Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
730 PM EDT Sat Jun 19 2021
Valid 12Z Wed Jun 23 2021 - 12Z Sun Jun 27 2021
...Heavy rain and wind threaten eastern Aleutians and Alaskan
Peninsula later next week as enhanced rainfall expands east into
the Alaska Panhandle...
...Guidance/Predictability Evaluation...
The WPC Alaskan medium range product suite was primarily derived
from a composite blend of relatively well clustered guidance of
the 12Z GFS/GEFS mean/ECMWF/00Z EC mean, along with some 12Z CMC
and CMC mean. Guidance forecast spread continues to indicate
above normal predictability on the synoptic scale pattern. Thus,
a general model blend trending toward the ensemble means for Days
6-8 should work fine as a starting point. This blend yielded a
rather deep cyclone for June to impact the eastern Aleutians to
the Alaskan Peninsula late next week before it gradually weakens
and meanders in the same vicinity by the weekend. More of the 06Z
GFS rather than the 12Z run was used in the blend since the 06Z
GFS was more compatible with the ensemble mean position of the
Aleutians low. This blend provided results that stayed pretty
close to WPC continuity.
...Weather/Threats Highlights...
A rather deep cyclone for this time of the year is forecast to
impact eastern Aleutians and the Alaskan Peninsula with gale-force
winds and a few inches of heavy rain possible later next week.
The moisture is expected to quickly expand eastward through the
southern coastal sections and into the Alaska Panhandle where
moderate to heavy rain is possible. A slow drying trend should
then work its way from west to east across the Aleutians as the
cyclone weakens while meandering over the eastern Aleutians.
Farther north across the rest of Alaska, rain chances should
gradually increase later next week across the northern portion of
the state where a stationary front becomes better defined. Rain
chances are expected to linger into the weekend for this region.
The gradual trend toward damp and cloudy conditions later next
week area wide will keep low temperatures warmer than average for
much of Alaska while high temperatures are expected to be slightly
above normal for the latter half of next week, cooling to near
normal by the weekend.
Kong
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