Graphical Hydro Meteorological Discussion

628
FXAK68 PAFC 171302
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
502 AM AKDT Wed Sep 17 2025

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

Generally quiet weather will prevail through much of the day for
Southcentral Alaska as the previous low responsible for rainfall
across the area over the past few days diminishes. Latest radar
imagery shows a few remaining showers across the Kenai Peninsula and
Cook Inlet area, but decreasing in coverage as the night progresses.
Much of Southcentral Alaska from the Kenai Peninsula northward
through Anchorage and the Mat-Su Valley is expected to have pleasant
weather today with a dose of sunshine.

Attention today will be focused on a strong low in the eastern
Gulf, currently analyzed just west of Baranof Island and trekking
north. Cloud cover currently extends out across much of the
eastern Gulf and into the eastern Chugach and Copper River Basin.
Rain associated with this system has been observed as far west as
Cordova thus far. Rain should continue to spread into far eastern
Prince William Sound this morning along with central portions of
the Copper Basin, while western portions of the sound likely see
no rain. The low quickly weakens on Wednesday as it moves inland
near Yakutat, causing precipitation to become showery and focus
along the southwestern slopes of the coastal mountains and the
Wrangells.

Wednesday night and beyond the forecast becomes less clear with
upper-level longwave troughing shifting east from the Bering Sea.
Moist southerly flow with a series of weak features ejecting from
the base of the trough will promote periods of rainfall over the
Gulf with upslope showers along much of the north Gulf coast
Thursday and Friday. With a shift to much weaker shortwaves, cross-
barrier flow will be more limited than previously anticipated, so
periods of light rain are possible for inland locations as more
potent shortwaves lift past the mountains. However, rainfall
accumulations are not expected to be very much.

Brown/Quesada

&&


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

Across Southwest Alaska, conditions are overcast to mostly cloudy
this morning due to mid level clouds streaming in from the
southeast from a remnant area of low pressure northeast of Kodiak
Island. Isolated shower activity and cloud cover has acted to help
insulate the atmosphere this morning and has kept low
temperatures 40F or warmer for most. Farther west, a ~980 mb gale
force low is nearly stationary and situated just to the north of
the Western Aleutians, with its strongest winds well offshore and
on its northwestern flank. Its front extends east-southeastward
across the Bering and Eastern Aleutians, with a weak area of low
pressure sitting to the south of King Cove and Sand Point. Looking
at satellite imagery, surface observations, and comparing to
current model guidance, it does seem that the overall model
consensus has been a little fast at bringing in precipitation to
the Eastern Aleutians with the frontal boundary.

Aloft, the flow is fairly zonal with the exceptions of a
shortwave lifting northeastward from the North Pacific towards the
front and a larger upper low over the Western Aleutians. By this
afternoon and evening, the gale force low affecting the Western
Aleutians begins moving eastward, starts a slow weakening trend,
and evolves into a complex low, keeping showery and windy
conditions in place for the near term. Heading into late
Wednesday, the shortwave looks to reinvigorate the front and
increase rainfall coverage from the Pribilof Islands southward to
Cold Bay. Most of the operational models have the complex low
moving eastward across the central Bering and Pribilof Islands
Thursday morning. This feature lingers across the eastern Bering
through Friday afternoon, keeping low impact weather as the main
story for much of the western domain through the end of the short
term.

-AM

&&


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

West-to-east zonal flow over the majority of the region will
maintain the unsettled weather pattern, however diminish the
likelihood for highly impactful weather patterns. Models have been
struggling coming to a consensus on timing the finer features and
shortwaves pushing through the region, particularly given the
zonal flow. Confidence however is strong that by Saturday
morning, a low pressure system will establish over the northern
Gulf of Alaska, bringing the potential for heavy rain and strong
winds to the Southcentral coast. Depending on the low`s
orientation, there is the chance for a barrier jet to form along
the marine areas of the northern Gulf Coast Friday into Saturday.
Through the weekend, rain is expected to continue along the Gulf
coast and into Southwest Alaska. Areas of gusty winds through the
southern gaps and passes of the Alaska Peninsula and Eastern
Aleutians that weekend as well, given the persistent northwesterly
flow in the area. In addition, southwesterly upper level flow
will bring the potential for rain to move up Cook Inlet and into
the Mat-Su Valleys. By Tuesday morning, agreement is generally
fair that a trough will remain over the Southcentral area, with a
ridge over the Aleutians. However, by Tuesday morning some
solutions are advertising a new trough to approach the western
periphery of the ridge much more rapidly than others. This will
lead to lower forecast confidence currently for early next week.

