231
FXAK69 PAFG 191435
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
635 AM AKDT Sat Oct 19 2024

.SYNOPSIS...
A powerful storm with significant potential impacts moves onshore
the West Coast Sunday, with the front quickly pushing east across
the Interior Monday. This storm will produce strong winds along
the West Coast resulting in elevated water and coastal flooding.
In addition to the strong winds, heavy precipitation, taking a
variety of forms (rain, snow, and possible freezing rain) is
expected across a large portion of northern Alaska. Highest
snowfall accumulations are expected along the south slopes of the
Western Brooks Range and the Upper Kobuk Valley where snow totals
will be in the 12 to 28 inches are expected. In favored upslope
areas of the Seward Peninsula and the Nulato Hills, accumulations
of 6 to 12 inches are possible. Across Interior hills and summits
above 1800 feet, snow amounts will likely exceed a foot, while
across the Middle Tanana Valley total snow accumulations of 6 to
10 inches are possible.

&&

.DISCUSSION...
Upper Levels and Analysis...
Aloft, at 500 mb, troughing extends southwest from a 503 dam
(decameter) low over northwestern Nunavut to a 525 dam low near
Hoonah. A ridge axis is draped from near Wrangel Island extending
south along the West Coast across the central Aleutians and into
the north Pacific. A weak shortwave moving across the top of the
ridge, extends from the Chukotsk Peninsula south to near Shemya
and tracks east across the West Coast this afternoon and evening,
across the central Interior Sunday morning, and east of the AlCan
border by Sunday afternoon. A 512 dam low over the northern Sea
of Okhotsk this morning deepens quickly to 493 dam by Sunday
afternoon as it moves to Chukotka. The low continues to deepen to
490 dam as it moves to be centered near Wrangel Island by Monday
afternoon. The low begins to weaken by Tuesday afternoon as it
moves to be near Point Lay. As this low lifts northeast southwest
flow aloft develops across much of northern Alaska. By Tuesday
morning the trough axis has marched across the Bering and
stretches from the low south to the Bering Strait to near
Nikolski. A piece of energy breaks off the main upper level low
Tuesday afternoon near northern Banks Island, while the original
weakens into an open wave and that trough axis moves from near
Utqiagvik south across the Western Interior.

At the surface, a trough extends west across the Beaufort from a
967 mb low over northern Nunavut. The trough weakens through the
weekend and moves east as the parent low lifts northeast. A 994 mb
low is 275 NM southwest of Wrangel Island with a front extending
across the Chukotsk Peninsula to St Lawrence Island to near the
Pribilofs. The front pushes east to the West Coast by late morning
overtaking a weaker front draped along the coast, continuing east
and extending from near Utqiagvik south to the Central Interior
Sunday morning, weakening as it continues towards the AlCan
border. A 986 mb low near the southern Kamchatka Peninsula quickly
deepens to 959 mb as it moves to northern Kamchatka Sunday
morning, continuing north northeast to be near Wrangel Island
Monday morning. The low weakens to 973 mb Tuesday morning as it
moves to 150 NM northwest of Point Lay and to 984 mb as the low
moves to 75 NM northwest of Point Lay. As this low tracks
northeast, it pushes a powerful front to the West Coast Sunday
afternoon and evening, to near Utqiagvik to the Central Interior
Monday morning and along the AlCan border by Monday evening.

Models...
The 19/00Z model suite initialized well aloft and at the surface
and are in good agreement with the overall synoptic pattern
through the weekend and into early next week. Deterministic models
and ensembles are fairly similar in their solutions. Given that,
made only minor changes to the inherited forecast. Bumped up the
southerly winds at Savoonga and Wales a few knots given the
favorable wind direction, as well as at Brevig Mission and Teller.
Models are painting the pressure gradient across the Alaska Range
Sunday night and Monday 2 to 4 mb weaker than what guidance
indicated yesterday. This would result in weaker winds across the
range. Will have to monitor this over the next few model runs to
see if the trend continues. Continued to advertise south winds
through the Alaska Range passes into the 65 mph range.

