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424
FXAK69 PAFG 172346
AFDAFG
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
346 PM AKDT Thu Oct 17 2024
SYNOPSIS...
Snow and blowing snow will be the main highlight over the E Arctic
the next couple of days. Quieter but much colder weather will
settle in over the Interior as temps plummet into the single
digits (with some below zero sprinkled in) over the E Interior
where arctic high pressure will build in. A weak front brings snow
and mixed precip to the West Coast Friday and Saturday, with that
front bringing light snow to the Interior and Fairbanks by
Saturday night into Sunday.
A powerful storm will roll into the West Coast Sunday and then
move across the Interior Monday through Wednesday, which will
bring widespread impacts to the Mainland.
DISCUSSION...
Upper Levels and Analysis...
There is a large upper trough carving itself out across the
Mainland and Yukon, with the center currently over the Canadian
Archipelago with a height of approximately 510 dam. Open ocean
extends into the high arctic, and snow showers with cold arctic
air moving across it are impacting most of the Arctic coast. 850
hpa temps over the Mainland range from -9C to -16C, which is the
coldest airmass of the season thus far.
Central and Eastern Interior...
Shallow snow showers continue cross the S interior and Alaska
Range with weak upslope flow coincident with marginally sufficient
moisture. Cloud coverage has continued to decrease this
afternoon, which will allow overnight temps to plummet tonight, as
well ast tomorrow night. Expecting widespread single digit lows
Fri and Sat morning, with some below zero temps in the typical
cold spots like Goldstream, Yukon Flats, etc.
A weak front will move into the Interior from the west later on
Saturday and through Sunday, bringing light snowfall to the
Interior, with an inch possible in lower valleys, and maybe a
couple inches in higher elevations.
West Coast and Western Interior...
A weak trough moving into western Alaska tonight is expect dto
bring light snow showers extending from the Seward Peninsula north
through Kotzebue to Point Hope. Accumulations with this first
wave will be minimal, generally less than an inch. On the heels of
this first wave is another weak frontal system which will impinge
upon the coast Friday Night into Saturday, bringing light snow
showers mixed with rain along the coast, with predominantly all
snow over the Interior and higher elevations. Snow amounts look to
be in the 1 to maybe 2 inch range, with this front exiting
Saturday night as the next much more powerful and impactful storm
moves in Sunday. This will be detailed more in the extended
section of this discussion, as well as in the Special Weather
Statement.
North Slope and Brooks Range...
Broad troughing and northwest flow across open waters will provide
plenty of instability driven ocean-effect snow shower activity
along the coast, especially across the E Arctic and down the
Dalton Hwy and into the E Brooks Range. Expect an additional 1 to
2 inches along the Arctic coast, with 1 to 3 for the Dalton Hwy
Corridor and higher elevations of the E Brooks Range. The bigger
story will be increasing west winds to sustained gale force from
Point Thomson to Kaktovik, which will support blizzard conditions,
thus the blizzard warning will remain in effect until Friday
afternoon for whiteout conditions. A weakening frontal system will
bring additional snow to the far Western Arctic on Fri night and
Sat and will move east into Sunday, bringing light snowfall to the
western half of the arctic and Brooks Range.
Extended Forecast Days 4-7...
A major late fall/early winter storm along with coastal storm
impacts will move into the West Coast on Sunday and then move
across the Interior Monday through Wednesday. Everything is
possible from 60+ mph winds along parts of the West Coast, heavy
rain, heavy mixed precip, and potential coastal flooding, along
with moderate to heavy snowfall across the Interior. The heaviest
snowfall will likely be in the Western and Central Brooks Range.
The big question mark will be the track of the warm front as the
degree of warm air over the Interior will be the deciding factor
between all snow, or a mix of rain/snow, or possibly even plain
old rain. Right now, there is less global model and ensemble
forecast clustering than there was yesterday, with a large percent
of the global ensemble guidance trending toward a stronger warm
front across the Interior, which could result in a changeover to
rainfall for parts of the S Interior, with heavy accumulating snow
further inland and across the higher terrain. Some of the guidance
remains less amplified and maintains a cooler/weaker warm frontal
progression, which would suggest less mixing to rain and more
snowfall. Bottom line, the Mainland from the Brooks Range south,
and along the West Coast will see a strong storm Sunday through
Tuesday, with impacts possibly lingering into the middle to end of
the week.
The one addition to this forecast is to add in a high wind watch
for the NW Arctic from Kivalina to Point Hope, where there is high
confidence in wind gusts of 65+ mph or higher.
