Graphical Hydro Meteorological Discussion

084
FXAK68 PAFC 190202
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
502 PM AKST Mon Nov 18 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Wednesday night)...

Key Messages:

* Widespread windy conditions will develop across Southcentral
this evening and persist into Tuesday. The strongest winds are
expected in the Matanuska Valley, and Thompson Pass/Valdez
areas. Areas of blowing and drifting snow are also likely along
area roadways.

* Air Temperatures and Wind Chills will continue to trend lower,
bringing the coldest air of the winter to Southcentral.

* The cold air outbreak will not be long-lived, with warming
temperatures during the latter half of the week. Dry conditions
will persist through the end of the week and perhaps beyond.

The highly amplified upper level flow over Alaska will continue
with a strong ridge over the Bering and a trough extending from
eastern mainland Alaska southward to the Northeast Pacific. The
approaching upper ridge from the west will bring deep northerly
flow over mainland Alaska with cold air advecting southward across
Southcentral and into the Gulf. This is leading to gusty gap
winds through mountain passes as well as bays along the coast. As
the surface low in the Gulf continues to exit southward, the
strong pressure gradients across Southcentral continue to
strengthen as high pressure builds over interior Alaska. Further
maintaining the gradient is a short-wave trough digging southward
across the eastern Interior toward the Copper River Basin tonight
into tomorrow evening, allowing for widespread windy conditions
and sub-zero wind chill temperatures through tomorrow afternoon.

Models are in good agreement on the track of the mentioned upper
level short-wave digging southward across the state and continuing
into the Gulf late tonight/early Tuesday. The passage of the
trough will enhance winds across the region, with strong northerly
flow, cold air advection, and subsidence behind the trough. Given
the track east of the Valdez/Cordova areas, as well as the timing
of forcing mechanisms for winds not being in sync, winds will be
gusty but should not strengthen enough to become damaging for
these areas. A High Wind Warning continues through early Tuesday
morning for Thompson Pass (75 mph gusts). The forecast for strong
winds across the Matanuska Valley and down Knik Arm toward north
Anchorage is on track, though the onset has been slightly slower
than expected. Regardless, winds are expected to pick up this
evening and persist through tomorrow morning. The special weather
statement highlighting the likelihood of blowing snow continues
into tomorrow morning as blowing and drifting snow across roadways
and reduction in visibility remains a threat.

Winds and sub-zero wind chills will begin to subside Tuesday
morning through Tuesday afternoon as the upper level ridge builds
in from the west. Closer to the coast, pressure and thermal
gradients will persist allowing for coastal gap winds to linger
through mid week. By Wednesday, warm air aloft will move in with
the upper level ridge. This will gradually warm temperatures
everywhere, with the most aggressive warming taking place in the
mountains. Below-zero low temperatures are expected to persist
through midweek for portions of the Copper River Basin as the
existing cold airmass in place is slow to warm up.


&&


.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Monday Night through Thursday)...

Key Points through mid-week:

* Strong winds through the gaps and passes from Cold Bay to Port
Heiden into tonight, decreasing by Tuesday morning.

* The first Arctic air mass moves over Southwest Alaska this
evening.

* Strong high pressure brings warm air to the Aleutians, Bering
Sea and most of Southwest Alaska late tomorrow through mid-
week.

An incredibly large ridge stretching from the Western Aleutians,
northwest trough the Bering, will continue to dominate the
weather pattern for the week. Overnight a weak upper level wave
will slide across the northern peripheries of the ridge, bringing
an increased chance for light snow showers to the Pribilof
Islands. This northerly wind regime, with mostly clear skies,
will bring in an incredibly cold temperatures across the interior
tonight. One caveat is where clouds linger and do not thin out
this evening, they will stick around overnight helping to keep
temperatures up.

Starting Tuesday afternoon, the previously mentioned upper level
disturbance will lower clouds along the Y-K Delta and produce
flurries. No snow accumulation is expected as the atmosphere won`t
be organized for efficient snow production. As the week pushes
on, the upper level ridge will keep inching east. A surge of
warmth is expected as this happens. Daytime highs from Tuesday
will go from the lower single digits to middle and upper 20`s by
Thursday. The lower level warmth will be maximized between H92 and
H85, anomalously reaching the 95th to 100th percentile (or
record) for temperature around the November 22-23rd date.

