Graphical Hydro Meteorological Discussion

402
FXAK68 PAFC 011309
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
509 AM AKDT Tue Jul 1 2025

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

As was mentioned yesterday, Southcentral Alaska remains in a col
between upper level ridging to the northeast and southwest, and
upper level lows to the west and southeast. The low to the west is
the one that is sending a front toward Kodiak and is bringing
some rain from Kamishak Bay to Kodiak early this morning. This
front will stall out today as the low digs to the southeast and
undercuts the weak ridge that is trying to build into Southcentral
from the north. The result will be rain for Kodiak Island today
into Wednesday night. The clearing over the Copper River Basin
early this morning should expand to the southwest today and
overcome the clouds moving in from the west over Cook Inlet and
the Susitna Valley. These mid and higher level clouds are
associated with that low to the west while the lower level clouds
persisting over Anchorage and along the western slopes of the
Talkeetna, Chugach and Kenai Mountains are due to the persistent
marine layer that has invaded the Cook Inlet region the past few
days. This shift in pattern should allow the Anchorage area and
other areas near Cook Inlet to finally clear out the clouds to a
better degree are the synoptic flow will finally turn to more
down-inlet and advect that marine airmass away from the area. In
addition, Turnagain Arm winds are expected to develop over
Anchorage the next two afternoons and evenings which will also
bring in a modified airmass to lower levels which should only help
the situation.

While some sunny breaks are expected over the region today into
Thursday, it will likely not be a complete clearing out of the
clouds as a short wave is expected to move into the Copper River
Basin on Wednesday and then toward the Cook Inlet region for
Thursday. There will be clouds associated with this shortwave and
rain is likely in the eastern Copper Basin as it moves through.
With it reaching that area in the early morning hours on
Wednesday, it is less likely to initiate Thunderstorms with it as
it goes though. However, after it passes through the area, the
atmosphere will likely be unstable enough for some thunderstorms
Wednesday afternoon and evening. One of the biggest forecast
questions this morning is how far westward the rain will progress
on Thursday.

&&


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

A mature low pressure system over the Alaska`s west coast
continues to bring gusty southerly winds and moderate to heavy
rain to the region today. Abundant tropical moisture being drawn
north across the Alaska Peninsula will deliver a swath of rain
from Togiak to King Salmon, up through Aniak and Sleetmute.
Additional rain amounts between 0.6 and 1.5 inches are expected
through this afternoon, with the heaviest totals expected from
Dillingham to the north. This system will slowly drift south
today before a triple point low forms south of the AKPEN Wednesday
morning, which will taper off precipitation by Wednesday
afternoon.

Meanwhile, for the rest of the Bering Sea, a ridge will build
behind the low, bringing quieter weather across the Western and
Central Aleutians tomorrow evening. The Eastern Aleutians will
continue to contend with northerly flow and rain showers
downstream of the ridge through Wednesday morning. Areas of fog
are likely to redevelop for the western Bering and Aleutians,
beneath the ridge, before the front of a new low out of Kamchatka
sweeps across the western Bering Thursday morning.

&&

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

Starting off the long term is the presence of an upper high in
northern Alaska. This, combined with an upper low in the Gulf of
Alaska will allow easterly flow into inland areas of
Southcentral. This flow will allow for chances for showers and
thunderstorms in the Copper River Basin, and the Talkeetna
Mountains for the 4th of July. Easterly storm motion may allow
some of these showers and thunderstorms to stream into the Susitna
Valley. Southwest Alaska will have a large low in the Bering
slowly make its way eastward. Heavy rainfall will impact the
Eastern Aleutians and Alaska Peninsula with the mainland coast
seeing rain by Saturday. The low will stall out just off the
Kuskokwim Delta coast and will continue to send fronts eastward,
bringing heavy rain to the Southwest mainland for the rest of the
weekend and into Monday.

Southcentral will see some ridging build in on Saturday. This
will result in a drying and warming trend for the region. The
Copper River Basin, Talkeetna Mountains, and the Susitna Valley
will retain chances for thunderstorms despite the ridge. This
drying trend will not last too long as a front from the low in
the Bering will arrive on Saturday. Heavy rainfall is expected
first in Kodiak on Saturday afternoon, then at the Southcentral
coastline. Anchorage and the Mat-Su Valley may receive rainfall
from this front as well if it orients correctly. This scenario is
uncertain as model agreement is quite poor at this moment.
Additional weaker fronts push into the Gulf into Monday with the
potential for scattered rainfall.

