Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 PM EDT Tue Sep 10 2019
Valid 12Z Sat Sep 14 2019 - 12Z Wed Sep 18 2019
Progressive and wavy upper pattern will tend to slow down next
week in response to an upstream deep trough nearing the Sakhalin
Oblast (north of Hokkaido). This favors ridging just west of the
Dateline and troughing along 160W by the end of the period. In
between, a modest system will traverse the Bering Sea this weekend
and push into western Alaska Sun/Mon before its triple point low
decays in the Gulf. Attendant frontal boundary may slow and stall
along 50N as the flow becomes more southwesterly rather than
westerly as heights buckle.
Global models/ensembles showed a better clustering of solutions
today vs 24 hrs ago. 12Z GFS was a bit quicker than all other
models and most ensembles, so used the 06Z GFS in part with the
00Z ECMWF to even out the quicker/slower forecasts, respectively,
vs the means. Trended toward a majority ensemble weighting by next
week Tue/Wed due to increased uncertainty in northern stream flow
across the North Slope (weakness may drift westward as troughing
settles into 160W) as well as southern stream (Pacific)
uncertainty in any wave development along the front.
Pattern will be fairly wet for southwestern/western areas through
Southcentral as the front comes through. Upper trough will
continue with lighter rainfall. Panhandle will see a brief break
in between departing system Saturday and next system late Monday.
Multi-day rainfall totals may exceed several inches (4-5") from
eastern Kenai to Yakutat with less rainfall farther inland.
Fracasso
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
- Heavy rain across portions of the Alaska Panhandle and mainland
Alaska, Fri, Sep 13.
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