Graphical Hydro Meteorological Discussion

907
FXAK68 PAFC 040055
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
455 PM AKDT Thu Apr 3 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Tonight through Sunday)...

High pressure extending west from Canada has afforded mostly
sunny skies that have allowed temperatures to warm into the 50s
across most of Southcentral Alaska, with some locations
approaching 60 degrees this afternoon. The pleasant weather will
deteriorate somewhat as a large low pressure system swirling in
the North Pacific lifts its occluded front to the Southcentral
coast tonight. The front will start to bring rain and some high
elevation snow to Kodiak Island as early as this evening before
spreading north into the Kenai Peninsula overnight as it stalls
out there through the weekend. The vast majority of impacts from
this storm will be along the coast, with easterly winds to gale
force over the northern Gulf of Alaska and moderate to heavy
rainfall. Snow levels will remain fairly high, starting out at
around 1000 to 1500 feet early Friday morning, then rising 1800 to
2500 feet by late Friday. Thus, snow should not be a big issue
along the road system.

Inland areas will remain mostly dry with strong downsloping flow,
though there could be an occasional brief period of light
precipitation as weak upper short-waves track inland. The first
chance for this appears to be tonight with the initial arrival of
the front bringing potential for light precipitation sweeping
north across interior areas through Friday morning. Similarly
expecting another shortwave to lift across the region Friday
night, with greater potential for some rain or snow, with
temperatures forecast to drop into the low to mid 30s, in the
Copper Basin. Otherwise, temperatures will remain above normal,
with a trend toward above freezing night-time temperatures due to
extensive cloud cover. By Sunday, an upper- level low elongates
across Western Alaska leading to weaker cross-barrier flow over
Southcentral and enhanced potential to draw moisture into inland
areas resulting in increased chances for precipitation.

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3: Today through Sunday)...

...Key Messages...

1) A Winter Storm Warning is in effect from 7AM Thursday to 4PM
AKDT Friday for the Eastern Aleutians.

2) A Blizzard Warning is in effect from 10PM Thursday to 7PM
AKDT Friday for the Kuskokwim Delta Coast and Nunivak Island.

3) A Special Weather Statement has been issued for the Pribilof
Islands from 1AM Friday to 7PM Friday for snowfall and strong
winds.

Currently, an upper level low over the Central Bering is aligning
well with a secondary upper low steadily approaching the region
from the North Pacific. This has formed an intense deformation
band of rain and snow for areas such as Nikolski and Unalaska.
Some of this moisture is spreading northward as the precipitation
on its northwestern flank pivots more so to the north and west
ahead of the low`s front paralleling the Aleutian Chain. In
combination with cold air advection on the backside of the surface
low, widespread gales and storm force wind gusts are impacting
the Eastern Aleutians, which is resulting in significant gap wind
gusts of 45-55+ kts through mountainous areas near Unalaska and
Akutan. Conditions should deteriorate following an expected peak
Friday morning. Accumulations of 10-18" of snow with winds
gusting upwards of 60 mph is likely for these areas by midday
Friday to Friday afternoon, with localized areas of 20"+ not out
of the realm of possibility. On the other hand, a robust southerly
to southeasterly flow will keep temperatures elevated into the
upper 30s to lower 40s for Sand Point eastbound, making this
primarily a rain event for the AK Pen and Southwest.

Snowfall also begins to spread northward by late Thursday to early
Friday, and conditions quickly start to go downhill for Nunivak
Island and the Kuskokwim Delta coast, including areas such as
Kipnuk, Mekoryuk, and Toksook Bay. As snow begins to fill in and
winds increase into Friday morning, blizzard conditions are likely
for these areas, especially Nunivak Island. Given the proximity to
surrounding sea ice, Mekoryuk has the best chance of seeing
blizzard and whiteout conditions from this storm, but these
conditions are still expected to be felt inland along the
Kuskokwim coast. These conditions will persist throughout the day
on Friday and finally slowly begin to wind down on Saturday
morning, perhaps lingering into Sunday. Areas within the Blizzard
Warning are expected to see 5-9"+ of snow with winds gusting
upwards of 40 mph.

For the Pribilof Islands, blowing snow due to strong winds could
reduce visibility down to a half mile at times from Friday
morning into late Friday afternoon. There is still some
uncertainty with the models on just how far the edge of the
aforementioned band of snow pushes westward, so snowfall totals
are more in question than blowing snow potential due to a strong
30-40kt fetch of northerly winds forecast to affect the Islands.
Even with lesser amounts of snow than other areas, light snowfall
accumulations with strong winds can still create blowing snow
conditions. Model consensus continues to suggest 1-3" of snowfall
for the Pribilof Islands by Saturday morning. As such a Special
Weather Statement has been issued for the Pribilofs from Friday
morning through Friday evening.

