Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
553 PM EDT Sun Aug 02 2020
Valid 12Z Thu Aug 06 2020 - 12Z Mon Aug 10 2020
...A Stormy Pattern for Alaska...
...Guidance Evaluation...
The WPC Alaskan medium range product suite was primarily derived
from a composite blend of well clustered guidance from the 12 UTC
GFS/ECMWF/UKMET and Canadian models and the 19 UTC National Blend
of Models on day 4/Thursday. The models offer a reasonably similar
larger scale pattern days 5-8, but now offer more system variance
than yesterday. Prefer to instead use a composite blend of the
more compatible 12 UTC GEFS/NAEFS/ECMWF ensemble means and 19 UTC
National Blend of Models, then apply manual adjustments to better
define systems consistent with upper support and predictability.
This solution maintains good WPC continuity.
...Weather Highlights/Threats and Predictability...
A lead surface low will fill over the eastern Gulf into Thursday
with modest lingering rains into southeast Alaska. Upstream,
guidance highlights a powerful low and frontal system for Bristol
Bay, Southwest/Western Alaska and the Alaskan Peninsula into
Thursday, The system will weaken into the Interior into the
weekend, but may remain a rain focus. Ample storm energy will
meanwhile transfer downstream into unsettled northern Gulf of
Alaska waters next Friday through next weekend and offers
potential for enhanced rains, especially over favored southern
tier Alaskan terrain. A potential third low near the Aleutians
late week may transfer energies downstream into the northern Gulf
of Alaska for the weekend. Substantial uncertainty remains with
this low, but recent flow history favors another round of enhanced
winds/waves and rain.
Schichtel
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