Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
339 PM EDT Wed Aug 14 2019
Valid 12Z Sun Aug 18 2019 - 12Z Thu Aug 22 2019
Amplified flow will transition back to a more typical high
latitude pattern with a deep upper low headed into the Bering Sea
next week. Models/ensembles were mostly in sync on the longwave
pattern change with expected detail differences. The ECMWF
ensemble mean has been a best guide in recent cycles (after a
fairly unusual deviation several days ago) with the GEFS mean next
best. This would transition troughing away from
eastern/southeastern areas toward the eastern Beaufort Sea in
response to a polar upper low. That low, per the ensembles, should
stay north of northern areas but the 00Z ECMWF did bring it toward
far northeastern Alaska (well south of the consensus).
Farther south, system approaching/passing over the Aleutians next
week has shown the best continuity and a consensus blend approach
served well. South of the Gulf, guidance has split on where to
track a surface system next Tue/Wed--yesterday the thought was
much closer to the southern Panhandle. ECMWF-led consensus (with
about half the GEFS/Canadian members) either show it meandering
near 50N or moving slowly northeast or east-northeastward toward
Haida Gwaii/southwestern British Columbia and a remnant trough to
its north-northwest. 12Z GFS was a northerly exception into the
Panhandle.
Wind/rain will accompany the Aleutians storm next week with the
heaviest amounts generally west of Adak. Southern portion of the
Panhandle may be at the confluence of Pacific moisture plume and
surface lift as a front on the south side of the upper low pushes
through the area. Several inches of rain are possible but this
will taper off farther north toward Juneau. Below normal
temperatures are expected there until heights start to rise later
next week.
Fracasso
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
No significant hazards are expected over Alaska during this
forecast period.
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