-CL

&&
.AVIATION...

PANC...VFR conditions and light winds will persist through the TAF
period.

&&


$$

229
FXAK69 PAFG 172256
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
256 PM AKDT Wed Sep 17 2025

.SYNOPSIS...
A closed low working north along the Alcan Border today will
continue to bring a steady band of rain to the Central/Eastern
Interior today into tonight, lifting north through the Brooks
Range and onto the North Slope tonight and Thursday. So far today,
Eagle has already picked up 0.58" of rain and counting. Rain
showers will continue to spread into the Central Interior this
afternoon into tonight, with the bulk of heaviest precipitation
staying east of Fairbanks. Colder air further north combined with
wrap around bands of moisture around the low and northerly upslope
flow into the Brooks Range will support a mix of rain and snow
further north, ultimately changing over to predominant snow
throughout the day Thursday. Should the transition over to snow
prove quicker or slower than expected, this would lead to locally
higher or lower totals across the eastern Arctic Coast. Overall,
the bulk of snowfall is expected to be in the Brooks Range east of
Anaktuvuk Pass and east of Prudhoe Bay along the Arctic Coast.
Winds will see an uptick as the low works its way north, leading
to areas of blowing snow at times further northeast. The Western
Interior and West Coast will continue to remain quiet and mostly
dry outside of isolated showers around Southwest Alaska to the
Seward Peninsula.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...
- Scattered showers this afternoon and evening as a steady band
of rain lifts north along the Alcan Border through the Eastern
Interior.

- Showers continue into Thursday morning before drying out
through the afternoon with mixed sun and clouds.

- Partly to mostly sunny later in the day Thursday into Friday
ahead of increasing clouds building in Friday night into
Saturday.

- Highs in the 40s/50s today, warming to the 50s/60s for Thursday
and Friday, ahead of a gradual cooldown starting this weekend.

West Coast and Western Interior...
- Quiet and mostly dry conditions continue, with isolated showers
across Southwest Alaska to the Seward Peninsula.

- Mix of sun and clouds across the Western Interior and Coast
through the weekend.

- Highs in the 40s/50s through Saturday, ahead of a gradual
cooldown starting early next week.

North Slope and Brooks Range...

- Steady band of precipitation continues working north along the
Alcan Border into the Central/Eastern Brooks Range and Eastern
Arctic Plains with a mix of rain, snow, and breezy winds.

- Mix of rain and snow transitioning to predominant snow
especially further east tonight and throughout the day Thursday.

- QPF totals tonight into Thursday along and east of the Dalton
Highway around 0.25-1.00" with drier conditions favored further
west.

- Snow Accumulations Tonight to Thursday Night:
- 2-4" along the Dalton Highway from MM220 to Sagwon
- 2-4" along the Eastern Arctic Coast east of Prudhoe Bay,
locally higher/lower dependent on rain/snow transition.
- 5-10" across higher elevations of the Brooks Range east of the
Dalton Highway.

- Isolated to scattered rain and snow showers continue Friday
through the weekend with lighter overall amounts expected.

- Highs remain steady in the 30s/40s into early next week.

&&

.FORECAST ANALYSIS AND DISCUSSION...Today through Saturday.
Early afternoon satellite imagery shows a closed low lifting
north along the Alcan Border, supporting scattered to widespread
precipitation across the Central/Eastern Interior today that will
lift north through the Brooks Range and onto the North Slope later
today into Thursday. Rain will continue to lift north later today
into tonight as progressively drier conditions return to the
Interior. As moisture lifting north encounters a colder airmass
over the Arctic, this will support a rain/snow mix in the Brooks
Range/eastern Arctic Plains transitioning to predominant snow
tonight into Thursday. Colder air further north combined with wrap
around bands of moisture around the low and northerly upslope
flow into the Brooks Range will support a mix of rain and snow,
ultimately changing over to predominant snow throughout the day
Thursday. Should the transition over to snow prove quicker or
slower than expected, this would lead to locally higher or lower
totals across the eastern Arctic Coast. As the low moves over the
ocean on Thursday, it will strengthen and bring northwest/west
winds along the coast with gusts of 20 to 35 mph beginning on
Thursday and continuing through the weekend. Strongest winds will
then shift to being out of the north along the West Coast south
to the northern Bering Sea by Friday as north/northwest winds
continue along the Arctic Coast.