For the western Bering, the ridge of high pressure will have
transitioned east come Wednesday to Thursday. A weak area of low
pressure will shoot north out of the Pacific, crossing Shemya by
Thursday afternoon. Winds will increase to the east of this low as
a warm front lifts across the Aleutians, bringing more warmth and
rain.

&&

.LONG TERM FORECAST (Days 4 through 7: Friday through Monday)...

On the Alaska Weather map, high pressure muscles its way across
the Southern half of the state through the forecast period. This
ridge brings light winds, dry conditions and more moderate
temperatures in the zonal flow across most of the state through
the weekend, although coolest overall temperatures should linger
over the Eastern Interior through Monday. Precipitation, if any,
will be light and intermittent through the weekend.

The most active weather is expected across the Western Aleutians
and Bering, as a number of low and troughs ride up over the
Western flank of the ridge. These weak systems bring areas of
occasionally moderate rainfall and some gusty winds. Forecast
models indicate weak waves through the weekend, but stepping up by
the new week with more developed lows working into the pattern
from the North Pacific Sunday into Monday. These stronger lows
bring locally heavy rains and gustier winds up to gale force over
the Western Aleutians and Bering, drifting into the Central
Aleutians and Bering for Monday.


&&

.AVIATION...

PANC...VFR conditions will persist. The development of the gusty
northerly winds was delayed this afternoon, but once they do
finally develop, expect winds to steadily strengthen and during
the overnight hours. The strongest core of winds will come out of
the Matanuska Valley and down Knik Arm. However, there is nothing
to drive these winds all the way south to PANC. Thus, expect wind
gusts will peak right around 30 kts. Winds will then quickly
diminish during the day Tuesday as a ridge builds in from the
west.

&&


$$

686
FXAK69 PAFG 191351
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
451 AM AKST Tue Nov 19 2024

.SYNOPSIS...An impactful and highly amplified weather pattern
continues across northern Alaska with hazards in effect for strong
winds, heavy snow, blizzard conditions, and mixed precipitation. A
strong cold front currently arriving at the West Coast will bring
blizzard conditions north of the Bering Strait and to the Arctic
Coast west of Utqiagvik. The trailing warm front is only 6 to 9
hours behind the cold front and will turn snow into a mix of snow,
rain, and freezing rain for most areas along the coast south of
Kivalina later today. The fronts will weaken as they move into the
Interior, though light freezing drizzle is still possible in the
Tanana Valley Wednesday and Wednesday night as the warm front
arrives. Very cold temperatures in the Interior this morning will
warm rapidly this afternoon as cloud cover arrives from the west.

.KEY MESSAGES...

Central and Eastern Interior...

- There is a slight chance of freezing drizzle on Wednesday across
the Tanana Valley, however, forecast uncertainty remains high on
if precipitation will reach the surface. Widespread impacts are
not expected at this time.

- Southeast winds at Eagle will gust to 40 mph with wind chills as
low as 45 below zero. A Wind Advisory remains in effect Tuesday
night through Thursday morning.

- Southwest winds over Eagle Summit will gust to 45 mph late
Tuesday night and Wednesday, which will bring blowing snow and
difficult travel conditions.

North Slope and Brooks Range...

- Multiple Blizzard Warnings have been issued for the North
Central Brooks Range over to the NW Arctic Coast with wind gusts
up to 75 mph, snow accumulations up to 7 inches, and blowing
snow. Winds will gradually diminish Wednesday morning but
snowfall is expected to continue.

- Winter Storm Warnings have been issued for the Noatak Valley
and Lower Kobuk Valley with snow accumulations up to 10 inches,
ice accumulations up to a light glaze, wind gusts up to 50mph,
and blowing snow.

- High Wind Warning has been issued for the Central Brooks Range,
primarily for Anaktuvuk Pass with sustained south winds up to
40mph and winds gusts up to 65mph expected Tuesday morning
through Wednesday morning.

- Minor coastal erosion is possible west of Utqiagvik today
through Wednesday to to strong southwest winds causing slightly
elevated water levels.

West Coast and Western Interior...

