Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
508 PM EDT Mon Sep 23 2019
Valid 12Z Fri Sep 27 2019 - 12Z Tue Oct 01 2019
Through the course the extended range the synoptic pattern will
become increasingly amplified. A significant upper-level ridge
will be building toward southern Alaska, which will in turn aid in
the amplification of the longwave trough over the Bering Sea/North
Pacific Ocean. Brisk low level winds will be transporting PW
values of 0.75 to 1.25 inches into southwest/southern Alaska from
a cutoff low in the central Pacific Ocean. Scattered to widespread
precipitation will spread from the Aleutians northward to southern
Mainland this weekend and shifting toward the Southeast by early
next week.
The initial blend for this package began with an equal blend of
the 00Z CMC/ECWMF/UKMET, 00/06Z GFS and the 00Z ensemble
transitioning to 40% EC/GFS 60% means by the end of the period.
This helped reduce some of the timing issues with the cut-off
low/precipitation.
Campbell
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 much of southwestern Alaska, Sun, Sep 29.
- Heavy precipitation across portions of the Alaska Panhandle and
southern Alaska, Mon, Sep 30.
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