Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
633 PM EDT Tue Jul 20 2021
Valid 12Z Sat Jul 24 2021 - 12Z Wed Jul 28 2021
...Guidance/Predictability Evaluation...
The latest available model guidance was reasonably clustered for
the Alaska region such that the days 4-6 forecast was primarily a
blend of the 12Z GFS/ECMWF/CMC/UKMET deterministic runs. For the
remainder of the medium range period (days 7-8), the relatively
persistent upper level troughing over the region is forecast with
varying degrees of amplitude and strength. The main areas of
question lie with shortwave energy tracking across the Aleutians
and also dropping down across the northwest mainland area. The
stagnant cut off low in the Gulf of Alaska is forecast to subside
late in the forecast period, except for the deterministic GFS,
which keeps its feature throughout. Given the clustering of the
signal but lower confidence in the details, the ensemble means
were a good approach for the 500 pattern and subsequent surface
features. The ECENS was favored to maintain some continuity from
the last cycle.
...Weather/Threats Highlights...
Rain showers are expected for the eastern Kenai Peninsula on
Saturday and east into the Panhandle on Saturday and Sunday ahead
of a storm system over the Gulf of Alaska. There is reasonable
convergence between guidance for marginally hazardous rainfall
totals, in the area, but
dry antecedent conditions will limit any impact from the rain.
Additionally, generally below normal temperatures are expected
across the mainland through the period, particularly in the Far
North. These temperatures are not expected to be hazardous at this
time.
Taylor
Hazards:
No significant hazards are expected over Alaska during this
forecast period.
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook 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