North Slope and Brooks Range...
A front marches east across the North Slope and Brooks Range today
into Sunday, spreading snow to the Western Arctic coast by this
afternoon. Snow spreads eastward tonight and Sunday. Snow amounts
generally light at 2 inches or less. Attention then shifts west to
a powerful front approaching from the west on Sunday. As this
front tracks eastward across the Western Arctic Coat and Western
Brooks Range, strong southerly winds will develop. South winds of
40 to 50 mph with gusts up to 75 mph are possible from west of
Point Lay to Point Hope Sunday afternoon through early Monday
morning. The strongest winds are expected at Cape Lisburne. High
Wind Watches were upgraded to High Wind Warnings for these
locations. They may need to be extended as a secondary surge of
southwest winds develops Monday afternoon. Elsewhere along the
coast, strong gales are possible all the way to Utqiagvik. In the
Brooks Range, south winds of 40 to 50 mph are possible, especially
in the passes. Heavy snow will likely fall along the front as it
shifts east, Sunday evening into Monday. The combination of
falling snow and strong winds will produce areas of blowing snow,
especially along the Dalton Highway, where visibility may be
reduced below 1 mile at times and a Winter Weather Advisory may be
needed Sunday night into Monday for blowing snow. The strong
southwest winds will produce elevated water levels along the
coastline from Utqiagvik west. A Coastal Flood Warning is in
effect for the Northern Arctic Coast, where water levels are
expected to be 2 to 3 feet above normal high tide Sunday night
into Tuesday. Coastal Flood Advisories are in effect for the
Western Arctic Coast from Sunday afternoon through Tuesday
afternoon and Northwestern Arctic Coast from Sunday night through
Tuesday afternoon.

West Coast and Western Interior...
A weak front stretched along the West Coast this morning will be
overtaken by another front pushing onshore later this morning.
This front will push east across the Western Interior through
early Sunday morning. Expect a mix of snow and rain along the
coast and all snow as it moves inland. Only light accumulations
expected with this front, generally 2 inches or less. On Sunday, a
powerful front will move to the West Coast, accompanied by strong
south to southwest winds. The strongest winds are expected across
St Lawrence Island and the Bering Strait Coast where south to
southwest winds of 30 to 45 mph are expected with gusts up to 65
mph. Elsewhere along the coast, expect gusts up to 55 mph. These
strong winds will produce elevated water along the coast beginning
Sunday evening, with coastal flooding possible all along the West
Coast. Coastal Flood Warnings have been issued for Eastern Norton
Sound and the Yukon Delta Coast with Coastal Flood Advisories in
place for the remainder of the West Coast coastline. Across inland
areas expect south to southwest winds gusting to 45 mph Sunday
afternoon into Monday. In addition to the strong winds, heavy
precipitation is expected. Snow will give way to heavy rainfall as
warm air surges in and snow levels climb to 3000 to 5000 feet.
Heavy wet snow will fall across the Kobuk and Noatak Valleys.
Rain showers will turn to snow showers Monday night and Tuesday as
colder air shifts inland. Highest snowfall accumulations are
expected along the south slopes of the Western Brooks Range and
the Upper Kobuk Valley where snow totals will be in the 12 to 28
inches are expected. In favored upslope areas of the Seward
Peninsula and the Nulato Hills, accumulations of 6 to 12 inches
are possible. Winter Storm Watches remain in effect for the south
slopes of the Western Brooks Range, the Noatak Valley, and the
Upper Kobuk Valleys. Elsewhere across the Western Interior,
accumulations of 4 to 6 inches of snow expected in Huslia, Ruby,
and Kaltag from Sunday through Monday night.

