Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
359 PM EDT Wed Sep 11 2019
Valid 12Z Sun Sep 15 2019 - 12Z Thu Sep 19 2019
Upper troughing is forecast to settle into central/interior Alaska
due to an incoming Bering system and an Arctic upper low dropping
southward early next week. This shuffling will work in tandem with
deepening troughing over the Sakhalin Oblast (north of Hokkaido)
and ridging near the Dateline in the mid-latitudes.
Blend of the recent GFS/ECMWF guidance (deterministic and ensemble
data) offered a good starting point to the forecast. 12Z GFS was
deeper than nearly all ensemble members with the Bering surface
low late Sunday (as were earlier runs) but a blend with the ECMWF
and ensembles tempered that to a more modest 992mb low. Attendant
frontal boundary will likely slow and stall along 50N as a surface
wave develops and deepens as northern stream troughing rotates
into across the AKPen. This may take that low into the Gulf by
next Wed/Thu.
Pattern will be fairly wet for southwestern/western areas through
Southcentral as the front comes through then into the Panhandle
with westerly flow. Multi-day rainfall totals may exceed several
inches (4-5") from eastern Kenai to Yakutat into the Panhandle
with less rainfall farther inland. However, inland rainfall
around the Alaska Range will be more anomalous relative to
climatology vs the normally wetter coastline.
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 mainland Alaska, Sun-Mon, Sep
15-Sep 16.
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