-AM/CL

&&


.LONG TERM FORECAST (Days 4 through 7: Sunday to Wednesday)...

The most significant feature on the Alaska Weather map is an
elongated trough stretching from the Arctic through Interior
Alaska to the Gulf of Alaska through the forecast period. Closed
lows over Northern Alaska and the Gulf weaken through midweek.
Although there is some oscillation within the elongated trough,
there is little movement. Ridges over the Western Canadian
Provinces and the Bering also weaken through the period. Forecast
continuity remains good with a GFS / ECMWF / Canadian blend, but
minor differences with shortwaves gliding through the pattern
represent the variations and short term changes in forecast.

A moderately strong surface low over the Southern Gulf of Alaska
spreads locally heavy rainfall from the Eastern Aleutians over the
Alaska Peninsula through Monday. Gusty winds over the AKPEN
linger through midweek. Locally heavy rains marches across Kodiak
Island and the rest of Southcentral Coastal zones through
Wednesday. Areas of locally moderate snow spread over Southwest
Alaska into the Interior, and diminish through midweek. A well
developed low and front approaches the Western Aleutians for
Sunday, but dissipates to the South of the chain by Tuesday.

- Kutz

&&.AVIATION...

PANC...Southeasterly Turnagain Arm winds gusting to around 25 kt
(30 mph) will continue through this evening. After that, VFR
conditions and light winds will persist through tomorrow morning.


&&




$$

506
FXAK69 PAFG 032141
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
141 PM AKDT Thu Apr 3 2025

.SYNOPSIS...
A front brings more snow to the West Coast tonight through Saturday
with the highest amounts in the Yukon Delta. Light snow showers
reach the North Slope Friday evening and last through Monday.
Southerly winds across the Alaska Range are bringing warmer weather
to the Interior through the weekend. Generally quiet weather
expected early next week.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...
-Temperatures warm through Saturday with highs in the mid to upper
40s today from Fairbanks to the south and east. Temperatures
increase to around 50 Friday and Saturday with the highest
temperatures reaching potentially into the mid 50s just north of the
Alaska Range.
-Southerly winds increase through the Alaska Range with gusts up to
45 mph expected in Isabel Pass through Saturday with a brief period
of gusts reaching to near 50 mph possible overnight Saturday into
Sunday. Areas south of Healy will see lower speeds with gusts
reaching only into the 30-40 mph range.
-Some moderate northeasterly winds tonight through Friday across the
Yukon Flats and the Dalton Highway Summits. The strongest winds will
be across the Dalton Highway Summits with gusts up to 30mph through
Friday evening.
-Low temperatures fall below freezing for much of the Interior
resulting in freeze-thaw cycles through the weekend.

West Coast and Western Interior...
-Snow and blowing snow for the Yukon Delta Coast with a winter
weather advisory in effect. 4 to 6 inches of snow is expected to
fall across the delta from this evening through Saturday morning
with gusty northerly winds near the coast. Gusts up to 30 mph
generally expected with up to 40mph possible near Hooper Bay and
Chevak. Where these stronger winds overlap with falling snow
visibility is expected to fall to a half mile or less at times.
-The front bringing snow to the Delta will bring lesser amounts of 2
to 3 inches from the eastern Norton Sound through Ambler and into
the Western Brooks Range. This front will move east Saturday
afternoon and bring similar snowfall to the rest of the Western
Interior by Sunday evening.

North Slope and Brooks Range..
-Scattered light snow showers across the North Slope east of Point
Lay Friday with accumulations less than 1 inch. Snow becomes more
widespread Saturday and Sunday with accumulations 1 to 2 inches.
-Winds shift easterly midday Friday with the strongest winds from
Point Thompson east reaching up to gusts of 30 mph. Winds peak
overnight Friday into Saturday with winds 15mph and less across the
eastern North Slope Saturday and Sunday.
-There may be brief periods of reduced visibility due to blowing
snow where these scattered snow showers and stronger winds overlap
Friday.

