Graphical Hydro Meteorological Discussion

162
FXAK68 PAFC 180127
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
527 PM AKDT Tue Jun 17 2025

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

Currently, a front is passing through Southcentral Alaska. Rain
chances have increased as a result, even in the Anchorage area.
However, most precipitation from this front is on the light side
and many areas are not receiving precipitation. Cooler
temperatures are accompanying this front due to increased cloud
cover. The Copper River basin, however, is relatively clear and
so, warmer. Winds are calm in inland areas, but still remain
elevated in gap regions in the waters due to lingering effects of
a coastal ridge. Thunderstorms area forming in the Copper River
Basin and the Talkeetna mountains due to higher instability.
Easterly flow will give a chance for a couple thunderstorms to
move west off the foothills toward Talkeetna. This easterly flow
is being caused by a low in the Gulf and an area of high pressure
over northern Alaska.

Wednesday will see skies begin clear as higher pressure builds in
to Southcentral Alaska. There is a bit of uncertainty how fast
this will take place, so high temperatures will be warmer or
cooler depending on when the cloud deck dissipates. Higher
instability will be present due to the warmer temperatures, so the
Copper River Basin and the Susitna Valley will have higher
thunderstorm coverage. These storms may bring localized gusty
winds and heavy rainfall. The aforementioned easterly flow will
allow some of these storms to flow over valleys. Thursday will
likely be the warmest day with temperatures reaching the 70s and
80s in inland regions. Instability will also be high, meaning
scattered thunderstorms in the aforementioned areas are likely
with smaller chances in the Chugach and Kenai Mountains. The ridge
of high pressure will extend deeper south into the Gulf on
Friday. This will decrease chances for rain somewhat. The upper
easterly flow will shift to variable, so thunderstorms will
generally remain in the foothills of mountain ranges. A front
pushes into Kodiak Island by early Saturday, increasing winds and
precipitation chances. It remains to be seen how the front will
affect the mainland when it arrives.

-JAR

&&


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

High pressure over most of interior Alaska continues to bring
warm temperatures to Southwest while low pressure encompasses the
Bering Sea. Thunderstorms have already been been observed
developing in the Kuskokwim Valley and Bristol Bay region today,
kicking off what will likely be an active evening of convection
for the region. A Red Flag Warning for lightning has been issued
through midnight tonight to highlight this threat. The best
chances for lightning will be between Aniak and Lime Village and
areas north, but isolated strikes further south can not be ruled
out. An easterly upper level wave will bring light rain and cloud
clover through the night. A slightly more stable atmosphere will
develop over Southwest tomorrow before thunderstorm chances
increase again on Thursday afternoon. Fire starts from lightning
are on the rise across the state due to a favorable convective
weather pattern and long summer days continuing convection through
the late evening hours, so this is something we will keep a close
eye on in the coming days.

Tomorrow, a gale-force North Pacific low will move just south of
the Central Aleutians. Widespread rain and small craft to gale
force winds will encompass much of the Bering Sea by tomorrow
night. The frontal system will push east through Thursday,
bringing rain and elevated southeasterly winds to the Eastern
Aleutians and Alaska Peninsula through Friday morning.

&&


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

The weather pattern across the Alaskan region continues under a
broad upper level trough centered mostly over the Bering.
Shortwaves and transient lows slip off across the Alaska Peninsula
into the Gulf of Alaska. These transient lows undercut a ridge
that extends across Northern Alaska, with the Southern portions
sliding into Canada. Individual models and model ensembles support
the large scale pattern through the weekend, but begin to vary
somewhat during the second half of the forecast period.

Scattered rain showers and possible thunderstorms will dot much
of the Southern Mainland through the period. Continued warmer
temperatures increase the likelihood of convection through
Tuesday, especially around the Alaska Range and Eastern Interior.
A weakening Central Aleutian surface low extends a front over the
Northern Bering into Western Alaska. Areas of rain associated with
the front continue over across Southwest Alaska and the AKPEN
into Kodiak Island through Sunday. Further West, a well developed
Eastern Asian low and front pushes across the Western and Central
Aleutians and Bering through Tuesday.

- Kutz

&&


.AVIATION...

PANC...Winds are expected to be from the South to Southwest around
5 to 10 kts overnight and into Wednesday. The challenge with this
direction is that it may bring MVFR ceilings back over the
terminal after midnight as that pesky marine layer, though
weaker, is still present over the Inlet. It does look like even if
these MVFR ceilings do develop again overnight, they should
mostly burn off by afternoon as drier air filters into the area
for Wednesday.

