Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
758 PM EDT Fri Jun 18 2021
Valid 12Z Tue Jun 22 2021 - 12Z Sat Jun 26 2021
...Heavy rainfall threat for portions of coastal Southcentral next
week...
...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/EC mean/ECMWF, along with some previous WPC
continuity and 00Z ECMWF. Guidance forecast spread continues to
indicate above normal predictability on the synoptic scale
pattern.
...Weather/Threats Highlights...
The first storm system during this forecast period will be
weakening across the Gulf region by early next week, which will
likely produce unsettled maritime conditions along with periods of
rain from the Alaskan Peninsula to the southeast panhandle. A
stronger storm system builds south of the Aleutians and should
track slowly to the east for the middle part of next week. This
would result in more widespread moderate to heavy showers from the
Alaska Peninsula to the southeast panhandle as an occluded surface
low will advect copious moisture northward across the region, with
perhaps a few inches of rainfall possible for some areas.
The weather pattern is expected to become more amplified by the
Tuesday to Thursday time period as an upper level ridge builds in
across eastern Alaska, which is in response to the meandering
upper level gyre over the Aleutians. This will result in warm
temperatures across much of the Interior next week, especially for
those areas that have mostly clear skies. Cooler than average
temperatures are expected for coastal areas of the Gulf of Alaska
coast where cloudy skies and frequent showers will prevail.
Hamrick
Hazards:
- Heavy rain across portions of southern Alaska, Wed-Sat, Jun
23-Jun 26.
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
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