Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 PM EDT Sun Oct 27 2019
Valid 12Z Thu Oct 31 2019 - 12Z Mon Nov 04 2019
Upper ridging is forecast to remain just south of the Gulf of
Alaska late this week through next weekend as additional ridging
moves through the Bering Sea into western Alaska. This will favor
troughing from the North Pacific initially into southwestern
Alaska then the Panhandle.
Models and ensembles show generally good agreement on the longwave
pattern evolution and a blend of the 12Z GFS and 00Z
ECMWF/UKMET/Canadian sufficed to start (with some ensemble
weighting to smooth out some timing/track differences with the
lead system over the AKPEN). ECMWF and its ensembles nudged the
track of that system northwestward into Bristol Bay vs staying
just to the southeast of AKPEN and into Kodiak, so a modest
compromise was used as the surface low should weaken and reform in
the Gulf regardless. That front will push into the Panhandle but
linger for a couple days atop upper ridging to its south. By next
Sun/Mon, as ridging moves into the western mainland, some upper
troughing could push the front southward to the southern
Panhandle. Back to the Bering, the 00Z ECMWF was likely too
aggressive with its surface low, tracking it right into the upper
ridge. Preferred to take the system northeastward into eastern
Russia like the ensembles.
Rain/snow will spread across the AKPEN and Southcentral into
southeastern areas later in the week as the lead Pacific front
makes steady progress northeastward then eastward. Precipitation
will linger over the Panhandle with WSW flow aloft around the
stationary frontal boundary. Next Bering system may only affect
the Aleutians if it refrains from moving eastward into the ridge.
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