&&


$$

819
FXAK69 PAFG 172213
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
213 PM AKDT Tue Jun 17 2025

.SYNOPSIS...
Hot, dry and windy weather continues in the Northern Interior with
widely scattered to numerous thunderstorms from the Eastern to
Western Interior. Red Flag Warnings are issued and can be found
on our website. Heat Advisories continue for the Central and
Eastern Interior today though will likely be let to expire in most
spots except the Northern Interior tomorrow. There is also
ongoing flooding on the North Slope with Flood Watches, Advisories
and Warnings issued.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...
- Hot weather continues with highs in the mid to upper 80s through
at least midweek.
- See Heat Advisory for more details.

- Increasing coverage of thunderstorms today with widely scattered
storms across much of the Southern Interior, with Scattered
storms from Manley Hot Springs west.
- Scattered storms from Tanana to the Middle Tanana Valley
tomorrow with isolated to widely scattered storms elsewhere.
- Some storms may be strong to severe, especially tomorrow
afternoon/evening with 1" hail and/or 60 mph winds possible.

West Coast and Western Interior...
- Wide area of thunderstorms likely this afternoon and tonight
with numerous thunderstorm activity from Galena to McGrath.
- Thunderstorms can persist through the night, and some storms
may be strong to severe with 1" hail and/or 60 mph winds
possible.

- Temperatures remain warmer than average in the Interior and
near, to slightly above normal along the coast.

North Slope and Brooks Range..
- Continued warm temperatures with 50s/60s along the eastern
coast, upper 40s from Utqiagvik southwest, 70s to near 80
inland and 60s/70s in the Brooks Range.

- Scattered showers with isolated to widely scattered storms are
expected each afternoon in the Brooks Range and Southern Arctic
Plain through the end of the week.

&&

.FORECAST ANALYSIS AND DISCUSSION...
A 572 decameter high over the Eastern Brooks Range keeps pumping
easterly flow and numerous shortwaves into the Interior which is
sparking thunderstorms each afternoon. This is also the reason
most of the state is very warm. Out west, there is a 545 decameter low
near the Gulf of Anadyr which shears apart and moves southwest
tonight. Otherwise, this big ridge over the Interior will be the
main player in our weather as it hangs around through the week
before models try to break it down. As we know, ridge break down
is not handled well by models and usually, troughs or lows cannot
barrel through the high like some of the models are showing (i.e
the GFS). What will most likely happen is a solution similar to
the CMC, ECMWF and ICON. These keep the ridge in place, and
brings southerly flow to Western Alaska by early next week,
ridging over the Interior, and maybe a degrading ridge by the
middle of next week.

&&

.FIRE WEATHER...
Hot, dry, windy and thunderstorms is the name of the game Tuesday
afternoon. Fortunately in the Northern Interior we will be
dropping our Red Flag Warning tonight as winds lessen.
Temperatures will continue to be around 85 to 90 with min RHs
around 20% from Bettles to the Yukon Flats through Thursday. A Red
Flag Warning in Southwest Alaska is in effect Tuesday afternoon
through Tuesday night for lightning. In the Lower and Middle
Tanana Valley, a Red Flag Warning will be in effect from 4PM
Wednesday through Wednesday night at midnight for lightning as
well. Luckily these thunderstorms will be wet and come with
briefly heavy rain. Otherwise, conditions look to remain warm with
min RHs in the 20-30% range across much of the Interior with the
lowest RHs in the Northern Interior. Thunderstorms will be around
each day through the end of the week, but the most intense
lightning days will be Tuesday in the Western Interior and
Wednesday in the Tanana Valley with the potential for a decrease
in activity on Thursday, though confidence is medium.

&&

.HYDROLOGY...
Continued flooding on the Colville, Kuparuk and Sag Rivers on the
North Slope. On the Sag, an emergency closure of the Dalton
Highway from Mp 305 to Mp 356 continues due to a major washout at
Mp 315. Water levels have begun to drop on the Sag, there is still
water over parts of the highway, but at the very least, there are
signs of improvement. The Colville at Umiat has crested and will
very gradually drop, but there is still a lot of water that has to
go through there before they are completely out of the woods. On
the Kuparuk, Spine Road has seen some water over it, which is
typical for the area, but with water levels continuing to rise, it
water will likely continue to be on the road. Additional flooding
is expected to occur on these rivers for at least the next couple
of days.

&&

.EXTENDED FORECAST DAYS 4-7...
Ridging over the Eastern Interior with southerly to southwesterly
flow over the Western Interior and West Coast. There will likely
be some rain and the potential for cooler temperatures over the
West Coast with shortwaves and lows moving north from the Gulf of
Alaska bringing periods of rain by next week. Thunderstorms and
warm temperatures will continue in the Central/Eastern Interior
and North Slope through the weekend and perhaps into next week.

