Graphical Hydro Meteorological Discussion

094
FXAK68 PAFC 300041
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
441 PM AKDT Sat Jun 29 2024

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

A Bering Sea low is continuing to sink south with its front
pushing northward into the western Gulf and nearing Kodiak Island
by late tonight. Steady rainfall has already started. Models
consensus on total rainfall amounts differ quite a bit for Kodiak,
but on the low end Kodiak City could see a quarter inch through
Monday and up to an inch on the higher end. The expected total is
around three quarter inch or so through Sunday night. Kodiak could
start to see decreasing chances for rain Monday morning, though
the synoptic pattern will not change very much and chances for
showers will remain possible through the short term forecast for
Kodiak Island.

The upper ridge will start to build back into the central
interior of Alaska with ridge axis positioning itself along to
just north of the eastern Alaska Range by Sunday. Isolated
thunderstorms are possible along the slopes of the Alaska Range
and Wrangell Mountains Sunday, though models are hinting that a
low end instability axis might extend over towards the Talkeetna
Mountains and northern Susitna Valley Sunday afternoon.

With the Bering low and front to the south and west, and the
upper ridge building back west to the north...Southcentral will
see increasing easterly flow resulting in a more unsettled pattern
for the latter half of the weekend into early next week. Rain
showers will become more widespread overnight tonight into Sunday
morning for the northern Gulf as remnant lows in the eastern Gulf
become easterly waves. More widely scattered showers expected for
the Copper River Basin and northern Susitna Valley. The eastern
Kenai, Prince William Sound, and northern Gulf coast will see the
bulk of precipitation as the western Kenai, Anchorage Bowl, and
Mat-Su Valley will likely see downsloping set-up with lesser
chances for any showers. Chances for showers will gradually
decrease early Monday along the coast, but remain isolated to
scattered closer to terrain of the Susitna Valley and Copper River
Basin through Tuesday. Lastly, increasing pressure gradients
along the Gulf coast will result in gusty gap winds developing for
the Turnagain Arm and Copper Basin. The pressure gradient, and
therefore winds, could weaken Tuesday.

- PP / rux

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA/ALEUTIANS
(Days 1 through 3: Saturday night through Tuesday)...

A broad, longwave trough continues to sit over the Bering,
anchored by a vertically stacked low centered north of Atka.
Downstream of this feature, a shortwave trough and attendant
surface front are moving from the eastern Aleutians to the Alaska
Peninsula this evening. The result is continued widespread shower
activity stretching from coastal Bristol Bay north to the
Kuskokwim Delta. Southeasterly winds ahead of the front are gusty
along the Southwest coast this afternoon. Extensive cloud cover
over Southwest Alaska is also helping to keep temperatures on the
cooler side.

The aforementioned low will slowly slide southeast through
Sunday, bringing persistent showers to the eastern half of the
Aleutian Chain, as well as coastal Southwest Alaska. In the wake
of the low, gusty northwesterly winds are expected from west of
the Pribilofs south across the central Aleutians due, in part, to
increasing instability as colder air works in aloft.

A secondary upper-level wave will move over interior Southwest
Sunday. This feature will produce widespread showers for the
Middle Kuskokwim Valley. An isolated thunderstorm is also
possible; however, convective parameters are marginal at best.

By Sunday evening, a large amplitude ridge of high pressure will
build over the western Bering and push eastward through at least
the end of the forecast period. Widespread fog is likely
underneath the ridge as temperatures at the surface remain quite
cool but temperatures aloft (~850mb) warm to 10C or warmer. The
ridge axis, as well as the fog, moves east from the western Being
to the central Bering and Pribilof Islands for Monday and Tuesday.

-TM

&&
.LONG TERM FORECAST (Days 4 through 7)...


Low pressure will move eastward through the Gulf of Alaska through
the end of next week. Its eastward trek will be inhibited
by the ridge in the Copper River Basin/Southcentral through this
time. Isolated to scattered thunderstorms are possible in the
Copper River Basin toward the end of the week, too. Model
disparity of the low`s location and ridge`s westward progression
is high therefore, confidence in exact impacts and locations is
low. However, there remains high confidence that a ridge will
build into the Aleutians through the week.

-DJ

&&

.AVIATION...

