Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
451 PM EDT Fri Mar 18 2022
Valid 12Z Tue Mar 22 2022 - 12Z Sat Mar 26 2022
...Pattern Overview...
A lingering main feature near Alaska for the medium range period
will be a mean upper low with multiple centers of focus at times
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
into next week. A series of low pressure systems will bring a
multi-day period of unsettled weather through the Panhandle and
occasionally up into the southern coast. 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/warming
upper ridge setting up over a dry northwest/northern Alaska by
early period to limit eastward progression. Downstream in this
pattern, modestly cooling upper troughing would have a period to
amplify more over an unsettled Mainland before the pattern will
likely evolve and moderate.
...Guidance/Predictability Assessment...
WPC Alaskan medium range guidance was primarily derived from a
composite of best clustered guidance from the 12 UTC GFS/EC/UKMET
for Days 4/5 (Tuesday/Wednesday) before switching to a blend of
the semi-compatible GEFS/NAEFS/ECMWF ensemble means for days 6-8.
This forecast plan maintains excellent WPC product continuity in a
pattern whose overall predictability lowers from average to below
average over time. The WPC Hazards Outlook Desk has also added a
threat for heavy precipitation (coastal rains/terrain snows) for
the Southeast Panhandle centering around Tuesday considering wet
antecedent conditions. The models are now in better agreement for
there and nearby regions for this time period and the forecast
also now has increased ensemble support.
...Weather/Hazard Highlights...
Precipitation through much of the period is expected to focus from
coastal south-central Alaska to especially the southeastern
Alaskan Panhandle given the general northern Pacific storm track
into the Gulf to include several deepened lows that will each
offer a maritime threat. 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/deepened system approaches and accordingly, the WPC
Hazards Desk has added a threat for heavy precipitation to focus
across Southeast AK around Tue now that guidance is in better
agreement.
Farther north, some periods of snow are also possible with
unsettled conditions aloft over mainly the eastern Interior
through mainly mid week. Meanwhile, slow low/frontal system
progression over the Aleutians and the Bering Sea next week should
still lead to subsequent low re-development and weather focus
through southwest Alaska to the western Gulf of Alaska into later
next week where wrapping winds/precipitation could also present an
emerging maritime and coastal focus.
Schichtel
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle,
Tue, Mar 22.
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