Overall with this system, the bulk of snowfall is expected to be
in the Brooks Range east of Anaktuvuk Pass and east of Prudhoe Bay
along the Arctic Plains. Winds will see an uptick as the low
works its way north, leading to areas of blowing snow at times
further northeast. Our latest snowfall expectations remain right
in line with the HREF ensemble mean, showing a broad 2-4" along
the Dalton Highway from MM220 to Sagwon, 2-4" along the Eastern
Arctic Coast east of Prudhoe Bay, and 5-10" across higher
elevations of the Brooks Range east of the Dalton Highway. Have
expanded our Special Weather Statement for snow amounts to include
the Eastern Brooks Range north to the Arctic Coast to account for
higher overall snow totals in the latest forecast.

Otherwise, generally quiet weather will persist over Northern
Alaska heading into the weekend with only minor rain or snow
chances. Temperatures will be near normal heading into the
weekend, ahead of a gradual cooldown for early next week as a
broad troughing pattern encompasses the state.

&&

.HYDROLOGY...No concerns at this time.

&&

.EXTENDED FORECAST DAYS 4-7...Sunday through next Wednesday.
Ensemble model agreement remains good through the extended
period, showing a series of closed lows working east through the
Aleutians into the Gulf of Alaska this weekend as a broad
troughing pattern encompasses the state. This overall unsettled
pattern will keep isolated to scattered showers going across
Northern Alaska this weekend into early next week as temperatures
see a cooling trend across the board. Precipitation amounts during
this time frame continue to look light overall, with limited
organization helping to keep rain and snow chances light and
showery in nature.

Coastal Hazard Potential Days 3 and 4...None

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ810.
Small Craft Advisory for PKZ811-857.
Small Craft Advisory for PKZ815.
Small Craft Advisory for PKZ816-851.
Small Craft Advisory for PKZ817.
Small Craft Advisory for PKZ854-861.
Small Craft Advisory for PKZ856.
Small Craft Advisory for PKZ858.
Small Craft Advisory for PKZ859.
Small Craft Advisory for PKZ860.
&&

$$

MacKay

690
FXAK67 PAJK 171835 CCA
AFDAJK

Southeast Alaska Forecast Discussion National Weather Service Juneau
AK 949 AM AKDT Wed Sep 17 2025

.UPDATE...Updated aviation section for the 18z issuance.
Additionally, the low center is beginning to move over the Coast
mountains, with a bulk of the higher wind speeds shifting towards
Icy Strait northward. High wind warning have been cancelled for
Prince of Wales Island and Metlakatla as the low has moved
sufficiently far north. Still expecting to see gusts up to 30 mph
continuing for the southern panhandle.

&&

.SHORT TERM...The storm force low continues to move across the area
this morning. With the current track of the low, it appears that a
jump inland will be expected later today. With this track further to
the east and inland, the high wind warning was expanded to include
more of the Inner Channels as there an increased likelihood for a
surge of wind behind the low. For the rest of the panhandle, strong
winds are expected this morning with the exception of Yakutat which
will likely see less significant winds due to the more easterly
track of the low. With the mixing from the winds, temperatures this
morning are starting out rather warm due to the mixing inhibiting
cooling. After this low moves out of the area, we will see a brief
break before a second front moves into the area.

.LONG TERM.../Thursday through Sunday/ Through the rest of the week
and into the weekend, systems will continue to bring rain across the
panhandle with little to no breaks between systems. The
precipitation amounts are looking to be impactful due to the longer
duration of moderate to heavy rainfall. EFIs are showing an
increasing trend of confidence of extreme precipitation as the
systems move through, along with a shift of tails of 0 over the
northern panhandle 00Z Friday through 00Z Saturday and over the
southern panhandle 00Z Saturday through 00Z Sunday.

This is also something to keep an eye on moving forward due to
indications of it being a potential AR event from Thursday through
Sunday. GEFS and EC AR guidance shows potential for a moderate AR
event that will be long duration with a lower peak in IVT. Models
still are showing a bit of spread in the precipitation amounts
across the panhandle, and are not fully aligned on where the higher
IVT values will impact, with the GEFS bringing it more southward to
the coast of British Columbia while the EC has it approaching closer
to the southern panhandle.

Overall expecting 2 to 3 inches across the northern Gulf coast in 24
hours Thursday, and around 1 inch for the rest of the panhandle. As
it moves to impact the rest of the panhandle, Friday into Saturday,
the 24 hour totals for the central and southern panhandle will be
between 2 and 3 inches as well. The highest rates are expected to be
Friday into Saturday afternoon, with areas in the central panhandle
(Juneau, Sitka, and Petersburg) having a 40 to 50% chance of
exceeding 3 inches by midday Saturday when using the NBM 5.0 and 4.3
probabilities. The southern panhandle, particularly around
Ketchikan, may be somewhere to watch closely as guidance begins to
narrow down on precipitation values for this time frame, as NBM
probabilities show a 60% chance of exceeding 3 inches in 24 hours, a
30 to 40% chance of exceeding 4 inches, and a 15% chance of
exceeding 5 inches in 24 hours. The most 24 hour accumulation Friday
afternoon through Saturday afternoon is expected to be between 2.5
and 3 inches, though higher amounts may be expected if the IVT
values are directed more along the southern panhandle on the 20th.

