Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
508 PM EST Sat Feb 08 2020
Valid 12Z Wed Feb 12 2020 - 12Z Sun Feb 16 2020
...Guidance and Uncertainty Assessment...
Latest models still offer less than stellar run to run continuity
and greater than normal forecast spread overall, but there are
some signs of improvement. This may be especially evident with the
last few runs of the ECMWF that have been in better agreement with
at least NAEFS/ECMWF ensemble means during the first half of this
medium range forecast period into Thursday morning. Accordingly
and after collaboration with the local WFO offices, the forecast
starting point for the WPC Alaskan product suite was a blend of
the reasonably compatable guidance from the 12 UTC ECMWF and
NAEFS/ECMWF ensemble means with the 19 UTC National Blend of
Models. Forecaster adjustments were again applied to the blend to
add increased detail consistent with individual weather feature
predictability and support, especially as per the deepening of
offshore lows.
...Weather Pattern and Hazards Highlights...
The mid-upper flow pattern next week will feature a mean
trough/low over the Aleutians/Bering Sea and a gradually weakening
downstream ridge shifting from Southwest Alaska to over the
Interior and Southern Alaska. This pattern favors development of a
series of potentially deep storms to focus a threat of heavy
precipitation/winds/seas across the Aleutians/Bering Sea. Pattern
de-amplification/progression over time should spread activity to
western Alaska, the Alaska Peninsula/Southwest Alaska and southern
Alaska.
Meanwhile, lead surface high pressure/cold air settled over the
Interior moderates later next week as heights gradually rise as
the early weak upper trough shifts eastward into Canada. Arctic
stream energies digging into the base of this trough may combine
with an uncertain influx of eastward progressing northeast Pacific
to Gulf of Alaska trough energies cutting underneath the mainland
to meanwhile support a several lows that will present some heavier
precipitation threats to the Southeast Panhandle.
Schichtel
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