Graphical Hydro Meteorological Discussion

470
FXAK68 PAFC 190059
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
459 PM AKDT Tue Aug 18 2026

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

A complex longwave trough continues to drift over much of the
greater Alaska region this afternoon, with several embedded
smaller troughs slowly moving northeast along an axis between the
Aleutians and the northern Yukon. With the leading trough well
into the Yukon, gap winds are beginning to trend down as the
north-south pressure gradient slowly relaxes, and this weakening
trend should continue tonight. A smaller shortwave currently over
Southcentral has brought some shower redevelopment this afternoon,
especially over the Talkeetna Mountains. This shortwave will move
to the Copper Basin late tonight, shifting any lingering shower
activity to there while the rest of Southcentral briefly dries
out. Some higher elevations may maintain showers overnight
tonight. By tomorrow morning, this shortwave will move into the
Yukon.

Right on the heels of the system currently overhead, an upper
level low moves from the Aleutians to the AKPen late tonight. At
the surface, an occluded front moves into the Gulf. This will send
renewed bands of rain quickly northeast, reaching Kodiak Island
by tomorrow morning, then shifting to up the Cook Inlet to the
MatSu and to Prince William Sound by tomorrow afternoon. With
proper timing of a shortwave, some light precipitation may spill
over into the Copper River Basin Wednesday evening. Models hint at
the development of a weak triple-point low in the Gulf southeast
of Kodiak Island Wednesday afternoon. As this low forms, the front
will sharpen somewhat Wednesday evening into Thursday morning as
it approaches the northern Gulf Coast. With a bit of a coastal
ridge, the sharper pressure gradient will result in a weak barrier
jet, bringing some easterly small-craft winds offshore the
northern Gulf Coast Wednesday night into Thursday morning.

Southerly flow ahead of the slow moving upper low over the AKPen
will continue to stream moisture northwards into Southcentral.
This maintains widespread chances of showers Thursday through
Friday. Thursday appears to be the wetter day with better
orientation of upper level flow pulling moisture northward. The
heaviest precipitation will be along the northern Gulf Coast,
especially at and east of Prince William Sound due to the occluded
front moving onshore. Steady precipitation looks to spill into the
Wrangell Mountains as well, with more showery and lighter rain for
the rest of Southcentral. The low passes over Kodiak Island
Thursday evening into Friday, which should limit precipitation
there during that timeframe. Though the low eventually points the
most favorable moisture towards the AKPen, chances for showers
continue across Southcentral on Friday, with the steadiest rain
again along the northern Gulf Coast east of Prince William Sound.
In summary, overcast, cool, and showery conditions will continue
for Southcentral through Friday.

- PA

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(Days 1 through 3: This afternoon through Friday evening)...

The active, but non-impactful weather pattern continues across
the Bering Sea, Alaska Peninsula (AKPEN), and Southwest Mainland
through Thursday. Satellite imagery shows a vertically stacked low
pressure system track along the Eastern Aleutians and moving
slowly eastward with time. Isolated showers across Southwest will
become more widespread beginning tonight and last through
Thursday as the weak low along the Eastern Aleutians moves into
Bristol Bay by Wednesday evening. Waves of rain will lift into
Southwest and the AKPEN out ahead of it. The low in Bristol Bay
Wednesday night and Thursday will slowly move southeastward to the
southwest Gulf of Alaska by early Friday morning as showers
continue along the Southwest Interior.

Farther to the west, an upper-level trough will dive
southeastward out of the Arctic, across Siberia, and into the
northern Bering Sea by Thursday afternoon. A surface low will spin
up in the northern Bering as well Thursday afternoon. As the low
digs southeast to around Saint Matthew Island Friday morning, rain
will overspread Mainland Southwest from the Bering through the
day on Friday. Expect southerly small-craft winds with gale-force
gusts stretching from the Bering all the way to the Kuskokwim
Delta Coast Friday.

Coastal flooding is of low concern currently (less than a 10
percent chance) as the tidal influence will be low, and the fact
that this storm has trended weaker in today`s guidance than in
previous days. Regardless of storm strength, this looks to be
quite a wet system with moderate to heavy rain across the Pribilof
Islands to Coastal Southwest through Friday. Rain tapers off
across the Pribilof Islands beginning Friday afternoon as it picks
up intensity across Southwest by then. Back behind this system, a
ridge builds in across the western Bering and Western Aleutians
Friday afternoon and evening. Stay tuned for forecast updates
regarding this late week storm.