- Multiple Blizzard Warnings remain in effect from Point
Hope southward to Kotzebue Sound to the Bering Strait Coast
Monday night into Wednesday with wind gusts up to 55 mph, snow
accumulations up to 6 inches, and blowing snow. Main concern
will be a brief period of freezing rain resulting in a light ice
glaze along the Bering Strait and Seward Peninsula Coast on
Tuesday and Wednesday.

- A High Surf Advisory remains in effect from Kivalina and Red
Dog with minor coastal erosion expected with water levels
reaching up to 2 to 4ft above the normal high tide line starting
Tuesday night into Wednesday.

- For the Western Interior and Yukon Delta, multiple Winter
Weather Advisories have been issued with snow accumulations up
to 4 inches, ice accumulations of a light glaze and wind gusts
up to 45 mph.

- Elevated water and minor coastal erosion, along with the
potential for ice moving up onto the beach today and tonight
mainly north of the Bering Strait.

&&

.DISCUSSION...High pressure is firmly in place over Interior
Alaska, centered just north of Dawson City, Yukon at 1044 mb.
Another surface high, this one highly anomalous, lies over
Nikolski at 1042 mb. A sharp upper level ridge is anchored around
this high, with Interior Alaska under cold northerly flow on the
east side of the ridge. A 990 mb low is located near Wrangel
Island this morning with a cold front extending southeast and
along with West Coast north of the Yukon Delta. The warm front for
this system trails by only 6-9 hours and will cause much of the
hazardous weather, bringing mixed precipitation to the West Coast
and eventually the possibility of freezing drizzle to the
Interior. Winds with the cold front will be quite strong, mostly
Gale Force across the entire West Coast and North Slope with
localized Storm Force winds. Cape Lisburne has gusted as high as
87 mph so far this morning.

Both the cold and the warm fronts will weaken substantially as
they move into the Interior Tuesday through Wednesday. A
secondary cold front will plow into the Western Arctic Coast on
Wednesday, bringing additional snowfall and blizzard conditions.
By Thursday, the remnants of this front will move over the
Interior, turning the precipitation type back to snow. The ridge
aloft bring dry conditions for most all of the area on Friday.

We made minor edits in the forecast on winds to match current
observations as well as on precipitation types. We adjusted some
precip types based on the latest model guidance and added a slight
chance of freezing drizzle to the Tanana Valley Wednesday
afternoon and Wednesday night. Added a Winter Weather Advisory for
mixed precipitation to for St. Lawrence Island in effect through
1pm Wednesday and cancelled the Winter Weather Advisories through
Alaska Range Passes as conditions have improved there, though it
remains breezy from the north.

Coastal Hazard Potential Days 3 and 4...Strong southwest to west
winds develop Tuesday and persist into Wednesday across the West
Coast and north to Utqiagvik. These winds will result in elevated
water and minor beach erosion mainly north of the Bering Strait.
A High Surf Advisory is in effect for Kivalina and Red Dog Dock.

Extended Forecast for Days 4 Through 7...The highly amplified pattern
looks to continue and bring more active weather to the area. A
strong upper level ridge will dominate Friday before a shortwave
will attempt to weaken the ridge from the west on Saturday and
Sunday. This feature is looking to be more and more successful
with each model run and will likely spread additional mixed
precipitation to the West Coast on Saturday and snow to the
Interior on Sunday. Models diverge thereafter, but generally
indicate continued ridging which will bring strong inversions to
the Interior. Minor perturbations working through the zonal flow
will result in scattered periods of precipitation, particularly
for the North Slope and West Coast.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Blizzard Warning for AKZ801-806-807-815-817-820-821.
Blizzard Warning for AKZ802-803.
Winter Storm Warning for AKZ814-816.
High Surf Advisory for AKZ815.
Winter Weather Advisory for AKZ818-823>826.
Winter Weather Advisory for AKZ819-828>830.
Winter Weather Advisory for AKZ822.
Winter Weather Advisory for AKZ827.
Winter Weather Advisory for AKZ804.
Wind Advisory for AKZ835.
High Wind Warning for AKZ809.
PK...Small Craft Advisory for PKZ801-802-850-853.
Heavy Freezing Spray Warning for PKZ802-807.
Brisk Wind Advisory for PKZ803-805.
Gale Warning for PKZ804-852.
Gale Warning for PKZ806.
Gale Warning for PKZ807-817-854-856-858.
Gale Warning for PKZ808-855.
Gale Warning for PKZ809.
Gale Warning for PKZ810.
Storm Warning for PKZ811-857.
Gale Warning for PKZ812.
Brisk Wind Advisory for PKZ813-814-860.
Brisk Wind Advisory for PKZ815.
Gale Warning for PKZ816.
Gale Warning for PKZ851.
Heavy Freezing Spray Warning for PKZ852.
Heavy Freezing Spray Warning for PKZ853.
Heavy Freezing Spray Warning for PKZ856.
Gale Warning for PKZ859.
Brisk Wind Advisory for PKZ861.
&&

