Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
421 PM EDT Thu Sep 12 2019
Valid 12Z Mon Sep 16 2019 - 12Z Fri Sep 20 2019
Active pattern will continue for Alaska next week, driven in part
by an Arctic upper low dropping southward early next week, a
deepening troughing over the Sakhalin Oblast (north of Hokkaido),
and ridging near the Dateline in the mid-latitudes. 00Z/06Z
models/ensembles were in decent overall agreement with some
timing/track/depth changes over the Bering and north Pacific.
Blend of the 06Z GFS/00Z ECMWF guidance (deterministic and
ensemble data) offered a good starting point to the forecast. 12Z
GFS forecast a sfc wave to develop along the front of the lead
Gulf system and move it much farther northward across/along the
Aleutians where almost no ensembles members showed a low.
Discounted the 12Z GFS for now given the lack of support. Still
expect the attendant frontal boundary to slow and stall along 50N
that would support a surface wave along it, but took this
northeastward toward/into the Gulf (per the ensembles and previous
forecast) around Thu then into the Panhandle around next Friday.
Pattern will be fairly wet for Southcentral eastward into the
Panhandle with westerly to southwesterly flow. Multi-day rainfall
totals may exceed several inches (4-6") from Cordova to Yakutat
through the Panhandle with less rainfall farther inland,
especially north of the Alaska Range.
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 southwestern Alaska, Sun-Mon,
Sep 15-Sep 16.
- Heavy rain across portions of the Alaska Panhandle and
southeastern mainland Alaska, Thu, Sep 19.
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