Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
704 PM EDT Thu Oct 08 2020
Valid 12Z Mon Oct 12 2020 - 12Z Fri Oct 16 2020
...Overview and Guidance/Predictability Assessment...
Initially, models are generally clustered well with the lows near
the Kenai and crossing the Aleutians. Noted that the 12Z UKMET is
running a mb deeper and faster than other guidance with these to
features, while lagging behind/south by about 6-12 hrs with the
low in the North Pacific tracking toward the Southeast/British
Columbia. The 12Z GFS continues to be more so an outlier
especially with the system in the North Pacific- it is the
furthest south and tracks the low offshore of the
Washington/Oregon coast while the rest of the guidance aimed for
Vancouver and areas to the north. Models diverge a bit during
Monday and into Tuesday but lock on to the low near/south of the
Kenai by Tuesday night/Wednesday. The 12Z ECZEMA suggests a
deepening of the low more over the central Gulf by the end of the
extended period.
The ECWMF has been persistent with the evolution of these three
features the past few days. The latest CMC has trended toward a
similar solution as the ECWMF. The preferred model blend largely
relied on the 12Z ECWMF/CMC with minor weighting of the UKMET
early on and then gradually increasing the inclusion of the ECWMF
and ensemble means for Wednesday and beyond.
...Weather/Threats Highlights...
Much of the southern coast and portions of the panhandle with have
precipitation throughout the extended period, with periods of
heavier intensity especially the Southeast and areas of higher
terrain Tuesday through at least Friday. Cloud cover will hang
around for much of the southern half of the state and for the
North Slope for several days.
There continues to be spread with where the low will track,
however, if it tracks to the eastern Gulf/south of the panhandle,
this favors higher precipitation to the southern islands and drier
further north. Cooler temperatures are expected to filter into
from the north through the week with will aid in lowering heights
aloft. This could scattered precipitation at times over the
mainland which will be in the gradient between Arctic high
pressure and Gulf low pressure. The Aleutians should see brisk
and unsettled conditions.
Daily highs will mainly range from the 30s to 50s from north to
south this weekend, however cooler air will begin to settle in
over the state. Highs will range from the upper teens near the
Arctic to the 40s in across the southern Mainland/panhandle by
next week and overnight lows will range from the 10s to the
30s/40s. For portions of the Panhandle and the southern coast this
will be near or slightly below normal for mid-October.
Campbell
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
Hazards:
- Heavy precipitation across much of the Alaska Panhandle, Tue,
Oct 13 and Thu, Oct 15
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