Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
630 PM EDT Thu Mar 17 2022
Valid 12Z Mon Mar 21 2022 - 12Z Fri Mar 25 2022
...Pattern Overview...
It remains the case that one main feature near Alaska for the
medium range period will be a mean upper low with possibly
multiple centers of focus at times meandering in the Gulf of
Alaska. Energies near the Alaska Peninsula combined with an active
storm track across the northeastern Pacific will serve to
redevelop and reinforce mean low pressure across the Gulf next
week. A series of low pressure systems will bring a sustained
period of unsettled weather through the Panhandle and occasionally
up into the southern coast for much of the period. A low near the
Kamchatka Peninsula will swing a cold front through the Aleutians
and lead low focus over the Bering Sea next week, with a blocky
upper ridge setting up over northwest Alaska to limit eastward
progression. Downstream in this pattern, upper troughing would
also begin to amplify more over an unsettled Mainland as an upper
ridge/high settles into northwest AK, albeit with less certainty.
...Guidance/Predictability Assessment...
The 12 UTC ECMWF/UKMET/Canadian model solutions seem best
clustered and reasonable days 4-6 (Mon-Wed). A composite offers
decent product continuity and average predictability with an
improving signal both for a warming ridge/high building aloft over
northwest/northern AK and a cooling/unsettling low system focus
centered over the Alaskan Interior and the Gulf of Alaska.
However, the 12 UTC GFS is more of an outlier over the Gulf and
brings a less likely deeper low into Southeast Alaska midweek that
was discounted for deterministic products given the overall
pattern. Forecast spread increases rapidly into day 7/8 so prefer
a composite of the much more compatible 12 UTC GEFS/NAEFS/ECMWF
ensemble means to preserve product continuity. This overall
forecast plan was collaborated with Alaskan offices.
...Weather/Hazard Highlights...
Precipitation through much of the period is expected to focus from
south-central Alaska to especially southeastern Alaska given the
general northern Pacific storm track into the Gulf to include
several deepened lows. The region will experience varying rainfall
intensities depending on uncertain surface low progressions. While
precipitation does not appear to be very intense overall most
periods, recent heavy rain/snow across the area could make it more
sensitive to additional impacts. Amounts seem most likely to pick
up early next week with best organized system approaches. Farther
north, some periods of snow are also possible with unsettled
conditions aloft over the Interior next week. Meanwhile, slow
low/frontal system progression over the Aleutians and the Bering
Sea next week may lead to subsequent low re-development and
weather focus through southwest Alaska to the western Gulf of
Alaska into later next week.
Schichtel
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