Graphical Hydro Meteorological Discussion

208
FXAK68 PAFC 131443
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
543 AM AKST Mon Jan 13 2025

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

The powerful low that moved through Southcentral yesterday has
moved north and weakened as compared to yesterday. That is leaving
southwest Alaska under south-to-southwest flow aloft early this
morning. There is a short wave trailing the low that has moved
northward overnight and is bringing mainly rain showers with it
and some gusty southerly winds in its wake. These winds and
showers should diminish as the morning wears on as it moves into
the Susitna Valley and into the Interior this afternoon. For the
north Gulf coast, there will be persistent rain and snow showers
through the day, but the heaviest ones are expected to be through
mid-morning in the Thompson Pass area where there may be some snow
rates of 1 to 2 inches an hour. The next low can be seen on
satellite approaching the Gulf of Alaska from the south. This low
is not as strong as this past one an is tracking farther east.
This should bring some snow back to the north Gulf coast this
evening and overnight. The main dynamics of this low will be east
of the area, though there is some uncertainty as to whether there
could be a little bit of snow that develops over the Anchorage and
Matanuska Valley areas this evening as another weak shortwave
moves up Cook Inlet and mets the westernmost part of the moisture
from this low. Even if there is some snow in these areas, it won`t
be much accumulation at all. However, once we get to this
evening, it should be cold enough for any precipitation to be snow
for the next few days for all areas of Southcentral.

A low will and upper level trough will move into the area again
Tuesday night. This low looks to bring some snow to the Gulf coast
and coastal mountains, but the way the upper level trough is
undercutting the Kenai Peninsula, it will likely be little or
nothing for any inland areas.

&&


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

The large storm-force low pressure system in the eastern Bering
Sea is continuing to produce gusty easterly winds across the
Eastern Aleutians and Alaska Peninsula. Rain and snow will
continue for Southwest Alaska through tonight, though
precipitation has become more showery in nature as colder air
continues to wrap in behind the system leading to minimal
additional snow accumulation through this evening before tapering
off overnight. As the storm continues to lift northward along the
western Alaskan coast this evening, winds will pick back up and
turn westerly- southwesterly for Southwest Alaska with sustained
winds of 30 to 35 mph along the coast.

Southwesterly winds contribute to continued coastal flooding
potential, with a Coastal Flood Advisory remaining in effect for
the Kuskokwim Delta coast, particularly between Kipnuk and
Kwigillingok coincident with high tide tonight and Monday evening.
A High Surf Advisory also remains in effect as the strong onshore
push of winds through Bristol Bay will bring elevated water
levels there as well for high tide tonight through early Monday
morning. The main threat with this is likely to be high surf and
potential for coastal erosion along the Bristol Bay coast.

Out west, a compact gale-force low tracks near the western
Aleutians. With a cold air mass moving into the western Bering
Sea, there is also potential for blowing snow for those islands
this evening through Monday morning, however the showery nature of
precipitation will likely make visibility reductions below one
mile intermittent. The cold air mass spreads across the Bering Sea
and into Southwest Alaska with the northward exit of the large
low tonight, dropping temperatures into the 20s for Monday, the
teens Monday night, and single digits by Tuesday night. Expect
this colder air mass to also bring drier conditions across the
region as well for the beginning of the week. The gale force low
over the western Bering tracks into the northern Bering for
Tuesday, spreading snow showers as far as the Pribilof Islands
before diminishing by Wednesday morning.

-JH/Quesada

&&


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

On the Alaska Weather map, an elongated upper level trough
stretching from the Russian Far East across the Aleutians and
Bering. This trough gets a little boost from passing shortwaves to
reorient over Southwest Alaska and the Gulf of Alaska for
midweek, before continuing its Eastward track into Canada by
Thursday. An upper ridge building across the Western Aleutians
Tuesday moves to extend across the Gulf of Alaska and Western
Alaska into Northeast Russia through the end of the week.
Deterministic GFS and ECMWF carry the features and changes well
through Thursday with the Canadian models joining up into the
weekend.

A decaying surface low on the Southcentral coast spreads locally
heavy rains along the coastal locations, with locally heavy snow
further inland and over higher elevations through Wednesday. A
second low over the Shumagin Islands brings mostly rain with snow
over Bristol Bay from the Eastern Aleutians, Alaskan Peninsula and
Kodiak Island through midweek, before moving over the Kenai
Peninsula before dissipating over Prince William Sound Thursday.
Bands of snow progress across the Bering through Thursday. A well
developed North Pacific low and fronts spreads snow changing to
rain across the Western and Central Aleutians Wednesday and
continues over The Bering, Southwest Alaska and the AKPEN by
Friday. Gusty winds with gale force gusts work their way from the
Central Aleutians over the AKPEN and Bering through Friday.

&&

.AVIATION...