Coastal Hazard Potential Days 3 and 4...High surf and coastal
flooding are likely Monday and Tuesday as a strong low moves
inland. At this time, the areas that will likely be most impacted
are from the Bering Strait to Point Lay, though the YK Delta and
Norton Sound will also see elevated water levels and possible
coastal flooding.
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Coastal Flood Watch for AKZ801-815>818-820>822-824-825.
High Wind Watch for AKZ801.
Coastal Flood Watch for AKZ802-803.
Winter Storm Watch for AKZ813.
Winter Storm Watch for AKZ814.
High Wind Watch for AKZ815.
Coastal Flood Watch for AKZ827.
Blizzard Warning for AKZ805.
PK...Small Craft Advisory for PKZ810.
Small Craft Advisory for PKZ811.
Small Craft Advisory for PKZ814-860.
Heavy Freezing Spray Warning for PKZ814.
Gale Warning for PKZ815-861.
Heavy Freezing Spray Warning for PKZ815.
Small Craft Advisory for PKZ856.
Small Craft Advisory for PKZ857.
Heavy Freezing Spray Warning for PKZ860.
Heavy Freezing Spray Warning for PKZ861.
&&
$$
828
FXAK68 PAFC 180036
AFDAFC
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
436 PM AKDT Thu Oct 17 2024
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Today through Sunday morning)...
Cool northerly flow continues this afternoon, with gusty gap
winds along coastal mountains, including passes near Whittier,
Seward and Valdez. By this evening, colder air continues to
stream down from the north with the passage of the next
shortwave. This should allow strong winds to develop out of Broad
Pass and the Mat Valley while strong winds continue nearly steady
state in and around Valdez, Thompson Pass and the Copper River
Delta.
Northerly gap winds will reach peak intensity Friday as a low
moves into the southeastern Gulf while the upper ridge in place
over the Bering and western Mainland amplifies and encroaches into
Southcentral from the west. Wind gusts on Friday will peak near
40 to 55 mph across parts of the Matanuska Valley, while Valdez
could see intermittent gusts as high as 55 to 65 mph through
Friday night. Given dry conditions and a general lack of low
elevation snow cover, areas of blowing dust will be possible with
the strongest winds blowing out of the Mat Valley and the Copper
River Delta. Some minor blowing and drifting of snow will also be
possible through Thompson Pass with winds gusting up to 65 mph
through Friday night.
On Saturday, the pattern shifts as the Gulf low dissipates and
the upper level ridge over the Bering expands east into
Southcentral. Prevailing upper flow will weaken and become
northwesterly through Sunday morning, allowing gap winds to
weaken along the northern Gulf, but persisting south of Shelikof
Strait and across the Cook Inlet entrance through late Sunday
night.
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3)...
As the cold air mass remains over Southwest Alaska, temperatures
remain cold with lows in the 20s and upper teens for the next
couple of nights. A front will pass through the Kuskokwim Delta
region on Saturday, allowing for a chance of mixed precipitation
closer to the coast and light snowfall further east near Aniak.
Accumulations will be light at around 0.5 to 1 inch. Warm air
advection follows behind the front, increasing temperatures above
freezing and transitioning any snow still falling to rain.
The low that has affected the central Aleutians will be
assimilated into a new low that will traverse to the Gulf of
Alaska. The interaction between this low and a broad ridge over
the Bering allows for favorable wind directions and pressure
gradients for near gale force gap winds in the Eastern Aleutians
and the Alaska Peninsula on Friday. A front will pass through the
western Aleutians early Friday, kicking off higher chances for
precipitation and small craft winds for that region. This front
will erode near the Central Aleutians and strong ridging will
build in, keeping conditions calm and drier.
On Sunday, a deep Siberian low`s front will move into the Bering.
Heavier precipitation as well as gale force winds will accompany
this front as it traverses through the Bering Sea, the Aleutian
Islands and eventually the Kuskokwim Delta. The southwesterly gale
force winds from this front combined with high tide has the
potential for flooding along the Kuskokwim Delta coast on Monday.
&&
.LONG TERM FORECAST (Days 4 through 7: Monday through Thursday)...
The upper level ridge stretching from the Arctic through the
Eastern Interior to the Gulf of Alaska crosses the Canadian Border
on Tuesday. A strong Arctic low moves from the Chukotsk Peninsula
into the Canadian Arctic through the forecast period. Stretching
from this down to the Aleutians low is a well developed trough
that moves to the Eastern Mainland by Thursday. Gradient remains
substantial after the trough passage, with a long slightly
cyclonic fetch extending to Eastern Asia. A well clustered GFS /
ECMWF / UKMET and Canadian ensemble carries the continuity of the
features through midweek before uncertainty rears up once the
larger features have moved on.
