113
FXAK02 KWNH 092347
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
647 PM EST Thu Jan 09 2025

Valid 12Z Mon Jan 13 2025 - 12Z Fri Jan 17 2025

...Strong storm system to bring heavy precipitation and high winds
to portions of the southern Mainland and Southeast Alaska this
weekend into early next week...


...General Overview...

An active weather pattern is forecast across Alaska this weekend
into early next week as multiple energetic disturbances pivot
around an upper low parked just west of the state. The strongest
storm system is will move north across the Aleutians and western
Alaska this weekend, and bring heavy precipitation and high winds
to the southern Mainland and Southeast Alaska. This system will be
followed by a few weaker systems that will track through the Gulf.
Mid-to-late next week, the pattern will shift and ridging will
strengthen across the state while troughing develops over the
northern Pacific. A couple slow but strong Pacific systems will be
possible late next week, but are not currently forecast to be
impactful in Alaska.


...Model Guidance Assessment...

Model guidance shows surprisingly good agreement through the
medium range forecast period. The deterministic models show good
agreement on timing and strength of features through Tuesday, so a
general blend of the GFS/ECMWF/CMC was used as a starting point
for WPC`s forecast. After Tuesday, spread increases among
deterministic model solutions, but the ensemble mean solutions
from the GEFS/ECENS/CMCE remain in good agreement. WPC`s forecast
blend used increasing amounts of the ensemble means for Wednesday
through Friday, with heavier weights placed on the ECENS/GEFS over
the CMCE. The most uncertainty in the forecast will be surrounding
the two Pacific systems late in the period, where there is some
model spread on location ans strength of these features. However,
there does seem to be good agreement on the speed and track.


...Weather/Hazards Highlights...

The strong low pressure system that will track north across the
Aleutians and western Alaska will have a trailing front that
extends back into the Gulf. Moisture streaming ahead of this front
will focus over the southern Mainland on Sunday, and heavy
precipitation is expected. Precipitation will fall as snow at high
elevations, but there will likely be mixed precipitation or rain
in areas where daytime highs reach above freezing. Rain falling on
snow covered ground could cause additional snowmelt and flooding
issues in low elevation areas where runoff is enhanced. The
strength of this system will result in a tight pressure gradient
across the state that will support strong onshore winds over the
southern Mainland and western Alaska. Strong winds will also be
possible in the central Alaska Range. The focus for heavy
precipitation will shift to Southeast Alaska on Monday as the
system progresses, then a quick series of weaker systems will
track through the Gulf early/mid next week, which will continue
precipitation chances across this region through at least mid-week.

Quieter weather is forecast for the second half of the week as
high pressure builds from the Gulf of Alaska to the Arctic. The
next storm systems are expected to approach from the Pacific late
next week, but be slowed down by high pressure ridging. The first
will likely track south of the Aleutians, and the second looks
like it will make a slow approach towards the Bering Sea.
Increasing precipitation chances are expected across the Aleutians
as the second system approaches.

Temperatures are forecast to be well above normal across nearly
the whole state through Tuesday as southerly flow pushes in a
warm, moist air mass. Downsloping winds along the Alaska Range
will enhance warming for portions of the interior, and high
temperatures could reach 35-40 degrees. Above freezing
temperatures could cause problems for areas where snow cover is
needed for transportation and could exacerbate snowmelt/flooding
concerns. Temperatures look like they will trend back to near
normal during the second half of the week under high pressure.
Arctic high pressure will nudge down into northern Alaska, and
high temperatures will drop back below zero.


Dolan


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

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