Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
643 PM EDT Wed Jul 22 2020
Valid 12Z Sun Jul 26 2020 - 12Z Thu Jul 30 2020
...Overview and Guidance Evaluation...
Breakdown/pattern shift across the western/central Pacific has
still left the guidance a bit lost in how things evolve next week.
With the weakening/splitting upper high over northeastern Russia,
lower heights will fill in to its east (near the North Slope).
Models and ensembles have had trouble with how this unfolds,
whether it will be in one or two pieces, and then where it may go.
After perhaps a jump 24 hrs ago, consensus seems to have favored
the ensemble means over the deterministic models which favors
maintaining the closed low closer to northwestern areas of Alaska.
To the south, a system out of the central Pacific may move
east-northeastward and slip into the southwest side of an upper
low over the Gulf, fall just short and meander to the north, or
perhaps both (in some sheared capacity). Consensus still favors
its eventual slide eastward around the middle of next week, as the
edge of lower heights around the upper low nudges a bit
southwestward into the Bering. Confidence remained below average
again today due to the many disparate solutions.
In light of the uncertainty, favored the 00Z ECMWF ensemble mean
over the entirety of the forecast period with support from the 12Z
GEFS mean except across the north central Pacific (GEFS mean was
still more progressive). Though any deterministic solution was
plausible, none could really be favored more than the other given
their continuity (or lack thereof).
...Weather Highlights/Threats...
Gulf system on Sunday will provide some heavier rain to at least
the Panhandle as it moves inland, followed be showers on Monday as
the trough follows along. Some heavier rain may be possible over
interior locations as well. More scattered rain/showers will
accompany and precede the front over northwestern areas next week,
and across the Aleutians. Temperatures will generally be below
normal over much of the state owing to the upper trough/low. By
the end of the period, temperatures should moderate somewhat but
the pattern remains quite uncertain.
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
Hazards:
- Heavy rain across portions of the Alaska Panhandle and mainland
Alaska, Sun-Tue, Jul 26-Jul 28.
- Heavy rain across portions of mainland Alaska, Mon-Tue, Jul
27-Jul 28.
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