&&

.FORECAST ANALYSIS AND DISCUSSION...
At the surface the last remnants of the system that brought snow to
the Interior and West Coast this week moves northeast into Canada.
Pressure builds in the Interior from the southeast as this system
exits. A 977mb low south of Kodiak Island extends a front north into
the YK Delta this evening and stretching north to Ambler and the
Central Brooks Range by Friday afternoon. This will provide moderate
snowfall to the Yukon Delta Coast tonight through Saturday morning
and lesser amounts north of the delta. Northerly winds increase on
the western side of this feature through the Bering Strait and along
the YK Delta Coast and easterly winds increase across the North
Slope tonight as air is pulled across the state into the low. Some
moderate northeasterly winds across the Interior Friday, especially
at higher elevations and along the Dalton highway summits, helping
to feed into the low, but the front moving east Saturday afternoon
will cut off this flow in the Interior and weaken the winds on the
West Coast and North Slope.

Aloft, there is a 494 dam low in the high Arctic and a 550 dam ridge
over Canada and the eastern Interior today. A 512 dam low south of
Kodiak Island is creating a broad trough from the Arctic, through
the Bering Strait, and into the Northern Pacific. As this trough and
the ridge push against each other creating southerly flow across the
Alaska Range and keeping temperatures warm in the Interior. There
will be some moderate gap winds through Alaska Range passes with
wind gusts peaking at 35-45 mph. This pattern holds steady through
the weekend, but Sunday night into Monday an upper level shortwave
low out of eastern Siberia moves south and east towards the West
Coast accelerating ridge breakdown early next week. Models are in
very poor agreement on this feature with the GFS and NAM having
solutions significantly further north than the ECMWF and Canadian
solutions, however all models are showing a pattern of broad
troughing across the region by midweek with generally benign weather
expected.

&&

.EXTENDED FORECAST DAYS 4-7...
Model disagreement is high, but broad troughing across the area is
expected following ridge breakdown early next week. Some light snow
is possible across most of the area by the end of next week, but
details are very uncertain. It should be significantly lighter than
what the West Coast and Interior experienced this week given
significantly lower moisture content across the region. Winds are
expected to be generally light and variable with temperatures
remaining near climatic normals.

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


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Winter Weather Advisory for AKZ825.
PK...Gale Warning for PKZ801-802-850.
Brisk Wind Advisory for PKZ803-851.
Brisk Wind Advisory for PKZ804-805-852-853.
Brisk Wind Advisory for PKZ806-854.
Brisk Wind Advisory for PKZ814-815-861.
Brisk Wind Advisory for PKZ816.
Brisk Wind Advisory for PKZ817.
&&

$$

Stokes

787
FXAK67 PAJK 032337
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
337 PM AKDT Thu Apr 3 2025

.SHORT TERM...Near 47N 158W a storm force surface low is
maturing, being reinforced by a parent trough at 500mb with
positive vorticity advection (PVA) upstream of the main trough
axis. Satellite derived winds and model guidance show strong
agreement with the current the situation; 25 to 33 knot winds
associated with the triple point on the eastern flank and a broad
fetch of gale force SW winds behind that feature. This low will
continue to lift north and east into the Gulf of Alaska over the
next 24 hours as PVA crosses downstream of the trough axis,
indicating full maturity, with the low aloft closing. Expect the
coast to begin to feel E-SE winds freshen up overnight Thursday,
reaching gale force by Friday morning. Of particular concern is
Cape Suckling, where 45 knots sustained winds gusting to storm
force later Friday is becoming more likely; certainly, a bit of an
Alaskan rodeo for this time of year. For further details on
winds, see Marine Section.

Regarding precipitation, for sea-level locations light to moderate
rain arrives Friday along the northern coast and pushes east
across the Panhandle overnight into Saturday morning. Heaviest
rainfall expected Saturday morning into Sunday. For much greater
detail see Hydrology section.

.LONG TERM...The deep low currently situated south of the Aleutian Islands is
continuing to move northeast. A front extending from this low
pressure center will move into the eastern Gulf along the outer
coastline by Friday night, with gale force winds being expected just
along the outer coast and lasting into Saturday morning. A weak to
moderate atmospheric river is expected to bring up plenty of
moisture into this system, however the majority of the moisture is
expected to stay just off the outer coast of the panhandle. The
highest precipitation rates will be just west of Yakutat, with
Yakutat itself being expected to see around 2 inches of total liquid
precipitation throughout the weekend. The rest of the outer coastal
areas as well as POW, Ketchikan, and Annette Island will see some
decent amounts of precipitation during this weekend, between 0.5 to
1 inch of liquid precipitation in 24 hours on Saturday, before
dissipating into Sunday. The front will push through the panhandle
Sunday into Monday morning, bringing some lighter rates of rainfall
as it pushes northeast. This will also bring some precipitation to
the border of the Klondike Highway, which along with lower snow
levels of less than 3,000 feet and wet bulb temperatures of less
than 32, will likely fall as a rain snow mix with very little of it
actually accumulating by Monday morning.

