Graphical Hydro Meteorological Discussion

357
FXAK68 PAFC 301303
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
503 AM AKDT Mon Jun 30 2025

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

A shortwave is rotating southwestward through the Copper river
Basin and as far west as the Matanuska Valley early this morning,
bringing showers to Glennallen and Palmer, as well as to areas
around Prince William Sound. This shortwave will begin to track
more north-to-south as the day goes on in response to weak
ridging over the western Alaska Range southward to Kodiak. The
pressure rises associated with the ridging will also keep
southwesterly flow through Cook Inlet today which will keep clouds
packed up along the western slopes of the Chugach, Kenai, and
Talkeetna Mountains through tonight. By Tuesday, the shortwave
should be well out of the area and the weak ridging over
Southcentral which should allow some semblance of clearing, though
Wednesday actually looks like a more likely day for the nice
weather day of the week as the surface and upper level ridge will
be better aligned resulting in better subsidence as well as the
synoptic flow no longer driving the moisture up Cook Inlet which
should result in less cloud cover. By early Tuesday, a front
associated with a low in the Bering will send a front into the
Kodiak area and then slide south of the ridge into the Gulf on
Wednesday. This should result in rain across Kodiak for Tuesday
and Wednesday, though it is a factor in increasing the ridging for
other parts of Southcentral on Wednesday.

This pattern will also keep the northeastern Copper Basin in the
periphery of the ridge which means the potential for
thunderstorms due to enough ridging to warm up the surface but not
enough subsidence to keep them from developing. Therefore, there
will be a chance for thunderstorms near the Alaska Range from
approximately Paxson and eastward the next few afternoon and
evenings.

&&


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

The mature low that has emerged off of the Kamchatka Peninsula
continues to push eastwards into the western Bering, with its warm
front reaching coastal southwest Alaska this morning and its
trailing cold front draped across the southern Bering and
Aleutians. The arrival of the front overnight has been as
advertised with gusty southerly winds and abundant rainfall as the
system continues to be supplied with plentiful moisture from the
tropical Pacific.

Ongoing moderate to heavy rain at times is expected to continue
for the Kuskokwim Delta Coast through this evening. Rain will
continue to work into Bristol Bay and the interior Kuskokwim Delta
through this morning and early afternoon. Reinforcing shots of
warm air and moisture get pulled northward into the Western and
Central Aleutians as well as the Pribilof Islands this morning
through tonight. This activity moves east to the Eastern Aleutians
and southern Alaska Peninsula (AKPEN) for Tuesday as the initial
front begins to occlude and moves further inland to the Kuskokwim
Valley. The heaviest rain looks to fall across the Kuskokwim Delta
Coast this morning and afternoon and across the Bristol Bay
Coast, southern AKPEN, and western Kuskokwim Valley for Tuesday.

In addition to the widespread rain, gusty south-southwesterly
winds will also accompany this system. Gusts of 35 to 40 kt are
possible by this afternoon for Unalaska Bay and Cold Bay. Similar
gusts are also possible across Kuskokwim Bay, likely resulting in
rough seas along with the potential of localized areas of coastal
erosion. The gusty winds will extend into the Kuskokwim Delta,
with winds gusting as high as 40 mph for Bethel.

Rain continues to linger across mainland Southwest through
Tuesday evening with the heaviest along the southern AKPEN as the
low tracks to the eastern Bering. The development of a triple
point low to the south of the AKPEN will continue to bring
additional rainfall to the AKPEN, Bristol Bay, and Southwest
Alaska coast into Wednesday.

A ridge builds in behind the low across the rest of the Bering
with quieter weather across the Western and Central Aleutians
Tuesday evening as the Eastern Aleutians contend with northerly
flow and rain showers downstream of the ridge. Areas of fog are
likely to redevelop for the western Bering and Aleutians,
underneath the ridge.

-JH/TM

&&
.LONG TERM FORECAST (Days 4 through 7: Thursday through
Sunday)...

The long term forecast remains on track. A strong upper ridge
will build in over the northern half of Alaska through the end of
the week. This, combined with a persistent upper low in the
Alexander Archipelago will channel easterly waves through
Southcentral Alaska. This pattern will favor showers and
thunderstorms in the Copper River Basin and the Lower Kuskokwim
Valley for the end of the week including the 4th of July. The
Anchorage and Mat-Su Valley regions may see showers with chances
increasing the further north you go. The Kuskokwim Delta and the
western parts of Bristol Bay will also receive showers, but due
to the marine influence, thunderstorms are unlikely. The eastern
part of the Gulf coast from Cordova east will receive periodic
bouts of rainfall as the waves pass through. Meanwhile, the Bering
will start with slight ridging on Thursday, allowing for less
active weather. However, by Friday, a large low will swing in from
the west, increasing wind speeds and rain chances into the
weekend.

