows were manually deepened in WPC
surface progs to be more consistent with favorable upper support
predictability and to counter weakening effects inherent from the
blending process.
...Weather/Hazards Highlights...
There remains a well defined guidance signal favoring closed upper
low/trough and deep cyclogenesis emergence into the Gulf of Alaska
Sun/Mon whose enhanced onshore moisture fetch and circulation is
expected to fuel a threat of heavy precipitation and high
winds/waves from the Gulf into southern and southeast Alaska.
Subsequent energies and system interactions/developments are all
over the place in deterministic guidance, albeit in a overall
favorable larger scale pattern in guidance. Accordingly, expect an
unsettled pattern with multiple lows to persist next week over the
Gulf, with main onshore effect focus into southern/southeast
Alaska. Significant system details may not be revealed until
shorter time frames, perhaps 3-4 days in advance. The ensemble
mean based WPC surface progs hint at but do not explicitly depict
these less predictable lows around a main centered low position.
Given potential intensity of these systems, there may be strong
winds and hazardous marine conditions. This pattern should also
favor some much above normal temperatures into the Interior next
week.
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
Hazards:
- Heavy precipitation for southern Alaska and the Alaska
Panhandle, Sun-Mon, Jan 10-Jan 11.
- High winds for southern Alaska, Sun-Mon, Jan 10-Jan 11.
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