Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
427 PM EDT Sun Sep 29 2019
Valid 12Z Thu Oct 03 2019 - 12Z Mon Oct 07 2019
Complicated flow pattern over the high latitudes (and even
mid-latitudes) yields a rather low confidence forecast overall.
However, the 12Z GFS and 00Z ECMWF offer reasonable clustering
near a subset of the ensemble consensus that aligns with the
forecast of TS Mitag and its extratropical transition into the
flow. This should yield downstream ridging into the western then
central Bering next Sun/Mon ahead of ex-Mitag which favors the
GEFS/Canadian ensembles rather than the flattened (perhaps by way
of averaging its 50 members) ECMWF ensemble mean. With low
confidence, opted to forge a middle ground but with more emphasis
on the GEFS mean.
Change in the forecast with the system along 50N Thu results in
more northern stream influence across western areas Friday with an
incoming system. That has trended slower and a bit deeper but
otherwise has been somewhat consistent over the past couple of
days. By next Sunday, ex-Mitag should likely be lifting to near
Kamchatka but there remains a large degree of spread (even from
its day 3 forecast). Consensus position would be slower than the
GFS (which is typically fast) but a bit quicker than the ECMWF
(typically a bit slow).
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
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