Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
728 PM EDT Sun Mar 14 2021
Valid 12Z Thu Mar 18 2021 - 12Z Mon Mar 22 2021
...Overview and Guidance/Uncertainty Assessment...
The blocky pattern persists with the latest run of model guidance,
at least for the first half of the extended forecast with the
leading trough/low over the Gulf of Alaska, weak ridging behind it
and a trough over western Bering Sea/eastern Siberia. Overall,
there is decent clustering and agreement with the large scale
setup with typical spread on specific details. These differences
increase through the second half of the extended forecast, which
decreases confidence on the timing, strength and location of
features. A couple waves of low pressure are expected to lift
toward the Southeast coast and along southern mainland early in
the period, then with some ridging expected to develop aloft for
day 6-8 over western mainland Alaska.
For this issuance the preferred WPC blend began with equal parts
of the 12Z ECWMF/GFS/UKMET and shifted to a steady increase of the
GEFS mean and the ECWMF ensemble means for days 6 and beyond.
...Weather/Hazards Highlights...
With the waves of low pressure approaching the southern Mainland
and the Southeast, these areas could have periods of scattered to
widespread precipitation. A majority of the Mainland with be
mostly quiet and dry. The Aleutians could also have several rounds
of precipitation. Most of the region will have temperatures near
seasonal average, or slightly below average through the extended
period. The North Slope is forecast to have temperatures warmer
than seasonal average.
Campbell
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 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