Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
801 PM EDT Wed Jun 23 2021
Valid 12Z Mon Jun 28 2021 - 12Z Fri Jul 02 2021
...Rainy conditions expected for portions of the Aleutians,
Alaskan Peninsula, Kenai Peninsula, and the panhandle...
...Guidance/Predictability Evaluation...
Like the past few runs of the model guidance, there is general
consensus with the mean trough and multiple low pressure systems
moving through the circulation over the Aleutians and Bering Sea
earlier in the extended period. Cooler air will filter into
northwest potions of the Arctic Coast, so this portion of the
state will see temperatures drop a few degrees. The model spread
beyond day 5 show struggling with the strength and placement of
the ridge over the Gulf of Alaska, southern and southeast portions
of the Mainland. With the ridge expected to take up residence
somewhere over the Gulf of Alaska by early in the week, and
staying there, it will favor continued heat (after the wave
passing through Friday) for portions of the Mainland but
particularly the Panhandle for the rest of the extended period.
The ridge will also help weaken the individual surface lows
crossing the Aleutians as they approach the western Gulf of
Alaska. This will largely keep the showers over the Aleutians,
western and portions of southwest Alaska.
The WPC Alaskan medium range product suite was a composite blend
of 12Z GFS/ECWMF/CMC/UKMET for the early periods and then
weighting of the 12Z GEFS Mean and the 00Z ECWMF Ensemble Mean was
incrementally increased beyond day 5 to account for the magnified
spread in the pattern evolution.
Campbell
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