Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
330 PM EDT Tue Oct 29 2019
Valid 12Z Sat Nov 02 2019 - 12Z Wed Nov 06 2019
Upper level ridging is forecast to remain just south of the Gulf
of Alaska through much of the medium range period, only beginning
to slide southeastward as deep troughing enters the western
Bering/Aleutians by day 7-8 (Tue-Wed). A cold front gets pushed
into the Panhandle region this weekend as upper level troughing
slides southward across the eastern mainland while a warm,
eventually becoming stationary, front lingers in the Gulf atop the
upper ridge. Meanwhile, upper ridging across the Bering/eastern
Russia slides eastward towards the western Mainland by early next
week as a deep upper/surface low ends up somewhere near the
western Aleutians.
Early period model agreement lends to a majority deterministic
blend days 4-5 between the ECMWF/GFS, with small contributions
from the ensembles (ECENS/NAEFS/GEFS) to smooth out the smaller
scale differences. There remains question to timing/strength of
the upper trough as it slides through the mainland with the GFS
faster/weaker than a more amplified/slower ECMWF (likely a result
of stronger ridging upstream). The ensemble means seemed to
provide a good middle ground for this feature. Across the
Bering/Aleutians, models may be trending farther south with a
developing surface low than previous runs, with most models
somewhere near or south of the Aleutians by day 8. Timing
differences remain as well as details in the larger scale trough
as a whole across the western Bering so a mainly ensemble mean
blend seemed to be the best course of action for today at this
longer lead time.
Sensible weather wise, rain/elevation snows will continue across
the Panhandle/southeastern areas with west-southwest flow aloft
around the stationary frontal boundary in the Gulf with locally
heavy precipitation possible especially early in the period. The
next Bering Sea/Aleutians system should bring another round of
rain to portions of the western Aleutians by early next week.
Temperatures across the eastern Mainland should trend cooler/below
normal underneath upper level troughing, with moderation back to
near or even a bit above normal by next week especially across the
North Slope region as as upper ridging builds north of the state.
Santorelli
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 precipitation across portions of the Alaska Panhandle,
Fri, Nov 1.
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