Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
605 PM EDT Fri May 15 2020
Valid 12Z Tue May 19 2020 - 12Z Sat May 23 2020
...Guidance/Predictability Assessment...
The WPC medium range Alaskan product suite was mainly derived from
a composite of reasonably well clustered guidance from the 12 UTC
GFS/ECMWF/Canadian through next midweek along with the 19 UTC
National Blend of Models, This pattern offers above average
forecast predictability. The composite of these models was
combined with increasingly weighted guidance over time from even
better clustered guidance from the 12 UTC GEFS/ECMWF ensemble
means days 6-8. This solution maintains excellent WPC continuity.
...Weather/Hazard Highlights...
A main storm track will bring a series of closed upper
lows/troughs and deepened surface systems along with an enhancing
moisture and wrapping heavy precipitation threat from the
Aleutians through the Alaskan Peninsula and Gulf of AK/southern
AK.
A lead low will work into the Gulf of AK into Tuesday/Wednesday,
with a second deeper storm methodically on its heels from the
Aleutians to the Gulf of AK Tuesday into next Saturday. This
system has trended a bit slower and deeper than yesterday and that
seems reasonable given upper flow amplitude. These lows will also
offer a maritime wind/wave hazard from the northern
Pacific/southern Bering Sea eastward with redevelopment/slow
progression into the Gulf of Alaska.
Farther inland, Arctic surface high pressure will linger from the
North Slope to the Interior in a pattern with modest precipitation
potential under less certain upper troughing, but the ECMWF has
been handling the details a bit better recently.
Schichtel
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 portions of southern coastal areas of
Alaska, Tue, May 19 and Thu, May 21.
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