662
FXAK69 PAFG 180803
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
1203 AM AKDT Wed Sep 18 2024

.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 and and chances for snow even down into the
Interior.

&&

.DISCUSSION...

Upper Levels and Analysis...
A 530 dam low is moving east across the Bristol Bay region, in the
form of a strong occluded low. The low center is currently
analyzed around 991 mb near King Salmon. There is a weak shortwave
trough over the NW Arctic, and another over the E Beaufort Sea.
Weak flow dominates over N Mainland. The only notable gradient is
over the AK Range where the south gradient is pushing gusts to 50
mph in the E Alaska Range, but this will wane quickly this
morning.

Forecast and Model Discussion...
The low to our south will continue to shift east and weaken as it
traverses the Gulf of Alaska. Weak shortwave trough energy aloft
will move east across the Mainland and bring chances for rain
showers over the Interior later today through Thursday. A stronger
arctic trough is projected to dig south across the North Slope and
into the Interior Thursday night into the weekend, which will
bring snow chances to the Brooks Range and eventually into the
higher elevations of the Interior. We favored a strong blend to
NAM nest early for winds then the GFS thereafter, which
introduces more chances for precip after Friday than the prior
forecast had given the westward shift with the arctic trough.

Central and Eastern Interior...
Moisture will continue to move north today with increasing chances
for light rainfall/showers by later this afternoon. On/off showers
will prevail through Friday but will slowly be tapering off. The
best chance for light rainfall accumulations will be tonight and
Thursday for the S Interior and Alaska Range with light snowfall
down to 2500 feet in the Alaska Range. Temps are on the downtrend
for the late week as an arctic trough digs south and brings down
cooler air along with chances for potential light snowfall down as
low as 1000 feet by Sat morning for parts of the E Interior.

West Coast and Western Interior...
Light showers will move across the West Coast and Interior all the
way into the late week as the flow turns westerly/onshore behind
the deep low moving into the Gulf of AK. Light snow will be
possible over the W Brooks Range for the later week as an arctic
trough digs south, with light snowfall accumulations at
elevation. This same trough will dry the remainder of the area out
Friday and Saturday as the north winds kick in.

Extended Forecast Days 4-7...
An arctic trough digging over the Mainland will be the highlight
beginning this weekend. The global numerical model guidance is
strongly trending toward a solution of what the GFS has been
showing for the past couple days, which is a stronger arctic
trough crossing the Brooks Range and setting up over the Central
and Eastern Interior Saturday through Tuesday of next week. The
ECMWF has completely flipped from the past several days and now
also supports this pattern evolution, which means it will be
cooling with increasing chances for lower elevation snowfall over
parts of the Interior this weekend. Large uncertainty at this
juncture with any chances for snowfall, but it should be noted
that there is a chance, possible even down to valley elevations.

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 PKZ802-850-853.
     Small Craft Advisory for PKZ803-852.
     Small Craft Advisory for PKZ804.
     Small Craft Advisory for PKZ805.
     Small Craft Advisory for PKZ806.
     Small Craft Advisory for PKZ807.
     Small Craft Advisory for PKZ816-817-854-857.
     Small Craft Advisory for PKZ851.
     Small Craft Advisory for PKZ856.
&&

$$

Ahsenmacher