Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
642 PM EDT Mon Aug 24 2020
Valid 12Z Fri Aug 28 2020 - 12Z Tue Sep 01 2020
...Overview and Guidance Evaluation/Preferences...
Behind a late-week system tracking from the Alaska
Peninsula/Kodiak Island across the Gulf of Alaska and Panhandle,
guidance continues to advertise a significant large-scale pattern
change toward a mean upper low over the Bering Sea and downstream
ridge aloft building over the Northeast Pacific and eastern
mainland/western Canada. There is good agreement that a strong
North Pacific into Bering Sea storm will usher in this change,
with a broad area of wet/windy conditions.
The latest model guidance showed average to slightly above average
agreement and this allowed for a heavy component of the available
deterministic guidance to be used (12Z ECMWF/GFS/UKMET/CMC) for
the day 4-6 forecast with higher components of the 00Z ECENS and
06Z GEFS means for the latter portions of the forecast period.
...Weather Highlights/Threats...
Continue to expect a broad area of precipitation and stronger
winds to accompany the storm forecast to track from the North
Pacific into the Bering Sea during the period. Recent trends have
held back the northward progression of impacts a bit but there is
still reasonable consensus that enhanced precip/winds should reach
the Alaska Peninsula and then extend into the southwestern third
to half of the mainland over the course of the weekend. Some
moisture could reach as far east as the Panhandle by Sun or Mon.
Significant precip totals will be possible along the southern
coast and over some areas of favored terrain in the southwestern
mainland. The system tracking from near Kodiak Island to the
Panhandle Thu-Fri will bring some focused precipitation to areas
along the southern coast and Panhandle. There will also be a
broader area of scattered precip over portions of the mainland
late this week. A drier trend will progress west to east behind
this system and before the approach of moisture ahead of the
Aleutians/Bering Sea storm.
Below normal highs will prevail most of the period from the North
Slope through the eastern and southern-southeastern mainland and
Panhandle. Western areas will see the best potential for above
normal highs. There will be greater coverage of above normal
readings for low temperatures. Expect highest anomalies for lows
late this week to be over the northeastern mainland. Flow ahead
of the Aleutians/Bering Sea storm should spread warmer min
temperatures across much of the state during the weekend and early
next week.
Rausch/Taylor
No significant hazards are expected over Alaska during this
forecast period.
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