The weekend sees the upper ridge in the north flatten out. There
is quite a bit of uncertainty in how exactly this will play out,
but most guidance does agree that the ridge will reduce at some
point. As for our forecast area, the aforementioned large ridge in
the Bering will swing over into the Gulf of Alaska by Sunday,
bringing increased wind speeds and rain chances for first the Gulf
coast, then the rest of inland Southcentral by Monday. There is
good model agreement on this scenario with the main difference
being the exact track of the low when it moves into the Gulf of
Alaska.

&&.AVIATION...

PANC...Monday morning will see some occasional MVFR ceilings as
persistent south-to-southwest low level winds will allow clouds to
continue to pack up along the Chugach Mountains and westward to
over the airport. A weak short wave is tracking from northeast to
southwest over the Chugach this morning as well. this could bring
in some showers to the airport as it moves over, but visibilities
are expected to remain VFR despite any showers.
Ceilings should rise as the day progresses, but a solid increase
in ceilings is not likely until sometime on Tuesday.

&&


$$

232
FXAK69 PAFG 292048
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
1248 PM AKDT Sun Jun 29 2025

.SYNOPSIS...
Warming and drying trend across the Interior will continue this
week. A low approaches the West Coast Sunday night and will bring
rain to areas from the Seward Peninsula south and the Nulato
Hills west. Areas of low clouds and fog at night across the
Central and Eastern Arctic Coast. Widely scattered thunderstorms
expected this afternoon across the Brooks Range and Fortymile
Country.

&&

KEY WEATHER MESSAGES...
Central and Eastern Interior...
- The Southeastern Interior from the Fortymile Country south
through the Upper Tanana Valley to the Eastern Alaska Range will
have showers and thunderstorms increase into Wednesday. Isolated
activity is possible today over the White Mountains and Western
Alaska Range.

- Temperatures in the mid 70s today in most Interior valleys
soar into the mid 80s on Wednesday.

- Hot...dry and windy conditions might develop by Wednesday in the
higher terrain of the central interior increasing wildfire
concerns.

West Coast and Western Interior...
- A Bering Sea storm will spread more rain into the West Coast and
Western Interior from the Seward Peninsula south to Bristol Bay. These
rains will be heaviest Monday, but lighter showers may persist
through mid week.

- Southeasterly winds over western Alaska increase tonight into
Tuesday. Sustained values of 20 to 30 mph expected for most
areas in Bering Sea through the Bering Strait. Southeast winds
15 to 25 mph develop late Monday through the Norton and
Kotzebue Sounds.

North Slope and Brooks Range..
- Low stratus and fog continue at night along the Eastern Arctic
Coast. Conditions should improve during the day.

- Isolated showers and thunderstorms continue over the central and
eastern Brooks Range...and should spread to the western Brooks
Range by late Tuesday.

&&

.FORECAST ANALYSIS AND DISCUSSION...
Upper level high pressure will strengthen over northeast Alaska
the next several days. The northeasterly flow around this high
will focus showers and thunderstorms over the Fortymile Country
down into the eastern Alaskan Range. This will be enhanced today
and Monday by wrap around flow from the low over the Gulf of
Alaska. Storm activity will also be enhanced on Wednesday as a
strong short wave moves down from the Northern Yukon. In the west
a Bering Sea low pressure system will spread rain and breezy
southeasterly winds over the Western Interior from the Seward
Peninsula south to Bristol Bay tonight through Tuesday. The
central and eastern Interior will experience a warming and drying
trend during this time. A heat advisory might be needed for
Wednesday afternoon for Fairbanks and adjacent zones. Fire weather
concerns will also ramp up and smoke may start to be an issue
again. In the extended more of the same with persistence under
the High Pressure ridge as low pressure continues over the Gulf.

&&

.FIRE WEATHER...
Warming and drying trend will occur for much of the central and
eastern Interior as high pressure aloft strengthens. Temperatures
will soar into the mid 80s with minimum humidities dropping into
the 20s. By Wednesday winds might increase enough to support
hot...dry...and windy Red Flag Warning conditions. We will
continue to monitor zones 834...835 and 838...and coordinate as
necessary. Disturbances will cause shower and thunderstorm
activity to be focused over the Fortymile Country down into the
Eastern Alaska Range. Isolated storms remain possible over the
White Mountains. Out west a Bering sea storm will spread rain and
strong southeast winds from the Seward Peninsula south to Bristol
Bay. This pattern is expected to eventually bring some rain to the
western Brooks Range by late Tuesday.

&&

.HYDROLOGY...
No concerns along the rivers. Rain in the southeastern Interior
will lead to some slight rises in rivers there, but no impacts are
expected.

&&

.EXTENDED FORECAST DAYS 4-7...
Coastal Hazard Potential Days 3 and 4...None

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ801-850-856.
Small Craft Advisory for PKZ802-805.
Small Craft Advisory for PKZ806.
Small Craft Advisory for PKZ807.
Brisk Wind Advisory for PKZ811.
Small Craft Advisory for PKZ816.
Small Craft Advisory for PKZ817.
Small Craft Advisory for PKZ851.
Small Craft Advisory for PKZ852.
Small Craft Advisory for PKZ853.
Small Craft Advisory for PKZ854.