The surface weather map brings in a moderately strong front that
moves into Western Alaska late Monday. Widespread windy conditions
with gale force gusts and locally heavy rain marches across the
Western Bering Sunday. Areas of gale force winds continues across
the Central to Northern Bering around St Lawrence and St Matthew
Islands through Tuesday, diminishing Wednesday. This system
continues spreads over the Western Alaska coasts with the
possibilities of local coastal flooding late Monday and Tuesday.
As the front moves inland, rain becomes mixed with snow or changes
to all snow over the Interior and Northern slopes of the Alaska
Range by Wednesday. The downwind precipitation shield reduces the
chances of rain or rain and snow mixed across Southcentral Alaska
through midweek. A surface low develops on the front in the Gulf
on Wednesday, increasing the chance for rain or rain-snow mixed to
spread across Southcentral Alaska through Thursday.
&&
.AVIATION...
PANC...VFR conditions will persist. Northerly winds 10 to 15 kt
with occasional gusts to 25 kt are expected through Friday.
&&
$$
913
FXAK67 PAJK 172302
AFDAJK
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
302 PM AKDT Thu Oct 17 2024
.SHORT TERM...Cold air and overrunning moisture have allowed for
the first snows of the year for Haines and Skagway this morning.
Cold air from Canada continues to move into the Northern Panhandle
this afternoon and moisture from the Gulf of Alaska continues to
overrun this cold air. With this overrunning, we are seeing snow
still being reported in the Haines and Skagway area. As we head
through the evening and overnight hours, the cold air is expected
to work farther south down Lynn Canal. This cold air combined with
moisture being pushed over the area will allow for most places to
see a cold rain overnight witht the exception of the northern
panhandle. The Icy Strait corridor could see a mix of rain and
snow during the evening and overnight hours with this cold air
moving in. If the precipitation rates are strong enough, a
complete switch over to snow would not be out of the question as
well as seeing some light accumulation. But overall thinking is
that there will be little to no accumulation otherwise.
Farther south, the winds are expected to increase tomorrow as a
stronger low approaches the area from the south before moving inland
near the Dixon Entrance. This will bring another shot of moisture to
the area as well as increase wind speeds through the Inner Channels.
The heaviest moisture looks to remain south of the area for Friday
and into Saturday morning. But a transient low will remain over the
northern Gulf heading into the weekend allowing for a general
unsettled weather to continue into the start of the weekend.
.LONG TERM.../Saturday through Tuesday/...Saturday begins the
outflow pattern with NW flow aloft and a surface low pressure
system passing over/slightly south of the southern panhandle.
Strong breezes to near gales out of Lynn Canal, Taku Inlet, and
the upper arms of Glacier Bay are likely as the low passes south.
With the winds comes the cold as well: temperatures will dip into
the mid 20s by late Sunday and through Monday morning for the
northern half of the panhandle and likely get to at least below
freezing for the southern panhandle. In sheltered areas such as
the back of Mendenhall Valley, temperatures could dip as low as 20
degrees.
The pattern will shift yet again on Tuesday as a frontal band from
a potent system far up near the north slope will push all the way
over from the Bering Sea over the SE AK. Currently, this system
looks to bring rain and snow transitioning to all rain as
southerly flow becomes dominant. No major accumulations of snow or
rain is expected.
&&
.AVIATION...Deteriorating conditions across much of the panhandle
as two separate weather systems impact the region. Across the
north, areas like Skagway and Haines will see lower ceilings and
reduced visibilities as snowfall continues into Friday. Across the
southern half of the area, some LLWS is expected as a separate
system brings rain, wind, and by late Thursday night into Friday,
diminishing ceilings. MVFR conditions across the N half of the
area, dipping into IFR occasionally during periods of heavier
snowfall are expected, while MVFR conditions will linger for
longer in the S half of the area.
&&
.MARINE...A weak low in the northern gulf and high pressure in the
Yukon have allowed for a outflow situation to develop in the
northern inner channels. A second low is expected to move up from
the Northern Pacific bringing increased winds ands seas to the area
as it passes through the Dixon Entrance area. Current thinking is
that the strongest winds will be storm force but will remain south
of the area in Hecate Strait. Gales are expected to move into
Clarence Strait. Heading into the weekend, outflow conditions look
to expand across the area as we head into the start of next week.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory from 10 PM this evening to 1 PM AKDT
Friday for AKZ318-319.
Small Craft Advisory until 4 PM AKDT this afternoon for AKZ322.
MARINE...Gale Warning for PKZ651.
Small Craft Advisory for PKZ012-013-021-022-031-032-036-053-
641>644-661>664-671-672.
&&
$$
SHORT TERM/MARINE...SF
LONG TERM....NC
AVIATION...GFS
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