Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
407 PM EDT Tue Sep 24 2019
Valid 12Z Sat Sep 28 2019 - 12Z Wed Oct 02 2019
Models and ensembles show a reasonably well clustered flow pattern
forecast at medium range time scales, bolstering forecast
confidence in development of highly amplified flow. The WPC medium
range product suite was primarily derived from a composite blend
of the latest GFS/ECMWF and GEFS/ECMWF ensemble means, with some
trend to weight ensembles more in this blend at longer time frames
amid gradually growing uncertainty. This solution maintains
excellent WPC continuity as coordinated with local Alaskan WFOs.
In this pattern a significant and warming upper-level ridge will
build over Alaska as an unsettling longwave trough strongly
amplifies upstream over the Bering Sea/North Pacific Ocean. Brisk
low level winds will transport lead precipitable water values of
0.75 to 1.25 inches northward into the state, including some
tropical moisture associated with former tropical system Tapah.
Scattered to widespread precipitation will spread from the
Aleutians into southwest/western/interior Alaska later this week
and then into southern/southeast Alaska on the western periphery
of the slowly eastward shifting ridge early next week as energies
work increasingly into the Gulf of Alaska.
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 precipitation across portions of the Alaska Panhandle and
mainland Alaska, Mon-Tue, Sep 30-Oct 1.
- Heavy rain across portions of mainland Alaska, Sun, Sep 29.
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