PANC...A secondary round of strong southerly winds ongoing is
expected to slowly diminish as the day progresses. The higher end
gusts as strong as 35 to 40 kts are not expected to persist for
more than a few hours this morning, and gusts should quickly drop
to 25 kts or lower by this afternoon, then go light and variable
by this evening. Rain showers could intermittently move over the
terminal and briefly cause ceilings to dip into MVFR range
throughout the morning, but otherwise VFR conditions are expected
through this evening. There will be potential for fog and/or low
stratus development after winds shut off tonight with possible
MVFR conditions or lower returning.

&&
$$

574
FXAK69 PAFG 132151
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
1251 PM AKST Mon Jan 13 2025



.SYNOPSIS...
A strong low continues to move north along the West Coast this
morning with chinook warming over the E Interior still ongoing,
but weakening. As the chinook ends this afternoon, parts of the
Interior will see a stray snow shower along with falling temps and
locally slick roads. Snow showers and some blowing snow will
impact the West Coast as that occurs, with some minor water over
ice a possibility as that low shifts inland. Blowing snow over the
arctic coast is coming to an end this morning.

.DISCUSSION...

Key Weather Messages and Summaries:

Central and Eastern Interior...

- High winds in and near the Alaska Range have ended, but they
will remain gusty into the 50 to 60 mph range into the afternoon.
Wind advisories will persist through this afternoon.

- With chinook winds waning, temps will be hovering around the
freezing mark today, then dropping below freezing tonight. Any
water on ice along roads, sidewalks, and other surfaces will
become dangerously slick.

- Winds will remain blustery in the Interior, with localized gusts
to 35 mph as a cold front comes through. Winter Weather
Advisories in effect for the Steese Highway towards Eagle
Summit.

- Chance for snow showers increase over the Interior Monday and
Tuesday as some moisture makes it way into the Interior.
Accumulations around 1 to 3 inches possible over the E
Interior.

- High pressure and cooling temps Tue night through Wed night.
Overnight lows are back below zero Tue night and Wed night for
Interior valleys.


West Coast and Western Interior...

- A strong cold front sweeps across the coastal regions and
Interior with some local snow showers and squalls today, with
gale force gusts.

- General snowfall accumulations of 1 to 3 inches is possible for
most locations, but 3 to 6 inches is possible in the W Brooks
Range. Light snow showers persist into Tue for the N Interior
and W Brooks Range then high pressure settles in.

- Southwest winds behind the low and cold air advection into
Norton Sound and along the YK delta may promote water over ice
along beaches and near the shore through tonight.

North Slope and Brooks Range...

- Blowing Snow and low visibility possible for the E Arctic slope
Tue evening into Wed.

- South winds and a cold front will move across the Arctic coast
later today and tonight. Light snow showers and minor blowing
snow with southwest winds will occur over the Arctic Coast into
Wed.

- High pressure builds Wed and Thu with falling temps and light
winds.

Forcast Confidence and Extended Forecast Days 4-7...Continued
warm on Monday, then turning colder. Upper level flow turns more
southwestly on Monday and Tuesday and the upper level low over the
Seward Penn will track Northeast over the Brooks Range Tuesday
and Wed. Snow could develop over the Interior as some moisture
pushes across the area from the southwest. Colder air will filter
back into the Interior through the week as ridging builds over the
Interior.

A chance for snow will occur over the SE Interior with a system
moving from the Gulf into the SE Interior and E Alaska Range.
Cooler temps and troughing with weak high pressure will develop
later on Thursday with a chance for stormy weather to return to SW
AK by Friday. Chinook flow could return to the Interior with
warmer temps and windy conditions over the Alaska Range for next
weekend.

Coastal Hazard Potential Days 3 and 4...See SPS for the West Coast
for coastal hazard details.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Wind Advisory for AKZ837-849.
Winter Weather Advisory for AKZ834-850.
Winter Weather Advisory for AKZ805.
Winter Weather Advisory for AKZ809.
PK...Brisk Wind Advisory for PKZ802-803-817-853-854.
Small Craft Advisory for PKZ804.
Heavy Freezing Spray Warning for PKZ804.
Brisk Wind Advisory for PKZ805-852.
Brisk Wind Advisory for PKZ807.
Brisk Wind Advisory for PKZ808-809-855.
Brisk Wind Advisory for PKZ811-812.
Brisk Wind Advisory for PKZ813.
Brisk Wind Advisory for PKZ814.
Brisk Wind Advisory for PKZ815.
Brisk Wind Advisory for PKZ816-850-851-857-858.
Brisk Wind Advisory for PKZ856.
Brisk Wind Advisory for PKZ859.
Brisk Wind Advisory for PKZ860-861.
&&

$$

239
FXAK67 PAJK 131447
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
547 AM AKST Mon Jan 13 2025

.SHORT TERM.../through Monday night/...
Quick hits:
-Today`s gale force low will bring another round of rain and wind
to the panhandle.
-Colder air in place at the higher elevations of the highways will
support snow.
-As the front tracks through, elevated wind speeds and gusty winds
are expected.