Winds in these upcoming systems are expected to be at most high end
gales, with the majority of the increased winds to be along the
outer Gulf coastline, particularly the northern Gulf coast on
Thursday night.

&&

.AVIATION...Overall, the storm force low is relatively on track,
with only minor changes in timing. Naturally with storm force lows,
the main impact is strong speed shear and some directional shear due
to terrain, but lack of strong moisture and strong surface winds
mean that CIGs and VIS are not expected to be below MVFR conditions
for most locations. As typical with these types of systems, pushed
back arrival time for Haines and Skagway slightly for the higher
wind speeds. Still expecting stout land winds across mainly areas
from Kake northward now, with gusts up to 52 knots over TAF sites.
Kept LLWS values of around 40-60 kts shifting from SE to SW around
1000-2000 ft, with multiple PIREPs indicating its occurrence. Toned
down Sitka LLWS from radar observations, but expecting speeds to
pick up once more with stronger SWerlies. Yakutat is the largest
change, as the low center tracks slightly east of the TAF site. As
such, expecting to see lighter winds for longer with little to no
wind shear and lower CIGs.

&&

.MARINE...
Outside (Gulf and Coastal waters): The storm force low moving
through the area continues to impact the outside waters. Areas to
the east and south of the low center continue to report gales to
storm force with storm force gusts. Farther north and west, winds
continue to be weaker. Seas continue to be elevated for areas
experiencing gales to storm force winds. Cape Edgecumbe is reporting
15 ft seas while the Dixon entrance buoy is still reporting around
20 ft waves with a 11 second period. As the low moves inland, winds
will continue to diminish but seas are going to remain elevated.

Inside (Inner Channels): Winds across the Inner Channels are a tale
of two areas. Ahead of the front, winds generally remain light with
the exception of a few wind prone areas. Behind and along the
incoming front is a different story. Winds remain elevated with
gales to strong gales being reported with storm force gusts. There
have been a few local reports of storm force winds, particularly
along Cape Decision and constricted parts of Chatham. Going through
the day, winds are expected to increase as the front pushes through
before starting diminish behind the front. As the low moves farther
north, winds are expected to increase with the jump across the Coast
Mountains into the Interior. This will likely bring gales to
significant portions of the Inner Channels later this morning
through the evening.

&&

.HYDROLOGY...Rain continues across the panhandle this morning as
strong front pushes inland. Highest precipitation amounts with this
system are expected across the central and northern panhandle, with
between 1 and 2 inches expected through Wednesday night to areas
north of Sitka, with higher accumulations possible along the NE Gulf
coast and for higher terrain areas. Yakutat will see between 1.5 and
2.5 inches total as the low moves into the northeast Gulf by
Wednesday night. In contrast, the southern panhandle, will only see
between 0.5 and 1 inch in 24 hours from this frontal passage through
Wednesday night. No significant flooding is expected at this time,
but rivers and streams will see rises due to the rainfall.

Rainfall will continue through the week and into the weekend, with
the systems moving through Thursday onwards bringing an expected 2
to 3 inches of rainfall in 24 hours as a potential moderate AR moves
into the panhandle. This largely appears to be a longer duration,
lower intensity event lasting Thursday through Sunday with some
areas seeing chances of getting above 3 inches in 24 hours. The
heaviest rates look to be between 0.25 and 0.35 inches every 3
hours, with potential for higher rainfall amounts due to orographic
forcing.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind until 4 PM AKDT this afternoon for AKZ317.
High Wind Warning until 7 PM AKDT this evening for AKZ318-319-
322-323-327.
High Wind Warning until 4 PM AKDT this afternoon for AKZ320-321-
325.
Strong Wind until 6 PM AKDT this evening for AKZ324.
Strong Wind from 4 PM this afternoon to 6 PM AKDT this evening
for AKZ325.
MARINE...Gale Warning for PKZ011>013-021-022-031>035-641>644-661>664.
Small Craft Advisory for PKZ036-053-651-652-671-672.

&&

$$

SHORT TERM...SF
LONG TERM...Contino
AVIATION...NC
MARINE...SF
HYDROLOGY...NM

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