&&


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

The long term period begins with an amplified upper-level pattern
across Alaska as a deep trough and embedded upper low move across
the Bering and toward Southwest Alaska through the weekend. Strong
southwesterly flow ahead of the trough will connote to transport
moisture northward, supporting periods of rain across Southwest
Alaska and the Alaska Peninsula (AKPEN) Saturday. The trough
gradually shifts east into mainland Alaska Sunday into Monday,
allowing steadier precipitation to spread into portions of
Southcentral while becoming more showery farther west.

By Monday, the upper low becomes centered over mainland Alaska as
the associated trough encompasses much of the state. This will
maintain cooler and unsettled conditions with scattered showers
across much of southern Alaska. Guidance then shows the trough
continuing eastward into Canada Tuesday while heights begin to
rise from the west. This should allow conditions to gradually
improve across Southwest Alaska and the Bering, though lingering
cyclonic flow may keep showers around portions of Southcentral.

Model agreement remains reasonable with the overall evolution of
the upper-level pattern, though differences increase early next
week regarding the exact position and progression of the upper
low. These differences will ultimately influence the placement of
heavier precipitation and stronger winds. overall, an unsettled
and relatively cool pattern begins to shift eastward Tuesday as
heights gradually rise over the western Bering.


LM


&&


.AVIATION...

PANC...VFR conditions are expected to remain through the TAF
period, though periods of showers may causing ceilings to dip to
MVFR at times. Gusty southerly to southeasterly winds will persist
through the day, though will gradually diminish this afternoon.


&&

$$

757
FXAK69 PAFG 182249
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
249 PM AKDT Tue Aug 18 2026

.KEY MESSAGES...
Central and Eastern Interior...
- Slightly warmer temperatures expected Wednesday with high
temps in the mid to upper 60`s as the region briefly dries
out.

- Rain chances will be minimal Wednesday through Thursday with
only spotty showers expected. Better chances for scattered
showers and thunderstorms return Friday.

West Coast and Western Interior...
- Strong northerly winds through the Bering Straight will
diminish by late afternoon and evening. Southerly flow return
to the Strait Thursday with speeds increasing through the day.

- Scattered rain showers expected to linger across portions of
the western Interior Wednesday and Thursday with total
additional rainfall of .25" to .50" through the period.

- More widespread precipitation will overspread much of the west
coast Friday as yet another storm system enters the Bering
Sea.

North Slope and Brooks Range...
- A weak disturbance will bring cooler temps to the North Slope
Wednesday followed by slightly warmer temps Thursday and
Friday.

- Occasional light showers will track across the North Slope and
Brooks Range Wednesday through Thursday as a disturbance
crosses the region. Total additional rainfall of .25" to .50 "
possible over the higher terrain of the Brooks Range with .10"
to as much as .25" expected across closer to the Arctic
coastline.

- Steadier rainfall will approach the western Arctic Coast and
western Brooks Range Friday, eventually spreading eastwards
into the upcoming weekend.
&&

.SYNOPSIS...
Scattered rain showers will continue at times, especially across
northern and western parts of the region as additional
disturbances approach the next couple of days. Meanwhile mainly
dry and slightly warmer conditions will set in through Thursday
for the central and eastern Interior. By Friday another storm
enters the Bering with widespread rainfall for the west while
chances for Thunderstorms return to much of the Interior of
Alaska.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
The upper feature responsible for heavy precipitation that fell
across parts of the Central Interior and Brooks Range is now
making a quick exit to the northeast and was located over the
northern Yukon Territory as of early Tuesday afternoon. However
a trailing trough extending southwest into Interior Alaska has
continued to provide a focus for additional light to moderate
rainfall which looks to continue into early Wednesday before
that activity settles down. Meanwhile a shortwave trough is
quickly racing across the Chukchi Sea and should bring yet an
additional round of showers to the Brooks Range and North Slope
Wednesday and Thursday. Not to be left out of the mix is the
Western Interior where models all hint at additional showers
Wednesday and Thursday as well as a low over the Aleutians
sends shortwave energy up their way. However, it appears that
none of this activity will be sufficient enough to result in
any short term hydro concerns.

Temps obviously continue to run a bit on the cool side thanks to
the current unsettled weather pattern, However portions of the
Central and Eastern Interior should see a slight increase in
temps the next few days as weak ridging builds across the
eastern Interior. This will continue to pose some concern for
fire weather, especially across portions of the upper Tanana
where dry conditions have persisted. In addition this area could
well see some additional thunderstorm activity later in the week
as easterly flow brings back some moisture.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
A troughing pattern will persist across Alaska through the weekend
as a series of shortwaves moves through the Bering and western
Alaska, maintaining a moist and unsettled regime. A weak low moving
south into the Bering from Siberia on Friday will reinforce
southerly moisture transport into western Alaska, with additional
shortwaves rotating through this trough bringing periodic showers
across western Alaska, the Brooks Range, and eventually into the
Interior. Showers are expected to remain more intermittent and
isolated across the Interior, with the best chances for more
persistent rainfall remain across the West Coast and higher terrain.
Temperatures will trend cooler throughout the period as increasing
cloud cover and precipitation limit diurnal heating, with highs
generally in the 50s and 60s.

