Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
510 PM EDT Tue Jun 29 2021
Valid 12Z Sat Jul 03 2021 - 12Z Wed Jul 07 2021
...Unsettled weather expected from portions of the Aleutians to
the southern Coast...
...Overview and Guidance/Predictability Evaluation...
The guidance shows reasonably good agreement on the movement of a
deep cyclone from near the Aleutians/Bering Sea eastward into the
far north Pacific/near the Gulf of AK. There are detail issues,
with the 12z Canadian bodily moving a deeper surface low from
south of the Aleutians into the northeast Pacific late in the
period. Per coordination with Anchorage, it seems more likely
that a new low would form as the mid-level system shifts eastward.
The 12z GFS/12z ECMWF also appear to be breaking down the top of
the amplified ridge just northeast of AK too much. The pressures,
fronts, and 500 hPa heights used a compromise of the 00z UKMET,
00z Canadian, 12z GFS, 12z ECMWF on late Friday before slowly
substituting in the 12z NAEFS and 00z ECMWF ensemble means for the
UKMET and Canadian solutions. The remainder of the grids are more
evenly weighted to the deterministic and ensemble mean guidance
through the period.
...Weather/Threats Highlights...
Unsettled weather will shift across the AK Peninsula and Kodiak
island into south-central AK and eventually southeast AK with
periods of showers and breezy conditions as a low and its
attendant fronts move through. Moisture should also extend
northward into parts of the western mainland bringing rainfall to
the region during the weekend. As upper level ridging is slow to
erode across eastern Alaska, especially the first half of the
period, east-central AK should be the warmest with highs in the
70s. Elsewhere across Alaska should be near or below normal
underneath increasingly/mostly cloudy skies and upper level
troughing.
Roth
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