Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
634 PM EDT Thu Jun 25 2020
Valid 12Z Mon Jun 29 2020 - 12Z Fri Jul 03 2020
...Overview and Weather/Hazard Highlights...
Heights are forecast to gradually rise across Alaska during the
extended period as an initially deep upper low centered over the
Bering Strait gradually weakens and breaks apart. One component of
this system is forecast to move east across mainland Alaska along
with a weakening surface front Tue-Wed and perhaps into Southeast
Alaska by Thu as an upper low, generating unsettled/showery
conditions across those areas as it passes. Elsewhere, a low
pressure system crossing the North Pacific is forecast to enter
the southern Bering Sea on Wed, with the associated front sweeping
east across the Aleutians through Fri, with another similar system
following quickly behind it. Showery conditions along with gusty
winds should accompany these system across the Aleutians, and
perhaps into portions of the Alaska Peninsula by next Friday. As
the northern extent of an upper ridge slowly builds north into
Alaska next week, initially below average temperatures should
begin to gradually warm. High temperatures are forecast to be 10
to 15 deg F below average across much of mainland Alaska over the
weekend, with temperatures gradually inching closer to seasonal
norms toward the middle of next week (particularly close to the
coast).
...Guidance/Predictability Assessment...
The 12Z GFS was used heavily early in the forecast period, with
emphasis quickly shifting toward an ensemble mean-heavy
(ECENS/GEFS) blend by day 6 (Wed) and continuing through day 8
(Fri). The GFS was generally representative of the overall
guidance consensus on day 4 (Mon) with the system approaching the
Aleutians and with Bering Strait upper low that begins to break
down. After that, timing/intensity differences generally increase
across the board, making any deterministic solutions not
particularly useful alone from day 6 onward - hence the short to
more emphasis on the ensemble means.
Ryan
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: 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