The pattern becomes increasingly active late in the period as
another shortwave moves northeastward through the trough, bringing a
broader area of precipitation into northern Alaska Sunday into
Monday. Ensemble guidance continues to show some spread in the
timing and amplitude of this feature so confidence in specific
precipitation totals remains limited, with some models showing
totals up to an inch. However, the overall signal favors continued
cool and unsettled conditions rather than a return into a warmer,
drier pattern.

Coastal Hazard Potential...
No Coastal Hazards are expected in the forecast period.

&&

.FIRE WEATHER...
Over the last 24 hours, much of the state has seen quiet fire
weather conditions with scattered showers and persistent cloud
cover. That said, majority of the fire weather concerns will be
focused over the Upper Tanana over the next couple of days. The
upper-level pattern shows westerly flow across much of the state. A
trough will slowly work its way W to E across the North Slope
throughout the night, bringing chances for isolated thunderstorms.
This will also help bring a brief cooling trend to the North Slope
on Wednesday. Over the Interior, the westerly flow has resulted in
widespread showers and overcast clouds which is expected to persist
through the night. The associated shortwave will continue to push
east over the Yukon through the night, allowing for a brief period
of ridging to build up over Eastern Alaska.

On Wednesday, temperatures will be slightly warmer across much of
the Interior. This ridging will also help keep minimum RHs dry
across the Upper-Tanana. However, this will help weaken the gusty
winds that have been seen over the last day or so. The S/SW flow
setting up over the Eastern Interior, from the strengthening ridge,
will provide a very slight chance for isolated thunderstorms over
Fortymile Country on Wednesday and Thursday. Another shortwave will
be moving east across the Alaska Peninsula and into the northern
portion of the Gulf throughout the day Thursday into Friday. By
Friday afternoon, the low is expected to be far enough east to
switch the upper-level pattern to southeasterly over the Eastern
Interior. This will provide more scattered chances for thunderstorms
Friday afternoon. A more pronounced front will be moving east out of
Siberia and move toward the West Coast on Friday, bringing the next
chance for wetting rains with up to 0.5" possible through Saturday
morning. The heaviest rainfall is expected along the coast around
the Norton Sound.

Looking at temperatures starting Wednesday; the Interior will see
highs in the mid 60s to low 70s, while the North Slope and West
Coast will see highs in the mid to upper 50s. These high
temperatures will remain consistent over the Interior through the
end of the week, while there will be a slight cooling trend
elsewhere by the start of the weekend. Regarding minimum RHs, the
driest conditions will be seen over the Upper Tanana over the next
couple of days with the building ridge over Eastern Alaska. Minimum
values in this area are expected to be between 30 and 35 percent.
Conditions will begin to moderate by the start of the weekend as the
ridge breaks down.

&&

.HYDROLOGY...
Despite recent heavy rainfall across portions of the Central
Interior and Brooks Range, rivers and streams have not seen
significant rises in water levels. While some smaller creeks and
streams could still reach bankfull with additional showers
tonight and tomorrow, no flooding is currently anticipated.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
MARINE...Small Craft Advisory until 4 PM AKDT this afternoon for PKZ806-
807.
Small Craft Advisory until 1 PM AKDT this afternoon for PKZ808-
855-856.
&&

$$

KEY MESSAGES...Laney
SYNOPSIS...Laney
SHORT TERM...Laney
LONG TERM...Cruz
FIRE WEATHER...Twombly

787
FXAK67 PAJK 182311
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
311 PM AKDT Tue Aug 18 2026

.SYNOPSIS...

Key Messages:

- More seasonable temperatures will prevail through the end of the
week with mostly cloudy skies and periods of rain, especially
across the north, as multiple systems traverse the region.

- Increasing winds and building seas are expected over the Gulf
waters late Wednesday into Thursday.

&&

.SHORT TERM.../Through Thursday Night/...Plenty of clouds remain
in place across the region this afternoon under a light onshore
flow. While organized precipitation has come to an end, there are
still a few areas of drizzle and light rain. Weak high pressure is
attempting to push into the southern panhandle and will bring a
few more breaks in the clouds and perhaps some robust intervals of
sun to these areas through this evening. Patchy fog is again
expected to form tonight, especially in sheltered locales that
experience some clearing this evening.