-JAR

&&.AVIATION...

PANC...MVFR ceiling should slowly lift through the morning hours
with VFR conditions remaining after that. The southeasterly
Turnagain Arm winds are expected to develop this afternoon and
persist into the overnight hours before settling down some. These
winds along with a change in the pattern over the region should
help prevent the low level clouds from developing again.

&&


$$

819
FXAK69 PAFG 012211
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
211 PM AKDT Tue Jul 1 2025

.SYNOPSIS...
The northeast flow around the high pressure will increase on
Wednesday. Windy conditions will develop Wednesday over the
higher terrain of the central and eastern Interior increasing
the fire danger. A disturbance will spread some showers and
isolated thunderstorms over the eastern Interior and eastern
Alaska Range near the Canadian border early Wednesday. In
western Alaska rain along the coast from Bristol Bay to the
Seward Peninsula will diminish tonight.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...
- The Fortymile Country...Upper Tanana Valley and Eastern Alaska
Range will have isolated showers and thunderstorms today and
Wednesday.

- Temperatures in the upper 70s today in most Interior valleys
warm into lower 80s on Wednesday.

- Hot...dry and windy conditions will develop Wednesday in the
higher terrain of the Central and Eastern interior increasing
wildfire concerns.

West Coast and Western Interior...
- Rain along the West Coast and far Western Interior from the
Seward Peninsula south to Bristol Bay. These rains will
gradually diminish on Wednesday.

- Southeasterly winds over western Alaska remain strong into
tonight before diminishing Wednesday. 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 tonight
through the Norton and Kotzebue Sounds.

North Slope and Brooks Range..
- Warmer and drier conditions over the next several days.

- Strong east winds with low stratus and fog at night will
continue along the Arctic Coast.

- Isolated showers today over the far western Brooks Range.

&&

.FORECAST ANALYSIS AND DISCUSSION...
High pressure centered over the central Arctic Coast will
continue to dominate the weather pattern for the Interior through
the weekend. Warmer and drier conditions will continue into the
weekend. Northeast winds will increase enough on Wednesday to
warrant the Red Flag Warning for mainly the higher terrain of the
central and eastern Interior. Coordination took place with AICC
and our IMETs. Those winds decrease on Thursday but the low level
instability will still support convective plume development over
the fires. In western Alaska rain along the coast from Bristol
Bay to the Seward Peninsula will diminish by tonight and Wednesday
as the Bering Sea low weakens and moves south. We definitely have
low level haze from wildfire smoke south of Fairbanks toward the
Alaska Range. The WRF pushes the smoke west as the northeast flow
increases Wednesday. That might help keep the wildfire smoke from
deteriorating conditions until this weekend. In the extended the
High Pressure ridge remains centered over the Arctic Coast.
Shortwaves will undercut the ridge in the easterly flow and should
increase thunderstorm coverage. Timing of those shortwaves is
uncertain right now. Best take attm is isolated showers and storms
over the Alaska Range westward to the Nulato Hills Friday and
Saturday.


&&

.FIRE WEATHER...
Critical fire weather continues to develop over the next 24 hours
as much drier air as pushed into the region from the
Arctic/Yukon. Winds still look gusty out of the east-northeast;
by-and-large most of the interior should see 15 to 20 mph gusts by
Wednesday afternoon. For folks on fires in more complex terrain,
keep a watchful eye on channels/gaps/valleys exposed to the
northeast and also along ridgetops, where locally higher winds of
30mph is possible. Confidence is high for temperatures to reach
into the low to mid 80s over the next few days, with minimum RH
hitting the low 20s to upper teens. Given the dry air, recovery of
RH in the morning is generally expected to worsen, perhaps
reaching as high as 60%.

Thunderstorms will impact the eastern Tanana Valley late this
afternoon and Wednesday, with the potential for these storms to
penetrate further into the interior. Keep a watchful eye on any
developing thunderstorms as steering winds will push them to the
west. Erratic and gusty outflow winds could reach 30 to 40 mph.

&&

.HYDROLOGY...
No concerns along the rivers. No impacts are expected from the rain
in the west or along the eastern Alaska Range the next couple days.

