Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
758 PM EDT Mon Aug 10 2020
Valid 12Z Fri Aug 14 2020 - 12Z Tue Aug 18 2020
...Guidance Evaluation and Preferences...
A mostly progressive pattern will continue across the northern
Pacific into next week with a storm track along 50-55N. Farther
north, a more uncertain northern stream through the Arctic will
waver along and north of 70N. The 12Z ECMWF paired best with the
ensembles, but the 12Z GFS/Canadian/UKMET were close enough to use
as a deterministic influence at least for the Fri-Sun period.
Thereafter, the Canadian appeared too deep and far to the west in
the Gulf with troughing while the GFS was likely too deep with
troughing over NW Alaska as the ensembles only slowly eroded the
upper ridge from western areas (eastern Bering Sea). Nevertheless,
still expect troughing to push out of the Bering Strait by the end
of the period per the latest guidance, but the models and even
ensembles have been inconsistent in the flow north of 65N the past
few days. Trended to just and ensemble mean blend by next Tue amid
uncertainty in the timing of the next Bering/Aleutian system
streaming eastward.
...Weather Highlights/Threats...
Lead system Fri-Sat will push through the Gulf and then into the
Panhandle by Sunday. Modest to heavier rain is possible as the
parent low lingers in the Gulf Monday but the fronts push ashore.
Ensemble guidance shows the possibility of several inches of rain
over the Panhandle, particularly over southern sections closer to
the triple point and moisture-laden air. Next Bering system will
bring showers to the Aleutians and across southwestern areas
around the same time as a front to the northwest could spark some
showers as well. Amounts may be light due to limited moisture.
Daytime temperatures will be cooler than normal along
southern/southeastern coastal areas but warmer than normal over
the Interior and especially western/southwestern areas. Highs in
the 70s are forecast. To the north, the North Slope/Brooks Range
will trend cooler during the period as heights lower into next
week.
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
Hazards:
- Heavy rain across much of the Alaska Panhandle, Sun-Mon, Aug
16-Aug 17.
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