252
FXAK69 PAFG 182227
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
227 PM AKDT Wed Sep 18 2024

.DISCUSSION...

.SYNOPSIS...
A powerful occluded low is moving inland over Bristol Bay this
morning. That low shifts east today and eventually clouds and
shower chances increase over the Alaska Range and Southern
Interior into Thursday night. An arctic trough will bring colder
air and accumulating snow chances to the Brooks Range and Arctic
beginning Thursday. The arctic trough will dig south this weekend
bringing colder air and chances for snow even down into the Interior.

.DISCUSSION...

Upper Levels and Analysis...
A strong occluded low pressure system of around 530 dam is
transiting eastward across the Kenai Peninsula and will continue
to fill as it propagates across the Prince William Sound by later
this evening. There is also a weak shortwave transitioning slowly
across the NW Arctic. Winds will continue to weaken across the
eastern Alaska Range through the evening as the low pressure to
the south continues to pull away. Models have begin to show more
of a stronger trough deepening over the Mainland by this weekend,
which will allow for much colder temperatures to be advected in
from the north.

Forecast and Model Discussion...
As the low to the south further weakens as it moves into the Gulf
of Alaska, the loosening gradient will allow winds to will
continue to weaken over the E Alaska Range. The weak troughing
is expected to keep the chances of rain going across most of the
Mainland and Interior region later this evening and through
Thursday. There will be a stronger through moving in this weekend,
which will allow for colder air advection from the North Slope
and bring the chance of snow down in the Interior, especially by
Saturday night. GFS has continued to have a better and more
reliable handle of this and will continue to be blended in more.
Temperatures will likely continue to trend below the seasonal
average into early next week.

Central and Eastern Interior...
With residual moisture in place and weak troughing, the
possibility of on and off showers will continue over portions of
the Mainland, and this will likely prevail through Friday. There
will likely be snowfall accumulations across the Alaska Range,
especially for elevations around 2000 ft and above tonight. The
colder air moving in this weekend could support snowfall down to
the valley floor of the Interior, and especially light
accumulations around 1000 ft and above. It is more likely to see
accumulating snow by Saturday night.

West Coast and Western Interior...
There will still be the possibility of light showers across the
West Coast and Interior all the way into the late week with
continued flow being more westerly. There could be snowfall
across the western Brooks Range by later in the week and though
the weekend as the trough deepens from the north. There will be
some drier air moving in on Friday, and also though into Saturday
as more northerly winds become predominant will the deepening low
across the North Shore.

Extended Forecast Days 4-7...
With the deepening trough over the Mainland this weekend, and much
colder temperatures expected as a result, it could allow for some
of the first snowfall to make it down into the Interior, even for
the lower elevations. Models, and particularly the GFS, have also
been trending towards the arctic trough this weekend of becoming
stronger as it moves across the Brooks Range and then setting
setting up over the Central and Eastern Interior through Tuesday
of next week. The ECMWF has also continued to align more with this
solution and also agrees with the trend towards a colder airmass
advection which may support measurable snowfall down to the
valley floor of the Interior this weekend.

.Coastal Hazard Potential Days 3 and 4...None.

.HYDROLOGY...
Rainfall of 0.5 to 0.75 inches fell over the YK Delta and Lower
Yukon Valley/Middle Kusko Valley the last 24 hours. Smaller
stream and larger stem river rises are occurring, but will not be
significant. Elsewhere, no concerns as rivers are running low due
to fairly low snow levels.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ801.
     Small Craft Advisory for PKZ803-852.
     Small Craft Advisory for PKZ804.
     Small Craft Advisory for PKZ805.
&&

$$