PANC...VFR conditions with light wind will persist through
Saturday afternoon. Slightly strong southeast winds out of the
Turnagain Arm may brush ANC this evening, but confidence remains
low. General light and southerly winds are expected to prevail
this evening. Confidence is significantly higher that strong,
gusty southeast winds will increase in strength Sunday afternoon
and continue through through into early Sunday night.

&&
$$

123
FXAK69 PAFG 300905 CCA
AFDAFG

Northern Alaska Forecast Discussion...CORRECTED National Weather
Service Fairbanks AK 1123 AM AKDT Sat Jun 29 2024

.SYNOPSIS...
Warm weather will continue over much of the Interior through the
weekend and into early next week. Areas of dense smoke from fires
burning is reducing visibilities over the Middle Tanana Valley.
Smoke will be in and out through the weekend. Dense smoke advisories
expected to continue. Isolated storms will persist into the weekend.

&&

.DISCUSSION...

Analysis and Model Discussion...

A strong vertically stacked low will remain in the central Bering
Sea then drift across the Aleutians on Sunday as a 540 dam Low.
Ridging will persist over the Interior this weekend. A trough will
push across the eastern North slope late Sunday into Monday. Another
low over Russia will push a front across Northwest Alaska on
Tuesday. Ridging over the Interior will slowly break down Monday and
Tuesday. Models in good agreement through the short term. The HRRR
smoke model showing smoke persisting over the Interior through the
weekend.

Interior...Warm weather will continue over much of the Interior
through the weekend. Highs in the mid 80s and a few upper 80s over
the Yukon Flats. Areas of dense smoke from fires burning is reducing
visibilities over the Middle Tanana Valley. Smoke will be in and out
through the weekend. Air across Fairbanks and North Pole is very
unhealthy this morning. Dense smoke advisories have been extended
into Sunday. Smoke may thin and visibility may improve in the
afternoon around Fairbanks but become dense again early morning on
Sunday. High pressure builds back in for the weekend with rising
temps back into the 80s, and much lower thunderstorm activity, with
that ridge aloft suppressing thunderstorm potential. Isolated to
widely scattered thunderstorms return over the southern Interior on
Sunday.

West Coast and Western Interior... High pressure in control over the
majority of the west coast.
Western Interior will remain warm over the weekend with highs in the
upper 70s to low 80s. Showers continue to rotate around the Yukon
Delta from the low in the southern Bering through the weekend.
Widely scattered thunderstorms are possible from Grayling to Mcgrath
on Sunday. Some of these storms will be fairly strong and may
produce small hail and gusty winds with copious lightning.
Monday is another warm day, with increasing southwesterly winds as a
low approaches the NW Arctic. Possible change in the pattern by
Tuesday with temps cooling and a front bringing rain showers to the
west coast. Temps could drop to the 60s Tuesday into Wednesday.

North Slope and Brooks Range... A little less thunderstorm activity
today but still a chance for isolated thunderstorms over the eastern
Brooks Range today from Anatuvak Pass to the AlCan border. On
Sunday, isolated storms return over the southern Interior. A front
will begin to impact northwest Alaska and the western Brooks Range
with strong west-southwesterly winds.

Extended Forecast Days 4-7... Long range models are coming more
inline with a fairly large pattern shift beginning Tuesday, as a
front from E Siberia moves inland across the NW Arctic and shifts
east along the Brooks Range and eventually into the Interior through
the remainder of the week. This will bring increasing west-southwest
winds across the Mainland each day, with increasing chances for
rainfall and cooler temps.


Coastal Hazard Potential Days 3 and 4...None.

&&

.FIRE WEATHER...
Warm and relatively dry over the Interior through the weekend and
into early Next week. Smoke and unhealthy air continues over the
Middle Tanana Valley down to Delta Junction. Dense Smoke Advisories
still in effect through Sunday. On Saturday, the thunderstorm threat
moves Anatuvak Pass to the AlCan border. For now, widely scattered
wet thunderstorms are expected. On Sunday, isolated to widely
scattered thunderstorms return over the southern Interior and
western Interior from Grayling to McGrath.

Major pattern shift begins Tue and Wed as the upper ridge breaks
down and a strong front moves into the NW Arctic and shifts east
through the week, bringing potential wetting rains and much cooler
temps, although strong southwest winds may create some critical fire
weather conditions prior to that. Will continue to monitor.