&&

$$

Maier

331
FXAK67 PAJK 301807 AAA
AFDAJK

Southeast Alaska Forecast Discussion...UPDATED
National Weather Service Juneau AK
1007 AM AKDT Mon Jun 30 2025

.UPDATE...For aviation 18Z product release and for hydrology
section for Taku River Glacier Lake Dam Outburst Flood release.

&&

.Aviation Update...Low pressure centered about 100 nm west of
Haida Guaii is moving north and weakening today. To the east of
the low the occlusion/warm front is also making slow progress
north across the central Alaska Panhandle today with heaviest
rains and lowest ceilings from Sitka to Petersburg. The rains will
work their way north today into the Gustavus and Juneau areas but
are expected to diminish as the front moves north toward Haines
and Sitka. For the southern Panhandle we expect mostly low
ceilings to IFR through late today into tonight however with
heavier rains diminishing. Elsewhere mostly IFR through tonight
into Tuesday morning with light rain and low ceilings, except for
Yakutat where we bring in MVFR toward 09Z.

&&

.Hydrology Update...Observations indicate Lake No Lake that drains
into the Taku River is releasing off the glacier this morning. We
have issued a Special Weather Statement highlighting main impacts
expected with this...mainly just below minor flood stage with
debris in the water being the main impact to expect. Crest on the
Taku is expected late tomorrow morning.

&&

.Previous Discussion...Issued at 636 AM AKDT Mon Jun 30 2025...

.SHORT TERM.../Through Monday Night/...Although there`s still some
relative uncertainty about the exact path of Monday`s weather
system, whether the surface low will stay offshore near Sitka or
move inland before dissipating, the overall outcome remains the
same. A warm front bringing precipitation will move through the
Panhandle on Monday, delivering moderate to heavy rain from the
southern Panhandle up to around Petersburg.

An upper-level shortwave will enhance lift due to divergence ahead
of the wave and vorticity advection along the trough. Combined
with strong warm air advection near 850 mb, this will increase
upward motion through Monday morning. The upper-level trough is
expected to reach northern Lynn Canal by the afternoon, but
mountain-induced shearing in the Inner Channels will keep low-
level advection limited to the southern Panhandle.

As a result, areas like Ketchikan, Metlakatla, and southern Prince of
Wales Island may see rainfall rates of 0.15 to 0.20 inches per
hour. Flooding is not expected due to the fast-moving nature of
the heaviest rainfall, though brief periods of reduced visibility
from heavy rain are possible.

Earlier concerns about gusty winds following the warm front, due
to dry air at 700-500 mb, have eased. Cold air advection appears
to be separate from the dry air, which reduces lapse rates and
available instability (CAPE). As a result, gusty winds are no
longer anticipated, since there are no strong forcing mechanisms
in place.

.LONG TERM...

Continued colder than normal temperatures, widespread overcast cloud
cover, and precipitation look to continue for the panhandle
through Tuesday, though more breaks in the cloud deck and less
rain could be in store for the latter half of the week, including
the Fourth of July. A cold upper level low will remain stationary
through July 3rd, before being ejected E into British Columbia,
only to be swiftly replaced by another cold upper level low moving
in from the W. While there is fairly solid confidence in the
larger synoptic scale pattern over the state during this timeframe
as a result, the same cannot be said for smaller scale details. In
particular, the various upper level troughs moving around the
first 500 mb low, have much less confidence on timing, strength,
and placement, as does the potential for a weak ridge in the lower
levels to try and build in during the latter half of the week.
What is known into next week is chances for rain will broadly
remain in the forecast, though the potential for fewer showers
July 3rd through the end of the week will exist.

Highest confidence is in the Monday/Tuesday system. A low will
stall and decay into an open trough off the coast of the AK
through the day on Tuesday before the remnants meander into the
panhandle and disintegrate entirely on Wednesday. During this
time, expect wave of showers to rotate around the decaying low,
moving into the panhandle and delivering rounds of rainfall to
much of the area. By Tuesday night, shower coverage will be
diminishing as the remnant trough continues to weaken.

Beyond Tuesday, confidence rapidly diminishes, but what can be
said is that cloud cover will linger and chances of rain showers
will continue, albeit diminished from what was previously
anticipated. Operational guidance indicates the potential for an
easterly wave moving across the northern half of the panhandle on
Wednesday. Alongside the easterly wave, chances for showers will
linger through the latter half of the week, but in the lull
between the former upper level low (which will be ejected
Wednesday), and the arrival of the next upper level low,
confidence has begun to grow that weak low level ridging will
attempt to build in. Should this ridging be sufficiently strong,
shower coverage will diminish across the area, and some
occasional breaks (and marginally warmer weather) are possible
Wednesday through the end of the week.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

$$

SHORT TERM...99
LONG TERM....99

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