Coastal Hazard Potential Days 3 and 4...None

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Red Flag Warning for AKZ929-930-952.
Flood Watch for AKZ804>806-808>810.
Red Flag Warning for AKZ931>934.
Heat Advisory for AKZ833>835-838>846.
Red Flag Warning for AKZ938>946.
PK...Small Craft Advisory for PKZ805.
Small Craft Advisory for PKZ811.
Brisk Wind Advisory for PKZ813-859.
Brisk Wind Advisory for PKZ814.
Brisk Wind Advisory for PKZ815.
Brisk Wind Advisory for PKZ855.
Small Craft Advisory for PKZ856.
Small Craft Advisory for PKZ857.
&&

$$

Bianco

391
FXAK67 PAJK 180555
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
955 PM AKDT Tue Jun 17 2025

.UPDATE...For 06z TAF issuance.

SHORT TERM.../ Through Wednesday night / road area of lower
pressure persists and spins up bands of showers into the southern
portion of the panhandle. Any light rain tonight limited to south
of Icy Strait area I suspect and another band will reinforce the
PoPS by morning. Yakutat area may stay in the dry with the easter
flow aloft. A ridge building over the west central gulf will drift
east Wednesday and start to shut off the precipitation still
falling across Southeast Alaska. Warming temperatures start the
later half of the week, but more on that in the long range section.

LONG TERM.../Thursday through Monday/... Some easterly rain
showers will continue across the panhandle into Thursday evening,
associated with both a low in the Gulf to the west of Haida Gwaii
and a low over British Columbia. These showers will begin to
decrease into Thursday night as a surface ridge approaches the
panhandle from the west, pushing the weakening low to the
southeast. This ridge, accompanied by an upper level ridge
building over the Gulf on Friday, will help to bring drier
weather, clearer skies, and some higher temperatures into this
weekend. Models showing 850mb temperatures of between 10 and 12
degrees C moving into the area alongside this ridge, which will
bring us some warm air advection that will also aid in bringing
temperatures up. This warm air advection alongside the surface
ridging will bring some areas of the panhandle to over 70 degrees
for their highs this weekend, with the highest temperatures
looking to be Saturday afternoon and in the southern panhandle.
There are some higher (14-15 degrees C) 850mb temperatures moving
along the border with British Columbia, though this will have
little impact on the panhandle outside of Dyea, which is expected
to see highs above 80 for the weekend. Temperatures will also be
higher due to the lack of cloud cover during Friday and the
weekend, resulting in likely even higher temperatures than the
models are showing due to the long sunlight hours and surface
heating. Temperatures will then begin to decrease again Sunday
into Monday through the majority of the panhandle, with only Hyder
looking like it will stay warmer for longer.

The higher temperatures in the Yukon Territory and
British Columbia alongside their potential for some convective
showers later in the week may result in some risk for wildfires,
which may bring some haze in to Haines and Skagway. As of now we
have put haze in for the majority of the midrange forecast for
just Haines and Skagway in anticipation of this.

Winds look to stay on the lighter side over the region for the
rest of the week into the weekend. However, the pressure gradient
in the northern panhandle may tighten as the surface ridge begins
to move in while a low remains over Canada to the northeast, which
may bring some elevated winds to Lynn Canal on Thursday. Friday
into Saturday morning there will be some elevated winds along the
southern outer coast and coming out of Chatham Strait and Clarence
Strait as the ridge continues to push east while a low remains
over British Columbia, bringing some 15 to 25 kt winds as the
gradient tightens. These winds are not expected to last however
as the ridge continues to push eastward Saturday into Sunday, with
winds decreasing to between 10 and 15 kt off the coast Sunday
into Monday.

&&

AVIATION...Predominantly VFR conditions throughout the panhandle
this evening into tonight. A broad low near Haida Gwaii will
continue to bring diminishing light showers to the southern
panhandle tonight along with broken cloud decks between 5000 and
10000 feet. Other impacts include the chance for fog over the
central and southern panhandle. In order for fog to develop, some
clearing will be needed. Other ingredients are in place with
decreasing winds and lowering temperatures. By Wednesday
afternoon, convection forming over BC is expected to advect over
the central and northern panhandle decreasing ceilings to MVFR
conditions in any heavier showers, along with erratic winds. Some
increasing winds with gusts to 20 to 25 kts will develop tomorrow
afternoon and evening, mainly in the northern part of the
panhandle. However no significant LLWS is expected during the TAF
period.

&&

MARINE...Outside Waters: Winds for the outer waters 10 to 15 kt
generally with a few areas reaching up to 20 kt. Southeast winds
for the waters west of Prince of Wales Island and west for the
northern central gulf over the top of the ridge along the western
gulf. The flow wraps back around to a NE pattern into the central.
gulf Seas less than 6 feet near the coast into Wednesday night.

Inside Waters:Generally light winds for inner channels with a few
areas up to 20-25 kt like Five Finger Light and southern Lynn
Canal near the Junction with Icy Strait. Local sea breezes for
the northern panhandle, and maybe a less extent tomorrow wind
there will be more clouds around.

&&

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

&&

$$

SHORT TERM...Bezenek
LONG TERM....Contino
AVIATION...STJ/EAB
MARINE...Bezenek

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