Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
546 PM EDT Sun Jun 20 2021
Valid 12Z Thu Jun 24 2021 - 12Z Mon Jun 28 2021
...Rainy conditions forecast for Aleutians, Alaskan Peninsula,
Kenai Peninsula, and southeast AK/panhandle later this week...
...Guidance/Predictability Evaluation...
The models continue to show a mean deep layer trough over the
Bering Sea with embedded cyclonic circulations that should bring a
few storms to the Aleutians and adjacent Alaska peninsula.
Guidance forecast spread continues to indicate above normal
predictability on the synoptic scale pattern. Thus, a general
model blend was used to produce a consensus-based forecast. The
WPC Alaskan medium range product suite was primarily derived from
a composite blend of clustered guidance of the 06-12Z GFS/12z GEFS
mean/00-12z ECMWF/00Z EC mean.
This blend yielded a rather deep cyclone for June to impact the
eastern Aleutians to the Alaskan Peninsula late this week before
it gradually weakens and meanders gradually west northwest into
the southern Bering Sea over the weekend. Strong integrated water
vapor transport downstream from this storm supports locally heavy
rain from the Kenai peninsula over to southeast AK/panhandle.
Farther north in northern Alaska, rain chances should gradually
increase later next week in response to a stationary front becomes
better defined. The higher precip amounts are forecast on Day 5.
Rain chances are expected to linger into the weekend for this
region before the front weakens.
Early next week, the aforementioned low decays, and a new cyclone
develops at the base of the Bering Sea trough in the north
Pacific, impacting the adjacent Aleutians, up to and including the
AK peninsula next Mon the 28th of June. This would bring the next
chance of showery and windy conditions across these regions.
Temperatures are expected to be above normal in southeast
AK/panhandle as the north Pacific upper ridge persists. Most of
the peninsula hovers near normal plus/minus a few degrees, with
the clouds and showers leading to slightly cooler than normal
conditions across the Aleutians and AK peninsula.
Petersen
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