Details:
Another gale force low will move north through the gulf today. As
the front pushes north, wind gusts over land areas will range from
30 to 40 mph as the front moves over your area. Once the front
clears your area though, winds should calm back down. Folks in
the southern panhandle could see gusts a little stronger, up to 45
mph. The time frame of these elevated wind gusts will be after
noon today through this evening. Marine winds will see a similar
trend, more details in the Marine section.

More moderate to heavy rain is likely again today with the frontal
passage. But with rivers pretty low, any impacts will be minor.

The colder air in place at the higher levels of the highways would
allow for snow again. A Winter Weather Advisory and Winter Storm
Warning has been issued for those areas.

.LONG TERM...
A gale force system will continue to push inland in the northern
gulf coast into Tuesday. Ample moisture transport along the
initial front will continue into Tuesday with higher elevation
highways expected to receive accumulating snow while at sea level
most communities will see cool rain. Precipitation will begin to
diminish in intensity and transition to showers later in the day
Tuesday. The best chance for communities at sea level to see a
transition to mix or wet snow would come later in the day Tuesday
as a wrap around cold front blows into the panhandle from the
West. As a result, communities particularly from Icy Strait
northward, could transition to a mix or very wet snow with highest
chance for accumulation being Haines and Skagway. Overall snow
levels will be lowering once more as we see a northerly wind shift
in the inner channels due to the next fast moving system
approaching the panhandle from the south. More on that below.

Big picture for the rest of the week: Active weather pattern is
still on track continuing from the short range through the middle of
the week with another system racing up from the south on Wednesday.
Depending on the track of this system and strength of northerly
winds ahead of it, the northern panhandle could see some overrunning
and thus additional snow accumulation. Models are coming into
further agreement though after this system on a break on the second
half of Thursday and into Friday. This break will be predicated on a
ridge of high pressure rotating into the gulf, combined with arctic
high pressure sliding into the interior from the north. This
combination should lead to some clearing skies and thus drier and
seasonably cooler weather at the end of the week with the next
system likely to impact SE AK sometime mid to late next weekend.
Some patchy fog could spring up Thursday into Friday due to
lingering showers and light and variable winds in the inner channels
before any residual moisture frosts out overnight. Under the
influence of this transient ridge, temperatures will struggle to get
much above freezing for the northern half of the panhandle Friday
and Saturday. Overall a complex pattern with many moving parts
through midweek with things becoming a bit clearer towards the
latter half of the week and weekend.

Into late week and the weekend, there are indications of some
colder air infiltrating the panhandle from the NW on Friday with
a brief period of outflow winds possible. This is not expected to
be very long lasting as the Yukon high moves off to the east
rather quickly. However, it will be enough for drier weather with
daytime highs struggling to get much above freezing in the
northern half of the panhandle Friday and Saturday.

&&

.AVIATION...

Variable flight conditions across the panhandle this morning with
low end VFR across the N panhandle, trending towards MVFR moving
southward towards S Panhandle. Not anticipating much, if any,
improvement in flight conditions through today as a strong quick
moving front pushes into the SEAK panhandle by 18z to 00z this
afternoon. Main aviation concern once again will be LLWS as front
pushes inland, as highlighted by the most recent AAWU forecast,
with strongest LLWS expected for coastal and southern TAF sites.
Winds will increase through 00z this afternoon, up to 25kts
sustained with isolated gusts up to 40kts possible. By this
afternoon and into the evening, expect predominate MVFR or worse
flight conditions to remain with CIGS AoB 3000ft and visibilities
down to 2 to 4 SM within heaviest showers. LLWS will gradually
dissipate through late Tuesday night.

&&

.MARINE...Today`s gale force low is tracking northward early this
morning. It will continue to track northward through the gulf,
reaching the Alaskan coast, just west of Yakutat, late Monday
night. As the low moves north, seas will build to 20 to 25 by late
this afternoon. These higher wave heights will last through most
of tonight with a subsiding trend Tuesday. Along the front, wind
speeds will be upwards of 30 to 35 knots with wind speeds around
the low at 20 to 30 knots.

As the front tracks into the inner channels, wind speeds in the
inner channels will increase to mostly 25 to 30 knots, however 30
to 35 knots will be found in Clarence Strait. Wind speeds will
increase from south to north, with most of the inner channels
seeing elevated wind speeds of 20 to 25 knots Monday night.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Storm Warning until 6 AM AKST Tuesday for AKZ318.
Winter Weather Advisory from noon today to 3 AM AKST Tuesday for
AKZ319.
Strong Wind from 3 PM AKST this afternoon through this evening
for AKZ328.
Strong Wind from 3 PM AKST this afternoon through late tonight
for AKZ330-332.
MARINE...Gale Warning for PKZ036-641>644-661>664-671-672.
Small Craft Advisory for PKZ012-013-022-031>035-053-651-652.

&&

$$

SHORT TERM...GJS
LONG TERM....STJ
AVIATION...NM
MARINE...GJS

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