Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
752 PM EDT Wed Jun 24 2020
Valid 12Z Sun Jun 28 2020 - 12Z Thu Jul 02 2020
...Guidance/Predictability Assessment...
The 12 UTC ECMWF provides a seemingly reasonable solution closest
to WPC continuity and near the middle of the model and ensemble
forecast envelope Sunday into Monday. In particular for a well
organized system reaching the Aleutians in that time frame, the 12
UTC ECMWF solution lies between the more progressive GFS/GEFS and
the less progressive UKMET and ECMWF ensemble mean. Opted to base
the WPC forecast on a blend of the 12 UTC GEFS/NAEFS/ECMWF
ensemble means into days 6-8 (Tue-next Thu) amid quickly growing
model forecast spread. Differences among ensemble means with
respect to these features were smaller, with also much greater
degree of consistency.
...Overview and Weather/Hazard Highlights...
Two main low pressure/frontal systems will affect AK early in the
extended forecast period, one over the Aleutians, and another over
portions of western/northwestern mainland Alaska.
A relatively deep low pressure system forecast to cross the
central Aleutians into Sun will bring showers and gusty winds.
System and energy transfer should spread organized precipitation
and unsettled conditions out across the Gulf of Alaska and inland
into the southern tier of AK early next week.
Farther north, low pressure north of Siberia will accompany a
frontal boundary across the Bering Strait and into western
mainland Alaska Sat-Mon. This system is expected to produce areas
of heavy rain and some mountain snow across portions of northwest
mainland Alaska, with the potential for high winds across areas
close to the Bering coast over the weekend. While widespread
precipitation across mainland Alaska should gradually subside
toward the middle of next week, persistent broad cyclonic flow
will result in continued unsettled conditions, with persistent
clouds and precipitation especially across mountain ranges.
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
Hazards:
- Heavy rain across portions of western mainland Alaska, Sat-Sun,
Jun 27-Jun 28.
- High winds across portions of western coastal Alaska, Sat, Jun
27.
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