Central and Eastern Interior...
Temperatures have plummeted this morning where skies have cleared
out with temperatures well below zero at Arctic Valley, Fort
Yukon, Bettles, and Livengood. A persistent stratus deck has
remained parked over the Tanana Valley, keeping temperatures from
bottoming out there. Under the stratus deck areas of light snow
are being reported. A front will push across the Central Interior
early Sunday morning weakening as it continues towards the AlCan
border. Light snow will accompany this front with accumulations of
1 to 2 inches. Attention then shifts to a powerful front moving
across the Interior as early as Sunday night, with heavy snow
transitioning to rain across the Central Interior. Across the
higher elevations of the Interior from the White Mountains north,
precip will stay all snow, with heavy accumulations likely. Strong
south winds develop across the Alaska Range as a strong pressure
gradient develops. South winds of 25 to 45 mph with gusts to 70
mph possible through Alaska Range passes. High Wind Watches remain
in effect. These strong winds and associated warmer air will
likely erode the cold air in place over the southern Interior and
Tanana Valley, at some point Monday morning, causing freezing
levels to rise and precip to change over to all rain across the
Central Interior. Heavy snow across the Fairbanks area will
likely turn to brief freezing rain and then transition to all
rain sometime Monday morning. Freezing levels are currently
projected to be around 1700-2200 feet on Monday afternoon. Above
that, expect heavy wet snow. Rain turns back to snow Monday night
as cold air pushes in. Snow totals remain difficult to pin down,
but the highest amounts will be in hills and summits above 1800
feet, where snow amounts will likely exceed a foot. Across the
Middle Tanana Valley total snow accumulations of 6 to 10 inches
are possible. QPF totals range from three quarters of an inch to
an inch and a half across the Central Interior extending east
across the Middle Tanana Valley and north to the south slopes of
the Central Brooks Range, further east, QPF totals will be less,
ranging from three tenths of an inch in Arctic Village to less
than two tenths at Northway.

Extended Forecast Days 4-7...On Wednesday, a cold upper trough will
still be in place over the Mainland with cold air advection and
blustery west winds moving across the Mainland. Snow showers will be
fairly widespread. Weak high pressure and arctic troughing looks to
remain in place into the weekend with cooling temps and continued
chances for light snow. The Pacific storm track will remain well to
the south.

Coastal Hazard Potential Days 3 and 4...Strong south to southwest
winds associated with a powerful front moving across the Bering
will produce elevated water along the coast beginning Sunday
evening, with coastal flooding possible all along the West Coast,
as well as along the Arctic Coast east to Utqiagvik. A Coastal
Flood Warning is in effect for the Northern Arctic Coast, where
water levels are expected to be 2 to 3 feet above normal high tide
Sunday night into Tuesday. Coastal Flood Advisories are in effect
for the Western Arctic Coast from Sunday afternoon through Tuesday
afternoon and Northwestern Arctic Coast from Sunday night through
Tuesday afternoon for water level rises of 4 to 6 feet above the
normal high tide line. Coastal Flood Warnings have been issued for
Eastern Norton Sound, where water levels are expected to rise 8 to
12 feet above the high tide line and the Yukon Delta Coast for
water levels of 5 to 8 feet above the high tide line with Coastal
Flood Advisories in place for the remainder of the West Coast
coastline.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...High Wind Warning for AKZ801.
     Coastal Flood Advisory for AKZ801-815>818-820-822.
     Coastal Flood Advisory for AKZ802.
     High Wind Watch for AKZ847-849.
     Winter Storm Watch for AKZ812-813-831.
     Winter Storm Watch for AKZ814.
     High Wind Warning for AKZ815.
     Winter Storm Watch for AKZ819.
     Coastal Flood Warning for AKZ803.
     High Wind Warning for AKZ821-827.
     Coastal Flood Advisory for AKZ821-827.
     Coastal Flood Warning for AKZ824.
     Coastal Flood Warning for AKZ825.
     Winter Storm Watch for AKZ832.
     Winter Storm Watch for AKZ834-838-842.
     Winter Storm Watch for AKZ839>841-843>845.
     Winter Storm Watch for AKZ847-848.
PK...Small Craft Advisory for PKZ807.
     Small Craft Advisory for PKZ809-815.
     Small Craft Advisory for PKZ810-857-861.
     Small Craft Advisory for PKZ811.
     Small Craft Advisory for PKZ812-817-850.
     Small Craft Advisory for PKZ814-860.
     Heavy Freezing Spray Warning for PKZ814-860-861.
     Heavy Freezing Spray Warning for PKZ815.
     Small Craft Advisory for PKZ816.
     Gale Warning for PKZ851.
     Small Craft Advisory for PKZ854.
     Small Craft Advisory for PKZ855.
     Small Craft Advisory for PKZ856.
     Small Craft Advisory for PKZ858.
&&

$$