An active weather pattern is expected to continue after this first
system with another front being expected to move into the northeast
and hit the panhandle Monday night into Tuesday. The majority of the
panhandle is expected to remain wet for most of this week as the
deep low in the Gulf is expected to stay stagnant off the west
coast, while smaller lows are expected to track up into the eastern
Gulf coast and bring even more precipitation by the end of the week.
This is largely due to the deep trough sitting over the Gulf and
bringing more of these lows up along the east Gulf coast from the
south.


&&

.AVIATION...End to the days of minimal hazards to aviation as gale
force front moves in Friday evening into Saturday from the west.
Rain hits NW coast first with a drop in CIG and VIS along with
increase in LLWS. As the front moves in widespread precip drops
conditions to MVFR/IFR. LLWS and increased turbulence mainly along
coastal areas. Rising freezing levels as warm mid level airmass
tracks in.


&&

.MARINE...Gulf: Our benign sea state will begin to change
overnight Thursday as our low lifts into the gulf, driving E-SE
gale force, to strong gale force, winds. Of most concern is Cape
Fairweather west towards Kayak Island, where persistent strong
gales Friday evening into Saturday are becoming more likely. The
biggest concern is the fresh seas stacking up on Kayak Island and
running west towards the Kenai Peninsula, higher than previously
anticipated. We have coordinated with WFO Anchorage to show 22 to
25 ft seas near Cape Suckling, a 3 to 5 ft increase from previous
forecasts. For the remainder of the coast, expecting fresh seas
building to 18 to 20ft Friday. Behind this system expect S-SW
swell of 15 to 18ft.

Inner Channels: Southerly onshore winds escalate Friday across
the inner channels, driving E-SE fresh to strong breezes across
most channels south of Icy Strait. Peril Strait will likely see
near-gales at times coming out into Salisbury Sound. As the front
moves over the region Saturday morning we will see gusty
southerly winds of strong breezes impact most areas.

&&

.HYDROLOGY...
1) Flooding is not anticipated.
2) Snow levels above 3000 ft for the majority of the panhandle,
reaching 8000ft for the central and southern coast.
3) 1 to 3 inches of 24 hr QPF at sea level, with the heaviest
amounts along the coast. Less moving into the interior panhandle.

After the onset of precipitation west of Yakutat on Friday, we will
begin to see a shift to a much higher availability of moisture
Friday night as an atmospheric river moves up into the eastern Gulf.
This will bring more moderate to even heavy precipitation Saturday,
with the majority of the heaviest rates being just west of Yakutat
and around Cape Suckling. The CW3E guidance shows both the EC and
GFS in agreement of it being a weak (AR-1) to potentially moderate
(AR-2) atmospheric river event for the northeast and southern
coasts, though with most of the moisture not making it into the
panhandle but rather staying further off the coast. This will still
bring 1 to 3 inches of rainfall to Yakutat and the northeast Gulf
coast during the weekend, and up to 1 inch of rainfall for the rest
of the region. Rivers may rise following this system, but flooding
is not anticipated at this time due to the dry soils at sea level
and mature snowpack at elevation that is likely to withstand the
rain.

As expected with most atmospheric rivers, we will see warmer air
moving into the region alongside higher snow levels as the system
comes in Friday. The snow levels Friday will be around 2000 ft,
before rapidly increasing to around 7000 ft along the coast into
Saturday morning. The northern panhandle will see snow levels get to
above 3000 ft before settling around 1500 to 2000 ft as we move into
next week. The snow level around the Klondike Highway will dip below
3000 ft on Friday, before increasing to 3500 ft on Saturday, before
dropping again to below 2000 ft Monday. This will give us some light
snow overnight on Friday along the higher elevations of the highway
near the border, before transitioning into rain into Saturday
afternoon. This will return to a mix by the start of the week, but
with little snowfall accumulating this event due to the lighter
precipitation rates, more hours of sunlight, and warmer road
surfaces moving into the daylight hours. For anyone at higher
elevations, above 4000 ft in the northern panhandle such as those
in the Chugach or St. Elias Mountains, expect feet of heavy and
wet snow.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale Warning for PKZ641-642-644-651-652-661>664-671-672.
Small Craft Advisory for PKZ022-035-036-053-643.

&&

$$

SHORT TERM...AP
LONG TERM....Contino
AVIATION...PRB
MARINE...AP
HYDROLOGY...AP/Contino

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