&&

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

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Red Flag Warning for AKZ931>935-938>947-949.
PK...Small Craft Advisory for PKZ804.
Small Craft Advisory for PKZ805.
Small Craft Advisory for PKZ807-856.
Small Craft Advisory for PKZ808-809-855.
Brisk Wind Advisory for PKZ813-859.
Small Craft Advisory for PKZ852.
Small Craft Advisory for PKZ858.
&&

$$

Maier/Park

048
FXAK67 PAJK 011806 AAA
AFDAJK

Southeast Alaska Forecast Discussion...UPDATED
National Weather Service Juneau AK
1006 AM AKDT Tue Jul 1 2025

.UPDATE...For Aviation 18Z product release...

&&

.AVIATION UPDATE...For the morning TAF update we continue the
trend with most of the rain tapering off gradually through the
late afternoon in the evening, but we will keep rain going for the
central and southern areas toward morning. Ceilings are going to
bounce between IFR and MVFR with passing rain activity, but
trending toward a period of MVFR or VFR toward early evening
before low ceilings of IFR to LIFR move back in tonight with
patchy fog. No wind shear areas to note today into tonight as the
weak low continues to diminish over the central Panhandle
today...however a bit of a seabreeze expected for Taiya Inlet and
the Skagway Airport this afternoon into early evening with SW
winds 15-25 kts.


&&

.PREVIOUS DISCUSSION...Issued at 604 AM AKDT Tue Jul 1 2025...

.SHORT TERM.../Through Tuesday Night/...Light rain is expected to
continue through Tuesday as a weakening low-pressure system over
the eastern Gulf moves inland across the Panhandle. A developing
ridge over the Gulf on Tuesday will support this inland movement,
shifting over the eastern Gulf by late Tuesday into Wednesday. As
a result, rain rates and chances will ease slightly, with a 60-70%
chance of about 0.1 inches every six hours. However, an upper-
level low will maintain periods of light rain, primarily affecting
the central Panhandle. No significant impacts are anticipated.
Winds will stay light across the region, except for a daily
increase in the northern Lynn Canal and Skagway area due to a
south-to-north thermal gradient.

.LONG TERM...Wednesday through Sunday...

We are looking for a pattern shift starting Wednesday as broad low
pressure over the eastern GULFAK weakens and weak ridging starts
to setup over SEAK. While a drier trend to the forecast Wednesday
into the weekend is expected, we won`t be rain free. The weak
nature of the ridge with periods of weak upper energy ejecting out
of the central GULFAK upper level low means that scattered showers
will still be around for Thursday and through the 4th of July
weekend. It should not be a washout and guidance does not have any
heavy precipitation through Saturday. We will have to watch an
approaching front moving east out of the central GULFAK on
Sunday. /Garmon

Temperatures at the end of the week begin to increase to near
typical values for this time of year with maximum temperatures in
the mid to high 60s. Low temperatures will remain in the low to mid
50s to end out the week.

&&

.MARINE...Outside Waters: As the low continues to weaken, push
northeastward into the Panhandle, and the pressure gradient continues
to further relax, the winds will continue to decrease down to
around 5 to 10 kts along the Outside Waters through Tuesday night.
Waves will also continue to subside down to near 3 ft with a
period around 10 seconds.

Inside Waters: As this low continues to diminish in strength, wind
directions across much of the Inner Channels will become southerly
by Tuesday afternoon. Tuesday afternoon, the northerly winds
across northern Lynn Canal will be overcome by a thermal gradient
that will allow for southerly winds of up to just shy of 20 kts.
Elsewhere, winds of 15 kts or less are expected, diminishing to 10
kts or less by Tuesday night.

&&

.HYDROLOGY...The Glacier Lake Outburst event on the Taku River has
ended. The river has crested early this morning at 40.91 feet,
never making it to action stage or minor flood stage, and will
continue to fall throughout the day, today. People who live or
recreate on the Taku River or around Taku Inlet should remain
alert of the river conditions and potential remaining hazardous
debris in the water. At 5AM, the river stage was 40.84 feet. It is
forecast to fall below 38 feet by late this afternoon or early
evening.

&&


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

&&

$$

SHORT TERM...JLC
LONG TERM....Garmon
AVIATION...Garmon
MARINE...JLC
HYDROLOGY...JLC

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