Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
629 PM EDT Tue Aug 04 2020
Valid 12Z Sat Aug 08 2020 - 12Z Wed Aug 12 2020
...Guidance Evaluation...
The WPC Alaskan medium range product suite was primarily derived
from a composite blend of the 12 UTC GFS/ECMWF during days 4-5
(Sat-Sun). A gradual trend toward heavier weight placed on
ECENS/GEFS ensemble means was shown through time, with majority
ensemble means by days 7-8 (Tue-Wed). Guidance shows a reasonably
similar large scale pattern, and a relatively good consensus on
many of the details during the first half of the forecast period.
Detail differences become larger late in the forecast period,
although relatively good agreement continued at larger scales. The
described blend emphasizes some of the agreed-upon details of the
forecast early in the period, and smooths out some of the
differences late in the forecast period.
...Weather Highlights/Threats and Predictability...
A fairly active series of low pressure system from the Bering
Sea/Aleutians east across the Gulf of Alaska will keep wet
conditions in place across southern mainland Alaska and Southeast
Alaska through the weekend, with heavy rainfall possible. Farther
north, a weakening frontal boundary and topographical effects will
result in scattered convection across northern portions of the
Interior as well as the Brooks Range through the weekend,
gradually dwindling through early next week. In general, clouds
and precipitation will keep high temperatures across much of
Alaska several degrees below average, and low temperatures several
degrees above average. Guidance showed some consensus that another
frontal system should affect the Aleutians Mon-Tue, reaching the
Alaska Peninsula and southern mainland Alaska Tue night-Wed (as
the surface low crosses the southern/central Bering Sea). This
system should be accompanied by another round of more widespread
showers as well as potentially gusty winds.
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:
- Heavy rain across portions of mainland Alaska, Fri, Aug 7.
- Heavy rain across portions of the Alaska Panhandle and mainland
Alaska Fri-Sun, Aug 7-Aug 9.
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