Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
630 PM EST Fri Jan 26 2024
Valid 12Z Tue Jan 30 2024 - 12Z Sat Feb 03 2024
...Heavy precipitation and high winds for southern Alaska should
wane early next week as bitterly cold temperatures across the
interior are expected to moderate some...
...Overview...
An upper trough stuck over Alaska should finally begin to shift
eastward with time by the middle of next week as upper ridging
builds over the Bering Sea and eventually into Alaska. This should
help to moderate bitterly cold temperatures across much of the
Interior as well as ushering in a drier overall pattern. Upper
troughing over the Gulf the first half of the period though will
continue to support some lingering heavy rain and high wind threat
across Southeast Alaska as a surface low or two tracks towards the
Panhandle. Another storm system looks to approach the western
Aleutians by late week or next weekend.
...Guidance Evaluation/Preferences...
The large scale pattern remains overall agreeable in the ensembles
and models, but there is a lot of variability in the details of
individual systems and the evolution of the trough over Alaska as
it slowly shifts eastward. This seems to stem from uncertainties
still on the exact placement and tracking of the embedded upper
low which should initially be centered near the Bering Strait. The
GFS continues to be an outlier with this as it becomes much more
amplified with the trough, and pulls the low southward towards the
coast (related to it having a more northward pull on a deep
surface low approaching the southern AK Panhandle). There is
little support from the other guidance on this evolution,
including it's own ensemble mean. The CMC is also a little
different wanting to split energy, sending it more westward into
eastern Siberia while the ECMWF shows the best consistency with
the ensemble means showing a slow but steady shift to the east and
north and generally weaker troughing. Despite the differences over
the AK mainland, there is good agreement on ridging eventually
building back in over the western part of the state mid-week.
There is also general consensus that another upper low will
approach the western Aleutians late period, but variability on
exact placement of the surface low/lows.
The WPC forecast for today leaned heavily on the 12z ECMWF through
much of the period as it was the most consistent with the
agreeable ensemble means. Was able to maintain mostly
deterministic guidance the first few days or so of the period, but
quickly increased contributions from the ensemble means as the
forecast spread increased. On the large scale though, this
approach did maintain relatively good continuity with yesterdays
WPC forecast too.
...Weather/Hazards Highlights...
From this weekend and continuing into early next week (the very
beginning of this forecast period), Southeast Alaska will see
periods of heavy rain and snow (depending on location/elevation)
as a deep surface low and associated fronts lifts towards the
southern Panhandle region Monday-Tuesday. General troughing in the
Gulf may allow precipitation to linger beyond Tuesday, but should
wane in intensity with time as upper ridging moves in from the
west. Meanwhile, gusty gap winds are likely to continue early week
for Southern Alaska with a strong pressure gradient present. The
rest of the mainland should be mostly dry next week, with
precipitation moving across the Aleutians as the next system rolls
in to the domain.
Bitterly cold temperatures that are well below normal will
continue into early week, but should moderate with time mid to
later next week. Monday-Tuesday, overnight lows lower than -30F
will be widespread, with some -50s possible in favored valleys of
the Yukon Flats and Interior. Below normal temperatures will shift
eastward with time across the East and eventually into the
Southeast (replacing previously warmer than normal temperatures).
The western coast, Aleutians, and North Slope should eventually
warm up to modestly above average by late next week.
Santorelli
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