A weak disturbance aloft will approach the northern panhandle by
Wednesday morning and enhance the onshore flow. This will also
result in at least a chance of light rain for much of the area,
but persistent, heavier precipitation is not expected through the
day. Meanwhile, more significant low pressure and an associated
frontal system will approach the central Gulf by Wednesday
evening. South-southwesterly flow increases ahead of this feature.
A steadier rain will also overtake the northeast Gulf Coast and
then slowly spread into the northern panhandle by late Wednesday
night. On Thursday, some of this rain will slowly ease southeast
into the central panhandle as the front draws a little closer to
the coast. This trend likely persists into early Friday, but most
of the activity still appears to stay north of Frederick Sound
through this period. For more details on the Friday and beyond
forecast, please see the long term discussion below.

High temperatures Wednesday and Thursday will range from the
upper 50s to low 60s across the northeast Gulf Coast, and mainly
in the mid 60s to lower 70s in the southern panhandle, locally
warmer well inland.

.LONG TERM.../Friday through Monday/...Active weather will continue
into the long term forecast as multiple systems move into the Gulf
of Alaska. At the end the work week, a weak short wave moves into
the panhandle, as the ridge to the southwest of the area weakens.
The will bring light to moderate rain to the northern panhandle
Friday, spreading into the southern panhandle by Saturday morning. A
stronger low pressure system will then move into southeast into the
gulf Saturday into Sunday. There is still some differences on where
the location of this low will be over the gulf. If it is farther
offshore, rain amounts will be lower and less heavy. If the low
moves slightly closer to the panhandle, overall rain amounts will be
slightly more, especially for the southern panhandle. Many of the
solutions do not bring super strong gulf winds, with wind speeds
remaining around 20 to 30 kts Sunday. Confidence and model agreement
greatly decreases after the Sunday system, but the overall pattern
of onshore flow looks the most likely to continue.

Temperatures through the long term period remain near average with
high temperatures in the mid to high 60s. There are indications that
areas near Hyder will see temperatures into the mid to high 70s on
Friday. Other southern areas could also see some warmer temperatures
Friday as well, but not as warm as Hyder. The main indicators of
this is continued dry weather along with 850 temperatures between 12
to 15 C. The limiting factor will be the amount of cloud cover that
they receive as the low pressure system moves into the gulf bringing
more moisture into the area.

&&

.AVIATION...

Conditions have largely improved through the morning timeframe,
with many locations now reporting high MVFR to VFR. Overall
thoughts regarding the incoming front overnight tonight are mostly
unchanged, only minor timing changes. These timing changes are
largely to lean towards earlier lower conditions, as overall
moisture in the column is slightly more than anticipated this
morning. An incoming front tonight is expected to bring
conditions back down to MVFR, with CIGs between 1000 and 2500 ft
for the central and northern panhandle. There is the possibility
for IFR conditions, even if they do not strictly happen at TAF
sites, for the outer coast. Additionally, weak forcing will at
least bring a few light showers to drizzle for the aforementioned
areas. Lower CIGs were extended into the southern panhandle for
the incoming front, although not expecting these clouds to drop
below 2000 ft.

&&

.MARINE...

Outside: An incoming front overnight will transition the current
westerly 10 to 15 knot winds to south to southeasterly from south
to north. As the front approach the coastline, a barrier jet style
effect will increase wind speeds to around 20 knots, and further
to around 25 knots as the front moves near the northern gulf
coast. Expect to see, behind the front, a somewhat sharper
transition to southwesterlies at 15 knots before winds decrease.
One point of interest is to the west of Cape Spencer, where a
convergence point may bring winds above 25 knots near 46083. Wave
heights are expected to behave and largely be below 6 ft, with the
exception of east of Cape St Elias, where seas are likely to be
between 6 and 8 ft with highest winds.

Inside: The incoming front will begin to impact the panhandle
during the mid morning timeframe of Wednesday, gradually
increasing winds to up to 15 knots. Not expecting a bulk of the
energy to make it past the initial mountains to the panhandle,
due to a sharp ridge axis set up over the panhandle. Therefore,
went with a lower magnitude solution for much of the panhandle,
although local areas exposed to easterly winds, such as the
backside of Douglas, Icy Strait, and Cross Sound, may reach wind
speed of 20 knots from gap flow and terrain effects. Expecting to
see the wind threat largely fall off by the evening timeframe of
Wednesday, with the possibility of some patchy fog overnight.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ652-672.

&&

$$

SHORT TERM...MJB
LONG TERM...EAB
AVIATION...NC
MARINE...NC

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