Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
643 PM EST Thu Jan 20 2022
Valid 12Z Mon Jan 24 2022 - 12Z Fri Jan 28 2022
...A wet pattern with heavy precipitation possible will continue
into mid next week for Alaska's southern coast and Panhandle...
...Overview...
Guidance continues to show a very warm and wet pattern for early
next week, as a strong eastern Pacific mean ridge extends
northward into Alaska's mainland and northwestern Canada while a
mean trough axis persists farther west, with an embedded initially
fairly deep upper low over eastern Siberia that should drift north
and east with time. A shortwave/surface low initially near the
Alaska Peninsula on Monday will direct a moist flow into the state
and bring precipitation for southern parts of the state, and
spread eastward with time. Weak upper troughing and cooler/drier
surface high pressure is forecast to push west to east across much
of the mainland around midweek onward as the ridge axis relaxes
and shunts eastward into Canada.
...Guidance/Uncertainty Assessment...
The models show fairly good agreement through much of the period
on the overall, large scale pattern with differences in placement
and the details of individual surface lows lifting into the
region. Right off the bat, there's some latitudinal differences in
surface low placement near the Alaska Peninsula on Monday. The GFS
and CMC are notably north of the ECMWF, although the ensemble
means support a more south placement. Differences increase with
the next surface low into the Gulf mid-week as well as a deeper
low moving towards the central Aleutians. For both, the GFS and
ECMWF are closer to the ensemble means than the CMC and are the
preferred solutions. At the end of next week, the deterministic
solutions all show another strong surface low lifting towards the
eastern Aleutians. The ensemble means are noticeably weaker with
this final low, suggesting there may be greater uncertainties with
this low than the current deterministic runs suggest.
For days 4-6, the WPC blend leaned closely to the ECMWF and GFS
(slightly more weighting on the ECMWF) with smaller ensemble mean
proportions. Beyond, the blend increased to a 50/50 contribution
between the ensemble means and the GFS/ECMWF deterministic
solutions. This maintained good continuity with yesterdays WPC
forecast for days 4-7 as well.
...Weather/Hazard Highlights...
The deep layer southerly flow will bring in significant moisture
(precipitable water values generally +1.5 to +2.5 standard
deviations above normal) into Alaska for the first half of the
week. The highest precipitation totals are likely from the Alaska
Peninsula into Southcentral Alaska and spreading eastward into
mainly northern parts of the Alaska Panhandle. A period of gusty
winds are also likely for locations along the southern coast. Some
snow should also spread into the western part of the mainland as
well as the ridge breaks down and a cold front presses inland.
Across the mainland, a drier trend is likely by Thursday/Friday as
high pressure builds in. However, wet conditions should continue
across the Panhandle region through much of the week as moist flow
continues ahead of various systems in/near the Gulf. The
central-eastern Aleutians should also see an increase in moisture
by later next week and potentially stronger winds, as a deep
surface low or two impacts the region.
Widespread much above normal temperatures will continue through at
least next Monday underneath the upper-level ridge, with
temperatures 15-30F above average (locally higher) for much of the
mainland except the far western part. Temperatures will moderate
closer to normal and even shift to below normal from west to east
on Tuesday through Thursday as the ridge moves away from the state.
Santorelli
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Sun-Mon, Jan 23-Jan 24.
- High winds across portions of the Alaska Panhandle and mainland
Alaska, Mon, Jan 24.
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