$$

CHRIEST

620
FXAK67 PAJK 191318
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
418 AM AKST Tue Nov 19 2024

.SHORT TERM...Little changes were made to the forecast this
morning with the ongoing outflow pattern. Temperatures were
brought up just slightly as most locations have not cooled off as
quick as originally thought. Otherwise the going trend remains the
same with outflow winds increasing and cold temperatures for the
panhandle for the week. Even with the bump in temperatures,
conditions are still on track for the Cold Weather Advisory for
the Klondike Highway tonight. Some snow showers continue this
morning for the southern panhandle but should taper off through
the morning hours.

Outflow winds are expected to increase through Wednesday which
will bring windy conditions to locations that are favored.
Elsewhere, light winds will allow for radiational cooling to be
more pronounced during the overnight hours.

.LONG TERM.../Thursday through Tuesday/...The end of
the week and into the weekend will begin a transition from the
cold, dry, and windy northerly outflow conditions as the blocking
pattern over the region begins to break down. Diminishing pressure
gradients as the Yukon high and Low off the coast of Washington
state weaken. Winds will remain elevated into Friday with gales
over the inner channels and overland gusts in the 35 to 45 mph range
then the drop off Saturday into Sunday. Watching for any shortwaves
the might track down on lee side of the AK Gulf high Sunday into
Monday. Ensembles have light precip starting Monday but still
significant spread amongst the operational models at that time. As
the week progresses increasing probability of the next weather front
tracking in. But as with the early part of the week, operational
models have a much larger spread than ensembles. With the cold air
in place and a warm moist mid level air mass to the west behind the
ridge over running snow events are not out of the question.

&&

.AVIATION...LLWS through places like Lynn Canal, Stephens
Passage, and the Stikine River Valley. This includes the
communities of Skagway, Haines, Juneau and Wrangell as outflow
winds strengthen. Snow showers Tuesday morning for the southern
panhandle give way to widespread VFR spread to all of SE AK.


&&

.MARINE...Outflow winds will peak Tue night into Wed as strong
low pressure near Western Washington moves slightly offshore and
high pressure in Canada moves eastward, tightening the existing
pressure gradient. This combined with strong CAA near the northern
panhandle at 925-850 mb will result in storm force winds for Lynn
Canal and gales in Clarence Strait, Taku Inlet, Disenchantment
Bay, parts of Stephens Passage, and possibly the upper arms of
Glacier Bay. During the latter half of the week, strong
northerlies in Lynn Canal for an extended period of time will
generate fully developed seas near Point Retreat and southward
into northern Clarence Strait. On Wednesday into Thursday,
southern swell to 10 ft, generated from a storm far to the south
near the western coast of Washington State. With northerly winds
out of Clarence Strait, areas of combined seas up to 15 ft or
higher will be present offshore of PoW Island >15 NM.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 6 AM AKST this morning through late tonight for
AKZ318.
Cold Weather Advisory from 11 PM this evening to 9 AM AKST
Wednesday for AKZ318.
Strong Wind from this evening through late tonight for AKZ325.
Winter Weather Advisory until 5 AM AKST early this morning for
AKZ328.
MARINE...Storm Warning for PKZ012.
Gale Warning for PKZ013-022-031>033-053-641>644-651-661>664-671.
Small Craft Advisory for PKZ011-021-034>036-652-672.

&&

$$

SHORT TERM...SF
LONG TERM....PRB
AVIATION...GFS
MARINE...NC


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