&&

.HYDROLOGY...
Heavy rain showers and thunderstorms over the Brooks Range today may
feed into faster moving streams and cause rapid rises, which will
remain high into this weekend. Glacial fed rivers including the
Tanana are beginning to rise as warming temperatures lead to
increased high elevation snowmelt.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Dense Smoke Advisory for AKZ834-837-840-841-842-843-844-839.
PK...None.

&&

$$

Ahsenmacher

467
FXAK67 PAJK 292335
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
335 PM AKDT Sat Jun 29 2024

.SHORT TERM...Minor changes to the short term forecast at this
time as multiple weak shortwave troughs work around the periphery
of an upper level low situated near Haida Gwaii through Sunday.
Increased winds within inner channels, particular Lynn Canal,
through the rest of this afternoon as thermal gradient enhances
N/S flow with winds up to 15-20kts with an isolated gust up to
30mph possible. Frontal system has made slightly further
progression than anticipated with some light rain reaching the
surface via PAJN FAA Camera so slightly adjusted PoP chances
upward for the central and northern Panhandle through tonight.
Looking to tomorrow, anticipating the arrival of another shortwave
surface trough with bands of precip bringing isolated to
scattered showers across the panhandle. Highest precipitation
chances expected along the coast and along and south of a line
from Sitka to Angoon. Increasing cloud cover tonight over most of
the panhandle will keep minimum temperatures in the mid 50s. For
tomorrow, highs into the 60s across panhandle with isolated
locations in the northern panhandle breaking into the 70s if they
can make it out of cloud cover.


.LONG TERM...Little changes made to the long term forecast heading
through the middle of the week and the Independence Day holiday. A
weak frontal band from a decaying low will continue to bring
increased shower activity to the southern and central panhandle into
Monday before beginning to diminish. A ridge of high pressure will
build in from the south over the panhandle, leading to some skies
clearing by Wednesday for the inner channels. For the outer coast,
the transition to a more persistent WNW and overall onshore flow
will likely lead to marine layer clouds to push in on and off again,
which may lead to slightly lower daytime highs than communities
further inland. Overall maximum temperatures look to remain
seasonably warm ranging from the mid 60s to low 70s.

With the ridge building in, winds for the inner channels are set to
become more light and variable by Wednesday and into the later half
of the week, with the exception of local sea breeze effects such as
in northern Lynn Canal which may become more pronounced once skies
begin to clear out. For the gulf coast, modest winds of around 15 kt
are expected out of the NW as the ridge moves into position in the
eastern gulf before the gradient begins to slacken slightly.

Looking ahead to the Independence Day holiday, conditions look to be
fairly dry and warm Wednesday and on through Thursday morning. By
Thursday afternoon, model guidance begins to show signs of rain
returning to the panhandle from a system moving into the southern
gulf. Model spread is increasing during this timeframe though, so
there is lower forecaster confidence in terms of the timing of this
feature as well as the extent of its influence over the panhandle.

&&

.AVIATION...The marine layer is hanging tough over the south end
of Yakutat Bay and over the airport this afternoon with IFR CIGS
around 500 ft agl being reported there. We expect that layer to
sort of slip in and out of Yakutat into the evening with light seabreeze
out of the SW. Farther south, generally MVFR to VFR prevailing
over the central Panhandle, with IFR to MVFR CIGS and VSBYS in
rain being seen over the southern quarter of SEAK closer to the
decaying frontal boundary. For the next 24 hours, we expect the
more numerous coverage of showers to be along the outer coast
through this evening south of Cross Sound, with scattered showers
over the central inner channels. We expect any IFR conditions late
tonight into morning to be around Yakutat where the marine layer
is hanging along the coast, and for a few spots farther south near
the decaying boundary over the central Panhandle.


&&

.MARINE...A weak area of low pressure over the eastern Gulf of
Alaska will overspread intermittent rain over the panhandle
through Sunday. Anticipate elevated inner channel winds up to
15-20 kts and seas up to 2-3ft on Sunday afternoon within N/S
oriented channels as a weak trough pushes northward. General
drying trend moving into next week as a ridge of high pressure
becomes established over the Gulf of Alaska on Monday through
midweek.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ661>663.

&&

$$

SHORT TERM...NM
LONG TERM....STJ
AVIATION.....JG
MARINE.......NM

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